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 
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 
trace_fn(struct _Unwind_Context * ctx,void * opaque)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 
sigtrap(int sig,siginfo_t * info,void * ctx_void)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 
main()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