diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/Kconfig | 13 | ||||
| -rw-r--r-- | drivers/lguest/Makefile | 29 | ||||
| -rw-r--r-- | drivers/lguest/README | 47 | ||||
| -rw-r--r-- | drivers/lguest/core.c | 373 | ||||
| -rw-r--r-- | drivers/lguest/hypercalls.c | 312 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 647 | ||||
| -rw-r--r-- | drivers/lguest/lg.h | 260 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 534 | ||||
| -rw-r--r-- | drivers/lguest/lguest_user.c | 542 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 1194 | ||||
| -rw-r--r-- | drivers/lguest/segments.c | 228 | ||||
| -rw-r--r-- | drivers/lguest/x86/core.c | 718 | ||||
| -rw-r--r-- | drivers/lguest/x86/switcher_32.S | 388 |
13 files changed, 0 insertions, 5285 deletions
diff --git a/drivers/lguest/Kconfig b/drivers/lguest/Kconfig deleted file mode 100644 index ee035ec4526b..000000000000 --- a/drivers/lguest/Kconfig +++ /dev/null @@ -1,13 +0,0 @@ -config LGUEST - tristate "Linux hypervisor example code" - depends on X86_32 && EVENTFD && TTY - select HVC_DRIVER - ---help--- - This is a very simple module which allows you to run - multiple instances of the same Linux kernel, using the - "lguest" command found in the tools/lguest directory. - - Note that "lguest" is pronounced to rhyme with "fell quest", - not "rustyvisor". See tools/lguest/lguest.txt. - - If unsure, say N. If curious, say M. If masochistic, say Y. diff --git a/drivers/lguest/Makefile b/drivers/lguest/Makefile deleted file mode 100644 index c4197503900e..000000000000 --- a/drivers/lguest/Makefile +++ /dev/null @@ -1,29 +0,0 @@ -# Guest requires the device configuration and probing code. -obj-$(CONFIG_LGUEST_GUEST) += lguest_device.o - -# Host requires the other files, which can be a module. -obj-$(CONFIG_LGUEST) += lg.o -lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \ - segments.o lguest_user.o - -lg-$(CONFIG_X86_32) += x86/switcher_32.o x86/core.o - -Preparation Preparation!: PREFIX=P -Guest: PREFIX=G -Drivers: PREFIX=D -Launcher: PREFIX=L -Host: PREFIX=H -Switcher: PREFIX=S -Mastery: PREFIX=M -Beer: - @for f in Preparation Guest Drivers Launcher Host Switcher Mastery; do echo "{==- $$f -==}"; make -s $$f; done; echo "{==-==}" -Preparation Preparation! Guest Drivers Launcher Host Switcher Mastery: - @sh ../../tools/lguest/extract $(PREFIX) `find ../../* -name '*.[chS]' -wholename '*lguest*'` -Puppy: - @clear - @printf " __ \n (___()'\`;\n /, /\`\n \\\\\\\"--\\\\\\ \n" - @sleep 2; clear; printf "\n\n Sit!\n\n"; sleep 1; clear - @printf " __ \n ()'\`; \n /\\|\` \n / | \n(/_)_|_ \n" - @sleep 2; clear; printf "\n\n Stand!\n\n"; sleep 1; clear - @printf " __ \n ()'\`; \n /\\|\` \n /._.= \n /| / \n(_\_)_ \n" - @sleep 2; clear; printf "\n\n Good puppy!\n\n"; sleep 1; clear diff --git a/drivers/lguest/README b/drivers/lguest/README deleted file mode 100644 index b7db39a64c66..000000000000 --- a/drivers/lguest/README +++ /dev/null @@ -1,47 +0,0 @@ -Welcome, friend reader, to lguest. - -Lguest is an adventure, with you, the reader, as Hero. I can't think of many -5000-line projects which offer both such capability and glimpses of future -potential; it is an exciting time to be delving into the source! - -But be warned; this is an arduous journey of several hours or more! And as we -know, all true Heroes are driven by a Noble Goal. Thus I offer a Beer (or -equivalent) to anyone I meet who has completed this documentation. - -So get comfortable and keep your wits about you (both quick and humorous). -Along your way to the Noble Goal, you will also gain masterly insight into -lguest, and hypervisors and x86 virtualization in general. - -Our Quest is in seven parts: (best read with C highlighting turned on) - -I) Preparation - - In which our potential hero is flown quickly over the landscape for a - taste of its scope. Suitable for the armchair coders and other such - persons of faint constitution. - -II) Guest - - Where we encounter the first tantalising wisps of code, and come to - understand the details of the life of a Guest kernel. - -III) Drivers - - Whereby the Guest finds its voice and become useful, and our - understanding of the Guest is completed. - -IV) Launcher - - Where we trace back to the creation of the Guest, and thus begin our - understanding of the Host. - -V) Host - - Where we master the Host code, through a long and tortuous journey. - Indeed, it is here that our hero is tested in the Bit of Despair. - -VI) Switcher - - Where our understanding of the intertwined nature of Guests and Hosts - is completed. - -VII) Mastery - - Where our fully fledged hero grapples with the Great Question: - "What next?" - -make Preparation! -Rusty Russell. diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c deleted file mode 100644 index 0bf1e4edf04d..000000000000 --- a/drivers/lguest/core.c +++ /dev/null @@ -1,373 +0,0 @@ -/*P:400 - * This contains run_guest() which actually calls into the Host<->Guest - * Switcher and analyzes the return, such as determining if the Guest wants the - * Host to do something. This file also contains useful helper routines. -:*/ -#include <linux/module.h> -#include <linux/stringify.h> -#include <linux/stddef.h> -#include <linux/io.h> -#include <linux/mm.h> -#include <linux/vmalloc.h> -#include <linux/cpu.h> -#include <linux/freezer.h> -#include <linux/highmem.h> -#include <linux/slab.h> -#include <asm/paravirt.h> -#include <asm/pgtable.h> -#include <asm/uaccess.h> -#include <asm/poll.h> -#include <asm/asm-offsets.h> -#include "lg.h" - -unsigned long switcher_addr; -struct page **lg_switcher_pages; -static struct vm_struct *switcher_vma; - -/* This One Big lock protects all inter-guest data structures. */ -DEFINE_MUTEX(lguest_lock); - -/*H:010 - * We need to set up the Switcher at a high virtual address. Remember the - * Switcher is a few hundred bytes of assembler code which actually changes the - * CPU to run the Guest, and then changes back to the Host when a trap or - * interrupt happens. - * - * The Switcher code must be at the same virtual address in the Guest as the - * Host since it will be running as the switchover occurs. - * - * Trying to map memory at a particular address is an unusual thing to do, so - * it's not a simple one-liner. - */ -static __init int map_switcher(void) -{ - int i, err; - struct page **pagep; - - /* - * Map the Switcher in to high memory. - * - * It turns out that if we choose the address 0xFFC00000 (4MB under the - * top virtual address), it makes setting up the page tables really - * easy. - */ - - /* We assume Switcher text fits into a single page. */ - if (end_switcher_text - start_switcher_text > PAGE_SIZE) { - printk(KERN_ERR "lguest: switcher text too large (%zu)\n", - end_switcher_text - start_switcher_text); - return -EINVAL; - } - - /* - * We allocate an array of struct page pointers. map_vm_area() wants - * this, rather than just an array of pages. - */ - lg_switcher_pages = kmalloc(sizeof(lg_switcher_pages[0]) - * TOTAL_SWITCHER_PAGES, - GFP_KERNEL); - if (!lg_switcher_pages) { - err = -ENOMEM; - goto out; - } - - /* - * Now we actually allocate the pages. The Guest will see these pages, - * so we make sure they're zeroed. - */ - for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { - lg_switcher_pages[i] = alloc_page(GFP_KERNEL|__GFP_ZERO); - if (!lg_switcher_pages[i]) { - err = -ENOMEM; - goto free_some_pages; - } - } - - /* - * We place the Switcher underneath the fixmap area, which is the - * highest virtual address we can get. This is important, since we - * tell the Guest it can't access this memory, so we want its ceiling - * as high as possible. - */ - switcher_addr = FIXADDR_START - (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE; - - /* - * Now we reserve the "virtual memory area" we want. We might - * not get it in theory, but in practice it's worked so far. - * The end address needs +1 because __get_vm_area allocates an - * extra guard page, so we need space for that. - */ - switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE, - VM_ALLOC, switcher_addr, switcher_addr - + (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE); - if (!switcher_vma) { - err = -ENOMEM; - printk("lguest: could not map switcher pages high\n"); - goto free_pages; - } - - /* - * This code actually sets up the pages we've allocated to appear at - * switcher_addr. map_vm_area() takes the vma we allocated above, the - * kind of pages we're mapping (kernel pages), and a pointer to our - * array of struct pages. It increments that pointer, but we don't - * care. - */ - pagep = lg_switcher_pages; - err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep); - if (err) { - printk("lguest: map_vm_area failed: %i\n", err); - goto free_vma; - } - - /* - * Now the Switcher is mapped at the right address, we can't fail! - * Copy in the compiled-in Switcher code (from x86/switcher_32.S). - */ - memcpy(switcher_vma->addr, start_switcher_text, - end_switcher_text - start_switcher_text); - - printk(KERN_INFO "lguest: mapped switcher at %p\n", - switcher_vma->addr); - /* And we succeeded... */ - return 0; - -free_vma: - vunmap(switcher_vma->addr); -free_pages: - i = TOTAL_SWITCHER_PAGES; -free_some_pages: - for (--i; i >= 0; i--) - __free_pages(lg_switcher_pages[i], 0); - kfree(lg_switcher_pages); -out: - return err; -} -/*:*/ - -/* Cleaning up the mapping when the module is unloaded is almost... too easy. */ -static void unmap_switcher(void) -{ - unsigned int i; - - /* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */ - vunmap(switcher_vma->addr); - /* Now we just need to free the pages we copied the switcher into */ - for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) - __free_pages(lg_switcher_pages[i], 0); - kfree(lg_switcher_pages); -} - -/*H:032 - * Dealing With Guest Memory. - * - * Before we go too much further into the Host, we need to grok the routines - * we use to deal with Guest memory. - * - * When the Guest gives us (what it thinks is) a physical address, we can use - * the normal copy_from_user() & copy_to_user() on the corresponding place in - * the memory region allocated by the Launcher. - * - * But we can't trust the Guest: it might be trying to access the Launcher - * code. We have to check that the range is below the pfn_limit the Launcher - * gave us. We have to make sure that addr + len doesn't give us a false - * positive by overflowing, too. - */ -bool lguest_address_ok(const struct lguest *lg, - unsigned long addr, unsigned long len) -{ - return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr); -} - -/* - * This routine copies memory from the Guest. Here we can see how useful the - * kill_lguest() routine we met in the Launcher can be: we return a random - * value (all zeroes) instead of needing to return an error. - */ -void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes) -{ - if (!lguest_address_ok(cpu->lg, addr, bytes) - || copy_from_user(b, cpu->lg->mem_base + addr, bytes) != 0) { - /* copy_from_user should do this, but as we rely on it... */ - memset(b, 0, bytes); - kill_guest(cpu, "bad read address %#lx len %u", addr, bytes); - } -} - -/* This is the write (copy into Guest) version. */ -void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b, - unsigned bytes) -{ - if (!lguest_address_ok(cpu->lg, addr, bytes) - || copy_to_user(cpu->lg->mem_base + addr, b, bytes) != 0) - kill_guest(cpu, "bad write address %#lx len %u", addr, bytes); -} -/*:*/ - -/*H:030 - * Let's jump straight to the the main loop which runs the Guest. - * Remember, this is called by the Launcher reading /dev/lguest, and we keep - * going around and around until something interesting happens. - */ -int run_guest(struct lg_cpu *cpu, unsigned long __user *user) -{ - /* We stop running once the Guest is dead. */ - while (!cpu->lg->dead) { - unsigned int irq; - bool more; - - /* First we run any hypercalls the Guest wants done. */ - if (cpu->hcall) - do_hypercalls(cpu); - - /* - * It's possible the Guest did a NOTIFY hypercall to the - * Launcher. - */ - if (cpu->pending_notify) { - /* - * Does it just needs to write to a registered - * eventfd (ie. the appropriate virtqueue thread)? - */ - if (!send_notify_to_eventfd(cpu)) { - /* OK, we tell the main Launcher. */ - if (put_user(cpu->pending_notify, user)) - return -EFAULT; - return sizeof(cpu->pending_notify); - } - } - - /* - * All long-lived kernel loops need to check with this horrible - * thing called the freezer. If the Host is trying to suspend, - * it stops us. - */ - try_to_freeze(); - - /* Check for signals */ - if (signal_pending(current)) - return -ERESTARTSYS; - - /* - * Check if there are any interrupts which can be delivered now: - * if so, this sets up the hander to be executed when we next - * run the Guest. - */ - irq = interrupt_pending(cpu, &more); - if (irq < LGUEST_IRQS) - try_deliver_interrupt(cpu, irq, more); - - /* - * Just make absolutely sure the Guest is still alive. One of - * those hypercalls could have been fatal, for example. - */ - if (cpu->lg->dead) - break; - - /* - * If the Guest asked to be stopped, we sleep. The Guest's - * clock timer will wake us. - */ - if (cpu->halted) { - set_current_state(TASK_INTERRUPTIBLE); - /* - * Just before we sleep, make sure no interrupt snuck in - * which we should be doing. - */ - if (interrupt_pending(cpu, &more) < LGUEST_IRQS) - set_current_state(TASK_RUNNING); - else - schedule(); - continue; - } - - /* - * OK, now we're ready to jump into the Guest. First we put up - * the "Do Not Disturb" sign: - */ - local_irq_disable(); - - /* Actually run the Guest until something happens. */ - lguest_arch_run_guest(cpu); - - /* Now we're ready to be interrupted or moved to other CPUs */ - local_irq_enable(); - - /* Now we deal with whatever happened to the Guest. */ - lguest_arch_handle_trap(cpu); - } - - /* Special case: Guest is 'dead' but wants a reboot. */ - if (cpu->lg->dead == ERR_PTR(-ERESTART)) - return -ERESTART; - - /* The Guest is dead => "No such file or directory" */ - return -ENOENT; -} - -/*H:000 - * Welcome to the Host! - * - * By this point your brain has been tickled by the Guest code and numbed by - * the Launcher code; prepare for it to be stretched by the Host code. This is - * the heart. Let's begin at the initialization routine for the Host's lg - * module. - */ -static int __init init(void) -{ - int err; - - /* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */ - if (get_kernel_rpl() != 0) { - printk("lguest is afraid of being a guest\n"); - return -EPERM; - } - - /* First we put the Switcher up in very high virtual memory. */ - err = map_switcher(); - if (err) - goto out; - - /* We might need to reserve an interrupt vector. */ - err = init_interrupts(); - if (err) - goto unmap; - - /* /dev/lguest needs to be registered. */ - err = lguest_device_init(); - if (err) - goto free_interrupts; - - /* Finally we do some architecture-specific setup. */ - lguest_arch_host_init(); - - /* All good! */ - return 0; - -free_interrupts: - free_interrupts(); -unmap: - unmap_switcher(); -out: - return err; -} - -/* Cleaning up is just the same code, backwards. With a little French. */ -static void __exit fini(void) -{ - lguest_device_remove(); - free_interrupts(); - unmap_switcher(); - - lguest_arch_host_fini(); -} -/*:*/ - -/* - * The Host side of lguest can be a module. This is a nice way for people to - * play with it. - */ -module_init(init); -module_exit(fini); -MODULE_LICENSE("GPL"); -MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c deleted file mode 100644 index 83511eb0923d..000000000000 --- a/drivers/lguest/hypercalls.c +++ /dev/null @@ -1,312 +0,0 @@ -/*P:500 - * Just as userspace programs request kernel operations through a system - * call, the Guest requests Host operations through a "hypercall". You might - * notice this nomenclature doesn't really follow any logic, but the name has - * been around for long enough that we're stuck with it. As you'd expect, this - * code is basically a one big switch statement. -:*/ - -/* Copyright (C) 2006 Rusty Russell IBM Corporation - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2 of the License, or - (at your option) any later version. - - This program is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA -*/ -#include <linux/uaccess.h> -#include <linux/syscalls.h> -#include <linux/mm.h> -#include <linux/ktime.h> -#include <asm/page.h> -#include <asm/pgtable.h> -#include "lg.h" - -/*H:120 - * This is the core hypercall routine: where the Guest gets what it wants. - * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. - */ -static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) -{ - switch (args->arg0) { - case LHCALL_FLUSH_ASYNC: - /* - * This call does nothing, except by breaking out of the Guest - * it makes us process all the asynchronous hypercalls. - */ - break; - case LHCALL_SEND_INTERRUPTS: - /* - * This call does nothing too, but by breaking out of the Guest - * it makes us process any pending interrupts. - */ - break; - case LHCALL_LGUEST_INIT: - /* - * You can't get here unless you're already initialized. Don't - * do that. - */ - kill_guest(cpu, "already have lguest_data"); - break; - case LHCALL_SHUTDOWN: { - char msg[128]; - /* - * Shutdown is such a trivial hypercall that we do it in five - * lines right here. - * - * If the lgread fails, it will call kill_guest() itself; the - * kill_guest() with the message will be ignored. - */ - __lgread(cpu, msg, args->arg1, sizeof(msg)); - msg[sizeof(msg)-1] = '\0'; - kill_guest(cpu, "CRASH: %s", msg); - if (args->arg2 == LGUEST_SHUTDOWN_RESTART) - cpu->lg->dead = ERR_PTR(-ERESTART); - break; - } - case LHCALL_FLUSH_TLB: - /* FLUSH_TLB comes in two flavors, depending on the argument: */ - if (args->arg1) - guest_pagetable_clear_all(cpu); - else - guest_pagetable_flush_user(cpu); - break; - - /* - * All these calls simply pass the arguments through to the right - * routines. - */ - case LHCALL_NEW_PGTABLE: - guest_new_pagetable(cpu, args->arg1); - break; - case LHCALL_SET_STACK: - guest_set_stack(cpu, args->arg1, args->arg2, args->arg3); - break; - case LHCALL_SET_PTE: -#ifdef CONFIG_X86_PAE - guest_set_pte(cpu, args->arg1, args->arg2, - __pte(args->arg3 | (u64)args->arg4 << 32)); -#else - guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3)); -#endif - break; - case LHCALL_SET_PGD: - guest_set_pgd(cpu->lg, args->arg1, args->arg2); - break; -#ifdef CONFIG_X86_PAE - case LHCALL_SET_PMD: - guest_set_pmd(cpu->lg, args->arg1, args->arg2); - break; -#endif - case LHCALL_SET_CLOCKEVENT: - guest_set_clockevent(cpu, args->arg1); - break; - case LHCALL_TS: - /* This sets the TS flag, as we saw used in run_guest(). */ - cpu->ts = args->arg1; - break; - case LHCALL_HALT: - /* Similarly, this sets the halted flag for run_guest(). */ - cpu->halted = 1; - break; - case LHCALL_NOTIFY: - cpu->pending_notify = args->arg1; - break; - default: - /* It should be an architecture-specific hypercall. */ - if (lguest_arch_do_hcall(cpu, args)) - kill_guest(cpu, "Bad hypercall %li\n", args->arg0); - } -} - -/*H:124 - * Asynchronous hypercalls are easy: we just look in the array in the - * Guest's "struct lguest_data" to see if any new ones are marked "ready". - * - * We are careful to do these in order: obviously we respect the order the - * Guest put them in the ring, but we also promise the Guest that they will - * happen before any normal hypercall (which is why we check this before - * checking for a normal hcall). - */ -static void do_async_hcalls(struct lg_cpu *cpu) -{ - unsigned int i; - u8 st[LHCALL_RING_SIZE]; - - /* For simplicity, we copy the entire call status array in at once. */ - if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st))) - return; - - /* We process "struct lguest_data"s hcalls[] ring once. */ - for (i = 0; i < ARRAY_SIZE(st); i++) { - struct hcall_args args; - /* - * We remember where we were up to from last time. This makes - * sure that the hypercalls are done in the order the Guest - * places them in the ring. - */ - unsigned int n = cpu->next_hcall; - - /* 0xFF means there's no call here (yet). */ - if (st[n] == 0xFF) - break; - - /* - * OK, we have hypercall. Increment the "next_hcall" cursor, - * and wrap back to 0 if we reach the end. - */ - if (++cpu->next_hcall == LHCALL_RING_SIZE) - cpu->next_hcall = 0; - - /* - * Copy the hypercall arguments into a local copy of the - * hcall_args struct. - */ - if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n], - sizeof(struct hcall_args))) { - kill_guest(cpu, "Fetching async hypercalls"); - break; - } - - /* Do the hypercall, same as a normal one. */ - do_hcall(cpu, &args); - - /* Mark the hypercall done. */ - if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) { - kill_guest(cpu, "Writing result for async hypercall"); - break; - } - - /* - * Stop doing hypercalls if they want to notify the Launcher: - * it needs to service this first. - */ - if (cpu->pending_notify) - break; - } -} - -/* - * Last of all, we look at what happens first of all. The very first time the - * Guest makes a hypercall, we end up here to set things up: - */ -static void initialize(struct lg_cpu *cpu) -{ - /* - * You can't do anything until you're initialized. The Guest knows the - * rules, so we're unforgiving here. - */ - if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) { - kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0); - return; - } - - if (lguest_arch_init_hypercalls(cpu)) - kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); - - /* - * The Guest tells us where we're not to deliver interrupts by putting - * the range of addresses into "struct lguest_data". - */ - if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start) - || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end)) - kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); - - /* - * We write the current time into the Guest's data page once so it can - * set its clock. - */ - write_timestamp(cpu); - - /* page_tables.c will also do some setup. */ - page_table_guest_data_init(cpu); - - /* - * This is the one case where the above accesses might have been the - * first write to a Guest page. This may have caused a copy-on-write - * fault, but the old page might be (read-only) in the Guest - * pagetable. - */ - guest_pagetable_clear_all(cpu); -} -/*:*/ - -/*M:013 - * If a Guest reads from a page (so creates a mapping) that it has never - * written to, and then the Launcher writes to it (ie. the output of a virtual - * device), the Guest will still see the old page. In practice, this never - * happens: why would the Guest read a page which it has never written to? But - * a similar scenario might one day bite us, so it's worth mentioning. - * - * Note that if we used a shared anonymous mapping in the Launcher instead of - * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we - * need that to switch the Launcher to processes (away from threads) anyway. -:*/ - -/*H:100 - * Hypercalls - * - * Remember from the Guest, hypercalls come in two flavors: normal and - * asynchronous. This file handles both of types. - */ -void do_hypercalls(struct lg_cpu *cpu) -{ - /* Not initialized yet? This hypercall must do it. */ - if (unlikely(!cpu->lg->lguest_data)) { - /* Set up the "struct lguest_data" */ - initialize(cpu); - /* Hcall is done. */ - cpu->hcall = NULL; - return; - } - - /* - * The Guest has initialized. - * - * Look in the hypercall ring for the async hypercalls: - */ - do_async_hcalls(cpu); - - /* - * If we stopped reading the hypercall ring because the Guest did a - * NOTIFY to the Launcher, we want to return now. Otherwise we do - * the hypercall. - */ - if (!cpu->pending_notify) { - do_hcall(cpu, cpu->hcall); - /* - * Tricky point: we reset the hcall pointer to mark the - * hypercall as "done". We use the hcall pointer rather than - * the trap number to indicate a hypercall is pending. - * Normally it doesn't matter: the Guest will run again and - * update the trap number before we come back here. - * - * However, if we are signalled or the Guest sends I/O to the - * Launcher, the run_guest() loop will exit without running the - * Guest. When it comes back it would try to re-run the - * hypercall. Finding that bug sucked. - */ - cpu->hcall = NULL; - } -} - -/* - * This routine supplies the Guest with time: it's used for wallclock time at - * initial boot and as a rough time source if the TSC isn't available. - */ -void write_timestamp(struct lg_cpu *cpu) -{ - struct timespec now; - ktime_get_real_ts(&now); - if (copy_to_user(&cpu->lg->lguest_data->time, - &now, sizeof(struct timespec))) - kill_guest(cpu, "Writing timestamp"); -} diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c deleted file mode 100644 index 28433a155d67..000000000000 --- a/drivers/lguest/interrupts_and_traps.c +++ /dev/null @@ -1,647 +0,0 @@ -/*P:800 - * Interrupts (traps) are complicated enough to earn their own file. - * There are three classes of interrupts: - * - * 1) Real hardware interrupts which occur while we're running the Guest, - * 2) Interrupts for virtual devices attached to the Guest, and - * 3) Traps and faults from the Guest. - * - * Real hardware interrupts must be delivered to the Host, not the Guest. - * Virtual interrupts must be delivered to the Guest, but we make them look - * just like real hardware would deliver them. Traps from the Guest can be set - * up to go directly back into the Guest, but sometimes the Host wants to see - * them first, so we also have a way of "reflecting" them into the Guest as if - * they had been delivered to it directly. -:*/ -#include <linux/uaccess.h> -#include <linux/interrupt.h> -#include <linux/module.h> -#include <linux/sched.h> -#include "lg.h" - -/* Allow Guests to use a non-128 (ie. non-Linux) syscall trap. */ -static unsigned int syscall_vector = SYSCALL_VECTOR; -module_param(syscall_vector, uint, 0444); - -/* The address of the interrupt handler is split into two bits: */ -static unsigned long idt_address(u32 lo, u32 hi) -{ - return (lo & 0x0000FFFF) | (hi & 0xFFFF0000); -} - -/* - * The "type" of the interrupt handler is a 4 bit field: we only support a - * couple of types. - */ -static int idt_type(u32 lo, u32 hi) -{ - return (hi >> 8) & 0xF; -} - -/* An IDT entry can't be used unless the "present" bit is set. */ -static bool idt_present(u32 lo, u32 hi) -{ - return (hi & 0x8000); -} - -/* - * We need a helper to "push" a value onto the Guest's stack, since that's a - * big part of what delivering an interrupt does. - */ -static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val) -{ - /* Stack grows upwards: move stack then write value. */ - *gstack -= 4; - lgwrite(cpu, *gstack, u32, val); -} - -/*H:210 - * The set_guest_interrupt() routine actually delivers the interrupt or - * trap. The mechanics of delivering traps and interrupts to the Guest are the - * same, except some traps have an "error code" which gets pushed onto the - * stack as well: the caller tells us if this is one. - * - * "lo" and "hi" are the two parts of the Interrupt Descriptor Table for this - * interrupt or trap. It's split into two parts for traditional reasons: gcc - * on i386 used to be frightened by 64 bit numbers. - * - * We set up the stack just like the CPU does for a real interrupt, so it's - * identical for the Guest (and the standard "iret" instruction will undo - * it). - */ -static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, - bool has_err) -{ - unsigned long gstack, origstack; - u32 eflags, ss, irq_enable; - unsigned long virtstack; - - /* - * There are two cases for interrupts: one where the Guest is already - * in the kernel, and a more complex one where the Guest is in - * userspace. We check the privilege level to find out. - */ - if ((cpu->regs->ss&0x3) != GUEST_PL) { - /* - * The Guest told us their kernel stack with the SET_STACK - * hypercall: both the virtual address and the segment. - */ - virtstack = cpu->esp1; - ss = cpu->ss1; - - origstack = gstack = guest_pa(cpu, virtstack); - /* - * We push the old stack segment and pointer onto the new - * stack: when the Guest does an "iret" back from the interrupt - * handler the CPU will notice they're dropping privilege - * levels and expect these here. - */ - push_guest_stack(cpu, &gstack, cpu->regs->ss); - push_guest_stack(cpu, &gstack, cpu->regs->esp); - } else { - /* We're staying on the same Guest (kernel) stack. */ - virtstack = cpu->regs->esp; - ss = cpu->regs->ss; - - origstack = gstack = guest_pa(cpu, virtstack); - } - - /* - * Remember that we never let the Guest actually disable interrupts, so - * the "Interrupt Flag" bit is always set. We copy that bit from the - * Guest's "irq_enabled" field into the eflags word: we saw the Guest - * copy it back in "lguest_iret". - */ - eflags = cpu->regs->eflags; - if (get_user(irq_enable, &cpu->lg->lguest_data->irq_enabled) == 0 - && !(irq_enable & X86_EFLAGS_IF)) - eflags &= ~X86_EFLAGS_IF; - - /* - * An interrupt is expected to push three things on the stack: the old - * "eflags" word, the old code segment, and the old instruction - * pointer. - */ - push_guest_stack(cpu, &gstack, eflags); - push_guest_stack(cpu, &gstack, cpu->regs->cs); - push_guest_stack(cpu, &gstack, cpu->regs->eip); - - /* For the six traps which supply an error code, we push that, too. */ - if (has_err) - push_guest_stack(cpu, &gstack, cpu->regs->errcode); - - /* - * Now we've pushed all the old state, we change the stack, the code - * segment and the address to execute. - */ - cpu->regs->ss = ss; - cpu->regs->esp = virtstack + (gstack - origstack); - cpu->regs->cs = (__KERNEL_CS|GUEST_PL); - cpu->regs->eip = idt_address(lo, hi); - - /* - * There are two kinds of interrupt handlers: 0xE is an "interrupt - * gate" which expects interrupts to be disabled on entry. - */ - if (idt_type(lo, hi) == 0xE) - if (put_user(0, &cpu->lg->lguest_data->irq_enabled)) - kill_guest(cpu, "Disabling interrupts"); -} - -/*H:205 - * Virtual Interrupts. - * - * interrupt_pending() returns the first pending interrupt which isn't blocked - * by the Guest. It is called before every entry to the Guest, and just before - * we go to sleep when the Guest has halted itself. - */ -unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more) -{ - unsigned int irq; - DECLARE_BITMAP(blk, LGUEST_IRQS); - - /* If the Guest hasn't even initialized yet, we can do nothing. */ - if (!cpu->lg->lguest_data) - return LGUEST_IRQS; - - /* - * Take our "irqs_pending" array and remove any interrupts the Guest - * wants blocked: the result ends up in "blk". - */ - if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts, - sizeof(blk))) - return LGUEST_IRQS; - bitmap_andnot(blk, cpu->irqs_pending, blk, LGUEST_IRQS); - - /* Find the first interrupt. */ - irq = find_first_bit(blk, LGUEST_IRQS); - *more = find_next_bit(blk, LGUEST_IRQS, irq+1); - - return irq; -} - -/* - * This actually diverts the Guest to running an interrupt handler, once an - * interrupt has been identified by interrupt_pending(). - */ -void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more) -{ - struct desc_struct *idt; - - BUG_ON(irq >= LGUEST_IRQS); - - /* - * They may be in the middle of an iret, where they asked us never to - * deliver interrupts. - */ - if (cpu->regs->eip >= cpu->lg->noirq_start && - (cpu->regs->eip < cpu->lg->noirq_end)) - return; - - /* If they're halted, interrupts restart them. */ - if (cpu->halted) { - /* Re-enable interrupts. */ - if (put_user(X86_EFLAGS_IF, &cpu->lg->lguest_data->irq_enabled)) - kill_guest(cpu, "Re-enabling interrupts"); - cpu->halted = 0; - } else { - /* Otherwise we check if they have interrupts disabled. */ - u32 irq_enabled; - if (get_user(irq_enabled, &cpu->lg->lguest_data->irq_enabled)) - irq_enabled = 0; - if (!irq_enabled) { - /* Make sure they know an IRQ is pending. */ - put_user(X86_EFLAGS_IF, - &cpu->lg->lguest_data->irq_pending); - return; - } - } - - /* - * Look at the IDT entry the Guest gave us for this interrupt. The - * first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip - * over them. - */ - idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq]; - /* If they don't have a handler (yet?), we just ignore it */ - if (idt_present(idt->a, idt->b)) { - /* OK, mark it no longer pending and deliver it. */ - clear_bit(irq, cpu->irqs_pending); - /* - * set_guest_interrupt() takes the interrupt descriptor and a - * flag to say whether this interrupt pushes an error code onto - * the stack as well: virtual interrupts never do. - */ - set_guest_interrupt(cpu, idt->a, idt->b, false); - } - - /* - * Every time we deliver an interrupt, we update the timestamp in the - * Guest's lguest_data struct. It would be better for the Guest if we - * did this more often, but it can actually be quite slow: doing it - * here is a compromise which means at least it gets updated every - * timer interrupt. - */ - write_timestamp(cpu); - - /* - * If there are no other interrupts we want to deliver, clear - * the pending flag. - */ - if (!more) - put_user(0, &cpu->lg->lguest_data->irq_pending); -} - -/* And this is the routine when we want to set an interrupt for the Guest. */ -void set_interrupt(struct lg_cpu *cpu, unsigned int irq) -{ - /* - * Next time the Guest runs, the core code will see if it can deliver - * this interrupt. - */ - set_bit(irq, cpu->irqs_pending); - - /* - * Make sure it sees it; it might be asleep (eg. halted), or running - * the Guest right now, in which case kick_process() will knock it out. - */ - if (!wake_up_process(cpu->tsk)) - kick_process(cpu->tsk); -} -/*:*/ - -/* - * Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent - * me a patch, so we support that too. It'd be a big step for lguest if half - * the Plan 9 user base were to start using it. - * - * Actually now I think of it, it's possible that Ron *is* half the Plan 9 - * userbase. Oh well. - */ -static bool could_be_syscall(unsigned int num) -{ - /* Normal Linux SYSCALL_VECTOR or reserved vector? */ - return num == SYSCALL_VECTOR || num == syscall_vector; -} - -/* The syscall vector it wants must be unused by Host. */ -bool check_syscall_vector(struct lguest *lg) -{ - u32 vector; - - if (get_user(vector, &lg->lguest_data->syscall_vec)) - return false; - - return could_be_syscall(vector); -} - -int init_interrupts(void) -{ - /* If they want some strange system call vector, reserve it now */ - if (syscall_vector != SYSCALL_VECTOR) { - if (test_bit(syscall_vector, used_vectors) || - vector_used_by_percpu_irq(syscall_vector)) { - printk(KERN_ERR "lg: couldn't reserve syscall %u\n", - syscall_vector); - return -EBUSY; - } - set_bit(syscall_vector, used_vectors); - } - - return 0; -} - -void free_interrupts(void) -{ - if (syscall_vector != SYSCALL_VECTOR) - clear_bit(syscall_vector, used_vectors); -} - -/*H:220 - * Now we've got the routines to deliver interrupts, delivering traps like - * page fault is easy. The only trick is that Intel decided that some traps - * should have error codes: - */ -static bool has_err(unsigned int trap) -{ - return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17); -} - -/* deliver_trap() returns true if it could deliver the trap. */ -bool deliver_trap(struct lg_cpu *cpu, unsigned int num) -{ - /* - * Trap numbers are always 8 bit, but we set an impossible trap number - * for traps inside the Switcher, so check that here. - */ - if (num >= ARRAY_SIZE(cpu->arch.idt)) - return false; - - /* - * Early on the Guest hasn't set the IDT entries (or maybe it put a - * bogus one in): if we fail here, the Guest will be killed. - */ - if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b)) - return false; - set_guest_interrupt(cpu, cpu->arch.idt[num].a, - cpu->arch.idt[num].b, has_err(num)); - return true; -} - -/*H:250 - * Here's the hard part: returning to the Host every time a trap happens - * and then calling deliver_trap() and re-entering the Guest is slow. - * Particularly because Guest userspace system calls are traps (usually trap - * 128). - * - * So we'd like to set up the IDT to tell the CPU to deliver traps directly - * into the Guest. This is possible, but the complexities cause the size of - * this file to double! However, 150 lines of code is worth writing for taking - * system calls down from 1750ns to 270ns. Plus, if lguest didn't do it, all - * the other hypervisors would beat it up at lunchtime. - * - * This routine indicates if a particular trap number could be delivered - * directly. - */ -static bool direct_trap(unsigned int num) -{ - /* - * Hardware interrupts don't go to the Guest at all (except system - * call). - */ - if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num)) - return false; - - /* - * The Host needs to see page faults (for shadow paging and to save the - * fault address), general protection faults (in/out emulation) and - * device not available (TS handling) and of course, the hypercall trap. - */ - return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY; -} -/*:*/ - -/*M:005 - * The Guest has the ability to turn its interrupt gates into trap gates, - * if it is careful. The Host will let trap gates can go directly to the - * Guest, but the Guest needs the interrupts atomically disabled for an - * interrupt gate. It can do this by pointing the trap gate at instructions - * within noirq_start and noirq_end, where it can safely disable interrupts. - */ - -/*M:006 - * The Guests do not use the sysenter (fast system call) instruction, - * because it's hardcoded to enter privilege level 0 and so can't go direct. - * It's about twice as fast as the older "int 0x80" system call, so it might - * still be worthwhile to handle it in the Switcher and lcall down to the - * Guest. The sysenter semantics are hairy tho: search for that keyword in - * entry.S -:*/ - -/*H:260 - * When we make traps go directly into the Guest, we need to make sure - * the kernel stack is valid (ie. mapped in the page tables). Otherwise, the - * CPU trying to deliver the trap will fault while trying to push the interrupt - * words on the stack: this is called a double fault, and it forces us to kill - * the Guest. - * - * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. - */ -void pin_stack_pages(struct lg_cpu *cpu) -{ - unsigned int i; - - /* - * Depending on the CONFIG_4KSTACKS option, the Guest can have one or - * two pages of stack space. - */ - for (i = 0; i < cpu->lg->stack_pages; i++) - /* - * The stack grows *upwards*, so the address we're given is the - * start of the page after the kernel stack. Subtract one to - * get back onto the first stack page, and keep subtracting to - * get to the rest of the stack pages. - */ - pin_page(cpu, cpu->esp1 - 1 - i * PAGE_SIZE); -} - -/* - * Direct traps also mean that we need to know whenever the Guest wants to use - * a different kernel stack, so we can change the guest TSS to use that - * stack. The TSS entries expect a virtual address, so unlike most addresses - * the Guest gives us, the "esp" (stack pointer) value here is virtual, not - * physical. - * - * In Linux each process has its own kernel stack, so this happens a lot: we - * change stacks on each context switch. - */ -void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages) -{ - /* - * You're not allowed a stack segment with privilege level 0: bad Guest! - */ - if ((seg & 0x3) != GUEST_PL) - kill_guest(cpu, "bad stack segment %i", seg); - /* We only expect one or two stack pages. */ - if (pages > 2) - kill_guest(cpu, "bad stack pages %u", pages); - /* Save where the stack is, and how many pages */ - cpu->ss1 = seg; - cpu->esp1 = esp; - cpu->lg->stack_pages = pages; - /* Make sure the new stack pages are mapped */ - pin_stack_pages(cpu); -} - -/* - * All this reference to mapping stacks leads us neatly into the other complex - * part of the Host: page table handling. - */ - -/*H:235 - * This is the routine which actually checks the Guest's IDT entry and - * transfers it into the entry in "struct lguest": - */ -static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap, - unsigned int num, u32 lo, u32 hi) -{ - u8 type = idt_type(lo, hi); - - /* We zero-out a not-present entry */ - if (!idt_present(lo, hi)) { - trap->a = trap->b = 0; - return; - } - - /* We only support interrupt and trap gates. */ - if (type != 0xE && type != 0xF) - kill_guest(cpu, "bad IDT type %i", type); - - /* - * We only copy the handler address, present bit, privilege level and - * type. The privilege level controls where the trap can be triggered - * manually with an "int" instruction. This is usually GUEST_PL, - * except for system calls which userspace can use. - */ - trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF); - trap->b = (hi&0xFFFFEF00); -} - -/*H:230 - * While we're here, dealing with delivering traps and interrupts to the - * Guest, we might as well complete the picture: how the Guest tells us where - * it wants them to go. This would be simple, except making traps fast - * requires some tricks. - * - * We saw the Guest setting Interrupt Descriptor Table (IDT) entries with the - * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. - */ -void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi) -{ - /* - * Guest never handles: NMI, doublefault, spurious interrupt or - * hypercall. We ignore when it tries to set them. - */ - if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY) - return; - - /* - * Mark the IDT as changed: next time the Guest runs we'll know we have - * to copy this again. - */ - cpu->changed |= CHANGED_IDT; - - /* Check that the Guest doesn't try to step outside the bounds. */ - if (num >= ARRAY_SIZE(cpu->arch.idt)) - kill_guest(cpu, "Setting idt entry %u", num); - else - set_trap(cpu, &cpu->arch.idt[num], num, lo, hi); -} - -/* - * The default entry for each interrupt points into the Switcher routines which - * simply return to the Host. The run_guest() loop will then call - * deliver_trap() to bounce it back into the Guest. - */ -static void default_idt_entry(struct desc_struct *idt, - int trap, - const unsigned long handler, - const struct desc_struct *base) -{ - /* A present interrupt gate. */ - u32 flags = 0x8e00; - - /* - * Set the privilege level on the entry for the hypercall: this allows - * the Guest to use the "int" instruction to trigger it. - */ - if (trap == LGUEST_TRAP_ENTRY) - flags |= (GUEST_PL << 13); - else if (base) - /* - * Copy privilege level from what Guest asked for. This allows - * debug (int 3) traps from Guest userspace, for example. - */ - flags |= (base->b & 0x6000); - - /* Now pack it into the IDT entry in its weird format. */ - idt->a = (LGUEST_CS<<16) | (handler&0x0000FFFF); - idt->b = (handler&0xFFFF0000) | flags; -} - -/* When the Guest first starts, we put default entries into the IDT. */ -void setup_default_idt_entries(struct lguest_ro_state *state, - const unsigned long *def) -{ - unsigned int i; - - for (i = 0; i < ARRAY_SIZE(state->guest_idt); i++) - default_idt_entry(&state->guest_idt[i], i, def[i], NULL); -} - -/*H:240 - * We don't use the IDT entries in the "struct lguest" directly, instead - * we copy them into the IDT which we've set up for Guests on this CPU, just - * before we run the Guest. This routine does that copy. - */ -void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, - const unsigned long *def) -{ - unsigned int i; - - /* - * We can simply copy the direct traps, otherwise we use the default - * ones in the Switcher: they will return to the Host. - */ - for (i = 0; i < ARRAY_SIZE(cpu->arch.idt); i++) { - const struct desc_struct *gidt = &cpu->arch.idt[i]; - - /* If no Guest can ever override this trap, leave it alone. */ - if (!direct_trap(i)) - continue; - - /* - * Only trap gates (type 15) can go direct to the Guest. - * Interrupt gates (type 14) disable interrupts as they are - * entered, which we never let the Guest do. Not present - * entries (type 0x0) also can't go direct, of course. - * - * If it can't go direct, we still need to copy the priv. level: - * they might want to give userspace access to a software - * interrupt. - */ - if (idt_type(gidt->a, gidt->b) == 0xF) - idt[i] = *gidt; - else - default_idt_entry(&idt[i], i, def[i], gidt); - } -} - -/*H:200 - * The Guest Clock. - * - * There are two sources of virtual interrupts. We saw one in lguest_user.c: - * the Launcher sending interrupts for virtual devices. The other is the Guest - * timer interrupt. - * - * The Guest uses the LHCALL_SET_CLOCKEVENT hypercall to tell us how long to - * the next timer interrupt (in nanoseconds). We use the high-resolution timer - * infrastructure to set a callback at that time. - * - * 0 means "turn off the clock". - */ -void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta) -{ - ktime_t expires; - - if (unlikely(delta == 0)) { - /* Clock event device is shutting down. */ - hrtimer_cancel(&cpu->hrt); - return; - } - - /* - * We use wallclock time here, so the Guest might not be running for - * all the time between now and the timer interrupt it asked for. This - * is almost always the right thing to do. - */ - expires = ktime_add_ns(ktime_get_real(), delta); - hrtimer_start(&cpu->hrt, expires, HRTIMER_MODE_ABS); -} - -/* This is the function called when the Guest's timer expires. */ -static enum hrtimer_restart clockdev_fn(struct hrtimer *timer) -{ - struct lg_cpu *cpu = container_of(timer, struct lg_cpu, hrt); - - /* Remember the first interrupt is the timer interrupt. */ - set_interrupt(cpu, 0); - return HRTIMER_NORESTART; -} - -/* This sets up the timer for this Guest. */ -void init_clockdev(struct lg_cpu *cpu) -{ - hrtimer_init(&cpu->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS); - cpu->hrt.function = clockdev_fn; -} diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h deleted file mode 100644 index 2eef40be4c04..000000000000 --- a/drivers/lguest/lg.h +++ /dev/null @@ -1,260 +0,0 @@ -#ifndef _LGUEST_H -#define _LGUEST_H - -#ifndef __ASSEMBLY__ -#include <linux/types.h> -#include <linux/init.h> -#include <linux/stringify.h> -#include <linux/lguest.h> -#include <linux/lguest_launcher.h> -#include <linux/wait.h> -#include <linux/hrtimer.h> -#include <linux/err.h> -#include <linux/slab.h> - -#include <asm/lguest.h> - -struct pgdir { - unsigned long gpgdir; - bool switcher_mapped; - int last_host_cpu; - pgd_t *pgdir; -}; - -/* We have two pages shared with guests, per cpu. */ -struct lguest_pages { - /* This is the stack page mapped rw in guest */ - char spare[PAGE_SIZE - sizeof(struct lguest_regs)]; - struct lguest_regs regs; - - /* This is the host state & guest descriptor page, ro in guest */ - struct lguest_ro_state state; -} __attribute__((aligned(PAGE_SIZE))); - -#define CHANGED_IDT 1 -#define CHANGED_GDT 2 -#define CHANGED_GDT_TLS 4 /* Actually a subset of CHANGED_GDT */ -#define CHANGED_ALL 3 - -struct lg_cpu { - unsigned int id; - struct lguest *lg; - struct task_struct *tsk; - struct mm_struct *mm; /* == tsk->mm, but that becomes NULL on exit */ - - u32 cr2; - int ts; - u32 esp1; - u16 ss1; - - /* Bitmap of what has changed: see CHANGED_* above. */ - int changed; - - unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */ - - /* At end of a page shared mapped over lguest_pages in guest. */ - unsigned long regs_page; - struct lguest_regs *regs; - - struct lguest_pages *last_pages; - - /* Initialization mode: linear map everything. */ - bool linear_pages; - int cpu_pgd; /* Which pgd this cpu is currently using */ - - /* If a hypercall was asked for, this points to the arguments. */ - struct hcall_args *hcall; - u32 next_hcall; - - /* Virtual clock device */ - struct hrtimer hrt; - - /* Did the Guest tell us to halt? */ - int halted; - - /* Pending virtual interrupts */ - DECLARE_BITMAP(irqs_pending, LGUEST_IRQS); - - struct lg_cpu_arch arch; -}; - -struct lg_eventfd { - unsigned long addr; - struct eventfd_ctx *event; -}; - -struct lg_eventfd_map { - unsigned int num; - struct lg_eventfd map[]; -}; - -/* The private info the thread maintains about the guest. */ -struct lguest { - struct lguest_data __user *lguest_data; - struct lg_cpu cpus[NR_CPUS]; - unsigned int nr_cpus; - - u32 pfn_limit; - - /* - * This provides the offset to the base of guest-physical memory in the - * Launcher. - */ - void __user *mem_base; - unsigned long kernel_address; - - struct pgdir pgdirs[4]; - - unsigned long noirq_start, noirq_end; - - unsigned int stack_pages; - u32 tsc_khz; - - struct lg_eventfd_map *eventfds; - - /* Dead? */ - const char *dead; -}; - -extern struct mutex lguest_lock; - -/* core.c: */ -bool lguest_address_ok(const struct lguest *lg, - unsigned long addr, unsigned long len); -void __lgread(struct lg_cpu *, void *, unsigned long, unsigned); -void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned); -extern struct page **lg_switcher_pages; - -/*H:035 - * Using memory-copy operations like that is usually inconvient, so we - * have the following helper macros which read and write a specific type (often - * an unsigned long). - * - * This reads into a variable of the given type then returns that. - */ -#define lgread(cpu, addr, type) \ - ({ type _v; __lgread((cpu), &_v, (addr), sizeof(_v)); _v; }) - -/* This checks that the variable is of the given type, then writes it out. */ -#define lgwrite(cpu, addr, type, val) \ - do { \ - typecheck(type, val); \ - __lgwrite((cpu), (addr), &(val), sizeof(val)); \ - } while(0) -/* (end of memory access helper routines) :*/ - -int run_guest(struct lg_cpu *cpu, unsigned long __user *user); - -/* - * Helper macros to obtain the first 12 or the last 20 bits, this is only the - * first step in the migration to the kernel types. pte_pfn is already defined - * in the kernel. - */ -#define pgd_flags(x) (pgd_val(x) & ~PAGE_MASK) -#define pgd_pfn(x) (pgd_val(x) >> PAGE_SHIFT) -#define pmd_flags(x) (pmd_val(x) & ~PAGE_MASK) -#define pmd_pfn(x) (pmd_val(x) >> PAGE_SHIFT) - -/* interrupts_and_traps.c: */ -unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more); -void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more); -void set_interrupt(struct lg_cpu *cpu, unsigned int irq); -bool deliver_trap(struct lg_cpu *cpu, unsigned int num); -void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int i, - u32 low, u32 hi); -void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages); -void pin_stack_pages(struct lg_cpu *cpu); -void setup_default_idt_entries(struct lguest_ro_state *state, - const unsigned long *def); -void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, - const unsigned long *def); -void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta); -bool send_notify_to_eventfd(struct lg_cpu *cpu); -void init_clockdev(struct lg_cpu *cpu); -bool check_syscall_vector(struct lguest *lg); -int init_interrupts(void); -void free_interrupts(void); - -/* segments.c: */ -void setup_default_gdt_entries(struct lguest_ro_state *state); -void setup_guest_gdt(struct lg_cpu *cpu); -void load_guest_gdt_entry(struct lg_cpu *cpu, unsigned int i, - u32 low, u32 hi); -void guest_load_tls(struct lg_cpu *cpu, unsigned long tls_array); -void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt); -void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt); - -/* page_tables.c: */ -int init_guest_pagetable(struct lguest *lg); -void free_guest_pagetable(struct lguest *lg); -void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable); -void guest_set_pgd(struct lguest *lg, unsigned long gpgdir, u32 i); -#ifdef CONFIG_X86_PAE -void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 i); -#endif -void guest_pagetable_clear_all(struct lg_cpu *cpu); -void guest_pagetable_flush_user(struct lg_cpu *cpu); -void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir, - unsigned long vaddr, pte_t val); -void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages); -bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode); -void pin_page(struct lg_cpu *cpu, unsigned long vaddr); -unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr); -void page_table_guest_data_init(struct lg_cpu *cpu); - -/* <arch>/core.c: */ -void lguest_arch_host_init(void); -void lguest_arch_host_fini(void); -void lguest_arch_run_guest(struct lg_cpu *cpu); -void lguest_arch_handle_trap(struct lg_cpu *cpu); -int lguest_arch_init_hypercalls(struct lg_cpu *cpu); -int lguest_arch_do_hcall(struct lg_cpu *cpu, struct hcall_args *args); -void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start); - -/* <arch>/switcher.S: */ -extern char start_switcher_text[], end_switcher_text[], switch_to_guest[]; - -/* lguest_user.c: */ -int lguest_device_init(void); -void lguest_device_remove(void); - -/* hypercalls.c: */ -void do_hypercalls(struct lg_cpu *cpu); -void write_timestamp(struct lg_cpu *cpu); - -/*L:035 - * Let's step aside for the moment, to study one important routine that's used - * widely in the Host code. - * - * There are many cases where the Guest can do something invalid, like pass crap - * to a hypercall. Since only the Guest kernel can make hypercalls, it's quite - * acceptable to simply terminate the Guest and give the Launcher a nicely - * formatted reason. It's also simpler for the Guest itself, which doesn't - * need to check most hypercalls for "success"; if you're still running, it - * succeeded. - * - * Once this is called, the Guest will never run again, so most Host code can - * call this then continue as if nothing had happened. This means many - * functions don't have to explicitly return an error code, which keeps the - * code simple. - * - * It also means that this can be called more than once: only the first one is - * remembered. The only trick is that we still need to kill the Guest even if - * we can't allocate memory to store the reason. Linux has a neat way of - * packing error codes into invalid pointers, so we use that here. - * - * Like any macro which uses an "if", it is safely wrapped in a run-once "do { - * } while(0)". - */ -#define kill_guest(cpu, fmt...) \ -do { \ - if (!(cpu)->lg->dead) { \ - (cpu)->lg->dead = kasprintf(GFP_ATOMIC, fmt); \ - if (!(cpu)->lg->dead) \ - (cpu)->lg->dead = ERR_PTR(-ENOMEM); \ - } \ -} while(0) -/* (End of aside) :*/ - -#endif /* __ASSEMBLY__ */ -#endif /* _LGUEST_H */ diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c deleted file mode 100644 index b3256ff0d426..000000000000 --- a/drivers/lguest/lguest_device.c +++ /dev/null @@ -1,534 +0,0 @@ -/*P:050 - * Lguest guests use a very simple method to describe devices. It's a - * series of device descriptors contained just above the top of normal Guest - * memory. - * - * We use the standard "virtio" device infrastructure, which provides us with a - * console, a network and a block driver. Each one expects some configuration - * information and a "virtqueue" or two to send and receive data. -:*/ -#include <linux/init.h> -#include <linux/bootmem.h> -#include <linux/lguest_launcher.h> -#include <linux/virtio.h> -#include <linux/virtio_config.h> -#include <linux/interrupt.h> -#include <linux/virtio_ring.h> -#include <linux/err.h> -#include <linux/export.h> -#include <linux/slab.h> -#include <asm/io.h> -#include <asm/paravirt.h> -#include <asm/lguest_hcall.h> - -/* The pointer to our (page) of device descriptions. */ -static void *lguest_devices; - -/* - * For Guests, device memory can be used as normal memory, so we cast away the - * __iomem to quieten sparse. - */ -static inline void *lguest_map(unsigned long phys_addr, unsigned long pages) -{ - return (__force void *)ioremap_cache(phys_addr, PAGE_SIZE*pages); -} - -static inline void lguest_unmap(void *addr) -{ - iounmap((__force void __iomem *)addr); -} - -/*D:100 - * Each lguest device is just a virtio device plus a pointer to its entry - * in the lguest_devices page. - */ -struct lguest_device { - struct virtio_device vdev; - - /* The entry in the lguest_devices page for this device. */ - struct lguest_device_desc *desc; -}; - -/* - * Since the virtio infrastructure hands us a pointer to the virtio_device all - * the time, it helps to have a curt macro to get a pointer to the struct - * lguest_device it's enclosed in. - */ -#define to_lgdev(vd) container_of(vd, struct lguest_device, vdev) - -/*D:130 - * Device configurations - * - * The configuration information for a device consists of one or more - * virtqueues, a feature bitmap, and some configuration bytes. The - * configuration bytes don't really matter to us: the Launcher sets them up, and - * the driver will look at them during setup. - * - * A convenient routine to return the device's virtqueue config array: - * immediately after the descriptor. - */ -static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc) -{ - return (void *)(desc + 1); -} - -/* The features come immediately after the virtqueues. */ -static u8 *lg_features(const struct lguest_device_desc *desc) -{ - return (void *)(lg_vq(desc) + desc->num_vq); -} - -/* The config space comes after the two feature bitmasks. */ -static u8 *lg_config(const struct lguest_device_desc *desc) -{ - return lg_features(desc) + desc->feature_len * 2; -} - -/* The total size of the config page used by this device (incl. desc) */ -static unsigned desc_size(const struct lguest_device_desc *desc) -{ - return sizeof(*desc) - + desc->num_vq * sizeof(struct lguest_vqconfig) - + desc->feature_len * 2 - + desc->config_len; -} - -/* This gets the device's feature bits. */ -static u32 lg_get_features(struct virtio_device *vdev) -{ - unsigned int i; - u32 features = 0; - struct lguest_device_desc *desc = to_lgdev(vdev)->desc; - u8 *in_features = lg_features(desc); - - /* We do this the slow but generic way. */ - for (i = 0; i < min(desc->feature_len * 8, 32); i++) - if (in_features[i / 8] & (1 << (i % 8))) - features |= (1 << i); - - return features; -} - -/* - * To notify on reset or feature finalization, we (ab)use the NOTIFY - * hypercall, with the descriptor address of the device. - */ -static void status_notify(struct virtio_device *vdev) -{ - unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices; - - hcall(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset, 0, 0, 0); -} - -/* - * The virtio core takes the features the Host offers, and copies the ones - * supported by the driver into the vdev->features array. Once that's all - * sorted out, this routine is called so we can tell the Host which features we - * understand and accept. - */ -static void lg_finalize_features(struct virtio_device *vdev) -{ - unsigned int i, bits; - struct lguest_device_desc *desc = to_lgdev(vdev)->desc; - /* Second half of bitmap is features we accept. */ - u8 *out_features = lg_features(desc) + desc->feature_len; - - /* Give virtio_ring a chance to accept features. */ - vring_transport_features(vdev); - - /* - * The vdev->feature array is a Linux bitmask: this isn't the same as a - * the simple array of bits used by lguest devices for features. So we - * do this slow, manual conversion which is completely general. - */ - memset(out_features, 0, desc->feature_len); - bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8; - for (i = 0; i < bits; i++) { - if (test_bit(i, vdev->features)) - out_features[i / 8] |= (1 << (i % 8)); - } - - /* Tell Host we've finished with this device's feature negotiation */ - status_notify(vdev); -} - -/* Once they've found a field, getting a copy of it is easy. */ -static void lg_get(struct virtio_device *vdev, unsigned int offset, - void *buf, unsigned len) -{ - struct lguest_device_desc *desc = to_lgdev(vdev)->desc; - - /* Check they didn't ask for more than the length of the config! */ - BUG_ON(offset + len > desc->config_len); - memcpy(buf, lg_config(desc) + offset, len); -} - -/* Setting the contents is also trivial. */ -static void lg_set(struct virtio_device *vdev, unsigned int offset, - const void *buf, unsigned len) -{ - struct lguest_device_desc *desc = to_lgdev(vdev)->desc; - - /* Check they didn't ask for more than the length of the config! */ - BUG_ON(offset + len > desc->config_len); - memcpy(lg_config(desc) + offset, buf, len); -} - -/* - * The operations to get and set the status word just access the status field - * of the device descriptor. - */ -static u8 lg_get_status(struct virtio_device *vdev) -{ - return to_lgdev(vdev)->desc->status; -} - -static void lg_set_status(struct virtio_device *vdev, u8 status) -{ - BUG_ON(!status); - to_lgdev(vdev)->desc->status = status; - - /* Tell Host immediately if we failed. */ - if (status & VIRTIO_CONFIG_S_FAILED) - status_notify(vdev); -} - -static void lg_reset(struct virtio_device *vdev) -{ - /* 0 status means "reset" */ - to_lgdev(vdev)->desc->status = 0; - status_notify(vdev); -} - -/* - * Virtqueues - * - * The other piece of infrastructure virtio needs is a "virtqueue": a way of - * the Guest device registering buffers for the other side to read from or - * write into (ie. send and receive buffers). Each device can have multiple - * virtqueues: for example the console driver uses one queue for sending and - * another for receiving. - * - * Fortunately for us, a very fast shared-memory-plus-descriptors virtqueue - * already exists in virtio_ring.c. We just need to connect it up. - * - * We start with the information we need to keep about each virtqueue. - */ - -/*D:140 This is the information we remember about each virtqueue. */ -struct lguest_vq_info { - /* A copy of the information contained in the device config. */ - struct lguest_vqconfig config; - - /* The address where we mapped the virtio ring, so we can unmap it. */ - void *pages; -}; - -/* - * When the virtio_ring code wants to prod the Host, it calls us here and we - * make a hypercall. We hand the physical address of the virtqueue so the Host - * knows which virtqueue we're talking about. - */ -static void lg_notify(struct virtqueue *vq) -{ - /* - * We store our virtqueue information in the "priv" pointer of the - * virtqueue structure. - */ - struct lguest_vq_info *lvq = vq->priv; - - hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0, 0); -} - -/* An extern declaration inside a C file is bad form. Don't do it. */ -extern int lguest_setup_irq(unsigned int irq); - -/* - * This routine finds the Nth virtqueue described in the configuration of - * this device and sets it up. - * - * This is kind of an ugly duckling. It'd be nicer to have a standard - * representation of a virtqueue in the configuration space, but it seems that - * everyone wants to do it differently. The KVM coders want the Guest to - * allocate its own pages and tell the Host where they are, but for lguest it's - * simpler for the Host to simply tell us where the pages are. - */ -static struct virtqueue *lg_find_vq(struct virtio_device *vdev, - unsigned index, - void (*callback)(struct virtqueue *vq), - const char *name) -{ - struct lguest_device *ldev = to_lgdev(vdev); - struct lguest_vq_info *lvq; - struct virtqueue *vq; - int err; - - if (!name) - return NULL; - - /* We must have this many virtqueues. */ - if (index >= ldev->desc->num_vq) - return ERR_PTR(-ENOENT); - - lvq = kmalloc(sizeof(*lvq), GFP_KERNEL); - if (!lvq) - return ERR_PTR(-ENOMEM); - - /* - * Make a copy of the "struct lguest_vqconfig" entry, which sits after - * the descriptor. We need a copy because the config space might not - * be aligned correctly. - */ - memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config)); - - printk("Mapping virtqueue %i addr %lx\n", index, - (unsigned long)lvq->config.pfn << PAGE_SHIFT); - /* Figure out how many pages the ring will take, and map that memory */ - lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT, - DIV_ROUND_UP(vring_size(lvq->config.num, - LGUEST_VRING_ALIGN), - PAGE_SIZE)); - if (!lvq->pages) { - err = -ENOMEM; - goto free_lvq; - } - - /* - * OK, tell virtio_ring.c to set up a virtqueue now we know its size - * and we've got a pointer to its pages. Note that we set weak_barriers - * to 'true': the host just a(nother) SMP CPU, so we only need inter-cpu - * barriers. - */ - vq = vring_new_virtqueue(index, lvq->config.num, LGUEST_VRING_ALIGN, vdev, - true, lvq->pages, lg_notify, callback, name); - if (!vq) { - err = -ENOMEM; - goto unmap; - } - - /* Make sure the interrupt is allocated. */ - err = lguest_setup_irq(lvq->config.irq); - if (err) - goto destroy_vring; - - /* - * Tell the interrupt for this virtqueue to go to the virtio_ring - * interrupt handler. - * - * FIXME: We used to have a flag for the Host to tell us we could use - * the interrupt as a source of randomness: it'd be nice to have that - * back. - */ - err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED, - dev_name(&vdev->dev), vq); - if (err) - goto free_desc; - - /* - * Last of all we hook up our 'struct lguest_vq_info" to the - * virtqueue's priv pointer. - */ - vq->priv = lvq; - return vq; - -free_desc: - irq_free_desc(lvq->config.irq); -destroy_vring: - vring_del_virtqueue(vq); -unmap: - lguest_unmap(lvq->pages); -free_lvq: - kfree(lvq); - return ERR_PTR(err); -} -/*:*/ - -/* Cleaning up a virtqueue is easy */ -static void lg_del_vq(struct virtqueue *vq) -{ - struct lguest_vq_info *lvq = vq->priv; - - /* Release the interrupt */ - free_irq(lvq->config.irq, vq); - /* Tell virtio_ring.c to free the virtqueue. */ - vring_del_virtqueue(vq); - /* Unmap the pages containing the ring. */ - lguest_unmap(lvq->pages); - /* Free our own queue information. */ - kfree(lvq); -} - -static void lg_del_vqs(struct virtio_device *vdev) -{ - struct virtqueue *vq, *n; - - list_for_each_entry_safe(vq, n, &vdev->vqs, list) - lg_del_vq(vq); -} - -static int lg_find_vqs(struct virtio_device *vdev, unsigned nvqs, - struct virtqueue *vqs[], - vq_callback_t *callbacks[], - const char *names[]) -{ - struct lguest_device *ldev = to_lgdev(vdev); - int i; - - /* We must have this many virtqueues. */ - if (nvqs > ldev->desc->num_vq) - return -ENOENT; - - for (i = 0; i < nvqs; ++i) { - vqs[i] = lg_find_vq(vdev, i, callbacks[i], names[i]); - if (IS_ERR(vqs[i])) - goto error; - } - return 0; - -error: - lg_del_vqs(vdev); - return PTR_ERR(vqs[i]); -} - -static const char *lg_bus_name(struct virtio_device *vdev) -{ - return ""; -} - -/* The ops structure which hooks everything together. */ -static const struct virtio_config_ops lguest_config_ops = { - .get_features = lg_get_features, - .finalize_features = lg_finalize_features, - .get = lg_get, - .set = lg_set, - .get_status = lg_get_status, - .set_status = lg_set_status, - .reset = lg_reset, - .find_vqs = lg_find_vqs, - .del_vqs = lg_del_vqs, - .bus_name = lg_bus_name, -}; - -/* - * The root device for the lguest virtio devices. This makes them appear as - * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. - */ -static struct device *lguest_root; - -/*D:120 - * This is the core of the lguest bus: actually adding a new device. - * It's a separate function because it's neater that way, and because an - * earlier version of the code supported hotplug and unplug. They were removed - * early on because they were never used. - * - * As Andrew Tridgell says, "Untested code is buggy code". - * - * It's worth reading this carefully: we start with a pointer to the new device - * descriptor in the "lguest_devices" page, and the offset into the device - * descriptor page so we can uniquely identify it if things go badly wrong. - */ -static void add_lguest_device(struct lguest_device_desc *d, - unsigned int offset) -{ - struct lguest_device *ldev; - - /* Start with zeroed memory; Linux's device layer counts on it. */ - ldev = kzalloc(sizeof(*ldev), GFP_KERNEL); - if (!ldev) { - printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n", - offset, d->type); - return; - } - - /* This devices' parent is the lguest/ dir. */ - ldev->vdev.dev.parent = lguest_root; - /* - * The device type comes straight from the descriptor. There's also a - * device vendor field in the virtio_device struct, which we leave as - * 0. - */ - ldev->vdev.id.device = d->type; - /* - * We have a simple set of routines for querying the device's - * configuration information and setting its status. - */ - ldev->vdev.config = &lguest_config_ops; - /* And we remember the device's descriptor for lguest_config_ops. */ - ldev->desc = d; - - /* - * register_virtio_device() sets up the generic fields for the struct - * virtio_device and calls device_register(). This makes the bus - * infrastructure look for a matching driver. - */ - if (register_virtio_device(&ldev->vdev) != 0) { - printk(KERN_ERR "Failed to register lguest dev %u type %u\n", - offset, d->type); - kfree(ldev); - } -} - -/*D:110 - * scan_devices() simply iterates through the device page. The type 0 is - * reserved to mean "end of devices". - */ -static void scan_devices(void) -{ - unsigned int i; - struct lguest_device_desc *d; - - /* We start at the page beginning, and skip over each entry. */ - for (i = 0; i < PAGE_SIZE; i += desc_size(d)) { - d = lguest_devices + i; - - /* Once we hit a zero, stop. */ - if (d->type == 0) - break; - - printk("Device at %i has size %u\n", i, desc_size(d)); - add_lguest_device(d, i); - } -} - -/*D:105 - * Fairly early in boot, lguest_devices_init() is called to set up the - * lguest device infrastructure. We check that we are a Guest by checking - * pv_info.name: there are other ways of checking, but this seems most - * obvious to me. - * - * So we can access the "struct lguest_device_desc"s easily, we map that memory - * and store the pointer in the global "lguest_devices". Then we register a - * root device from which all our devices will hang (this seems to be the - * correct sysfs incantation). - * - * Finally we call scan_devices() which adds all the devices found in the - * lguest_devices page. - */ -static int __init lguest_devices_init(void) -{ - if (strcmp(pv_info.name, "lguest") != 0) - return 0; - - lguest_root = root_device_register("lguest"); - if (IS_ERR(lguest_root)) - panic("Could not register lguest root"); - - /* Devices are in a single page above top of "normal" mem */ - lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1); - - scan_devices(); - return 0; -} -/* We do this after core stuff, but before the drivers. */ -postcore_initcall(lguest_devices_init); - -/*D:150 - * At this point in the journey we used to now wade through the lguest - * devices themselves: net, block and console. Since they're all now virtio - * devices rather than lguest-specific, I've decided to ignore them. Mostly, - * they're kind of boring. But this does mean you'll never experience the - * thrill of reading the forbidden love scene buried deep in the block driver. - * - * "make Launcher" beckons, where we answer questions like "Where do Guests - * come from?", and "What do you do when someone asks for optimization?". - */ diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c deleted file mode 100644 index 4263f4cc8c55..000000000000 --- a/drivers/lguest/lguest_user.c +++ /dev/null @@ -1,542 +0,0 @@ -/*P:200 This contains all the /dev/lguest code, whereby the userspace - * launcher controls and communicates with the Guest. For example, - * the first write will tell us the Guest's memory layout and entry - * point. A read will run the Guest until something happens, such as - * a signal or the Guest doing a NOTIFY out to the Launcher. There is - * also a way for the Launcher to attach eventfds to particular NOTIFY - * values instead of returning from the read() call. -:*/ -#include <linux/uaccess.h> -#include <linux/miscdevice.h> -#include <linux/fs.h> -#include <linux/sched.h> -#include <linux/eventfd.h> -#include <linux/file.h> -#include <linux/slab.h> -#include <linux/export.h> -#include "lg.h" - -/*L:056 - * Before we move on, let's jump ahead and look at what the kernel does when - * it needs to look up the eventfds. That will complete our picture of how we - * use RCU. - * - * The notification value is in cpu->pending_notify: we return true if it went - * to an eventfd. - */ -bool send_notify_to_eventfd(struct lg_cpu *cpu) -{ - unsigned int i; - struct lg_eventfd_map *map; - - /* - * This "rcu_read_lock()" helps track when someone is still looking at - * the (RCU-using) eventfds array. It's not actually a lock at all; - * indeed it's a noop in many configurations. (You didn't expect me to - * explain all the RCU secrets here, did you?) - */ - rcu_read_lock(); - /* - * rcu_dereference is the counter-side of rcu_assign_pointer(); it - * makes sure we don't access the memory pointed to by - * cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy, - * but Alpha allows this! Paul McKenney points out that a really - * aggressive compiler could have the same effect: - * http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html - * - * So play safe, use rcu_dereference to get the rcu-protected pointer: - */ - map = rcu_dereference(cpu->lg->eventfds); - /* - * Simple array search: even if they add an eventfd while we do this, - * we'll continue to use the old array and just won't see the new one. - */ - for (i = 0; i < map->num; i++) { - if (map->map[i].addr == cpu->pending_notify) { - eventfd_signal(map->map[i].event, 1); - cpu->pending_notify = 0; - break; - } - } - /* We're done with the rcu-protected variable cpu->lg->eventfds. */ - rcu_read_unlock(); - - /* If we cleared the notification, it's because we found a match. */ - return cpu->pending_notify == 0; -} - -/*L:055 - * One of the more tricksy tricks in the Linux Kernel is a technique called - * Read Copy Update. Since one point of lguest is to teach lguest journeyers - * about kernel coding, I use it here. (In case you're curious, other purposes - * include learning about virtualization and instilling a deep appreciation for - * simplicity and puppies). - * - * We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we - * add new eventfds without ever blocking readers from accessing the array. - * The current Launcher only does this during boot, so that never happens. But - * Read Copy Update is cool, and adding a lock risks damaging even more puppies - * than this code does. - * - * We allocate a brand new one-larger array, copy the old one and add our new - * element. Then we make the lg eventfd pointer point to the new array. - * That's the easy part: now we need to free the old one, but we need to make - * sure no slow CPU somewhere is still looking at it. That's what - * synchronize_rcu does for us: waits until every CPU has indicated that it has - * moved on to know it's no longer using the old one. - * - * If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update. - */ -static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) -{ - struct lg_eventfd_map *new, *old = lg->eventfds; - - /* - * We don't allow notifications on value 0 anyway (pending_notify of - * 0 means "nothing pending"). - */ - if (!addr) - return -EINVAL; - - /* - * Replace the old array with the new one, carefully: others can - * be accessing it at the same time. - */ - new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1), - GFP_KERNEL); - if (!new) - return -ENOMEM; - - /* First make identical copy. */ - memcpy(new->map, old->map, sizeof(old->map[0]) * old->num); - new->num = old->num; - - /* Now append new entry. */ - new->map[new->num].addr = addr; - new->map[new->num].event = eventfd_ctx_fdget(fd); - if (IS_ERR(new->map[new->num].event)) { - int err = PTR_ERR(new->map[new->num].event); - kfree(new); - return err; - } - new->num++; - - /* - * Now put new one in place: rcu_assign_pointer() is a fancy way of - * doing "lg->eventfds = new", but it uses memory barriers to make - * absolutely sure that the contents of "new" written above is nailed - * down before we actually do the assignment. - * - * We have to think about these kinds of things when we're operating on - * live data without locks. - */ - rcu_assign_pointer(lg->eventfds, new); - - /* - * We're not in a big hurry. Wait until no one's looking at old - * version, then free it. - */ - synchronize_rcu(); - kfree(old); - - return 0; -} - -/*L:052 - * Receiving notifications from the Guest is usually done by attaching a - * particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will - * become readable when the Guest does an LHCALL_NOTIFY with that value. - * - * This is really convenient for processing each virtqueue in a separate - * thread. - */ -static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) -{ - unsigned long addr, fd; - int err; - - if (get_user(addr, input) != 0) - return -EFAULT; - input++; - if (get_user(fd, input) != 0) - return -EFAULT; - - /* - * Just make sure two callers don't add eventfds at once. We really - * only need to lock against callers adding to the same Guest, so using - * the Big Lguest Lock is overkill. But this is setup, not a fast path. - */ - mutex_lock(&lguest_lock); - err = add_eventfd(lg, addr, fd); - mutex_unlock(&lguest_lock); - - return err; -} - -/*L:050 - * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt - * number to /dev/lguest. - */ -static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input) -{ - unsigned long irq; - - if (get_user(irq, input) != 0) - return -EFAULT; - if (irq >= LGUEST_IRQS) - return -EINVAL; - - /* - * Next time the Guest runs, the core code will see if it can deliver - * this interrupt. - */ - set_interrupt(cpu, irq); - return 0; -} - -/*L:040 - * Once our Guest is initialized, the Launcher makes it run by reading - * from /dev/lguest. - */ -static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) -{ - struct lguest *lg = file->private_data; - struct lg_cpu *cpu; - unsigned int cpu_id = *o; - - /* You must write LHREQ_INITIALIZE first! */ - if (!lg) - return -EINVAL; - - /* Watch out for arbitrary vcpu indexes! */ - if (cpu_id >= lg->nr_cpus) - return -EINVAL; - - cpu = &lg->cpus[cpu_id]; - - /* If you're not the task which owns the Guest, go away. */ - if (current != cpu->tsk) - return -EPERM; - - /* If the Guest is already dead, we indicate why */ - if (lg->dead) { - size_t len; - - /* lg->dead either contains an error code, or a string. */ - if (IS_ERR(lg->dead)) - return PTR_ERR(lg->dead); - - /* We can only return as much as the buffer they read with. */ - len = min(size, strlen(lg->dead)+1); - if (copy_to_user(user, lg->dead, len) != 0) - return -EFAULT; - return len; - } - - /* - * If we returned from read() last time because the Guest sent I/O, - * clear the flag. - */ - if (cpu->pending_notify) - cpu->pending_notify = 0; - - /* Run the Guest until something interesting happens. */ - return run_guest(cpu, (unsigned long __user *)user); -} - -/*L:025 - * This actually initializes a CPU. For the moment, a Guest is only - * uniprocessor, so "id" is always 0. - */ -static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) -{ - /* We have a limited number of CPUs in the lguest struct. */ - if (id >= ARRAY_SIZE(cpu->lg->cpus)) - return -EINVAL; - - /* Set up this CPU's id, and pointer back to the lguest struct. */ - cpu->id = id; - cpu->lg = container_of(cpu, struct lguest, cpus[id]); - cpu->lg->nr_cpus++; - - /* Each CPU has a timer it can set. */ - init_clockdev(cpu); - - /* - * We need a complete page for the Guest registers: they are accessible - * to the Guest and we can only grant it access to whole pages. - */ - cpu->regs_page = get_zeroed_page(GFP_KERNEL); - if (!cpu->regs_page) - return -ENOMEM; - - /* We actually put the registers at the end of the page. */ - cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs); - - /* - * Now we initialize the Guest's registers, handing it the start - * address. - */ - lguest_arch_setup_regs(cpu, start_ip); - - /* - * We keep a pointer to the Launcher task (ie. current task) for when - * other Guests want to wake this one (eg. console input). - */ - cpu->tsk = current; - - /* - * We need to keep a pointer to the Launcher's memory map, because if - * the Launcher dies we need to clean it up. If we don't keep a - * reference, it is destroyed before close() is called. - */ - cpu->mm = get_task_mm(cpu->tsk); - - /* - * We remember which CPU's pages this Guest used last, for optimization - * when the same Guest runs on the same CPU twice. - */ - cpu->last_pages = NULL; - - /* No error == success. */ - return 0; -} - -/*L:020 - * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in - * addition to the LHREQ_INITIALIZE value). These are: - * - * base: The start of the Guest-physical memory inside the Launcher memory. - * - * pfnlimit: The highest (Guest-physical) page number the Guest should be - * allowed to access. The Guest memory lives inside the Launcher, so it sets - * this to ensure the Guest can only reach its own memory. - * - * start: The first instruction to execute ("eip" in x86-speak). - */ -static int initialize(struct file *file, const unsigned long __user *input) -{ - /* "struct lguest" contains all we (the Host) know about a Guest. */ - struct lguest *lg; - int err; - unsigned long args[3]; - - /* - * We grab the Big Lguest lock, which protects against multiple - * simultaneous initializations. - */ - mutex_lock(&lguest_lock); - /* You can't initialize twice! Close the device and start again... */ - if (file->private_data) { - err = -EBUSY; - goto unlock; - } - - if (copy_from_user(args, input, sizeof(args)) != 0) { - err = -EFAULT; - goto unlock; - } - - lg = kzalloc(sizeof(*lg), GFP_KERNEL); - if (!lg) { - err = -ENOMEM; - goto unlock; - } - - lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL); - if (!lg->eventfds) { - err = -ENOMEM; - goto free_lg; - } - lg->eventfds->num = 0; - - /* Populate the easy fields of our "struct lguest" */ - lg->mem_base = (void __user *)args[0]; - lg->pfn_limit = args[1]; - - /* This is the first cpu (cpu 0) and it will start booting at args[2] */ - err = lg_cpu_start(&lg->cpus[0], 0, args[2]); - if (err) - goto free_eventfds; - - /* - * Initialize the Guest's shadow page tables. This allocates - * memory, so can fail. - */ - err = init_guest_pagetable(lg); - if (err) - goto free_regs; - - /* We keep our "struct lguest" in the file's private_data. */ - file->private_data = lg; - - mutex_unlock(&lguest_lock); - - /* And because this is a write() call, we return the length used. */ - return sizeof(args); - -free_regs: - /* FIXME: This should be in free_vcpu */ - free_page(lg->cpus[0].regs_page); -free_eventfds: - kfree(lg->eventfds); -free_lg: - kfree(lg); -unlock: - mutex_unlock(&lguest_lock); - return err; -} - -/*L:010 - * The first operation the Launcher does must be a write. All writes - * start with an unsigned long number: for the first write this must be - * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use - * writes of other values to send interrupts or set up receipt of notifications. - * - * Note that we overload the "offset" in the /dev/lguest file to indicate what - * CPU number we're dealing with. Currently this is always 0 since we only - * support uniprocessor Guests, but you can see the beginnings of SMP support - * here. - */ -static ssize_t write(struct file *file, const char __user *in, - size_t size, loff_t *off) -{ - /* - * Once the Guest is initialized, we hold the "struct lguest" in the - * file private data. - */ - struct lguest *lg = file->private_data; - const unsigned long __user *input = (const unsigned long __user *)in; - unsigned long req; - struct lg_cpu *uninitialized_var(cpu); - unsigned int cpu_id = *off; - - /* The first value tells us what this request is. */ - if (get_user(req, input) != 0) - return -EFAULT; - input++; - - /* If you haven't initialized, you must do that first. */ - if (req != LHREQ_INITIALIZE) { - if (!lg || (cpu_id >= lg->nr_cpus)) - return -EINVAL; - cpu = &lg->cpus[cpu_id]; - - /* Once the Guest is dead, you can only read() why it died. */ - if (lg->dead) - return -ENOENT; - } - - switch (req) { - case LHREQ_INITIALIZE: - return initialize(file, input); - case LHREQ_IRQ: - return user_send_irq(cpu, input); - case LHREQ_EVENTFD: - return attach_eventfd(lg, input); - default: - return -EINVAL; - } -} - -/*L:060 - * The final piece of interface code is the close() routine. It reverses - * everything done in initialize(). This is usually called because the - * Launcher exited. - * - * Note that the close routine returns 0 or a negative error number: it can't - * really fail, but it can whine. I blame Sun for this wart, and K&R C for - * letting them do it. -:*/ -static int close(struct inode *inode, struct file *file) -{ - struct lguest *lg = file->private_data; - unsigned int i; - - /* If we never successfully initialized, there's nothing to clean up */ - if (!lg) - return 0; - - /* - * We need the big lock, to protect from inter-guest I/O and other - * Launchers initializing guests. - */ - mutex_lock(&lguest_lock); - - /* Free up the shadow page tables for the Guest. */ - free_guest_pagetable(lg); - - for (i = 0; i < lg->nr_cpus; i++) { - /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */ - hrtimer_cancel(&lg->cpus[i].hrt); - /* We can free up the register page we allocated. */ - free_page(lg->cpus[i].regs_page); - /* - * Now all the memory cleanups are done, it's safe to release - * the Launcher's memory management structure. - */ - mmput(lg->cpus[i].mm); - } - - /* Release any eventfds they registered. */ - for (i = 0; i < lg->eventfds->num; i++) - eventfd_ctx_put(lg->eventfds->map[i].event); - kfree(lg->eventfds); - - /* - * If lg->dead doesn't contain an error code it will be NULL or a - * kmalloc()ed string, either of which is ok to hand to kfree(). - */ - if (!IS_ERR(lg->dead)) - kfree(lg->dead); - /* Free the memory allocated to the lguest_struct */ - kfree(lg); - /* Release lock and exit. */ - mutex_unlock(&lguest_lock); - - return 0; -} - -/*L:000 - * Welcome to our journey through the Launcher! - * - * The Launcher is the Host userspace program which sets up, runs and services - * the Guest. In fact, many comments in the Drivers which refer to "the Host" - * doing things are inaccurate: the Launcher does all the device handling for - * the Guest, but the Guest can't know that. - * - * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we - * shall see more of that later. - * - * We begin our understanding with the Host kernel interface which the Launcher - * uses: reading and writing a character device called /dev/lguest. All the - * work happens in the read(), write() and close() routines: - */ -static const struct file_operations lguest_fops = { - .owner = THIS_MODULE, - .release = close, - .write = write, - .read = read, - .llseek = default_llseek, -}; -/*:*/ - -/* - * This is a textbook example of a "misc" character device. Populate a "struct - * miscdevice" and register it with misc_register(). - */ -static struct miscdevice lguest_dev = { - .minor = MISC_DYNAMIC_MINOR, - .name = "lguest", - .fops = &lguest_fops, -}; - -int __init lguest_device_init(void) -{ - return misc_register(&lguest_dev); -} - -void __exit lguest_device_remove(void) -{ - misc_deregister(&lguest_dev); -} diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c deleted file mode 100644 index a35d8d100165..000000000000 --- a/drivers/lguest/page_tables.c +++ /dev/null @@ -1,1194 +0,0 @@ -/*P:700 - * The pagetable code, on the other hand, still shows the scars of - * previous encounters. It's functional, and as neat as it can be in the - * circumstances, but be wary, for these things are subtle and break easily. - * The Guest provides a virtual to physical mapping, but we can neither trust - * it nor use it: we verify and convert it here then point the CPU to the - * converted Guest pages when running the Guest. -:*/ - -/* Copyright (C) Rusty Russell IBM Corporation 2013. - * GPL v2 and any later version */ -#include <linux/mm.h> -#include <linux/gfp.h> -#include <linux/types.h> -#include <linux/spinlock.h> -#include <linux/random.h> -#include <linux/percpu.h> -#include <asm/tlbflush.h> -#include <asm/uaccess.h> -#include "lg.h" - -/*M:008 - * We hold reference to pages, which prevents them from being swapped. - * It'd be nice to have a callback in the "struct mm_struct" when Linux wants - * to swap out. If we had this, and a shrinker callback to trim PTE pages, we - * could probably consider launching Guests as non-root. -:*/ - -/*H:300 - * The Page Table Code - * - * We use two-level page tables for the Guest, or three-level with PAE. If - * you're not entirely comfortable with virtual addresses, physical addresses - * and page tables then I recommend you review arch/x86/lguest/boot.c's "Page - * Table Handling" (with diagrams!). - * - * The Guest keeps page tables, but we maintain the actual ones here: these are - * called "shadow" page tables. Which is a very Guest-centric name: these are - * the real page tables the CPU uses, although we keep them up to date to - * reflect the Guest's. (See what I mean about weird naming? Since when do - * shadows reflect anything?) - * - * Anyway, this is the most complicated part of the Host code. There are seven - * parts to this: - * (i) Looking up a page table entry when the Guest faults, - * (ii) Making sure the Guest stack is mapped, - * (iii) Setting up a page table entry when the Guest tells us one has changed, - * (iv) Switching page tables, - * (v) Flushing (throwing away) page tables, - * (vi) Mapping the Switcher when the Guest is about to run, - * (vii) Setting up the page tables initially. -:*/ - -/* - * The Switcher uses the complete top PTE page. That's 1024 PTE entries (4MB) - * or 512 PTE entries with PAE (2MB). - */ -#define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1) - -/* - * For PAE we need the PMD index as well. We use the last 2MB, so we - * will need the last pmd entry of the last pmd page. - */ -#ifdef CONFIG_X86_PAE -#define CHECK_GPGD_MASK _PAGE_PRESENT -#else -#define CHECK_GPGD_MASK _PAGE_TABLE -#endif - -/*H:320 - * The page table code is curly enough to need helper functions to keep it - * clear and clean. The kernel itself provides many of them; one advantage - * of insisting that the Guest and Host use the same CONFIG_X86_PAE setting. - * - * There are two functions which return pointers to the shadow (aka "real") - * page tables. - * - * spgd_addr() takes the virtual address and returns a pointer to the top-level - * page directory entry (PGD) for that address. Since we keep track of several - * page tables, the "i" argument tells us which one we're interested in (it's - * usually the current one). - */ -static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr) -{ - unsigned int index = pgd_index(vaddr); - - /* Return a pointer index'th pgd entry for the i'th page table. */ - return &cpu->lg->pgdirs[i].pgdir[index]; -} - -#ifdef CONFIG_X86_PAE -/* - * This routine then takes the PGD entry given above, which contains the - * address of the PMD page. It then returns a pointer to the PMD entry for the - * given address. - */ -static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) -{ - unsigned int index = pmd_index(vaddr); - pmd_t *page; - - /* You should never call this if the PGD entry wasn't valid */ - BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT)); - page = __va(pgd_pfn(spgd) << PAGE_SHIFT); - - return &page[index]; -} -#endif - -/* - * This routine then takes the page directory entry returned above, which - * contains the address of the page table entry (PTE) page. It then returns a - * pointer to the PTE entry for the given address. - */ -static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) -{ -#ifdef CONFIG_X86_PAE - pmd_t *pmd = spmd_addr(cpu, spgd, vaddr); - pte_t *page = __va(pmd_pfn(*pmd) << PAGE_SHIFT); - - /* You should never call this if the PMD entry wasn't valid */ - BUG_ON(!(pmd_flags(*pmd) & _PAGE_PRESENT)); -#else - pte_t *page = __va(pgd_pfn(spgd) << PAGE_SHIFT); - /* You should never call this if the PGD entry wasn't valid */ - BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT)); -#endif - - return &page[pte_index(vaddr)]; -} - -/* - * These functions are just like the above, except they access the Guest - * page tables. Hence they return a Guest address. - */ -static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr) -{ - unsigned int index = vaddr >> (PGDIR_SHIFT); - return cpu->lg->pgdirs[cpu->cpu_pgd].gpgdir + index * sizeof(pgd_t); -} - -#ifdef CONFIG_X86_PAE -/* Follow the PGD to the PMD. */ -static unsigned long gpmd_addr(pgd_t gpgd, unsigned long vaddr) -{ - unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; - BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); - return gpage + pmd_index(vaddr) * sizeof(pmd_t); -} - -/* Follow the PMD to the PTE. */ -static unsigned long gpte_addr(struct lg_cpu *cpu, - pmd_t gpmd, unsigned long vaddr) -{ - unsigned long gpage = pmd_pfn(gpmd) << PAGE_SHIFT; - - BUG_ON(!(pmd_flags(gpmd) & _PAGE_PRESENT)); - return gpage + pte_index(vaddr) * sizeof(pte_t); -} -#else -/* Follow the PGD to the PTE (no mid-level for !PAE). */ -static unsigned long gpte_addr(struct lg_cpu *cpu, - pgd_t gpgd, unsigned long vaddr) -{ - unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; - - BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); - return gpage + pte_index(vaddr) * sizeof(pte_t); -} -#endif -/*:*/ - -/*M:007 - * get_pfn is slow: we could probably try to grab batches of pages here as - * an optimization (ie. pre-faulting). -:*/ - -/*H:350 - * This routine takes a page number given by the Guest and converts it to - * an actual, physical page number. It can fail for several reasons: the - * virtual address might not be mapped by the Launcher, the write flag is set - * and the page is read-only, or the write flag was set and the page was - * shared so had to be copied, but we ran out of memory. - * - * This holds a reference to the page, so release_pte() is careful to put that - * back. - */ -static unsigned long get_pfn(unsigned long virtpfn, int write) -{ - struct page *page; - - /* gup me one page at this address please! */ - if (get_user_pages_fast(virtpfn << PAGE_SHIFT, 1, write, &page) == 1) - return page_to_pfn(page); - - /* This value indicates failure. */ - return -1UL; -} - -/*H:340 - * Converting a Guest page table entry to a shadow (ie. real) page table - * entry can be a little tricky. The flags are (almost) the same, but the - * Guest PTE contains a virtual page number: the CPU needs the real page - * number. - */ -static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write) -{ - unsigned long pfn, base, flags; - - /* - * The Guest sets the global flag, because it thinks that it is using - * PGE. We only told it to use PGE so it would tell us whether it was - * flushing a kernel mapping or a userspace mapping. We don't actually - * use the global bit, so throw it away. - */ - flags = (pte_flags(gpte) & ~_PAGE_GLOBAL); - - /* The Guest's pages are offset inside the Launcher. */ - base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE; - - /* - * We need a temporary "unsigned long" variable to hold the answer from - * get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't - * fit in spte.pfn. get_pfn() finds the real physical number of the - * page, given the virtual number. - */ - pfn = get_pfn(base + pte_pfn(gpte), write); - if (pfn == -1UL) { - kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte)); - /* - * When we destroy the Guest, we'll go through the shadow page - * tables and release_pte() them. Make sure we don't think - * this one is valid! - */ - flags = 0; - } - /* Now we assemble our shadow PTE from the page number and flags. */ - return pfn_pte(pfn, __pgprot(flags)); -} - -/*H:460 And to complete the chain, release_pte() looks like this: */ -static void release_pte(pte_t pte) -{ - /* - * Remember that get_user_pages_fast() took a reference to the page, in - * get_pfn()? We have to put it back now. - */ - if (pte_flags(pte) & _PAGE_PRESENT) - put_page(pte_page(pte)); -} -/*:*/ - -static bool check_gpte(struct lg_cpu *cpu, pte_t gpte) -{ - if ((pte_flags(gpte) & _PAGE_PSE) || - pte_pfn(gpte) >= cpu->lg->pfn_limit) { - kill_guest(cpu, "bad page table entry"); - return false; - } - return true; -} - -static bool check_gpgd(struct lg_cpu *cpu, pgd_t gpgd) -{ - if ((pgd_flags(gpgd) & ~CHECK_GPGD_MASK) || - (pgd_pfn(gpgd) >= cpu->lg->pfn_limit)) { - kill_guest(cpu, "bad page directory entry"); - return false; - } - return true; -} - -#ifdef CONFIG_X86_PAE -static bool check_gpmd(struct lg_cpu *cpu, pmd_t gpmd) -{ - if ((pmd_flags(gpmd) & ~_PAGE_TABLE) || - (pmd_pfn(gpmd) >= cpu->lg->pfn_limit)) { - kill_guest(cpu, "bad page middle directory entry"); - return false; - } - return true; -} -#endif - -/*H:331 - * This is the core routine to walk the shadow page tables and find the page - * table entry for a specific address. - * - * If allocate is set, then we allocate any missing levels, setting the flags - * on the new page directory and mid-level directories using the arguments - * (which are copied from the Guest's page table entries). - */ -static pte_t *find_spte(struct lg_cpu *cpu, unsigned long vaddr, bool allocate, - int pgd_flags, int pmd_flags) -{ - pgd_t *spgd; - /* Mid level for PAE. */ -#ifdef CONFIG_X86_PAE - pmd_t *spmd; -#endif - - /* Get top level entry. */ - spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); - if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { - /* No shadow entry: allocate a new shadow PTE page. */ - unsigned long ptepage; - - /* If they didn't want us to allocate anything, stop. */ - if (!allocate) - return NULL; - - ptepage = get_zeroed_page(GFP_KERNEL); - /* - * This is not really the Guest's fault, but killing it is - * simple for this corner case. - */ - if (!ptepage) { - kill_guest(cpu, "out of memory allocating pte page"); - return NULL; - } - /* - * And we copy the flags to the shadow PGD entry. The page - * number in the shadow PGD is the page we just allocated. - */ - set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags)); - } - - /* - * Intel's Physical Address Extension actually uses three levels of - * page tables, so we need to look in the mid-level. - */ -#ifdef CONFIG_X86_PAE - /* Now look at the mid-level shadow entry. */ - spmd = spmd_addr(cpu, *spgd, vaddr); - - if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) { - /* No shadow entry: allocate a new shadow PTE page. */ - unsigned long ptepage; - - /* If they didn't want us to allocate anything, stop. */ - if (!allocate) - return NULL; - - ptepage = get_zeroed_page(GFP_KERNEL); - - /* - * This is not really the Guest's fault, but killing it is - * simple for this corner case. - */ - if (!ptepage) { - kill_guest(cpu, "out of memory allocating pmd page"); - return NULL; - } - - /* - * And we copy the flags to the shadow PMD entry. The page - * number in the shadow PMD is the page we just allocated. - */ - set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags)); - } -#endif - - /* Get the pointer to the shadow PTE entry we're going to set. */ - return spte_addr(cpu, *spgd, vaddr); -} - -/*H:330 - * (i) Looking up a page table entry when the Guest faults. - * - * We saw this call in run_guest(): when we see a page fault in the Guest, we - * come here. That's because we only set up the shadow page tables lazily as - * they're needed, so we get page faults all the time and quietly fix them up - * and return to the Guest without it knowing. - * - * If we fixed up the fault (ie. we mapped the address), this routine returns - * true. Otherwise, it was a real fault and we need to tell the Guest. - */ -bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) -{ - unsigned long gpte_ptr; - pte_t gpte; - pte_t *spte; - pmd_t gpmd; - pgd_t gpgd; - - /* We never demand page the Switcher, so trying is a mistake. */ - if (vaddr >= switcher_addr) - return false; - - /* First step: get the top-level Guest page table entry. */ - if (unlikely(cpu->linear_pages)) { - /* Faking up a linear mapping. */ - gpgd = __pgd(CHECK_GPGD_MASK); - } else { - gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); - /* Toplevel not present? We can't map it in. */ - if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) - return false; - - /* - * This kills the Guest if it has weird flags or tries to - * refer to a "physical" address outside the bounds. - */ - if (!check_gpgd(cpu, gpgd)) - return false; - } - - /* This "mid-level" entry is only used for non-linear, PAE mode. */ - gpmd = __pmd(_PAGE_TABLE); - -#ifdef CONFIG_X86_PAE - if (likely(!cpu->linear_pages)) { - gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); - /* Middle level not present? We can't map it in. */ - if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) - return false; - - /* - * This kills the Guest if it has weird flags or tries to - * refer to a "physical" address outside the bounds. - */ - if (!check_gpmd(cpu, gpmd)) - return false; - } - - /* - * OK, now we look at the lower level in the Guest page table: keep its - * address, because we might update it later. - */ - gpte_ptr = gpte_addr(cpu, gpmd, vaddr); -#else - /* - * OK, now we look at the lower level in the Guest page table: keep its - * address, because we might update it later. - */ - gpte_ptr = gpte_addr(cpu, gpgd, vaddr); -#endif - - if (unlikely(cpu->linear_pages)) { - /* Linear? Make up a PTE which points to same page. */ - gpte = __pte((vaddr & PAGE_MASK) | _PAGE_RW | _PAGE_PRESENT); - } else { - /* Read the actual PTE value. */ - gpte = lgread(cpu, gpte_ptr, pte_t); - } - - /* If this page isn't in the Guest page tables, we can't page it in. */ - if (!(pte_flags(gpte) & _PAGE_PRESENT)) - return false; - - /* - * Check they're not trying to write to a page the Guest wants - * read-only (bit 2 of errcode == write). - */ - if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW)) - return false; - - /* User access to a kernel-only page? (bit 3 == user access) */ - if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER)) - return false; - - /* - * Check that the Guest PTE flags are OK, and the page number is below - * the pfn_limit (ie. not mapping the Launcher binary). - */ - if (!check_gpte(cpu, gpte)) - return false; - - /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */ - gpte = pte_mkyoung(gpte); - if (errcode & 2) - gpte = pte_mkdirty(gpte); - - /* Get the pointer to the shadow PTE entry we're going to set. */ - spte = find_spte(cpu, vaddr, true, pgd_flags(gpgd), pmd_flags(gpmd)); - if (!spte) - return false; - - /* - * If there was a valid shadow PTE entry here before, we release it. - * This can happen with a write to a previously read-only entry. - */ - release_pte(*spte); - - /* - * If this is a write, we insist that the Guest page is writable (the - * final arg to gpte_to_spte()). - */ - if (pte_dirty(gpte)) - *spte = gpte_to_spte(cpu, gpte, 1); - else - /* - * If this is a read, don't set the "writable" bit in the page - * table entry, even if the Guest says it's writable. That way - * we will come back here when a write does actually occur, so - * we can update the Guest's _PAGE_DIRTY flag. - */ - set_pte(spte, gpte_to_spte(cpu, pte_wrprotect(gpte), 0)); - - /* - * Finally, we write the Guest PTE entry back: we've set the - * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. - */ - if (likely(!cpu->linear_pages)) - lgwrite(cpu, gpte_ptr, pte_t, gpte); - - /* - * The fault is fixed, the page table is populated, the mapping - * manipulated, the result returned and the code complete. A small - * delay and a trace of alliteration are the only indications the Guest - * has that a page fault occurred at all. - */ - return true; -} - -/*H:360 - * (ii) Making sure the Guest stack is mapped. - * - * Remember that direct traps into the Guest need a mapped Guest kernel stack. - * pin_stack_pages() calls us here: we could simply call demand_page(), but as - * we've seen that logic is quite long, and usually the stack pages are already - * mapped, so it's overkill. - * - * This is a quick version which answers the question: is this virtual address - * mapped by the shadow page tables, and is it writable? - */ -static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr) -{ - pte_t *spte; - unsigned long flags; - - /* You can't put your stack in the Switcher! */ - if (vaddr >= switcher_addr) - return false; - - /* If there's no shadow PTE, it's not writable. */ - spte = find_spte(cpu, vaddr, false, 0, 0); - if (!spte) - return false; - - /* - * Check the flags on the pte entry itself: it must be present and - * writable. - */ - flags = pte_flags(*spte); - return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); -} - -/* - * So, when pin_stack_pages() asks us to pin a page, we check if it's already - * in the page tables, and if not, we call demand_page() with error code 2 - * (meaning "write"). - */ -void pin_page(struct lg_cpu *cpu, unsigned long vaddr) -{ - if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2)) - kill_guest(cpu, "bad stack page %#lx", vaddr); -} -/*:*/ - -#ifdef CONFIG_X86_PAE -static void release_pmd(pmd_t *spmd) -{ - /* If the entry's not present, there's nothing to release. */ - if (pmd_flags(*spmd) & _PAGE_PRESENT) { - unsigned int i; - pte_t *ptepage = __va(pmd_pfn(*spmd) << PAGE_SHIFT); - /* For each entry in the page, we might need to release it. */ - for (i = 0; i < PTRS_PER_PTE; i++) - release_pte(ptepage[i]); - /* Now we can free the page of PTEs */ - free_page((long)ptepage); - /* And zero out the PMD entry so we never release it twice. */ - set_pmd(spmd, __pmd(0)); - } -} - -static void release_pgd(pgd_t *spgd) -{ - /* If the entry's not present, there's nothing to release. */ - if (pgd_flags(*spgd) & _PAGE_PRESENT) { - unsigned int i; - pmd_t *pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); - - for (i = 0; i < PTRS_PER_PMD; i++) - release_pmd(&pmdpage[i]); - - /* Now we can free the page of PMDs */ - free_page((long)pmdpage); - /* And zero out the PGD entry so we never release it twice. */ - set_pgd(spgd, __pgd(0)); - } -} - -#else /* !CONFIG_X86_PAE */ -/*H:450 - * If we chase down the release_pgd() code, the non-PAE version looks like - * this. The PAE version is almost identical, but instead of calling - * release_pte it calls release_pmd(), which looks much like this. - */ -static void release_pgd(pgd_t *spgd) -{ - /* If the entry's not present, there's nothing to release. */ - if (pgd_flags(*spgd) & _PAGE_PRESENT) { - unsigned int i; - /* - * Converting the pfn to find the actual PTE page is easy: turn - * the page number into a physical address, then convert to a - * virtual address (easy for kernel pages like this one). - */ - pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); - /* For each entry in the page, we might need to release it. */ - for (i = 0; i < PTRS_PER_PTE; i++) - release_pte(ptepage[i]); - /* Now we can free the page of PTEs */ - free_page((long)ptepage); - /* And zero out the PGD entry so we never release it twice. */ - *spgd = __pgd(0); - } -} -#endif - -/*H:445 - * We saw flush_user_mappings() twice: once from the flush_user_mappings() - * hypercall and once in new_pgdir() when we re-used a top-level pgdir page. - * It simply releases every PTE page from 0 up to the Guest's kernel address. - */ -static void flush_user_mappings(struct lguest *lg, int idx) -{ - unsigned int i; - /* Release every pgd entry up to the kernel's address. */ - for (i = 0; i < pgd_index(lg->kernel_address); i++) - release_pgd(lg->pgdirs[idx].pgdir + i); -} - -/*H:440 - * (v) Flushing (throwing away) page tables, - * - * The Guest has a hypercall to throw away the page tables: it's used when a - * large number of mappings have been changed. - */ -void guest_pagetable_flush_user(struct lg_cpu *cpu) -{ - /* Drop the userspace part of the current page table. */ - flush_user_mappings(cpu->lg, cpu->cpu_pgd); -} -/*:*/ - -/* We walk down the guest page tables to get a guest-physical address */ -unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) -{ - pgd_t gpgd; - pte_t gpte; -#ifdef CONFIG_X86_PAE - pmd_t gpmd; -#endif - - /* Still not set up? Just map 1:1. */ - if (unlikely(cpu->linear_pages)) - return vaddr; - - /* First step: get the top-level Guest page table entry. */ - gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); - /* Toplevel not present? We can't map it in. */ - if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) { - kill_guest(cpu, "Bad address %#lx", vaddr); - return -1UL; - } - -#ifdef CONFIG_X86_PAE - gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); - if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) - kill_guest(cpu, "Bad address %#lx", vaddr); - gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t); -#else - gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t); -#endif - if (!(pte_flags(gpte) & _PAGE_PRESENT)) - kill_guest(cpu, "Bad address %#lx", vaddr); - - return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); -} - -/* - * We keep several page tables. This is a simple routine to find the page - * table (if any) corresponding to this top-level address the Guest has given - * us. - */ -static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) -{ - unsigned int i; - for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) - if (lg->pgdirs[i].pgdir && lg->pgdirs[i].gpgdir == pgtable) - break; - return i; -} - -/*H:435 - * And this is us, creating the new page directory. If we really do - * allocate a new one (and so the kernel parts are not there), we set - * blank_pgdir. - */ -static unsigned int new_pgdir(struct lg_cpu *cpu, - unsigned long gpgdir, - int *blank_pgdir) -{ - unsigned int next; - - /* - * We pick one entry at random to throw out. Choosing the Least - * Recently Used might be better, but this is easy. - */ - next = prandom_u32() % ARRAY_SIZE(cpu->lg->pgdirs); - /* If it's never been allocated at all before, try now. */ - if (!cpu->lg->pgdirs[next].pgdir) { - cpu->lg->pgdirs[next].pgdir = - (pgd_t *)get_zeroed_page(GFP_KERNEL); - /* If the allocation fails, just keep using the one we have */ - if (!cpu->lg->pgdirs[next].pgdir) - next = cpu->cpu_pgd; - else { - /* - * This is a blank page, so there are no kernel - * mappings: caller must map the stack! - */ - *blank_pgdir = 1; - } - } - /* Record which Guest toplevel this shadows. */ - cpu->lg->pgdirs[next].gpgdir = gpgdir; - /* Release all the non-kernel mappings. */ - flush_user_mappings(cpu->lg, next); - - /* This hasn't run on any CPU at all. */ - cpu->lg->pgdirs[next].last_host_cpu = -1; - - return next; -} - -/*H:501 - * We do need the Switcher code mapped at all times, so we allocate that - * part of the Guest page table here. We map the Switcher code immediately, - * but defer mapping of the guest register page and IDT/LDT etc page until - * just before we run the guest in map_switcher_in_guest(). - * - * We *could* do this setup in map_switcher_in_guest(), but at that point - * we've interrupts disabled, and allocating pages like that is fraught: we - * can't sleep if we need to free up some memory. - */ -static bool allocate_switcher_mapping(struct lg_cpu *cpu) -{ - int i; - - for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { - pte_t *pte = find_spte(cpu, switcher_addr + i * PAGE_SIZE, true, - CHECK_GPGD_MASK, _PAGE_TABLE); - if (!pte) - return false; - - /* - * Map the switcher page if not already there. It might - * already be there because we call allocate_switcher_mapping() - * in guest_set_pgd() just in case it did discard our Switcher - * mapping, but it probably didn't. - */ - if (i == 0 && !(pte_flags(*pte) & _PAGE_PRESENT)) { - /* Get a reference to the Switcher page. */ - get_page(lg_switcher_pages[0]); - /* Create a read-only, exectuable, kernel-style PTE */ - set_pte(pte, - mk_pte(lg_switcher_pages[0], PAGE_KERNEL_RX)); - } - } - cpu->lg->pgdirs[cpu->cpu_pgd].switcher_mapped = true; - return true; -} - -/*H:470 - * Finally, a routine which throws away everything: all PGD entries in all - * the shadow page tables, including the Guest's kernel mappings. This is used - * when we destroy the Guest. - */ -static void release_all_pagetables(struct lguest *lg) -{ - unsigned int i, j; - - /* Every shadow pagetable this Guest has */ - for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) { - if (!lg->pgdirs[i].pgdir) - continue; - - /* Every PGD entry. */ - for (j = 0; j < PTRS_PER_PGD; j++) - release_pgd(lg->pgdirs[i].pgdir + j); - lg->pgdirs[i].switcher_mapped = false; - lg->pgdirs[i].last_host_cpu = -1; - } -} - -/* - * We also throw away everything when a Guest tells us it's changed a kernel - * mapping. Since kernel mappings are in every page table, it's easiest to - * throw them all away. This traps the Guest in amber for a while as - * everything faults back in, but it's rare. - */ -void guest_pagetable_clear_all(struct lg_cpu *cpu) -{ - release_all_pagetables(cpu->lg); - /* We need the Guest kernel stack mapped again. */ - pin_stack_pages(cpu); - /* And we need Switcher allocated. */ - if (!allocate_switcher_mapping(cpu)) - kill_guest(cpu, "Cannot populate switcher mapping"); -} - -/*H:430 - * (iv) Switching page tables - * - * Now we've seen all the page table setting and manipulation, let's see - * what happens when the Guest changes page tables (ie. changes the top-level - * pgdir). This occurs on almost every context switch. - */ -void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) -{ - int newpgdir, repin = 0; - - /* - * The very first time they call this, we're actually running without - * any page tables; we've been making it up. Throw them away now. - */ - if (unlikely(cpu->linear_pages)) { - release_all_pagetables(cpu->lg); - cpu->linear_pages = false; - /* Force allocation of a new pgdir. */ - newpgdir = ARRAY_SIZE(cpu->lg->pgdirs); - } else { - /* Look to see if we have this one already. */ - newpgdir = find_pgdir(cpu->lg, pgtable); - } - - /* - * If not, we allocate or mug an existing one: if it's a fresh one, - * repin gets set to 1. - */ - if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs)) - newpgdir = new_pgdir(cpu, pgtable, &repin); - /* Change the current pgd index to the new one. */ - cpu->cpu_pgd = newpgdir; - /* - * If it was completely blank, we map in the Guest kernel stack and - * the Switcher. - */ - if (repin) - pin_stack_pages(cpu); - - if (!cpu->lg->pgdirs[cpu->cpu_pgd].switcher_mapped) { - if (!allocate_switcher_mapping(cpu)) - kill_guest(cpu, "Cannot populate switcher mapping"); - } -} -/*:*/ - -/*M:009 - * Since we throw away all mappings when a kernel mapping changes, our - * performance sucks for guests using highmem. In fact, a guest with - * PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is - * usually slower than a Guest with less memory. - * - * This, of course, cannot be fixed. It would take some kind of... well, I - * don't know, but the term "puissant code-fu" comes to mind. -:*/ - -/*H:420 - * This is the routine which actually sets the page table entry for then - * "idx"'th shadow page table. - * - * Normally, we can just throw out the old entry and replace it with 0: if they - * use it demand_page() will put the new entry in. We need to do this anyway: - * The Guest expects _PAGE_ACCESSED to be set on its PTE the first time a page - * is read from, and _PAGE_DIRTY when it's written to. - * - * But Avi Kivity pointed out that most Operating Systems (Linux included) set - * these bits on PTEs immediately anyway. This is done to save the CPU from - * having to update them, but it helps us the same way: if they set - * _PAGE_ACCESSED then we can put a read-only PTE entry in immediately, and if - * they set _PAGE_DIRTY then we can put a writable PTE entry in immediately. - */ -static void do_set_pte(struct lg_cpu *cpu, int idx, - unsigned long vaddr, pte_t gpte) -{ - /* Look up the matching shadow page directory entry. */ - pgd_t *spgd = spgd_addr(cpu, idx, vaddr); -#ifdef CONFIG_X86_PAE - pmd_t *spmd; -#endif - - /* If the top level isn't present, there's no entry to update. */ - if (pgd_flags(*spgd) & _PAGE_PRESENT) { -#ifdef CONFIG_X86_PAE - spmd = spmd_addr(cpu, *spgd, vaddr); - if (pmd_flags(*spmd) & _PAGE_PRESENT) { -#endif - /* Otherwise, start by releasing the existing entry. */ - pte_t *spte = spte_addr(cpu, *spgd, vaddr); - release_pte(*spte); - - /* - * If they're setting this entry as dirty or accessed, - * we might as well put that entry they've given us in - * now. This shaves 10% off a copy-on-write - * micro-benchmark. - */ - if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { - if (!check_gpte(cpu, gpte)) - return; - set_pte(spte, - gpte_to_spte(cpu, gpte, - pte_flags(gpte) & _PAGE_DIRTY)); - } else { - /* - * Otherwise kill it and we can demand_page() - * it in later. - */ - set_pte(spte, __pte(0)); - } -#ifdef CONFIG_X86_PAE - } -#endif - } -} - -/*H:410 - * Updating a PTE entry is a little trickier. - * - * We keep track of several different page tables (the Guest uses one for each - * process, so it makes sense to cache at least a few). Each of these have - * identical kernel parts: ie. every mapping above PAGE_OFFSET is the same for - * all processes. So when the page table above that address changes, we update - * all the page tables, not just the current one. This is rare. - * - * The benefit is that when we have to track a new page table, we can keep all - * the kernel mappings. This speeds up context switch immensely. - */ -void guest_set_pte(struct lg_cpu *cpu, - unsigned long gpgdir, unsigned long vaddr, pte_t gpte) -{ - /* We don't let you remap the Switcher; we need it to get back! */ - if (vaddr >= switcher_addr) { - kill_guest(cpu, "attempt to set pte into Switcher pages"); - return; - } - - /* - * Kernel mappings must be changed on all top levels. Slow, but doesn't - * happen often. - */ - if (vaddr >= cpu->lg->kernel_address) { - unsigned int i; - for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++) - if (cpu->lg->pgdirs[i].pgdir) - do_set_pte(cpu, i, vaddr, gpte); - } else { - /* Is this page table one we have a shadow for? */ - int pgdir = find_pgdir(cpu->lg, gpgdir); - if (pgdir != ARRAY_SIZE(cpu->lg->pgdirs)) - /* If so, do the update. */ - do_set_pte(cpu, pgdir, vaddr, gpte); - } -} - -/*H:400 - * (iii) Setting up a page table entry when the Guest tells us one has changed. - * - * Just like we did in interrupts_and_traps.c, it makes sense for us to deal - * with the other side of page tables while we're here: what happens when the - * Guest asks for a page table to be updated? - * - * We already saw that demand_page() will fill in the shadow page tables when - * needed, so we can simply remove shadow page table entries whenever the Guest - * tells us they've changed. When the Guest tries to use the new entry it will - * fault and demand_page() will fix it up. - * - * So with that in mind here's our code to update a (top-level) PGD entry: - */ -void guest_set_pgd(struct lguest *lg, unsigned long gpgdir, u32 idx) -{ - int pgdir; - - if (idx > PTRS_PER_PGD) { - kill_guest(&lg->cpus[0], "Attempt to set pgd %u/%u", - idx, PTRS_PER_PGD); - return; - } - - /* If they're talking about a page table we have a shadow for... */ - pgdir = find_pgdir(lg, gpgdir); - if (pgdir < ARRAY_SIZE(lg->pgdirs)) { - /* ... throw it away. */ - release_pgd(lg->pgdirs[pgdir].pgdir + idx); - /* That might have been the Switcher mapping, remap it. */ - if (!allocate_switcher_mapping(&lg->cpus[0])) { - kill_guest(&lg->cpus[0], - "Cannot populate switcher mapping"); - } - lg->pgdirs[pgdir].last_host_cpu = -1; - } -} - -#ifdef CONFIG_X86_PAE -/* For setting a mid-level, we just throw everything away. It's easy. */ -void guest_set_pmd(struct lguest *lg, unsigned long pmdp, u32 idx) -{ - guest_pagetable_clear_all(&lg->cpus[0]); -} -#endif - -/*H:500 - * (vii) Setting up the page tables initially. - * - * When a Guest is first created, set initialize a shadow page table which - * we will populate on future faults. The Guest doesn't have any actual - * pagetables yet, so we set linear_pages to tell demand_page() to fake it - * for the moment. - * - * We do need the Switcher to be mapped at all times, so we allocate that - * part of the Guest page table here. - */ -int init_guest_pagetable(struct lguest *lg) -{ - struct lg_cpu *cpu = &lg->cpus[0]; - int allocated = 0; - - /* lg (and lg->cpus[]) starts zeroed: this allocates a new pgdir */ - cpu->cpu_pgd = new_pgdir(cpu, 0, &allocated); - if (!allocated) - return -ENOMEM; - - /* We start with a linear mapping until the initialize. */ - cpu->linear_pages = true; - - /* Allocate the page tables for the Switcher. */ - if (!allocate_switcher_mapping(cpu)) { - release_all_pagetables(lg); - return -ENOMEM; - } - - return 0; -} - -/*H:508 When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ -void page_table_guest_data_init(struct lg_cpu *cpu) -{ - /* - * We tell the Guest that it can't use the virtual addresses - * used by the Switcher. This trick is equivalent to 4GB - - * switcher_addr. - */ - u32 top = ~switcher_addr + 1; - - /* We get the kernel address: above this is all kernel memory. */ - if (get_user(cpu->lg->kernel_address, - &cpu->lg->lguest_data->kernel_address) - /* - * We tell the Guest that it can't use the top virtual - * addresses (used by the Switcher). - */ - || put_user(top, &cpu->lg->lguest_data->reserve_mem)) { - kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); - return; - } - - /* - * In flush_user_mappings() we loop from 0 to - * "pgd_index(lg->kernel_address)". This assumes it won't hit the - * Switcher mappings, so check that now. - */ - if (cpu->lg->kernel_address >= switcher_addr) - kill_guest(cpu, "bad kernel address %#lx", - cpu->lg->kernel_address); -} - -/* When a Guest dies, our cleanup is fairly simple. */ -void free_guest_pagetable(struct lguest *lg) -{ - unsigned int i; - - /* Throw away all page table pages. */ - release_all_pagetables(lg); - /* Now free the top levels: free_page() can handle 0 just fine. */ - for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) - free_page((long)lg->pgdirs[i].pgdir); -} - -/*H:481 - * This clears the Switcher mappings for cpu #i. - */ -static void remove_switcher_percpu_map(struct lg_cpu *cpu, unsigned int i) -{ - unsigned long base = switcher_addr + PAGE_SIZE + i * PAGE_SIZE*2; - pte_t *pte; - - /* Clear the mappings for both pages. */ - pte = find_spte(cpu, base, false, 0, 0); - release_pte(*pte); - set_pte(pte, __pte(0)); - - pte = find_spte(cpu, base + PAGE_SIZE, false, 0, 0); - release_pte(*pte); - set_pte(pte, __pte(0)); -} - -/*H:480 - * (vi) Mapping the Switcher when the Guest is about to run. - * - * The Switcher and the two pages for this CPU need to be visible in the Guest - * (and not the pages for other CPUs). - * - * The pages for the pagetables have all been allocated before: we just need - * to make sure the actual PTEs are up-to-date for the CPU we're about to run - * on. - */ -void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) -{ - unsigned long base; - struct page *percpu_switcher_page, *regs_page; - pte_t *pte; - struct pgdir *pgdir = &cpu->lg->pgdirs[cpu->cpu_pgd]; - - /* Switcher page should always be mapped by now! */ - BUG_ON(!pgdir->switcher_mapped); - - /* - * Remember that we have two pages for each Host CPU, so we can run a - * Guest on each CPU without them interfering. We need to make sure - * those pages are mapped correctly in the Guest, but since we usually - * run on the same CPU, we cache that, and only update the mappings - * when we move. - */ - if (pgdir->last_host_cpu == raw_smp_processor_id()) - return; - - /* -1 means unknown so we remove everything. */ - if (pgdir->last_host_cpu == -1) { - unsigned int i; - for_each_possible_cpu(i) - remove_switcher_percpu_map(cpu, i); - } else { - /* We know exactly what CPU mapping to remove. */ - remove_switcher_percpu_map(cpu, pgdir->last_host_cpu); - } - - /* - * When we're running the Guest, we want the Guest's "regs" page to - * appear where the first Switcher page for this CPU is. This is an - * optimization: when the Switcher saves the Guest registers, it saves - * them into the first page of this CPU's "struct lguest_pages": if we - * make sure the Guest's register page is already mapped there, we - * don't have to copy them out again. - */ - /* Find the shadow PTE for this regs page. */ - base = switcher_addr + PAGE_SIZE - + raw_smp_processor_id() * sizeof(struct lguest_pages); - pte = find_spte(cpu, base, false, 0, 0); - regs_page = pfn_to_page(__pa(cpu->regs_page) >> PAGE_SHIFT); - get_page(regs_page); - set_pte(pte, mk_pte(regs_page, __pgprot(__PAGE_KERNEL & ~_PAGE_GLOBAL))); - - /* - * We map the second page of the struct lguest_pages read-only in - * the Guest: the IDT, GDT and other things it's not supposed to - * change. - */ - pte = find_spte(cpu, base + PAGE_SIZE, false, 0, 0); - percpu_switcher_page - = lg_switcher_pages[1 + raw_smp_processor_id()*2 + 1]; - get_page(percpu_switcher_page); - set_pte(pte, mk_pte(percpu_switcher_page, - __pgprot(__PAGE_KERNEL_RO & ~_PAGE_GLOBAL))); - - pgdir->last_host_cpu = raw_smp_processor_id(); -} - -/*H:490 - * We've made it through the page table code. Perhaps our tired brains are - * still processing the details, or perhaps we're simply glad it's over. - * - * If nothing else, note that all this complexity in juggling shadow page tables - * in sync with the Guest's page tables is for one reason: for most Guests this - * page table dance determines how bad performance will be. This is why Xen - * uses exotic direct Guest pagetable manipulation, and why both Intel and AMD - * have implemented shadow page table support directly into hardware. - * - * There is just one file remaining in the Host. - */ diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c deleted file mode 100644 index c4fb424dfddb..000000000000 --- a/drivers/lguest/segments.c +++ /dev/null @@ -1,228 +0,0 @@ -/*P:600 - * The x86 architecture has segments, which involve a table of descriptors - * which can be used to do funky things with virtual address interpretation. - * We originally used to use segments so the Guest couldn't alter the - * Guest<->Host Switcher, and then we had to trim Guest segments, and restore - * for userspace per-thread segments, but trim again for on userspace->kernel - * transitions... This nightmarish creation was contained within this file, - * where we knew not to tread without heavy armament and a change of underwear. - * - * In these modern times, the segment handling code consists of simple sanity - * checks, and the worst you'll experience reading this code is butterfly-rash - * from frolicking through its parklike serenity. -:*/ -#include "lg.h" - -/*H:600 - * Segments & The Global Descriptor Table - * - * (That title sounds like a bad Nerdcore group. Not to suggest that there are - * any good Nerdcore groups, but in high school a friend of mine had a band - * called Joe Fish and the Chips, so there are definitely worse band names). - * - * To refresh: the GDT is a table of 8-byte values describing segments. Once - * set up, these segments can be loaded into one of the 6 "segment registers". - * - * GDT entries are passed around as "struct desc_struct"s, which like IDT - * entries are split into two 32-bit members, "a" and "b". One day, someone - * will clean that up, and be declared a Hero. (No pressure, I'm just saying). - * - * Anyway, the GDT entry contains a base (the start address of the segment), a - * limit (the size of the segment - 1), and some flags. Sounds simple, and it - * would be, except those zany Intel engineers decided that it was too boring - * to put the base at one end, the limit at the other, and the flags in - * between. They decided to shotgun the bits at random throughout the 8 bytes, - * like so: - * - * 0 16 40 48 52 56 63 - * [ limit part 1 ][ base part 1 ][ flags ][li][fl][base ] - * mit ags part 2 - * part 2 - * - * As a result, this file contains a certain amount of magic numeracy. Let's - * begin. - */ - -/* - * There are several entries we don't let the Guest set. The TSS entry is the - * "Task State Segment" which controls all kinds of delicate things. The - * LGUEST_CS and LGUEST_DS entries are reserved for the Switcher, and the - * the Guest can't be trusted to deal with double faults. - */ -static bool ignored_gdt(unsigned int num) -{ - return (num == GDT_ENTRY_TSS - || num == GDT_ENTRY_LGUEST_CS - || num == GDT_ENTRY_LGUEST_DS - || num == GDT_ENTRY_DOUBLEFAULT_TSS); -} - -/*H:630 - * Once the Guest gave us new GDT entries, we fix them up a little. We - * don't care if they're invalid: the worst that can happen is a General - * Protection Fault in the Switcher when it restores a Guest segment register - * which tries to use that entry. Then we kill the Guest for causing such a - * mess: the message will be "unhandled trap 256". - */ -static void fixup_gdt_table(struct lg_cpu *cpu, unsigned start, unsigned end) -{ - unsigned int i; - - for (i = start; i < end; i++) { - /* - * We never copy these ones to real GDT, so we don't care what - * they say - */ - if (ignored_gdt(i)) - continue; - - /* - * Segment descriptors contain a privilege level: the Guest is - * sometimes careless and leaves this as 0, even though it's - * running at privilege level 1. If so, we fix it here. - */ - if (cpu->arch.gdt[i].dpl == 0) - cpu->arch.gdt[i].dpl |= GUEST_PL; - - /* - * Each descriptor has an "accessed" bit. If we don't set it - * now, the CPU will try to set it when the Guest first loads - * that entry into a segment register. But the GDT isn't - * writable by the Guest, so bad things can happen. - */ - cpu->arch.gdt[i].type |= 0x1; - } -} - -/*H:610 - * Like the IDT, we never simply use the GDT the Guest gives us. We keep - * a GDT for each CPU, and copy across the Guest's entries each time we want to - * run the Guest on that CPU. - * - * This routine is called at boot or modprobe time for each CPU to set up the - * constant GDT entries: the ones which are the same no matter what Guest we're - * running. - */ -void setup_default_gdt_entries(struct lguest_ro_state *state) -{ - struct desc_struct *gdt = state->guest_gdt; - unsigned long tss = (unsigned long)&state->guest_tss; - - /* The Switcher segments are full 0-4G segments, privilege level 0 */ - gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; - gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; - - /* - * The TSS segment refers to the TSS entry for this particular CPU. - */ - gdt[GDT_ENTRY_TSS].a = 0; - gdt[GDT_ENTRY_TSS].b = 0; - - gdt[GDT_ENTRY_TSS].limit0 = 0x67; - gdt[GDT_ENTRY_TSS].base0 = tss & 0xFFFF; - gdt[GDT_ENTRY_TSS].base1 = (tss >> 16) & 0xFF; - gdt[GDT_ENTRY_TSS].base2 = tss >> 24; - gdt[GDT_ENTRY_TSS].type = 0x9; /* 32-bit TSS (available) */ - gdt[GDT_ENTRY_TSS].p = 0x1; /* Entry is present */ - gdt[GDT_ENTRY_TSS].dpl = 0x0; /* Privilege level 0 */ - gdt[GDT_ENTRY_TSS].s = 0x0; /* system segment */ - -} - -/* - * This routine sets up the initial Guest GDT for booting. All entries start - * as 0 (unusable). - */ -void setup_guest_gdt(struct lg_cpu *cpu) -{ - /* - * Start with full 0-4G segments...except the Guest is allowed to use - * them, so set the privilege level appropriately in the flags. - */ - cpu->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; - cpu->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; - cpu->arch.gdt[GDT_ENTRY_KERNEL_CS].dpl |= GUEST_PL; - cpu->arch.gdt[GDT_ENTRY_KERNEL_DS].dpl |= GUEST_PL; -} - -/*H:650 - * An optimization of copy_gdt(), for just the three "thead-local storage" - * entries. - */ -void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt) -{ - unsigned int i; - - for (i = GDT_ENTRY_TLS_MIN; i <= GDT_ENTRY_TLS_MAX; i++) - gdt[i] = cpu->arch.gdt[i]; -} - -/*H:640 - * When the Guest is run on a different CPU, or the GDT entries have changed, - * copy_gdt() is called to copy the Guest's GDT entries across to this CPU's - * GDT. - */ -void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt) -{ - unsigned int i; - - /* - * The default entries from setup_default_gdt_entries() are not - * replaced. See ignored_gdt() above. - */ - for (i = 0; i < GDT_ENTRIES; i++) - if (!ignored_gdt(i)) - gdt[i] = cpu->arch.gdt[i]; -} - -/*H:620 - * This is where the Guest asks us to load a new GDT entry - * (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. - */ -void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi) -{ - /* - * We assume the Guest has the same number of GDT entries as the - * Host, otherwise we'd have to dynamically allocate the Guest GDT. - */ - if (num >= ARRAY_SIZE(cpu->arch.gdt)) { - kill_guest(cpu, "too many gdt entries %i", num); - return; - } - - /* Set it up, then fix it. */ - cpu->arch.gdt[num].a = lo; - cpu->arch.gdt[num].b = hi; - fixup_gdt_table(cpu, num, num+1); - /* - * Mark that the GDT changed so the core knows it has to copy it again, - * even if the Guest is run on the same CPU. - */ - cpu->changed |= CHANGED_GDT; -} - -/* - * This is the fast-track version for just changing the three TLS entries. - * Remember that this happens on every context switch, so it's worth - * optimizing. But wouldn't it be neater to have a single hypercall to cover - * both cases? - */ -void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls) -{ - struct desc_struct *tls = &cpu->arch.gdt[GDT_ENTRY_TLS_MIN]; - - __lgread(cpu, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES); - fixup_gdt_table(cpu, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1); - /* Note that just the TLS entries have changed. */ - cpu->changed |= CHANGED_GDT_TLS; -} - -/*H:660 - * With this, we have finished the Host. - * - * Five of the seven parts of our task are complete. You have made it through - * the Bit of Despair (I think that's somewhere in the page table code, - * myself). - * - * Next, we examine "make Switcher". It's short, but intense. - */ diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c deleted file mode 100644 index 516923926335..000000000000 --- a/drivers/lguest/x86/core.c +++ /dev/null @@ -1,718 +0,0 @@ -/* - * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation. - * Copyright (C) 2007, Jes Sorensen <jes@sgi.com> SGI. - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or - * NON INFRINGEMENT. See the GNU General Public License for more - * details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. - */ -/*P:450 - * This file contains the x86-specific lguest code. It used to be all - * mixed in with drivers/lguest/core.c but several foolhardy code slashers - * wrestled most of the dependencies out to here in preparation for porting - * lguest to other architectures (see what I mean by foolhardy?). - * - * This also contains a couple of non-obvious setup and teardown pieces which - * were implemented after days of debugging pain. -:*/ -#include <linux/kernel.h> -#include <linux/start_kernel.h> -#include <linux/string.h> -#include <linux/console.h> -#include <linux/screen_info.h> -#include <linux/irq.h> -#include <linux/interrupt.h> -#include <linux/clocksource.h> -#include <linux/clockchips.h> -#include <linux/cpu.h> -#include <linux/lguest.h> -#include <linux/lguest_launcher.h> -#include <asm/paravirt.h> -#include <asm/param.h> -#include <asm/page.h> -#include <asm/pgtable.h> -#include <asm/desc.h> -#include <asm/setup.h> -#include <asm/lguest.h> -#include <asm/uaccess.h> -#include <asm/i387.h> -#include "../lg.h" - -static int cpu_had_pge; - -static struct { - unsigned long offset; - unsigned short segment; -} lguest_entry; - -/* Offset from where switcher.S was compiled to where we've copied it */ -static unsigned long switcher_offset(void) -{ - return switcher_addr - (unsigned long)start_switcher_text; -} - -/* This cpu's struct lguest_pages (after the Switcher text page) */ -static struct lguest_pages *lguest_pages(unsigned int cpu) -{ - return &(((struct lguest_pages *)(switcher_addr + PAGE_SIZE))[cpu]); -} - -static DEFINE_PER_CPU(struct lg_cpu *, lg_last_cpu); - -/*S:010 - * We approach the Switcher. - * - * Remember that each CPU has two pages which are visible to the Guest when it - * runs on that CPU. This has to contain the state for that Guest: we copy the - * state in just before we run the Guest. - * - * Each Guest has "changed" flags which indicate what has changed in the Guest - * since it last ran. We saw this set in interrupts_and_traps.c and - * segments.c. - */ -static void copy_in_guest_info(struct lg_cpu *cpu, struct lguest_pages *pages) -{ - /* - * Copying all this data can be quite expensive. We usually run the - * same Guest we ran last time (and that Guest hasn't run anywhere else - * meanwhile). If that's not the case, we pretend everything in the - * Guest has changed. - */ - if (__this_cpu_read(lg_last_cpu) != cpu || cpu->last_pages != pages) { - __this_cpu_write(lg_last_cpu, cpu); - cpu->last_pages = pages; - cpu->changed = CHANGED_ALL; - } - - /* - * These copies are pretty cheap, so we do them unconditionally: */ - /* Save the current Host top-level page directory. - */ - pages->state.host_cr3 = __pa(current->mm->pgd); - /* - * Set up the Guest's page tables to see this CPU's pages (and no - * other CPU's pages). - */ - map_switcher_in_guest(cpu, pages); - /* - * Set up the two "TSS" members which tell the CPU what stack to use - * for traps which do directly into the Guest (ie. traps at privilege - * level 1). - */ - pages->state.guest_tss.sp1 = cpu->esp1; - pages->state.guest_tss.ss1 = cpu->ss1; - - /* Copy direct-to-Guest trap entries. */ - if (cpu->changed & CHANGED_IDT) - copy_traps(cpu, pages->state.guest_idt, default_idt_entries); - - /* Copy all GDT entries which the Guest can change. */ - if (cpu->changed & CHANGED_GDT) - copy_gdt(cpu, pages->state.guest_gdt); - /* If only the TLS entries have changed, copy them. */ - else if (cpu->changed & CHANGED_GDT_TLS) - copy_gdt_tls(cpu, pages->state.guest_gdt); - - /* Mark the Guest as unchanged for next time. */ - cpu->changed = 0; -} - -/* Finally: the code to actually call into the Switcher to run the Guest. */ -static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages) -{ - /* This is a dummy value we need for GCC's sake. */ - unsigned int clobber; - - /* - * Copy the guest-specific information into this CPU's "struct - * lguest_pages". - */ - copy_in_guest_info(cpu, pages); - - /* - * Set the trap number to 256 (impossible value). If we fault while - * switching to the Guest (bad segment registers or bug), this will - * cause us to abort the Guest. - */ - cpu->regs->trapnum = 256; - - /* - * Now: we push the "eflags" register on the stack, then do an "lcall". - * This is how we change from using the kernel code segment to using - * the dedicated lguest code segment, as well as jumping into the - * Switcher. - * - * The lcall also pushes the old code segment (KERNEL_CS) onto the - * stack, then the address of this call. This stack layout happens to - * exactly match the stack layout created by an interrupt... - */ - asm volatile("pushf; lcall *lguest_entry" - /* - * This is how we tell GCC that %eax ("a") and %ebx ("b") - * are changed by this routine. The "=" means output. - */ - : "=a"(clobber), "=b"(clobber) - /* - * %eax contains the pages pointer. ("0" refers to the - * 0-th argument above, ie "a"). %ebx contains the - * physical address of the Guest's top-level page - * directory. - */ - : "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir)) - /* - * We tell gcc that all these registers could change, - * which means we don't have to save and restore them in - * the Switcher. - */ - : "memory", "%edx", "%ecx", "%edi", "%esi"); -} -/*:*/ - -/*M:002 - * There are hooks in the scheduler which we can register to tell when we - * get kicked off the CPU (preempt_notifier_register()). This would allow us - * to lazily disable SYSENTER which would regain some performance, and should - * also simplify copy_in_guest_info(). Note that we'd still need to restore - * things when we exit to Launcher userspace, but that's fairly easy. - * - * We could also try using these hooks for PGE, but that might be too expensive. - * - * The hooks were designed for KVM, but we can also put them to good use. -:*/ - -/*H:040 - * This is the i386-specific code to setup and run the Guest. Interrupts - * are disabled: we own the CPU. - */ -void lguest_arch_run_guest(struct lg_cpu *cpu) -{ - /* - * Remember the awfully-named TS bit? If the Guest has asked to set it - * we set it now, so we can trap and pass that trap to the Guest if it - * uses the FPU. - */ - if (cpu->ts && user_has_fpu()) - stts(); - - /* - * SYSENTER is an optimized way of doing system calls. We can't allow - * it because it always jumps to privilege level 0. A normal Guest - * won't try it because we don't advertise it in CPUID, but a malicious - * Guest (or malicious Guest userspace program) could, so we tell the - * CPU to disable it before running the Guest. - */ - if (boot_cpu_has(X86_FEATURE_SEP)) - wrmsr(MSR_IA32_SYSENTER_CS, 0, 0); - - /* - * Now we actually run the Guest. It will return when something - * interesting happens, and we can examine its registers to see what it - * was doing. - */ - run_guest_once(cpu, lguest_pages(raw_smp_processor_id())); - - /* - * Note that the "regs" structure contains two extra entries which are - * not really registers: a trap number which says what interrupt or - * trap made the switcher code come back, and an error code which some - * traps set. - */ - - /* Restore SYSENTER if it's supposed to be on. */ - if (boot_cpu_has(X86_FEATURE_SEP)) - wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); - - /* Clear the host TS bit if it was set above. */ - if (cpu->ts && user_has_fpu()) - clts(); - - /* - * If the Guest page faulted, then the cr2 register will tell us the - * bad virtual address. We have to grab this now, because once we - * re-enable interrupts an interrupt could fault and thus overwrite - * cr2, or we could even move off to a different CPU. - */ - if (cpu->regs->trapnum == 14) - cpu->arch.last_pagefault = read_cr2(); - /* - * Similarly, if we took a trap because the Guest used the FPU, - * we have to restore the FPU it expects to see. - * math_state_restore() may sleep and we may even move off to - * a different CPU. So all the critical stuff should be done - * before this. - */ - else if (cpu->regs->trapnum == 7 && !user_has_fpu()) - math_state_restore(); -} - -/*H:130 - * Now we've examined the hypercall code; our Guest can make requests. - * Our Guest is usually so well behaved; it never tries to do things it isn't - * allowed to, and uses hypercalls instead. Unfortunately, Linux's paravirtual - * infrastructure isn't quite complete, because it doesn't contain replacements - * for the Intel I/O instructions. As a result, the Guest sometimes fumbles - * across one during the boot process as it probes for various things which are - * usually attached to a PC. - * - * When the Guest uses one of these instructions, we get a trap (General - * Protection Fault) and come here. We see if it's one of those troublesome - * instructions and skip over it. We return true if we did. - */ -static int emulate_insn(struct lg_cpu *cpu) -{ - u8 insn; - unsigned int insnlen = 0, in = 0, small_operand = 0; - /* - * The eip contains the *virtual* address of the Guest's instruction: - * walk the Guest's page tables to find the "physical" address. - */ - unsigned long physaddr = guest_pa(cpu, cpu->regs->eip); - - /* - * This must be the Guest kernel trying to do something, not userspace! - * The bottom two bits of the CS segment register are the privilege - * level. - */ - if ((cpu->regs->cs & 3) != GUEST_PL) - return 0; - - /* Decoding x86 instructions is icky. */ - insn = lgread(cpu, physaddr, u8); - - /* - * Around 2.6.33, the kernel started using an emulation for the - * cmpxchg8b instruction in early boot on many configurations. This - * code isn't paravirtualized, and it tries to disable interrupts. - * Ignore it, which will Mostly Work. - */ - if (insn == 0xfa) { - /* "cli", or Clear Interrupt Enable instruction. Skip it. */ - cpu->regs->eip++; - return 1; - } - - /* - * 0x66 is an "operand prefix". It means a 16, not 32 bit in/out. - */ - if (insn == 0x66) { - small_operand = 1; - /* The instruction is 1 byte so far, read the next byte. */ - insnlen = 1; - insn = lgread(cpu, physaddr + insnlen, u8); - } - - /* - * We can ignore the lower bit for the moment and decode the 4 opcodes - * we need to emulate. - */ - switch (insn & 0xFE) { - case 0xE4: /* in <next byte>,%al */ - insnlen += 2; - in = 1; - break; - case 0xEC: /* in (%dx),%al */ - insnlen += 1; - in = 1; - break; - case 0xE6: /* out %al,<next byte> */ - insnlen += 2; - break; - case 0xEE: /* out %al,(%dx) */ - insnlen += 1; - break; - default: - /* OK, we don't know what this is, can't emulate. */ - return 0; - } - - /* - * If it was an "IN" instruction, they expect the result to be read - * into %eax, so we change %eax. We always return all-ones, which - * traditionally means "there's nothing there". - */ - if (in) { - /* Lower bit tells means it's a 32/16 bit access */ - if (insn & 0x1) { - if (small_operand) - cpu->regs->eax |= 0xFFFF; - else - cpu->regs->eax = 0xFFFFFFFF; - } else - cpu->regs->eax |= 0xFF; - } - /* Finally, we've "done" the instruction, so move past it. */ - cpu->regs->eip += insnlen; - /* Success! */ - return 1; -} - -/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */ -void lguest_arch_handle_trap(struct lg_cpu *cpu) -{ - switch (cpu->regs->trapnum) { - case 13: /* We've intercepted a General Protection Fault. */ - /* - * Check if this was one of those annoying IN or OUT - * instructions which we need to emulate. If so, we just go - * back into the Guest after we've done it. - */ - if (cpu->regs->errcode == 0) { - if (emulate_insn(cpu)) - return; - } - break; - case 14: /* We've intercepted a Page Fault. */ - /* - * The Guest accessed a virtual address that wasn't mapped. - * This happens a lot: we don't actually set up most of the page - * tables for the Guest at all when we start: as it runs it asks - * for more and more, and we set them up as required. In this - * case, we don't even tell the Guest that the fault happened. - * - * The errcode tells whether this was a read or a write, and - * whether kernel or userspace code. - */ - if (demand_page(cpu, cpu->arch.last_pagefault, - cpu->regs->errcode)) - return; - - /* - * OK, it's really not there (or not OK): the Guest needs to - * know. We write out the cr2 value so it knows where the - * fault occurred. - * - * Note that if the Guest were really messed up, this could - * happen before it's done the LHCALL_LGUEST_INIT hypercall, so - * lg->lguest_data could be NULL - */ - if (cpu->lg->lguest_data && - put_user(cpu->arch.last_pagefault, - &cpu->lg->lguest_data->cr2)) - kill_guest(cpu, "Writing cr2"); - break; - case 7: /* We've intercepted a Device Not Available fault. */ - /* - * If the Guest doesn't want to know, we already restored the - * Floating Point Unit, so we just continue without telling it. - */ - if (!cpu->ts) - return; - break; - case 32 ... 255: - /* - * These values mean a real interrupt occurred, in which case - * the Host handler has already been run. We just do a - * friendly check if another process should now be run, then - * return to run the Guest again. - */ - cond_resched(); - return; - case LGUEST_TRAP_ENTRY: - /* - * Our 'struct hcall_args' maps directly over our regs: we set - * up the pointer now to indicate a hypercall is pending. - */ - cpu->hcall = (struct hcall_args *)cpu->regs; - return; - } - - /* We didn't handle the trap, so it needs to go to the Guest. */ - if (!deliver_trap(cpu, cpu->regs->trapnum)) - /* - * If the Guest doesn't have a handler (either it hasn't - * registered any yet, or it's one of the faults we don't let - * it handle), it dies with this cryptic error message. - */ - kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)", - cpu->regs->trapnum, cpu->regs->eip, - cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault - : cpu->regs->errcode); -} - -/* - * Now we can look at each of the routines this calls, in increasing order of - * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(), - * deliver_trap() and demand_page(). After all those, we'll be ready to - * examine the Switcher, and our philosophical understanding of the Host/Guest - * duality will be complete. -:*/ -static void adjust_pge(void *on) -{ - if (on) - write_cr4(read_cr4() | X86_CR4_PGE); - else - write_cr4(read_cr4() & ~X86_CR4_PGE); -} - -/*H:020 - * Now the Switcher is mapped and every thing else is ready, we need to do - * some more i386-specific initialization. - */ -void __init lguest_arch_host_init(void) -{ - int i; - - /* - * Most of the x86/switcher_32.S doesn't care that it's been moved; on - * Intel, jumps are relative, and it doesn't access any references to - * external code or data. - * - * The only exception is the interrupt handlers in switcher.S: their - * addresses are placed in a table (default_idt_entries), so we need to - * update the table with the new addresses. switcher_offset() is a - * convenience function which returns the distance between the - * compiled-in switcher code and the high-mapped copy we just made. - */ - for (i = 0; i < IDT_ENTRIES; i++) - default_idt_entries[i] += switcher_offset(); - - /* - * Set up the Switcher's per-cpu areas. - * - * Each CPU gets two pages of its own within the high-mapped region - * (aka. "struct lguest_pages"). Much of this can be initialized now, - * but some depends on what Guest we are running (which is set up in - * copy_in_guest_info()). - */ - for_each_possible_cpu(i) { - /* lguest_pages() returns this CPU's two pages. */ - struct lguest_pages *pages = lguest_pages(i); - /* This is a convenience pointer to make the code neater. */ - struct lguest_ro_state *state = &pages->state; - - /* - * The Global Descriptor Table: the Host has a different one - * for each CPU. We keep a descriptor for the GDT which says - * where it is and how big it is (the size is actually the last - * byte, not the size, hence the "-1"). - */ - state->host_gdt_desc.size = GDT_SIZE-1; - state->host_gdt_desc.address = (long)get_cpu_gdt_table(i); - - /* - * All CPUs on the Host use the same Interrupt Descriptor - * Table, so we just use store_idt(), which gets this CPU's IDT - * descriptor. - */ - store_idt(&state->host_idt_desc); - - /* - * The descriptors for the Guest's GDT and IDT can be filled - * out now, too. We copy the GDT & IDT into ->guest_gdt and - * ->guest_idt before actually running the Guest. - */ - state->guest_idt_desc.size = sizeof(state->guest_idt)-1; - state->guest_idt_desc.address = (long)&state->guest_idt; - state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1; - state->guest_gdt_desc.address = (long)&state->guest_gdt; - - /* - * We know where we want the stack to be when the Guest enters - * the Switcher: in pages->regs. The stack grows upwards, so - * we start it at the end of that structure. - */ - state->guest_tss.sp0 = (long)(&pages->regs + 1); - /* - * And this is the GDT entry to use for the stack: we keep a - * couple of special LGUEST entries. - */ - state->guest_tss.ss0 = LGUEST_DS; - - /* - * x86 can have a finegrained bitmap which indicates what I/O - * ports the process can use. We set it to the end of our - * structure, meaning "none". - */ - state->guest_tss.io_bitmap_base = sizeof(state->guest_tss); - - /* - * Some GDT entries are the same across all Guests, so we can - * set them up now. - */ - setup_default_gdt_entries(state); - /* Most IDT entries are the same for all Guests, too.*/ - setup_default_idt_entries(state, default_idt_entries); - - /* - * The Host needs to be able to use the LGUEST segments on this - * CPU, too, so put them in the Host GDT. - */ - get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; - get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; - } - - /* - * In the Switcher, we want the %cs segment register to use the - * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so - * it will be undisturbed when we switch. To change %cs and jump we - * need this structure to feed to Intel's "lcall" instruction. - */ - lguest_entry.offset = (long)switch_to_guest + switcher_offset(); - lguest_entry.segment = LGUEST_CS; - - /* - * Finally, we need to turn off "Page Global Enable". PGE is an - * optimization where page table entries are specially marked to show - * they never change. The Host kernel marks all the kernel pages this - * way because it's always present, even when userspace is running. - * - * Lguest breaks this: unbeknownst to the rest of the Host kernel, we - * switch to the Guest kernel. If you don't disable this on all CPUs, - * you'll get really weird bugs that you'll chase for two days. - * - * I used to turn PGE off every time we switched to the Guest and back - * on when we return, but that slowed the Switcher down noticibly. - */ - - /* - * We don't need the complexity of CPUs coming and going while we're - * doing this. - */ - get_online_cpus(); - if (cpu_has_pge) { /* We have a broader idea of "global". */ - /* Remember that this was originally set (for cleanup). */ - cpu_had_pge = 1; - /* - * adjust_pge is a helper function which sets or unsets the PGE - * bit on its CPU, depending on the argument (0 == unset). - */ - on_each_cpu(adjust_pge, (void *)0, 1); - /* Turn off the feature in the global feature set. */ - clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE); - } - put_online_cpus(); -} -/*:*/ - -void __exit lguest_arch_host_fini(void) -{ - /* If we had PGE before we started, turn it back on now. */ - get_online_cpus(); - if (cpu_had_pge) { - set_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE); - /* adjust_pge's argument "1" means set PGE. */ - on_each_cpu(adjust_pge, (void *)1, 1); - } - put_online_cpus(); -} - - -/*H:122 The i386-specific hypercalls simply farm out to the right functions. */ -int lguest_arch_do_hcall(struct lg_cpu *cpu, struct hcall_args *args) -{ - switch (args->arg0) { - case LHCALL_LOAD_GDT_ENTRY: - load_guest_gdt_entry(cpu, args->arg1, args->arg2, args->arg3); - break; - case LHCALL_LOAD_IDT_ENTRY: - load_guest_idt_entry(cpu, args->arg1, args->arg2, args->arg3); - break; - case LHCALL_LOAD_TLS: - guest_load_tls(cpu, args->arg1); - break; - default: - /* Bad Guest. Bad! */ - return -EIO; - } - return 0; -} - -/*H:126 i386-specific hypercall initialization: */ -int lguest_arch_init_hypercalls(struct lg_cpu *cpu) -{ - u32 tsc_speed; - - /* - * The pointer to the Guest's "struct lguest_data" is the only argument. - * We check that address now. - */ - if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1, - sizeof(*cpu->lg->lguest_data))) - return -EFAULT; - - /* - * Having checked it, we simply set lg->lguest_data to point straight - * into the Launcher's memory at the right place and then use - * copy_to_user/from_user from now on, instead of lgread/write. I put - * this in to show that I'm not immune to writing stupid - * optimizations. - */ - cpu->lg->lguest_data = cpu->lg->mem_base + cpu->hcall->arg1; - - /* - * We insist that the Time Stamp Counter exist and doesn't change with - * cpu frequency. Some devious chip manufacturers decided that TSC - * changes could be handled in software. I decided that time going - * backwards might be good for benchmarks, but it's bad for users. - * - * We also insist that the TSC be stable: the kernel detects unreliable - * TSCs for its own purposes, and we use that here. - */ - if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable()) - tsc_speed = tsc_khz; - else - tsc_speed = 0; - if (put_user(tsc_speed, &cpu->lg->lguest_data->tsc_khz)) - return -EFAULT; - - /* The interrupt code might not like the system call vector. */ - if (!check_syscall_vector(cpu->lg)) - kill_guest(cpu, "bad syscall vector"); - - return 0; -} -/*:*/ - -/*L:030 - * Most of the Guest's registers are left alone: we used get_zeroed_page() to - * allocate the structure, so they will be 0. - */ -void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start) -{ - struct lguest_regs *regs = cpu->regs; - - /* - * There are four "segment" registers which the Guest needs to boot: - * The "code segment" register (cs) refers to the kernel code segment - * __KERNEL_CS, and the "data", "extra" and "stack" segment registers - * refer to the kernel data segment __KERNEL_DS. - * - * The privilege level is packed into the lower bits. The Guest runs - * at privilege level 1 (GUEST_PL). - */ - regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL; - regs->cs = __KERNEL_CS|GUEST_PL; - - /* - * The "eflags" register contains miscellaneous flags. Bit 1 (0x002) - * is supposed to always be "1". Bit 9 (0x200) controls whether - * interrupts are enabled. We always leave interrupts enabled while - * running the Guest. - */ - regs->eflags = X86_EFLAGS_IF | X86_EFLAGS_FIXED; - - /* - * The "Extended Instruction Pointer" register says where the Guest is - * running. - */ - regs->eip = start; - - /* - * %esi points to our boot information, at physical address 0, so don't - * touch it. - */ - - /* There are a couple of GDT entries the Guest expects at boot. */ - setup_guest_gdt(cpu); -} diff --git a/drivers/lguest/x86/switcher_32.S b/drivers/lguest/x86/switcher_32.S deleted file mode 100644 index 40634b0db9f7..000000000000 --- a/drivers/lguest/x86/switcher_32.S +++ /dev/null @@ -1,388 +0,0 @@ -/*P:900 - * This is the Switcher: code which sits at 0xFFC00000 (or 0xFFE00000) astride - * both the Host and Guest to do the low-level Guest<->Host switch. It is as - * simple as it can be made, but it's naturally very specific to x86. - * - * You have now completed Preparation. If this has whet your appetite; if you - * are feeling invigorated and refreshed then the next, more challenging stage - * can be found in "make Guest". - :*/ - -/*M:012 - * Lguest is meant to be simple: my rule of thumb is that 1% more LOC must - * gain at least 1% more performance. Since neither LOC nor performance can be - * measured beforehand, it generally means implementing a feature then deciding - * if it's worth it. And once it's implemented, who can say no? - * - * This is why I haven't implemented this idea myself. I want to, but I - * haven't. You could, though. - * - * The main place where lguest performance sucks is Guest page faulting. When - * a Guest userspace process hits an unmapped page we switch back to the Host, - * walk the page tables, find it's not mapped, switch back to the Guest page - * fault handler, which calls a hypercall to set the page table entry, then - * finally returns to userspace. That's two round-trips. - * - * If we had a small walker in the Switcher, we could quickly check the Guest - * page table and if the page isn't mapped, immediately reflect the fault back - * into the Guest. This means the Switcher would have to know the top of the - * Guest page table and the page fault handler address. - * - * For simplicity, the Guest should only handle the case where the privilege - * level of the fault is 3 and probably only not present or write faults. It - * should also detect recursive faults, and hand the original fault to the - * Host (which is actually really easy). - * - * Two questions remain. Would the performance gain outweigh the complexity? - * And who would write the verse documenting it? -:*/ - -/*M:011 - * Lguest64 handles NMI. This gave me NMI envy (until I looked at their - * code). It's worth doing though, since it would let us use oprofile in the - * Host when a Guest is running. -:*/ - -/*S:100 - * Welcome to the Switcher itself! - * - * This file contains the low-level code which changes the CPU to run the Guest - * code, and returns to the Host when something happens. Understand this, and - * you understand the heart of our journey. - * - * Because this is in assembler rather than C, our tale switches from prose to - * verse. First I tried limericks: - * - * There once was an eax reg, - * To which our pointer was fed, - * It needed an add, - * Which asm-offsets.h had - * But this limerick is hurting my head. - * - * Next I tried haikus, but fitting the required reference to the seasons in - * every stanza was quickly becoming tiresome: - * - * The %eax reg - * Holds "struct lguest_pages" now: - * Cherry blossoms fall. - * - * Then I started with Heroic Verse, but the rhyming requirement leeched away - * the content density and led to some uniquely awful oblique rhymes: - * - * These constants are coming from struct offsets - * For use within the asm switcher text. - * - * Finally, I settled for something between heroic hexameter, and normal prose - * with inappropriate linebreaks. Anyway, it aint no Shakespeare. - */ - -// Not all kernel headers work from assembler -// But these ones are needed: the ENTRY() define -// And constants extracted from struct offsets -// To avoid magic numbers and breakage: -// Should they change the compiler can't save us -// Down here in the depths of assembler code. -#include <linux/linkage.h> -#include <asm/asm-offsets.h> -#include <asm/page.h> -#include <asm/segment.h> -#include <asm/lguest.h> - -// We mark the start of the code to copy -// It's placed in .text tho it's never run here -// You'll see the trick macro at the end -// Which interleaves data and text to effect. -.text -ENTRY(start_switcher_text) - -// When we reach switch_to_guest we have just left -// The safe and comforting shores of C code -// %eax has the "struct lguest_pages" to use -// Where we save state and still see it from the Guest -// And %ebx holds the Guest shadow pagetable: -// Once set we have truly left Host behind. -ENTRY(switch_to_guest) - // We told gcc all its regs could fade, - // Clobbered by our journey into the Guest - // We could have saved them, if we tried - // But time is our master and cycles count. - - // Segment registers must be saved for the Host - // We push them on the Host stack for later - pushl %es - pushl %ds - pushl %gs - pushl %fs - // But the compiler is fickle, and heeds - // No warning of %ebp clobbers - // When frame pointers are used. That register - // Must be saved and restored or chaos strikes. - pushl %ebp - // The Host's stack is done, now save it away - // In our "struct lguest_pages" at offset - // Distilled into asm-offsets.h - movl %esp, LGUEST_PAGES_host_sp(%eax) - - // All saved and there's now five steps before us: - // Stack, GDT, IDT, TSS - // Then last of all the page tables are flipped. - - // Yet beware that our stack pointer must be - // Always valid lest an NMI hits - // %edx does the duty here as we juggle - // %eax is lguest_pages: our stack lies within. - movl %eax, %edx - addl $LGUEST_PAGES_regs, %edx - movl %edx, %esp - - // The Guest's GDT we so carefully - // Placed in the "struct lguest_pages" before - lgdt LGUEST_PAGES_guest_gdt_desc(%eax) - - // The Guest's IDT we did partially - // Copy to "struct lguest_pages" as well. - lidt LGUEST_PAGES_guest_idt_desc(%eax) - - // The TSS entry which controls traps - // Must be loaded up with "ltr" now: - // The GDT entry that TSS uses - // Changes type when we load it: damn Intel! - // For after we switch over our page tables - // That entry will be read-only: we'd crash. - movl $(GDT_ENTRY_TSS*8), %edx - ltr %dx - - // Look back now, before we take this last step! - // The Host's TSS entry was also marked used; - // Let's clear it again for our return. - // The GDT descriptor of the Host - // Points to the table after two "size" bytes - movl (LGUEST_PAGES_host_gdt_desc+2)(%eax), %edx - // Clear "used" from type field (byte 5, bit 2) - andb $0xFD, (GDT_ENTRY_TSS*8 + 5)(%edx) - - // Once our page table's switched, the Guest is live! - // The Host fades as we run this final step. - // Our "struct lguest_pages" is now read-only. - movl %ebx, %cr3 - - // The page table change did one tricky thing: - // The Guest's register page has been mapped - // Writable under our %esp (stack) -- - // We can simply pop off all Guest regs. - popl %eax - popl %ebx - popl %ecx - popl %edx - popl %esi - popl %edi - popl %ebp - popl %gs - popl %fs - popl %ds - popl %es - - // Near the base of the stack lurk two strange fields - // Which we fill as we exit the Guest - // These are the trap number and its error - // We can simply step past them on our way. - addl $8, %esp - - // The last five stack slots hold return address - // And everything needed to switch privilege - // From Switcher's level 0 to Guest's 1, - // And the stack where the Guest had last left it. - // Interrupts are turned back on: we are Guest. - iret - -// We tread two paths to switch back to the Host -// Yet both must save Guest state and restore Host -// So we put the routine in a macro. -#define SWITCH_TO_HOST \ - /* We save the Guest state: all registers first \ - * Laid out just as "struct lguest_regs" defines */ \ - pushl %es; \ - pushl %ds; \ - pushl %fs; \ - pushl %gs; \ - pushl %ebp; \ - pushl %edi; \ - pushl %esi; \ - pushl %edx; \ - pushl %ecx; \ - pushl %ebx; \ - pushl %eax; \ - /* Our stack and our code are using segments \ - * Set in the TSS and IDT \ - * Yet if we were to touch data we'd use \ - * Whatever data segment the Guest had. \ - * Load the lguest ds segment for now. */ \ - movl $(LGUEST_DS), %eax; \ - movl %eax, %ds; \ - /* So where are we? Which CPU, which struct? \ - * The stack is our clue: our TSS starts \ - * It at the end of "struct lguest_pages". \ - * Or we may have stumbled while restoring \ - * Our Guest segment regs while in switch_to_guest, \ - * The fault pushed atop that part-unwound stack. \ - * If we round the stack down to the page start \ - * We're at the start of "struct lguest_pages". */ \ - movl %esp, %eax; \ - andl $(~(1 << PAGE_SHIFT - 1)), %eax; \ - /* Save our trap number: the switch will obscure it \ - * (In the Host the Guest regs are not mapped here) \ - * %ebx holds it safe for deliver_to_host */ \ - movl LGUEST_PAGES_regs_trapnum(%eax), %ebx; \ - /* The Host GDT, IDT and stack! \ - * All these lie safely hidden from the Guest: \ - * We must return to the Host page tables \ - * (Hence that was saved in struct lguest_pages) */ \ - movl LGUEST_PAGES_host_cr3(%eax), %edx; \ - movl %edx, %cr3; \ - /* As before, when we looked back at the Host \ - * As we left and marked TSS unused \ - * So must we now for the Guest left behind. */ \ - andb $0xFD, (LGUEST_PAGES_guest_gdt+GDT_ENTRY_TSS*8+5)(%eax); \ - /* Switch to Host's GDT, IDT. */ \ - lgdt LGUEST_PAGES_host_gdt_desc(%eax); \ - lidt LGUEST_PAGES_host_idt_desc(%eax); \ - /* Restore the Host's stack where its saved regs lie */ \ - movl LGUEST_PAGES_host_sp(%eax), %esp; \ - /* Last the TSS: our Host is returned */ \ - movl $(GDT_ENTRY_TSS*8), %edx; \ - ltr %dx; \ - /* Restore now the regs saved right at the first. */ \ - popl %ebp; \ - popl %fs; \ - popl %gs; \ - popl %ds; \ - popl %es - -// The first path is trod when the Guest has trapped: -// (Which trap it was has been pushed on the stack). -// We need only switch back, and the Host will decode -// Why we came home, and what needs to be done. -return_to_host: - SWITCH_TO_HOST - iret - -// We are lead to the second path like so: -// An interrupt, with some cause external -// Has ajerked us rudely from the Guest's code -// Again we must return home to the Host -deliver_to_host: - SWITCH_TO_HOST - // But now we must go home via that place - // Where that interrupt was supposed to go - // Had we not been ensconced, running the Guest. - // Here we see the trickness of run_guest_once(): - // The Host stack is formed like an interrupt - // With EIP, CS and EFLAGS layered. - // Interrupt handlers end with "iret" - // And that will take us home at long long last. - - // But first we must find the handler to call! - // The IDT descriptor for the Host - // Has two bytes for size, and four for address: - // %edx will hold it for us for now. - movl (LGUEST_PAGES_host_idt_desc+2)(%eax), %edx - // We now know the table address we need, - // And saved the trap's number inside %ebx. - // Yet the pointer to the handler is smeared - // Across the bits of the table entry. - // What oracle can tell us how to extract - // From such a convoluted encoding? - // I consulted gcc, and it gave - // These instructions, which I gladly credit: - leal (%edx,%ebx,8), %eax - movzwl (%eax),%edx - movl 4(%eax), %eax - xorw %ax, %ax - orl %eax, %edx - // Now the address of the handler's in %edx - // We call it now: its "iret" drops us home. - jmp *%edx - -// Every interrupt can come to us here -// But we must truly tell each apart. -// They number two hundred and fifty six -// And each must land in a different spot, -// Push its number on stack, and join the stream. - -// And worse, a mere six of the traps stand apart -// And push on their stack an addition: -// An error number, thirty two bits long -// So we punish the other two fifty -// And make them push a zero so they match. - -// Yet two fifty six entries is long -// And all will look most the same as the last -// So we create a macro which can make -// As many entries as we need to fill. - -// Note the change to .data then .text: -// We plant the address of each entry -// Into a (data) table for the Host -// To know where each Guest interrupt should go. -.macro IRQ_STUB N TARGET - .data; .long 1f; .text; 1: - // Trap eight, ten through fourteen and seventeen - // Supply an error number. Else zero. - .if (\N <> 8) && (\N < 10 || \N > 14) && (\N <> 17) - pushl $0 - .endif - pushl $\N - jmp \TARGET - ALIGN -.endm - -// This macro creates numerous entries -// Using GAS macros which out-power C's. -.macro IRQ_STUBS FIRST LAST TARGET - irq=\FIRST - .rept \LAST-\FIRST+1 - IRQ_STUB irq \TARGET - irq=irq+1 - .endr -.endm - -// Here's the marker for our pointer table -// Laid in the data section just before -// Each macro places the address of code -// Forming an array: each one points to text -// Which handles interrupt in its turn. -.data -.global default_idt_entries -default_idt_entries: -.text - // The first two traps go straight back to the Host - IRQ_STUBS 0 1 return_to_host - // We'll say nothing, yet, about NMI - IRQ_STUB 2 handle_nmi - // Other traps also return to the Host - IRQ_STUBS 3 31 return_to_host - // All interrupts go via their handlers - IRQ_STUBS 32 127 deliver_to_host - // 'Cept system calls coming from userspace - // Are to go to the Guest, never the Host. - IRQ_STUB 128 return_to_host - IRQ_STUBS 129 255 deliver_to_host - -// The NMI, what a fabulous beast -// Which swoops in and stops us no matter that -// We're suspended between heaven and hell, -// (Or more likely between the Host and Guest) -// When in it comes! We are dazed and confused -// So we do the simplest thing which one can. -// Though we've pushed the trap number and zero -// We discard them, return, and hope we live. -handle_nmi: - addl $8, %esp - iret - -// We are done; all that's left is Mastery -// And "make Mastery" is a journey long -// Designed to make your fingers itch to code. - -// Here ends the text, the file and poem. -ENTRY(end_switcher_text) |