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1// SPDX-License-Identifier: GPL-2.0-or-later2/*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 9a81c16b527528ad307843be5571111aa8d35a808 * Author: Al Viro <viro@zeniv.linux.org.uk>9 * Date: Mon Sep 20 21:48:57 2010 +010010 *11 * powerpc: fix double syscall restarts12 *13 * Make sigreturn zero regs->trap, make do_signal() do the same on all14 * paths. As it is, signal interrupting e.g. read() from fd 512 (==15 * ERESTARTSYS) with another signal getting unblocked when the first16 * handler finishes will lead to restart one insn earlier than it ought17 * to. Same for multiple signals with in-kernel handlers interrupting18 * that sucker at the same time. Same for multiple signals of any kind19 * interrupting that sucker on 64bit...20 */21#define _GNU_SOURCE22#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 will39 * be raised again and think there is a restart to be done because the40 * pending restarted syscall has 512 (ERESTARTSYS) in r3. The second41 * 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