tools/testing/selftests/x86/unwind_vdso.c

   1 /*
   2  * unwind_vdso.c - tests unwind info for AT_SYSINFO in the vDSO
   3  * Copyright (c) 2014-2015 Andrew Lutomirski
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms and conditions of the GNU General Public License,
   7  * version 2, as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * This tests __kernel_vsyscall's unwind info.
  15  */
  16
  17 #define _GNU_SOURCE
  18
  19 #include <features.h>
  20 #include <stdio.h>
  21
  22 #if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16
  23
  24 int main()
  25 {
  26         /* We need getauxval(). */
  27         printf("[SKIP]\tGLIBC before 2.16 cannot compile this test\n");
  28         return 0;
  29 }
  30
  31 #else
  32
  33 #include <sys/time.h>
  34 #include <stdlib.h>
  35 #include <syscall.h>
  36 #include <unistd.h>
  37 #include <string.h>
  38 #include <inttypes.h>
  39 #include <sys/mman.h>
  40 #include <signal.h>
  41 #include <sys/ucontext.h>
  42 #include <err.h>
  43 #include <stddef.h>
  44 #include <stdbool.h>
  45 #include <sys/ptrace.h>
  46 #include <sys/user.h>
  47 #include <sys/ucontext.h>
  48 #include <link.h>
  49 #include <sys/auxv.h>
  50 #include <dlfcn.h>
  51 #include <unwind.h>
  52
  53 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  54                        int flags)
  55 {
  56         struct sigaction sa;
  57         memset(&sa, 0, sizeof(sa));
  58         sa.sa_sigaction = handler;
  59         sa.sa_flags = SA_SIGINFO | flags;
  60         sigemptyset(&sa.sa_mask);
  61         if (sigaction(sig, &sa, 0))
  62                 err(1, "sigaction");
  63 }
  64
  65 #ifdef __x86_64__
  66 # define WIDTH "q"
  67 #else
  68 # define WIDTH "l"
  69 #endif
  70
  71 static unsigned long get_eflags(void)
  72 {
  73         unsigned long eflags;
  74         asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
  75         return eflags;
  76 }
  77
  78 static void set_eflags(unsigned long eflags)
  79 {
  80         asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
  81                       : : "rm" (eflags) : "flags");
  82 }
  83
  84 #define X86_EFLAGS_TF (1UL << 8)
  85
  86 static volatile sig_atomic_t nerrs;
  87 static unsigned long sysinfo;
  88 static bool got_sysinfo = false;
  89 static unsigned long return_address;
  90
  91 struct unwind_state {
  92         unsigned long ip;       /* trap source */
  93         int depth;              /* -1 until we hit the trap source */
  94 };
  95
  96 _Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
  97 {
  98         struct unwind_state *state = opaque;
  99         unsigned long ip = _Unwind_GetIP(ctx);
 100
 101         if (state->depth == -1) {
 102                 if (ip == state->ip)
 103                         state->depth = 0;
 104                 else
 105                         return _URC_NO_REASON;  /* Not there yet */
 106         }
 107         printf("\t  0x%lx\n", ip);
 108
 109         if (ip == return_address) {
 110                 /* Here we are. */
 111                 unsigned long eax = _Unwind_GetGR(ctx, 0);
 112                 unsigned long ecx = _Unwind_GetGR(ctx, 1);
 113                 unsigned long edx = _Unwind_GetGR(ctx, 2);
 114                 unsigned long ebx = _Unwind_GetGR(ctx, 3);
 115                 unsigned long ebp = _Unwind_GetGR(ctx, 5);
 116                 unsigned long esi = _Unwind_GetGR(ctx, 6);
 117                 unsigned long edi = _Unwind_GetGR(ctx, 7);
 118                 bool ok = (eax == SYS_getpid || eax == getpid()) &&
 119                         ebx == 1 && ecx == 2 && edx == 3 &&
 120                         esi == 4 && edi == 5 && ebp == 6;
 121
 122                 if (!ok)
 123                         nerrs++;
 124                 printf("[%s]\t  NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
 125                        (ok ? "OK" : "FAIL"),
 126                        eax, ebx, ecx, edx, esi, edi, ebp);
 127
 128                 return _URC_NORMAL_STOP;
 129         } else {
 130                 state->depth++;
 131                 return _URC_NO_REASON;
 132         }
 133 }
 134
 135 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
 136 {
 137         ucontext_t *ctx = (ucontext_t *)ctx_void;
 138         struct unwind_state state;
 139         unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
 140
 141         if (!got_sysinfo && ip == sysinfo) {
 142                 got_sysinfo = true;
 143
 144                 /* Find the return address. */
 145                 return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
 146
 147                 printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
 148                        ip, return_address);
 149         }
 150
 151         if (!got_sysinfo)
 152                 return;         /* Not there yet */
 153
 154         if (ip == return_address) {
 155                 ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
 156                 printf("\tVsyscall is done\n");
 157                 return;
 158         }
 159
 160         printf("\tSIGTRAP at 0x%lx\n", ip);
 161
 162         state.ip = ip;
 163         state.depth = -1;
 164         _Unwind_Backtrace(trace_fn, &state);
 165 }
 166
 167 int main()
 168 {
 169         sysinfo = getauxval(AT_SYSINFO);
 170         printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
 171
 172         Dl_info info;
 173         if (!dladdr((void *)sysinfo, &info)) {
 174                 printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
 175         } else {
 176                 printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
 177                        info.dli_fname, info.dli_fbase);
 178         }
 179
 180         sethandler(SIGTRAP, sigtrap, 0);
 181
 182         syscall(SYS_getpid);  /* Force symbol binding without TF set. */
 183         printf("[RUN]\tSet TF and check a fast syscall\n");
 184         set_eflags(get_eflags() | X86_EFLAGS_TF);
 185         syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
 186         if (!got_sysinfo) {
 187                 set_eflags(get_eflags() & ~X86_EFLAGS_TF);
 188
 189                 /*
 190                  * The most likely cause of this is that you're on Debian or
 191                  * a Debian-based distro, you're missing libc6-i686, and you're
 192                  * affected by libc/19006 (https://sourceware.org/PR19006).
 193                  */
 194                 printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
 195         }
 196
 197         if (get_eflags() & X86_EFLAGS_TF) {
 198                 printf("[FAIL]\tTF is still set\n");
 199                 nerrs++;
 200         }
 201
 202         if (nerrs) {
 203                 printf("[FAIL]\tThere were errors\n");
 204                 return 1;
 205         } else {
 206                 printf("[OK]\tAll is well\n");
 207                 return 0;
 208         }
 209 }
 210
 211 #endif  /* New enough libc */