1/*
2 * vdso_restorer.c - tests vDSO-based signal restore
3 * Copyright (c) 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 makes sure that sa_restorer == NULL keeps working on 32-bit
15 * configurations.  Modern glibc doesn't use it under any circumstances,
16 * so it's easy to overlook breakage.
17 *
18 * 64-bit userspace has never supported sa_restorer == NULL, so this is
19 * 32-bit only.
20 */
21
22#define _GNU_SOURCE
23
24#include <err.h>
25#include <stdio.h>
26#include <string.h>
27#include <signal.h>
28#include <unistd.h>
29#include <syscall.h>
30#include <sys/syscall.h>
31
32/* Open-code this -- the headers are too messy to easily use them. */
33struct real_sigaction {
34	void *handler;
35	unsigned long flags;
36	void *restorer;
37	unsigned int mask[2];
38};
39
40static volatile sig_atomic_t handler_called;
41
42static void handler_with_siginfo(int sig, siginfo_t *info, void *ctx_void)
43{
44	handler_called = 1;
45}
46
47static void handler_without_siginfo(int sig)
48{
49	handler_called = 1;
50}
51
52int main()
53{
54	int nerrs = 0;
55	struct real_sigaction sa;
56
57	memset(&sa, 0, sizeof(sa));
58	sa.handler = handler_with_siginfo;
59	sa.flags = SA_SIGINFO;
60	sa.restorer = NULL;	/* request kernel-provided restorer */
61
62	if (syscall(SYS_rt_sigaction, SIGUSR1, &sa, NULL, 8) != 0)
63		err(1, "raw rt_sigaction syscall");
64
65	raise(SIGUSR1);
66
67	if (handler_called) {
68		printf("[OK]\tSA_SIGINFO handler returned successfully\n");
69	} else {
70		printf("[FAIL]\tSA_SIGINFO handler was not called\n");
71		nerrs++;
72	}
73
74	sa.flags = 0;
75	sa.handler = handler_without_siginfo;
76	if (syscall(SYS_sigaction, SIGUSR1, &sa, 0) != 0)
77		err(1, "raw sigaction syscall");
78	handler_called = 0;
79
80	raise(SIGUSR1);
81
82	if (handler_called) {
83		printf("[OK]\t!SA_SIGINFO handler returned successfully\n");
84	} else {
85		printf("[FAIL]\t!SA_SIGINFO handler was not called\n");
86		nerrs++;
87	}
88}
89