212 lines
5 KiB
C
212 lines
5 KiB
C
/*
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* unwind_vdso.c - tests unwind info for AT_SYSINFO in the vDSO
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* Copyright (c) 2014-2015 Andrew Lutomirski
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* This tests __kernel_vsyscall's unwind info.
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*/
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#define _GNU_SOURCE
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#include <features.h>
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#include <stdio.h>
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#if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16
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int main()
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{
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/* We need getauxval(). */
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printf("[SKIP]\tGLIBC before 2.16 cannot compile this test\n");
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return 0;
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}
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#else
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#include <sys/time.h>
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#include <stdlib.h>
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#include <syscall.h>
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#include <unistd.h>
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#include <string.h>
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#include <inttypes.h>
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#include <sys/mman.h>
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#include <signal.h>
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#include <sys/ucontext.h>
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#include <err.h>
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#include <stddef.h>
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#include <stdbool.h>
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#include <sys/ptrace.h>
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#include <sys/user.h>
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#include <sys/ucontext.h>
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#include <link.h>
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#include <sys/auxv.h>
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#include <dlfcn.h>
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#include <unwind.h>
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static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
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int flags)
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{
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struct sigaction sa;
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memset(&sa, 0, sizeof(sa));
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sa.sa_sigaction = handler;
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sa.sa_flags = SA_SIGINFO | flags;
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sigemptyset(&sa.sa_mask);
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if (sigaction(sig, &sa, 0))
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err(1, "sigaction");
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}
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#ifdef __x86_64__
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# define WIDTH "q"
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#else
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# define WIDTH "l"
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#endif
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static unsigned long get_eflags(void)
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{
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unsigned long eflags;
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asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
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return eflags;
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}
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static void set_eflags(unsigned long eflags)
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{
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asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
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: : "rm" (eflags) : "flags");
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}
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#define X86_EFLAGS_TF (1UL << 8)
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static volatile sig_atomic_t nerrs;
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static unsigned long sysinfo;
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static bool got_sysinfo = false;
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static unsigned long return_address;
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struct unwind_state {
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unsigned long ip; /* trap source */
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int depth; /* -1 until we hit the trap source */
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};
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_Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
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{
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struct unwind_state *state = opaque;
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unsigned long ip = _Unwind_GetIP(ctx);
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if (state->depth == -1) {
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if (ip == state->ip)
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state->depth = 0;
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else
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return _URC_NO_REASON; /* Not there yet */
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}
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printf("\t 0x%lx\n", ip);
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if (ip == return_address) {
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/* Here we are. */
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unsigned long eax = _Unwind_GetGR(ctx, 0);
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unsigned long ecx = _Unwind_GetGR(ctx, 1);
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unsigned long edx = _Unwind_GetGR(ctx, 2);
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unsigned long ebx = _Unwind_GetGR(ctx, 3);
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unsigned long ebp = _Unwind_GetGR(ctx, 5);
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unsigned long esi = _Unwind_GetGR(ctx, 6);
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unsigned long edi = _Unwind_GetGR(ctx, 7);
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bool ok = (eax == SYS_getpid || eax == getpid()) &&
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ebx == 1 && ecx == 2 && edx == 3 &&
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esi == 4 && edi == 5 && ebp == 6;
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if (!ok)
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nerrs++;
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printf("[%s]\t NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
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(ok ? "OK" : "FAIL"),
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eax, ebx, ecx, edx, esi, edi, ebp);
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return _URC_NORMAL_STOP;
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} else {
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state->depth++;
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return _URC_NO_REASON;
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}
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}
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static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
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{
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ucontext_t *ctx = (ucontext_t *)ctx_void;
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struct unwind_state state;
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unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
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if (!got_sysinfo && ip == sysinfo) {
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got_sysinfo = true;
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/* Find the return address. */
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return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
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printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
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ip, return_address);
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}
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if (!got_sysinfo)
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return; /* Not there yet */
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if (ip == return_address) {
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ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
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printf("\tVsyscall is done\n");
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return;
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}
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printf("\tSIGTRAP at 0x%lx\n", ip);
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state.ip = ip;
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state.depth = -1;
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_Unwind_Backtrace(trace_fn, &state);
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}
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int main()
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{
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sysinfo = getauxval(AT_SYSINFO);
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printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
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Dl_info info;
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if (!dladdr((void *)sysinfo, &info)) {
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printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
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} else {
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printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
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info.dli_fname, info.dli_fbase);
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}
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sethandler(SIGTRAP, sigtrap, 0);
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syscall(SYS_getpid); /* Force symbol binding without TF set. */
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printf("[RUN]\tSet TF and check a fast syscall\n");
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set_eflags(get_eflags() | X86_EFLAGS_TF);
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syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
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if (!got_sysinfo) {
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set_eflags(get_eflags() & ~X86_EFLAGS_TF);
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/*
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* The most likely cause of this is that you're on Debian or
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* a Debian-based distro, you're missing libc6-i686, and you're
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* affected by libc/19006 (https://sourceware.org/PR19006).
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*/
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printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
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}
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if (get_eflags() & X86_EFLAGS_TF) {
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printf("[FAIL]\tTF is still set\n");
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nerrs++;
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}
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if (nerrs) {
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printf("[FAIL]\tThere were errors\n");
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return 1;
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} else {
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printf("[OK]\tAll is well\n");
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return 0;
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}
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}
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#endif /* New enough libc */
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