diff options
Diffstat (limited to 'arch/um/kernel/skas')
| -rw-r--r-- | arch/um/kernel/skas/.gitignore | 2 | ||||
| -rw-r--r-- | arch/um/kernel/skas/Makefile | 38 | ||||
| -rw-r--r-- | arch/um/kernel/skas/mmu.c | 28 | ||||
| -rw-r--r-- | arch/um/kernel/skas/process.c | 4 | ||||
| -rw-r--r-- | arch/um/kernel/skas/stub.c | 10 | ||||
| -rw-r--r-- | arch/um/kernel/skas/stub_exe.c | 95 | ||||
| -rw-r--r-- | arch/um/kernel/skas/stub_exe_embed.S | 11 |
7 files changed, 148 insertions, 40 deletions
diff --git a/arch/um/kernel/skas/.gitignore b/arch/um/kernel/skas/.gitignore new file mode 100644 index 000000000000..c3409ced0f38 --- /dev/null +++ b/arch/um/kernel/skas/.gitignore @@ -0,0 +1,2 @@ +stub_exe +stub_exe.dbg diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile index 6f86d53e3d69..3384be42691f 100644 --- a/arch/um/kernel/skas/Makefile +++ b/arch/um/kernel/skas/Makefile @@ -3,14 +3,48 @@ # Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) # -obj-y := stub.o mmu.o process.o syscall.o uaccess.o +obj-y := stub.o mmu.o process.o syscall.o uaccess.o \ + stub_exe_embed.o + +# Stub executable + +stub_exe_objs-y := stub_exe.o + +stub_exe_objs := $(foreach F,$(stub_exe_objs-y),$(obj)/$F) + +# Object file containing the ELF executable +$(obj)/stub_exe_embed.o: $(src)/stub_exe_embed.S $(obj)/stub_exe + +$(obj)/stub_exe.dbg: $(stub_exe_objs) FORCE + $(call if_changed,stub_exe) + +$(obj)/stub_exe: OBJCOPYFLAGS := -S +$(obj)/stub_exe: $(obj)/stub_exe.dbg FORCE + $(call if_changed,objcopy) + +quiet_cmd_stub_exe = STUB_EXE $@ + cmd_stub_exe = $(CC) -nostdlib -o $@ \ + $(filter-out $(UM_GPROF_OPT) $(UM_GCOV_OPT),$(KBUILD_CFLAGS)) $(STUB_EXE_LDFLAGS) \ + $(filter %.o,$^) + +STUB_EXE_LDFLAGS = -Wl,-n -static + +targets += stub_exe.dbg stub_exe $(stub_exe_objs-y) + +# end # stub.o is in the stub, so it can't be built with profiling # GCC hardened also auto-enables -fpic, but we need %ebx so it can't work -> # disable it CFLAGS_stub.o := $(CFLAGS_NO_HARDENING) -UNPROFILE_OBJS := stub.o +CFLAGS_stub_exe.o := $(CFLAGS_NO_HARDENING) + +# Clang will call memset() from __builtin_alloca() when stack variable +# initialization is enabled, which is used in stub_exe.c. +CFLAGS_stub_exe.o += $(call cc-option, -ftrivial-auto-var-init=uninitialized) + +UNPROFILE_OBJS := stub.o stub_exe.o KCOV_INSTRUMENT := n include $(srctree)/arch/um/scripts/Makefile.rules diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c index 886ed5e65674..0eb5a1d3ba70 100644 --- a/arch/um/kernel/skas/mmu.c +++ b/arch/um/kernel/skas/mmu.c @@ -40,35 +40,13 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm) goto out_free; } - /* - * Ensure the new MM is clean and nothing unwanted is mapped. - * - * TODO: We should clear the memory up to STUB_START to ensure there is - * nothing mapped there, i.e. we (currently) have: - * - * |- user memory -|- unused -|- stub -|- unused -| - * ^ TASK_SIZE ^ STUB_START - * - * Meaning we have two unused areas where we may still have valid - * mappings from our internal clone(). That isn't really a problem as - * userspace is not going to access them, but it is definitely not - * correct. - * - * However, we are "lucky" and if rseq is configured, then on 32 bit - * it will fall into the first empty range while on 64 bit it is going - * to use an anonymous mapping in the second range. As such, things - * continue to work for now as long as we don't start unmapping these - * areas. - * - * Change this to STUB_START once we have a clean userspace. - */ - unmap(new_id, 0, TASK_SIZE); + /* Ensure the new MM is clean and nothing unwanted is mapped */ + unmap(new_id, 0, STUB_START); return 0; out_free: - if (new_id->stack != 0) - free_pages(new_id->stack, ilog2(STUB_DATA_PAGES)); + free_pages(new_id->stack, ilog2(STUB_DATA_PAGES)); out: return ret; } diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c index 68657988c8d1..05dcdc057af9 100644 --- a/arch/um/kernel/skas/process.c +++ b/arch/um/kernel/skas/process.c @@ -22,15 +22,13 @@ static int __init start_kernel_proc(void *unused) { block_signals_trace(); - cpu_tasks[0].task = current; - start_kernel(); return 0; } extern int userspace_pid[]; -extern char cpu0_irqstack[]; +static char cpu0_irqstack[THREAD_SIZE] __aligned(THREAD_SIZE); int __init start_uml(void) { diff --git a/arch/um/kernel/skas/stub.c b/arch/um/kernel/skas/stub.c index 5d52ffa682dc..796fc266d3bb 100644 --- a/arch/um/kernel/skas/stub.c +++ b/arch/um/kernel/skas/stub.c @@ -35,16 +35,6 @@ static __always_inline int syscall_handler(struct stub_data *d) return -1; } break; - case STUB_SYSCALL_MPROTECT: - res = stub_syscall3(__NR_mprotect, - sc->mem.addr, sc->mem.length, - sc->mem.prot); - if (res) { - d->err = res; - d->syscall_data_len = i; - return -1; - } - break; default: d->err = -95; /* EOPNOTSUPP */ d->syscall_data_len = i; diff --git a/arch/um/kernel/skas/stub_exe.c b/arch/um/kernel/skas/stub_exe.c new file mode 100644 index 000000000000..23c99b285e82 --- /dev/null +++ b/arch/um/kernel/skas/stub_exe.c @@ -0,0 +1,95 @@ +#include <sys/ptrace.h> +#include <sys/prctl.h> +#include <asm/unistd.h> +#include <sysdep/stub.h> +#include <stub-data.h> + +void _start(void); + +noinline static void real_init(void) +{ + struct stub_init_data init_data; + unsigned long res; + struct { + void *ss_sp; + int ss_flags; + size_t ss_size; + } stack = { + .ss_size = STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, + }; + struct { + void *sa_handler_; + unsigned long sa_flags; + void *sa_restorer; + unsigned long long sa_mask; + } sa = { + /* Need to set SA_RESTORER (but the handler never returns) */ + .sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO | 0x04000000, + /* no need to mask any signals */ + .sa_mask = 0, + }; + + /* set a nice name */ + stub_syscall2(__NR_prctl, PR_SET_NAME, (unsigned long)"uml-userspace"); + + /* Make sure this process dies if the kernel dies */ + stub_syscall2(__NR_prctl, PR_SET_PDEATHSIG, SIGKILL); + + /* read information from STDIN and close it */ + res = stub_syscall3(__NR_read, 0, + (unsigned long)&init_data, sizeof(init_data)); + if (res != sizeof(init_data)) + stub_syscall1(__NR_exit, 10); + + stub_syscall1(__NR_close, 0); + + /* map stub code + data */ + res = stub_syscall6(STUB_MMAP_NR, + init_data.stub_start, UM_KERN_PAGE_SIZE, + PROT_READ | PROT_EXEC, MAP_FIXED | MAP_SHARED, + init_data.stub_code_fd, init_data.stub_code_offset); + if (res != init_data.stub_start) + stub_syscall1(__NR_exit, 11); + + res = stub_syscall6(STUB_MMAP_NR, + init_data.stub_start + UM_KERN_PAGE_SIZE, + STUB_DATA_PAGES * UM_KERN_PAGE_SIZE, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED, + init_data.stub_data_fd, init_data.stub_data_offset); + if (res != init_data.stub_start + UM_KERN_PAGE_SIZE) + stub_syscall1(__NR_exit, 12); + + /* setup signal stack inside stub data */ + stack.ss_sp = (void *)init_data.stub_start + UM_KERN_PAGE_SIZE; + stub_syscall2(__NR_sigaltstack, (unsigned long)&stack, 0); + + /* register SIGSEGV handler */ + sa.sa_handler_ = (void *) init_data.segv_handler; + res = stub_syscall4(__NR_rt_sigaction, SIGSEGV, (unsigned long)&sa, 0, + sizeof(sa.sa_mask)); + if (res != 0) + stub_syscall1(__NR_exit, 13); + + stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0); + + stub_syscall2(__NR_kill, stub_syscall0(__NR_getpid), SIGSTOP); + + stub_syscall1(__NR_exit, 14); + + __builtin_unreachable(); +} + +__attribute__((naked)) void _start(void) +{ + /* + * Since the stack after exec() starts at the top-most address, + * but that's exactly where we also want to map the stub data + * and code, this must: + * - push the stack by 1 code and STUB_DATA_PAGES data pages + * - call real_init() + * This way, real_init() can use the stack normally, while the + * original stack further down (higher address) will become + * inaccessible after the mmap() calls above. + */ + stub_start(real_init); +} diff --git a/arch/um/kernel/skas/stub_exe_embed.S b/arch/um/kernel/skas/stub_exe_embed.S new file mode 100644 index 000000000000..6d8914fbe8f1 --- /dev/null +++ b/arch/um/kernel/skas/stub_exe_embed.S @@ -0,0 +1,11 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <linux/init.h> +#include <linux/linkage.h> + +__INITDATA + +SYM_DATA_START(stub_exe_start) + .incbin "arch/um/kernel/skas/stub_exe" +SYM_DATA_END_LABEL(stub_exe_start, SYM_L_GLOBAL, stub_exe_end) + +__FINIT |