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 <link.h>
  48 #include <sys/auxv.h>
  49 #include <dlfcn.h>
  50 #include <unwind.h>
  51
  52 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  53                        int flags)
  54 {
  55         struct sigaction sa;
  56         memset(&sa, 0, sizeof(sa));
  57         sa.sa_sigaction = handler;
  58         sa.sa_flags = SA_SIGINFO | flags;
  59         sigemptyset(&sa.sa_mask);
  60         if (sigaction(sig, &sa, 0))
  61                 err(1, "sigaction");
  62 }
  63
  64 #ifdef __x86_64__
  65 # define WIDTH "q"
  66 #else
  67 # define WIDTH "l"
  68 #endif
  69
  70 static unsigned long get_eflags(void)
  71 {
  72         unsigned long eflags;
  73         asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
  74         return eflags;
  75 }
  76
  77 static void set_eflags(unsigned long eflags)
  78 {
  79         asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
  80                       : : "rm" (eflags) : "flags");
  81 }
  82
  83 #define X86_EFLAGS_TF (1UL << 8)
  84
  85 static volatile sig_atomic_t nerrs;
  86 static unsigned long sysinfo;
  87 static bool got_sysinfo = false;
  88 static unsigned long return_address;
  89
  90 struct unwind_state {
  91         unsigned long ip;       /* trap source */
  92         int depth;              /* -1 until we hit the trap source */
  93 };
  94
  95 _Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
  96 {
  97         struct unwind_state *state = opaque;
  98         unsigned long ip = _Unwind_GetIP(ctx);
  99
 100         if (state->depth == -1) {
 101                 if (ip == state->ip)
 102                         state->depth = 0;
 103                 else
 104                         return _URC_NO_REASON;  /* Not there yet */
 105         }
 106         printf("\t  0x%lx\n", ip);
 107
 108         if (ip == return_address) {
 109                 /* Here we are. */
 110                 unsigned long eax = _Unwind_GetGR(ctx, 0);
 111                 unsigned long ecx = _Unwind_GetGR(ctx, 1);
 112                 unsigned long edx = _Unwind_GetGR(ctx, 2);
 113                 unsigned long ebx = _Unwind_GetGR(ctx, 3);
 114                 unsigned long ebp = _Unwind_GetGR(ctx, 5);
 115                 unsigned long esi = _Unwind_GetGR(ctx, 6);
 116                 unsigned long edi = _Unwind_GetGR(ctx, 7);
 117                 bool ok = (eax == SYS_getpid || eax == getpid()) &&
 118                         ebx == 1 && ecx == 2 && edx == 3 &&
 119                         esi == 4 && edi == 5 && ebp == 6;
 120
 121                 if (!ok)
 122                         nerrs++;
 123                 printf("[%s]\t  NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
 124                        (ok ? "OK" : "FAIL"),
 125                        eax, ebx, ecx, edx, esi, edi, ebp);
 126
 127                 return _URC_NORMAL_STOP;
 128         } else {
 129                 state->depth++;
 130                 return _URC_NO_REASON;
 131         }
 132 }
 133
 134 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
 135 {
 136         ucontext_t *ctx = (ucontext_t *)ctx_void;
 137         struct unwind_state state;
 138         unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
 139
 140         if (!got_sysinfo && ip == sysinfo) {
 141                 got_sysinfo = true;
 142
 143                 /* Find the return address. */
 144                 return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
 145
 146                 printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
 147                        ip, return_address);
 148         }
 149
 150         if (!got_sysinfo)
 151                 return;         /* Not there yet */
 152
 153         if (ip == return_address) {
 154                 ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
 155                 printf("\tVsyscall is done\n");
 156                 return;
 157         }
 158
 159         printf("\tSIGTRAP at 0x%lx\n", ip);
 160
 161         state.ip = ip;
 162         state.depth = -1;
 163         _Unwind_Backtrace(trace_fn, &state);
 164 }
 165
 166 int main()
 167 {
 168         sysinfo = getauxval(AT_SYSINFO);
 169         printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
 170
 171         Dl_info info;
 172         if (!dladdr((void *)sysinfo, &info)) {
 173                 printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
 174         } else {
 175                 printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
 176                        info.dli_fname, info.dli_fbase);
 177         }
 178
 179         sethandler(SIGTRAP, sigtrap, 0);
 180
 181         syscall(SYS_getpid);  /* Force symbol binding without TF set. */
 182         printf("[RUN]\tSet TF and check a fast syscall\n");
 183         set_eflags(get_eflags() | X86_EFLAGS_TF);
 184         syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
 185         if (!got_sysinfo) {
 186                 set_eflags(get_eflags() & ~X86_EFLAGS_TF);
 187
 188                 /*
 189                  * The most likely cause of this is that you're on Debian or
 190                  * a Debian-based distro, you're missing libc6-i686, and you're
 191                  * affected by libc/19006 (https://sourceware.org/PR19006).
 192                  */
 193                 printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
 194         }
 195
 196         if (get_eflags() & X86_EFLAGS_TF) {
 197                 printf("[FAIL]\tTF is still set\n");
 198                 nerrs++;
 199         }
 200
 201         if (nerrs) {
 202                 printf("[FAIL]\tThere were errors\n");
 203                 return 1;
 204         } else {
 205                 printf("[OK]\tAll is well\n");
 206                 return 0;
 207         }
 208 }
 209
 210 #endif  /* New enough libc */