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