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Linux/tools/testing/selftests/x86/unwind_vdso.c

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  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 

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