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Diffstat (limited to 'drivers/lguest/x86/core.c')
| -rw-r--r-- | drivers/lguest/x86/core.c | 718 |
1 files changed, 0 insertions, 718 deletions
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); -} |