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 
main()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 
sethandler(int sig,void (* handler)(int,siginfo_t *,void *),int flags)46 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
47 		       int flags)
48 {
49 	struct sigaction sa;
50 	memset(&sa, 0, sizeof(sa));
51 	sa.sa_sigaction = handler;
52 	sa.sa_flags = SA_SIGINFO | flags;
53 	sigemptyset(&sa.sa_mask);
54 	if (sigaction(sig, &sa, 0))
55 		err(1, "sigaction");
56 }
57 
58 static volatile sig_atomic_t nerrs;
59 static unsigned long sysinfo;
60 static bool got_sysinfo = false;
61 static unsigned long return_address;
62 
63 struct unwind_state {
64 	unsigned long ip;	/* trap source */
65 	int depth;		/* -1 until we hit the trap source */
66 };
67 
trace_fn(struct _Unwind_Context * ctx,void * opaque)68 _Unwind_Reason_Code trace_fn(struct _Unwind_Context * ctx, void *opaque)
69 {
70 	struct unwind_state *state = opaque;
71 	unsigned long ip = _Unwind_GetIP(ctx);
72 
73 	if (state->depth == -1) {
74 		if (ip == state->ip)
75 			state->depth = 0;
76 		else
77 			return _URC_NO_REASON;	/* Not there yet */
78 	}
79 	printf("\t  0x%lx\n", ip);
80 
81 	if (ip == return_address) {
82 		/* Here we are. */
83 		unsigned long eax = _Unwind_GetGR(ctx, 0);
84 		unsigned long ecx = _Unwind_GetGR(ctx, 1);
85 		unsigned long edx = _Unwind_GetGR(ctx, 2);
86 		unsigned long ebx = _Unwind_GetGR(ctx, 3);
87 		unsigned long ebp = _Unwind_GetGR(ctx, 5);
88 		unsigned long esi = _Unwind_GetGR(ctx, 6);
89 		unsigned long edi = _Unwind_GetGR(ctx, 7);
90 		bool ok = (eax == SYS_getpid || eax == getpid()) &&
91 			ebx == 1 && ecx == 2 && edx == 3 &&
92 			esi == 4 && edi == 5 && ebp == 6;
93 
94 		if (!ok)
95 			nerrs++;
96 		printf("[%s]\t  NR = %ld, args = %ld, %ld, %ld, %ld, %ld, %ld\n",
97 		       (ok ? "OK" : "FAIL"),
98 		       eax, ebx, ecx, edx, esi, edi, ebp);
99 
100 		return _URC_NORMAL_STOP;
101 	} else {
102 		state->depth++;
103 		return _URC_NO_REASON;
104 	}
105 }
106 
sigtrap(int sig,siginfo_t * info,void * ctx_void)107 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
108 {
109 	ucontext_t *ctx = (ucontext_t *)ctx_void;
110 	struct unwind_state state;
111 	unsigned long ip = ctx->uc_mcontext.gregs[REG_EIP];
112 
113 	if (!got_sysinfo && ip == sysinfo) {
114 		got_sysinfo = true;
115 
116 		/* Find the return address. */
117 		return_address = *(unsigned long *)(unsigned long)ctx->uc_mcontext.gregs[REG_ESP];
118 
119 		printf("\tIn vsyscall at 0x%lx, returning to 0x%lx\n",
120 		       ip, return_address);
121 	}
122 
123 	if (!got_sysinfo)
124 		return;		/* Not there yet */
125 
126 	if (ip == return_address) {
127 		ctx->uc_mcontext.gregs[REG_EFL] &= ~X86_EFLAGS_TF;
128 		printf("\tVsyscall is done\n");
129 		return;
130 	}
131 
132 	printf("\tSIGTRAP at 0x%lx\n", ip);
133 
134 	state.ip = ip;
135 	state.depth = -1;
136 	_Unwind_Backtrace(trace_fn, &state);
137 }
138 
main()139 int main()
140 {
141 	sysinfo = getauxval(AT_SYSINFO);
142 	printf("\tAT_SYSINFO is 0x%lx\n", sysinfo);
143 
144 	Dl_info info;
145 	if (!dladdr((void *)sysinfo, &info)) {
146 		printf("[WARN]\tdladdr failed on AT_SYSINFO\n");
147 	} else {
148 		printf("[OK]\tAT_SYSINFO maps to %s, loaded at 0x%p\n",
149 		       info.dli_fname, info.dli_fbase);
150 	}
151 
152 	sethandler(SIGTRAP, sigtrap, 0);
153 
154 	syscall(SYS_getpid);  /* Force symbol binding without TF set. */
155 	printf("[RUN]\tSet TF and check a fast syscall\n");
156 	set_eflags(get_eflags() | X86_EFLAGS_TF);
157 	syscall(SYS_getpid, 1, 2, 3, 4, 5, 6);
158 	if (!got_sysinfo) {
159 		set_eflags(get_eflags() & ~X86_EFLAGS_TF);
160 
161 		/*
162 		 * The most likely cause of this is that you're on Debian or
163 		 * a Debian-based distro, you're missing libc6-i686, and you're
164 		 * affected by libc/19006 (https://sourceware.org/PR19006).
165 		 */
166 		printf("[WARN]\tsyscall(2) didn't enter AT_SYSINFO\n");
167 	}
168 
169 	if (get_eflags() & X86_EFLAGS_TF) {
170 		printf("[FAIL]\tTF is still set\n");
171 		nerrs++;
172 	}
173 
174 	if (nerrs) {
175 		printf("[FAIL]\tThere were errors\n");
176 		return 1;
177 	} else {
178 		printf("[OK]\tAll is well\n");
179 		return 0;
180 	}
181 }
182 
183 #endif	/* New enough libc */
184