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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Test that a syscall does not get restarted twice, handled by trap_norestart()
*
* Based on Al's description, and a test for the bug fixed in this commit:
*
* commit 9a81c16b527528ad307843be5571111aa8d35a80
* Author: Al Viro <viro@zeniv.linux.org.uk>
* Date: Mon Sep 20 21:48:57 2010 +0100
*
* powerpc: fix double syscall restarts
*
* Make sigreturn zero regs->trap, make do_signal() do the same on all
* paths. As it is, signal interrupting e.g. read() from fd 512 (==
* ERESTARTSYS) with another signal getting unblocked when the first
* handler finishes will lead to restart one insn earlier than it ought
* to. Same for multiple signals with in-kernel handlers interrupting
* that sucker at the same time. Same for multiple signals of any kind
* interrupting that sucker on 64bit...
*/
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "utils.h"
static void SIGUSR1_handler(int sig)
{
kill(getpid(), SIGUSR2);
/*
* SIGUSR2 is blocked until the handler exits, at which point it will
* be raised again and think there is a restart to be done because the
* pending restarted syscall has 512 (ERESTARTSYS) in r3. The second
* restart will retreat NIP another 4 bytes to fail case branch.
*/
}
static void SIGUSR2_handler(int sig)
{
}
static ssize_t raw_read(int fd, void *buf, size_t count)
{
register long nr asm("r0") = __NR_read;
register long _fd asm("r3") = fd;
register void *_buf asm("r4") = buf;
register size_t _count asm("r5") = count;
asm volatile(
" b 0f \n"
" b 1f \n"
" 0: sc 0 \n"
" bns 2f \n"
" neg %0,%0 \n"
" b 2f \n"
" 1: \n"
" li %0,%4 \n"
" 2: \n"
: "+r"(_fd), "+r"(nr), "+r"(_buf), "+r"(_count)
: "i"(-ENOANO)
: "memory", "r6", "r7", "r8", "r9", "r10", "r11", "r12", "ctr", "cr0");
if (_fd < 0) {
errno = -_fd;
_fd = -1;
}
return _fd;
}
#define DATA "test 123"
#define DLEN (strlen(DATA)+1)
int test_restart(void)
{
int pipefd[2];
pid_t pid;
char buf[512];
if (pipe(pipefd) == -1) {
perror("pipe");
exit(EXIT_FAILURE);
}
pid = fork();
if (pid == -1) {
perror("fork");
exit(EXIT_FAILURE);
}
if (pid == 0) { /* Child reads from pipe */
struct sigaction act;
int fd;
memset(&act, 0, sizeof(act));
sigaddset(&act.sa_mask, SIGUSR2);
act.sa_handler = SIGUSR1_handler;
act.sa_flags = SA_RESTART;
if (sigaction(SIGUSR1, &act, NULL) == -1) {
perror("sigaction");
exit(EXIT_FAILURE);
}
memset(&act, 0, sizeof(act));
act.sa_handler = SIGUSR2_handler;
act.sa_flags = SA_RESTART;
if (sigaction(SIGUSR2, &act, NULL) == -1) {
perror("sigaction");
exit(EXIT_FAILURE);
}
/* Let's get ERESTARTSYS into r3 */
while ((fd = dup(pipefd[0])) != 512) {
if (fd == -1) {
perror("dup");
exit(EXIT_FAILURE);
}
}
if (raw_read(fd, buf, 512) == -1) {
if (errno == ENOANO) {
fprintf(stderr, "Double restart moved restart before sc instruction.\n");
_exit(EXIT_FAILURE);
}
perror("read");
exit(EXIT_FAILURE);
}
if (strncmp(buf, DATA, DLEN)) {
fprintf(stderr, "bad test string %s\n", buf);
exit(EXIT_FAILURE);
}
return 0;
} else {
int wstatus;
usleep(100000); /* Hack to get reader waiting */
kill(pid, SIGUSR1);
usleep(100000);
if (write(pipefd[1], DATA, DLEN) != DLEN) {
perror("write");
exit(EXIT_FAILURE);
}
close(pipefd[0]);
close(pipefd[1]);
if (wait(&wstatus) == -1) {
perror("wait");
exit(EXIT_FAILURE);
}
if (!WIFEXITED(wstatus)) {
fprintf(stderr, "child exited abnormally\n");
exit(EXIT_FAILURE);
}
FAIL_IF(WEXITSTATUS(wstatus) != EXIT_SUCCESS);
return 0;
}
}
int main(void)
{
test_harness_set_timeout(10);
return test_harness(test_restart, "sig sys restart");
}
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