diff options
Diffstat (limited to 'tools/testing/selftests/x86/syscall_arg_fault.c')
| -rw-r--r-- | tools/testing/selftests/x86/syscall_arg_fault.c | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/tools/testing/selftests/x86/syscall_arg_fault.c b/tools/testing/selftests/x86/syscall_arg_fault.c new file mode 100644 index 000000000..bff474b5e --- /dev/null +++ b/tools/testing/selftests/x86/syscall_arg_fault.c @@ -0,0 +1,237 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * syscall_arg_fault.c - tests faults 32-bit fast syscall stack args + * Copyright (c) 2015 Andrew Lutomirski + */ + +#define _GNU_SOURCE + +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <sys/signal.h> +#include <sys/ucontext.h> +#include <err.h> +#include <setjmp.h> +#include <errno.h> + +#include "helpers.h" + +/* Our sigaltstack scratch space. */ +static unsigned char altstack_data[SIGSTKSZ]; + +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), + int flags) +{ + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); +} + +static volatile sig_atomic_t sig_traps; +static sigjmp_buf jmpbuf; + +static volatile sig_atomic_t n_errs; + +#ifdef __x86_64__ +#define REG_AX REG_RAX +#define REG_IP REG_RIP +#else +#define REG_AX REG_EAX +#define REG_IP REG_EIP +#endif + +static void sigsegv_or_sigbus(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t*)ctx_void; + long ax = (long)ctx->uc_mcontext.gregs[REG_AX]; + + if (ax != -EFAULT && ax != -ENOSYS) { + printf("[FAIL]\tAX had the wrong value: 0x%lx\n", + (unsigned long)ax); + printf("\tIP = 0x%lx\n", (unsigned long)ctx->uc_mcontext.gregs[REG_IP]); + n_errs++; + } else { + printf("[OK]\tSeems okay\n"); + } + + siglongjmp(jmpbuf, 1); +} + +static volatile sig_atomic_t sigtrap_consecutive_syscalls; + +static void sigtrap(int sig, siginfo_t *info, void *ctx_void) +{ + /* + * KVM has some bugs that can cause us to stop making progress. + * detect them and complain, but don't infinite loop or fail the + * test. + */ + + ucontext_t *ctx = (ucontext_t*)ctx_void; + unsigned short *ip = (unsigned short *)ctx->uc_mcontext.gregs[REG_IP]; + + if (*ip == 0x340f || *ip == 0x050f) { + /* The trap was on SYSCALL or SYSENTER */ + sigtrap_consecutive_syscalls++; + if (sigtrap_consecutive_syscalls > 3) { + printf("[WARN]\tGot stuck single-stepping -- you probably have a KVM bug\n"); + siglongjmp(jmpbuf, 1); + } + } else { + sigtrap_consecutive_syscalls = 0; + } +} + +static void sigill(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t*)ctx_void; + unsigned short *ip = (unsigned short *)ctx->uc_mcontext.gregs[REG_IP]; + + if (*ip == 0x0b0f) { + /* one of the ud2 instructions faulted */ + printf("[OK]\tSYSCALL returned normally\n"); + } else { + printf("[SKIP]\tIllegal instruction\n"); + } + siglongjmp(jmpbuf, 1); +} + +int main() +{ + stack_t stack = { + .ss_sp = altstack_data, + .ss_size = SIGSTKSZ, + }; + if (sigaltstack(&stack, NULL) != 0) + err(1, "sigaltstack"); + + sethandler(SIGSEGV, sigsegv_or_sigbus, SA_ONSTACK); + /* + * The actual exception can vary. On Atom CPUs, we get #SS + * instead of #PF when the vDSO fails to access the stack when + * ESP is too close to 2^32, and #SS causes SIGBUS. + */ + sethandler(SIGBUS, sigsegv_or_sigbus, SA_ONSTACK); + sethandler(SIGILL, sigill, SA_ONSTACK); + + /* + * Exercise another nasty special case. The 32-bit SYSCALL + * and SYSENTER instructions (even in compat mode) each + * clobber one register. A Linux system call has a syscall + * number and six arguments, and the user stack pointer + * needs to live in some register on return. That means + * that we need eight registers, but SYSCALL and SYSENTER + * only preserve seven registers. As a result, one argument + * ends up on the stack. The stack is user memory, which + * means that the kernel can fail to read it. + * + * The 32-bit fast system calls don't have a defined ABI: + * we're supposed to invoke them through the vDSO. So we'll + * fudge it: we set all regs to invalid pointer values and + * invoke the entry instruction. The return will fail no + * matter what, and we completely lose our program state, + * but we can fix it up with a signal handler. + */ + + printf("[RUN]\tSYSENTER with invalid state\n"); + if (sigsetjmp(jmpbuf, 1) == 0) { + asm volatile ( + "movl $-1, %%eax\n\t" + "movl $-1, %%ebx\n\t" + "movl $-1, %%ecx\n\t" + "movl $-1, %%edx\n\t" + "movl $-1, %%esi\n\t" + "movl $-1, %%edi\n\t" + "movl $-1, %%ebp\n\t" + "movl $-1, %%esp\n\t" + "sysenter" + : : : "memory", "flags"); + } + + printf("[RUN]\tSYSCALL with invalid state\n"); + if (sigsetjmp(jmpbuf, 1) == 0) { + asm volatile ( + "movl $-1, %%eax\n\t" + "movl $-1, %%ebx\n\t" + "movl $-1, %%ecx\n\t" + "movl $-1, %%edx\n\t" + "movl $-1, %%esi\n\t" + "movl $-1, %%edi\n\t" + "movl $-1, %%ebp\n\t" + "movl $-1, %%esp\n\t" + "syscall\n\t" + "ud2" /* make sure we recover cleanly */ + : : : "memory", "flags"); + } + + printf("[RUN]\tSYSENTER with TF and invalid state\n"); + sethandler(SIGTRAP, sigtrap, SA_ONSTACK); + + if (sigsetjmp(jmpbuf, 1) == 0) { + sigtrap_consecutive_syscalls = 0; + set_eflags(get_eflags() | X86_EFLAGS_TF); + asm volatile ( + "movl $-1, %%eax\n\t" + "movl $-1, %%ebx\n\t" + "movl $-1, %%ecx\n\t" + "movl $-1, %%edx\n\t" + "movl $-1, %%esi\n\t" + "movl $-1, %%edi\n\t" + "movl $-1, %%ebp\n\t" + "movl $-1, %%esp\n\t" + "sysenter" + : : : "memory", "flags"); + } + set_eflags(get_eflags() & ~X86_EFLAGS_TF); + + printf("[RUN]\tSYSCALL with TF and invalid state\n"); + if (sigsetjmp(jmpbuf, 1) == 0) { + sigtrap_consecutive_syscalls = 0; + set_eflags(get_eflags() | X86_EFLAGS_TF); + asm volatile ( + "movl $-1, %%eax\n\t" + "movl $-1, %%ebx\n\t" + "movl $-1, %%ecx\n\t" + "movl $-1, %%edx\n\t" + "movl $-1, %%esi\n\t" + "movl $-1, %%edi\n\t" + "movl $-1, %%ebp\n\t" + "movl $-1, %%esp\n\t" + "syscall\n\t" + "ud2" /* make sure we recover cleanly */ + : : : "memory", "flags"); + } + set_eflags(get_eflags() & ~X86_EFLAGS_TF); + +#ifdef __x86_64__ + printf("[RUN]\tSYSENTER with TF, invalid state, and GSBASE < 0\n"); + + if (sigsetjmp(jmpbuf, 1) == 0) { + sigtrap_consecutive_syscalls = 0; + + asm volatile ("wrgsbase %%rax\n\t" + :: "a" (0xffffffffffff0000UL)); + + set_eflags(get_eflags() | X86_EFLAGS_TF); + asm volatile ( + "movl $-1, %%eax\n\t" + "movl $-1, %%ebx\n\t" + "movl $-1, %%ecx\n\t" + "movl $-1, %%edx\n\t" + "movl $-1, %%esi\n\t" + "movl $-1, %%edi\n\t" + "movl $-1, %%ebp\n\t" + "movl $-1, %%esp\n\t" + "sysenter" + : : : "memory", "flags"); + } + set_eflags(get_eflags() & ~X86_EFLAGS_TF); +#endif + + return 0; +} |