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 volatile sig_atomic_t nerrs; 47 static unsigned long sysinfo; 48 static bool got_sysinfo = false; 49 static unsigned long return_address; 50 51 struct unwind_state { 52 unsigned long ip; /* trap source */ 53 int depth; /* -1 until we hit the trap source */ 54 }; 55 56 _Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque) 57 { 58 struct unwind_state *state = opaque; 59 unsigned long ip = _Unwind_GetIP(ctx); 60 61 if (state->depth == -1) { 62 if (ip == state->ip) 63 state->depth = 0; 64 else 65 return _URC_NO_REASON; /* Not there yet */ 66 } 67 printf("\t 0x%lx\n", ip); 68 69 if (ip == return_address) { 70 /* Here we are. */ 71 unsigned long eax = _Unwind_GetGR(ctx, 0); 72 unsigned long ecx = _Unwind_GetGR(ctx, 1); 73 unsigned long edx = _Unwind_GetGR(ctx, 2); 74 unsigned long ebx = _Unwind_GetGR(ctx, 3); 75 unsigned long ebp = _Unwind_GetGR(ctx, 5); 76 unsigned long esi = _Unwind_GetGR(ctx, 6); 77 unsigned long edi = _Unwind_GetGR(ctx, 7); 78 bool ok = (eax == SYS_getpid || eax == getpid()) && 79 ebx == 1 && ecx == 2 && edx == 3 && 80 esi == 4 && edi == 5 && ebp == 6; 81 82 if (!ok) 83 nerrs++; 84 printf("[%s]\t NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n", 85 (ok ? "OK" : "FAIL"), 86 eax, ebx, ecx, edx, esi, edi, ebp); 87 88 return _URC_NORMAL_STOP; 89 } else { 90 state->depth++; 91 return _URC_NO_REASON; 92 } 93 } 94 95 static void sigtrap(int sig, siginfo_t *info, void *ctx_void) 96 { 97 ucontext_t *ctx = (ucontext_t *)ctx_void; 98 struct unwind_state state; 99 unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP]; 100 101 if (!got_sysinfo && ip == sysinfo) { 102 got_sysinfo = true; 103 104 /* Find the return address. */ 105 return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP]; 106 107 printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n", 108 ip, return_address); 109 } 110 111 if (!got_sysinfo) 112 return; /* Not there yet */ 113 114 if (ip == return_address) { 115 ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF; 116 printf("\tVsyscall is done\n"); 117 return; 118 } 119 120 printf("\tSIGTRAP at 0x%lx\n", ip); 121 122 state.ip = ip; 123 state.depth = -1; 124 _Unwind_Backtrace(trace_fn, &state); 125 } 126 127 int main() 128 { 129 sysinfo = getauxval(AT_SYSINFO); 130 printf("\tAT_SYSINFO is 0x%lx\n", sysinfo); 131 132 Dl_info info; 133 if (!dladdr((void *)sysinfo, &info)) { 134 printf("[WARN]\tdladdr failed on AT_SYSINFO\n"); 135 } else { 136 printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n", 137 info.dli_fname, info.dli_fbase); 138 } 139 140 sethandler(SIGTRAP, sigtrap, 0); 141 142 syscall(SYS_getpid); /* Force symbol binding without TF set. */ 143 printf("[RUN]\tSet TF and check a fast syscall\n"); 144 set_eflags(get_eflags() | X86_EFLAGS_TF); 145 syscall(SYS_getpid, 1, 2, 3, 4, 5, 6); 146 if (!got_sysinfo) { 147 set_eflags(get_eflags() & ~X86_EFLAGS_TF); 148 149 /* 150 * The most likely cause of this is that you're on Debian or 151 * a Debian-based distro, you're missing libc6-i686, and you're 152 * affected by libc/19006 (https://sourceware.org/PR19006). 153 */ 154 printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n"); 155 } 156 157 if (get_eflags() & X86_EFLAGS_TF) { 158 printf("[FAIL]\tTF is still set\n"); 159 nerrs++; 160 } 161 162 if (nerrs) { 163 printf("[FAIL]\tThere were errors\n"); 164 return 1; 165 } else { 166 printf("[OK]\tAll is well\n"); 167 return 0; 168 } 169 } 170 171 #endif /* New enough libc */ 172