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 */ 211