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}