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
18int 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
46static 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
58static volatile sig_atomic_t nerrs;
59static unsigned long sysinfo;
60static bool got_sysinfo = false;
61static unsigned long return_address;
62
63struct unwind_state {
64	unsigned long ip;	/* trap source */
65	int depth;		/* -1 until we hit the trap source */
66};
67
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
107static 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
139int 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