diff options
Diffstat (limited to 'tools/testing/selftests/x86/syscall_arg_fault.c')
| -rw-r--r-- | tools/testing/selftests/x86/syscall_arg_fault.c | 130 |
1 files changed, 130 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 000000000000..7db4fc9fa09f --- /dev/null +++ b/tools/testing/selftests/x86/syscall_arg_fault.c @@ -0,0 +1,130 @@ +/* + * syscall_arg_fault.c - tests faults 32-bit fast syscall stack args + * Copyright (c) 2015 Andrew Lutomirski + * + * This program is free software; you can redistribute it and/or modify + * it under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope 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. + */ + +#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> + +/* 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; + +static void sigsegv(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t*)ctx_void; + + if (ctx->uc_mcontext.gregs[REG_EAX] != -EFAULT) { + printf("[FAIL]\tAX had the wrong value: 0x%x\n", + ctx->uc_mcontext.gregs[REG_EAX]); + n_errs++; + } else { + printf("[OK]\tSeems okay\n"); + } + + siglongjmp(jmpbuf, 1); +} + +static void sigill(int sig, siginfo_t *info, void *ctx_void) +{ + 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, 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" + "pushl $0" /* make sure we segfault cleanly */ + : : : "memory", "flags"); + } + + return 0; +} |