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 */
203
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