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 */ 212
