tools/testing/selftests/x86/unwind_vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * unwind_vdso.c - tests unwind info for AT_SYSINFO in the vDSO
   4  * Copyright (c) 2014-2015 Andrew Lutomirski
   5  *
   6  * This tests __kernel_vsyscall's unwind info.
   7  */
   8
   9 #define _GNU_SOURCE
  10
  11 #include <features.h>
  12 #include <stdio.h>
  13
  14 #include "helpers.h"
  15
  16 #if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ < 16
  17
  18 int main()
  19 {
  20         /* We need getauxval(). */
  21         printf("[SKIP]\tGLIBC before 2.16 cannot compile this test\n");
  22         return 0;
  23 }
  24
  25 #else
  26
  27 #include <sys/time.h>
  28 #include <stdlib.h>
  29 #include <syscall.h>
  30 #include <unistd.h>
  31 #include <string.h>
  32 #include <inttypes.h>
  33 #include <sys/mman.h>
  34 #include <signal.h>
  35 #include <sys/ucontext.h>
  36 #include <err.h>
  37 #include <stddef.h>
  38 #include <stdbool.h>
  39 #include <sys/ptrace.h>
  40 #include <sys/user.h>
  41 #include <link.h>
  42 #include <sys/auxv.h>
  43 #include <dlfcn.h>
  44 #include <unwind.h>
  45
  46 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  47                        int flags)
  48 {
  49         struct sigaction sa;
  50         memset(&sa, 0, sizeof(sa));
  51         sa.sa_sigaction = handler;
  52         sa.sa_flags = SA_SIGINFO | flags;
  53         sigemptyset(&sa.sa_mask);
  54         if (sigaction(sig, &sa, 0))
  55                 err(1, "sigaction");
  56 }
  57
  58 static volatile sig_atomic_t nerrs;
  59 static unsigned long sysinfo;
  60 static bool got_sysinfo = false;
  61 static unsigned long return_address;
  62
  63 struct unwind_state {
  64         unsigned long ip;       /* trap source */
  65         int depth;              /* -1 until we hit the trap source */
  66 };
  67
  68 _Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
  69 {
  70         struct unwind_state *state = opaque;
  71         unsigned long ip = _Unwind_GetIP(ctx);
  72
  73         if (state->depth == -1) {
  74                 if (ip == state->ip)
  75                         state->depth = 0;
  76                 else
  77                         return _URC_NO_REASON;  /* Not there yet */
  78         }
  79         printf("\t  0x%lx\n", ip);
  80
  81         if (ip == return_address) {
  82                 /* Here we are. */
  83                 unsigned long eax = _Unwind_GetGR(ctx, 0);
  84                 unsigned long ecx = _Unwind_GetGR(ctx, 1);
  85                 unsigned long edx = _Unwind_GetGR(ctx, 2);
  86                 unsigned long ebx = _Unwind_GetGR(ctx, 3);
  87                 unsigned long ebp = _Unwind_GetGR(ctx, 5);
  88                 unsigned long esi = _Unwind_GetGR(ctx, 6);
  89                 unsigned long edi = _Unwind_GetGR(ctx, 7);
  90                 bool ok = (eax == SYS_getpid || eax == getpid()) &&
  91                         ebx == 1 && ecx == 2 && edx == 3 &&
  92                         esi == 4 && edi == 5 && ebp == 6;
  93
  94                 if (!ok)
  95                         nerrs++;
  96                 printf("[%s]\t  NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
  97                        (ok ? "OK" : "FAIL"),
  98                        eax, ebx, ecx, edx, esi, edi, ebp);
  99
 100                 return _URC_NORMAL_STOP;
 101         } else {
 102                 state->depth++;
 103                 return _URC_NO_REASON;
 104         }
 105 }
 106
 107 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
 108 {
 109         ucontext_t *ctx = (ucontext_t *)ctx_void;
 110         struct unwind_state state;
 111         unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
 112
 113         if (!got_sysinfo && ip == sysinfo) {
 114                 got_sysinfo = true;
 115
 116                 /* Find the return address. */
 117                 return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
 118
 119                 printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
 120                        ip, return_address);
 121         }
 122
 123         if (!got_sysinfo)
 124                 return;         /* Not there yet */
 125
 126         if (ip == return_address) {
 127                 ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
 128                 printf("\tVsyscall is done\n");
 129                 return;
 130         }
 131
 132         printf("\tSIGTRAP at 0x%lx\n", ip);
 133
 134         state.ip = ip;
 135         state.depth = -1;
 136         _Unwind_Backtrace(trace_fn, &state);
 137 }
 138
 139 int main()
 140 {
 141         sysinfo = getauxval(AT_SYSINFO);
 142         printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
 143
 144         Dl_info info;
 145         if (!dladdr((void *)sysinfo, &info)) {
 146                 printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
 147         } else {
 148                 printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
 149                        info.dli_fname, info.dli_fbase);
 150         }
 151
 152         sethandler(SIGTRAP, sigtrap, 0);
 153
 154         syscall(SYS_getpid);  /* Force symbol binding without TF set. */
 155         printf("[RUN]\tSet TF and check a fast syscall\n");
 156         set_eflags(get_eflags() | X86_EFLAGS_TF);
 157         syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
 158         if (!got_sysinfo) {
 159                 set_eflags(get_eflags() & ~X86_EFLAGS_TF);
 160
 161                 /*
 162                  * The most likely cause of this is that you're on Debian or
 163                  * a Debian-based distro, you're missing libc6-i686, and you're
 164                  * affected by libc/19006 (https://sourceware.org/PR19006).
 165                  */
 166                 printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
 167         }
 168
 169         if (get_eflags() & X86_EFLAGS_TF) {
 170                 printf("[FAIL]\tTF is still set\n");
 171                 nerrs++;
 172         }
 173
 174         if (nerrs) {
 175                 printf("[FAIL]\tThere were errors\n");
 176                 return 1;
 177         } else {
 178                 printf("[OK]\tAll is well\n");
 179                 return 0;
 180         }
 181 }
 182
 183 #endif  /* New enough libc */