1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Test that a syscall does not get restarted twice, handled by trap_norestart()
4 *
5 * Based on Al's description, and a test for the bug fixed in this commit:
6 *
7 * commit 9a81c16b527528ad307843be5571111aa8d35a80
8 * Author: Al Viro <viro@zeniv.linux.org.uk>
9 * Date:   Mon Sep 20 21:48:57 2010 +0100
10 *
11 *  powerpc: fix double syscall restarts
12 *
13 *  Make sigreturn zero regs->trap, make do_signal() do the same on all
14 *  paths.  As it is, signal interrupting e.g. read() from fd 512 (==
15 *  ERESTARTSYS) with another signal getting unblocked when the first
16 *  handler finishes will lead to restart one insn earlier than it ought
17 *  to.  Same for multiple signals with in-kernel handlers interrupting
18 *  that sucker at the same time.  Same for multiple signals of any kind
19 *  interrupting that sucker on 64bit...
20 */
21#define _GNU_SOURCE
22#include <sys/types.h>
23#include <sys/wait.h>
24#include <sys/syscall.h>
25#include <unistd.h>
26#include <signal.h>
27#include <errno.h>
28#include <stdlib.h>
29#include <stdio.h>
30#include <string.h>
31
32#include "utils.h"
33
34static void SIGUSR1_handler(int sig)
35{
36	kill(getpid(), SIGUSR2);
37	/*
38	 * SIGUSR2 is blocked until the handler exits, at which point it will
39	 * be raised again and think there is a restart to be done because the
40	 * pending restarted syscall has 512 (ERESTARTSYS) in r3. The second
41	 * restart will retreat NIP another 4 bytes to fail case branch.
42	 */
43}
44
45static void SIGUSR2_handler(int sig)
46{
47}
48
49static ssize_t raw_read(int fd, void *buf, size_t count)
50{
51	register long nr asm("r0") = __NR_read;
52	register long _fd asm("r3") = fd;
53	register void *_buf asm("r4") = buf;
54	register size_t _count asm("r5") = count;
55
56	asm volatile(
57"		b	0f		\n"
58"		b	1f		\n"
59"	0:	sc	0		\n"
60"		bns	2f		\n"
61"		neg	%0,%0		\n"
62"		b	2f		\n"
63"	1:				\n"
64"		li	%0,%4		\n"
65"	2:				\n"
66		: "+r"(_fd), "+r"(nr), "+r"(_buf), "+r"(_count)
67		: "i"(-ENOANO)
68		: "memory", "r6", "r7", "r8", "r9", "r10", "r11", "r12", "ctr", "cr0");
69
70	if (_fd < 0) {
71		errno = -_fd;
72		_fd = -1;
73	}
74
75	return _fd;
76}
77
78#define DATA "test 123"
79#define DLEN (strlen(DATA)+1)
80
81int test_restart(void)
82{
83	int pipefd[2];
84	pid_t pid;
85	char buf[512];
86
87	if (pipe(pipefd) == -1) {
88		perror("pipe");
89		exit(EXIT_FAILURE);
90	}
91
92	pid = fork();
93	if (pid == -1) {
94		perror("fork");
95		exit(EXIT_FAILURE);
96	}
97
98	if (pid == 0) { /* Child reads from pipe */
99		struct sigaction act;
100		int fd;
101
102		memset(&act, 0, sizeof(act));
103		sigaddset(&act.sa_mask, SIGUSR2);
104		act.sa_handler = SIGUSR1_handler;
105		act.sa_flags = SA_RESTART;
106		if (sigaction(SIGUSR1, &act, NULL) == -1) {
107			perror("sigaction");
108			exit(EXIT_FAILURE);
109		}
110
111		memset(&act, 0, sizeof(act));
112		act.sa_handler = SIGUSR2_handler;
113		act.sa_flags = SA_RESTART;
114		if (sigaction(SIGUSR2, &act, NULL) == -1) {
115			perror("sigaction");
116			exit(EXIT_FAILURE);
117		}
118
119		/* Let's get ERESTARTSYS into r3 */
120		while ((fd = dup(pipefd[0])) != 512) {
121			if (fd == -1) {
122				perror("dup");
123				exit(EXIT_FAILURE);
124			}
125		}
126
127		if (raw_read(fd, buf, 512) == -1) {
128			if (errno == ENOANO) {
129				fprintf(stderr, "Double restart moved restart before sc instruction.\n");
130				_exit(EXIT_FAILURE);
131			}
132			perror("read");
133			exit(EXIT_FAILURE);
134		}
135
136		if (strncmp(buf, DATA, DLEN)) {
137			fprintf(stderr, "bad test string %s\n", buf);
138			exit(EXIT_FAILURE);
139		}
140
141		return 0;
142
143	} else {
144		int wstatus;
145
146		usleep(100000);		/* Hack to get reader waiting */
147		kill(pid, SIGUSR1);
148		usleep(100000);
149		if (write(pipefd[1], DATA, DLEN) != DLEN) {
150			perror("write");
151			exit(EXIT_FAILURE);
152		}
153		close(pipefd[0]);
154		close(pipefd[1]);
155		if (wait(&wstatus) == -1) {
156			perror("wait");
157			exit(EXIT_FAILURE);
158		}
159		if (!WIFEXITED(wstatus)) {
160			fprintf(stderr, "child exited abnormally\n");
161			exit(EXIT_FAILURE);
162		}
163
164		FAIL_IF(WEXITSTATUS(wstatus) != EXIT_SUCCESS);
165
166		return 0;
167	}
168}
169
170int main(void)
171{
172	test_harness_set_timeout(10);
173	return test_harness(test_restart, "sig sys restart");
174}
175