// SPDX-License-Identifier: GPL-2.0
/*
* Test for remove_on_exec.
*
* Copyright (C) 2021, Google LLC.
*/
#define _GNU_SOURCE
/* We need the latest siginfo from the kernel repo. */
#include <sys/types.h>
#include <asm/siginfo.h>
#define __have_siginfo_t 1
#define __have_sigval_t 1
#define __have_sigevent_t 1
#define __siginfo_t_defined
#define __sigval_t_defined
#define __sigevent_t_defined
#define _BITS_SIGINFO_CONSTS_H 1
#define _BITS_SIGEVENT_CONSTS_H 1
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <linux/perf_event.h>
#include <pthread.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <unistd.h>
#include "../kselftest_harness.h"
static volatile int signal_count;
static struct perf_event_attr make_event_attr(void)
{
struct perf_event_attr attr = {
.type = PERF_TYPE_HARDWARE,
.size = sizeof(attr),
.config = PERF_COUNT_HW_INSTRUCTIONS,
.sample_period = 1000,
.exclude_kernel = 1,
.exclude_hv = 1,
.disabled = 1,
.inherit = 1,
/*
* Children normally retain their inherited event on exec; with
* remove_on_exec, we'll remove their event, but the parent and
* any other non-exec'd children will keep their events.
*/
.remove_on_exec = 1,
.sigtrap = 1,
};
return attr;
}
static void sigtrap_handler(int signum, siginfo_t *info, void *ucontext)
{
if (info->si_code != TRAP_PERF) {
fprintf(stderr, "%s: unexpected si_code %d\n", __func__, info->si_code);
return;
}
signal_count++;
}
FIXTURE(remove_on_exec)
{
struct sigaction oldact;
int fd;
};
FIXTURE_SETUP(remove_on_exec)
{
struct perf_event_attr attr = make_event_attr();
struct sigaction action = {};
signal_count = 0;
/* Initialize sigtrap handler. */
action.sa_flags = SA_SIGINFO | SA_NODEFER;
action.sa_sigaction = sigtrap_handler;
sigemptyset(&action.sa_mask);
ASSERT_EQ(sigaction(SIGTRAP, &action, &self->oldact), 0);
/* Initialize perf event. */
self->fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
ASSERT_NE(self->fd, -1);
}
FIXTURE_TEARDOWN(remove_on_exec)
{
close(self->fd);
sigaction(SIGTRAP, &self->oldact, NULL);
}
/* Verify event propagates to fork'd child. */
TEST_F(remove_on_exec, fork_only)
{
int status;
pid_t pid = fork();
if (pid == 0) {
ASSERT_EQ(signal_count, 0);
ASSERT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
while (!signal_count);
_exit(42);
}
while (!signal_count); /* Child enables event. */
EXPECT_EQ(waitpid(pid, &status, 0), pid);
EXPECT_EQ(WEXITSTATUS(status), 42);
}
/*
* Verify that event does _not_ propagate to fork+exec'd child; event enabled
* after fork+exec.
*/
TEST_F(remove_on_exec, fork_exec_then_enable)
{
pid_t pid_exec, pid_only_fork;
int pipefd[2];
int tmp;
/*
* Non-exec child, to ensure exec does not affect inherited events of
* other children.
*/
pid_only_fork = fork();
if (pid_only_fork == 0) {
/* Block until parent enables event. */
while (!signal_count);
_exit(42);
}
ASSERT_NE(pipe(pipefd), -1);
pid_exec = fork();
if (pid_exec == 0) {
ASSERT_NE(dup2(pipefd[1], STDOUT_FILENO), -1);
close(pipefd[0]);
execl("/proc/self/exe", "exec_child", NULL);
_exit((perror("exec failed"), 1));
}
close(pipefd[1]);
ASSERT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Child is running. */
/* Wait for exec'd child to start spinning. */
EXPECT_EQ(read(pipefd[0], &tmp, sizeof(int)), sizeof(int));
EXPECT_EQ(tmp, 42);
close(pipefd[0]);
/* Now we can enable the event, knowing the child is doing work. */
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
/* If the event propagated to the exec'd child, it will exit normally... */
usleep(100000); /* ... give time for event to trigger (in case of bug). */
EXPECT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Should still be running. */
EXPECT_EQ(kill(pid_exec, SIGKILL), 0);
/* Verify removal from child did not affect this task's event. */
tmp = signal_count;
while (signal_count == tmp); /* Should not hang! */
/* Nor should it have affected the first child. */
EXPECT_EQ(waitpid(pid_only_fork, &tmp, 0), pid_only_fork);
EXPECT_EQ(WEXITSTATUS(tmp), 42);
}
/*
* Verify that event does _not_ propagate to fork+exec'd child; event enabled
* before fork+exec.
*/
TEST_F(remove_on_exec, enable_then_fork_exec)
{
pid_t pid_exec;
int tmp;
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
pid_exec = fork();
if (pid_exec == 0) {
execl("/proc/self/exe", "exec_child", NULL);
_exit((perror("exec failed"), 1));
}
/*
* The child may exit abnormally at any time if the event propagated and
* a SIGTRAP is sent before the handler was set up.
*/
usleep(100000); /* ... give time for event to trigger (in case of bug). */
EXPECT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Should still be running. */
EXPECT_EQ(kill(pid_exec, SIGKILL), 0);
/* Verify removal from child did not affect this task's event. */
tmp = signal_count;
while (signal_count == tmp); /* Should not hang! */
}
TEST_F(remove_on_exec, exec_stress)
{
pid_t pids[30];
int i, tmp;
for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++) {
pids[i] = fork();
if (pids[i] == 0) {
execl("/proc/self/exe", "exec_child", NULL);
_exit((perror("exec failed"), 1));
}
/* Some forked with event disabled, rest with enabled. */
if (i > 10)
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
}
usleep(100000); /* ... give time for event to trigger (in case of bug). */
for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++) {
/* All children should still be running. */
EXPECT_EQ(waitpid(pids[i], &tmp, WNOHANG), 0);
EXPECT_EQ(kill(pids[i], SIGKILL), 0);
}
/* Verify event is still alive. */
tmp = signal_count;
while (signal_count == tmp);
}
/* For exec'd child. */
static void exec_child(void)
{
struct sigaction action = {};
const int val = 42;
/* Set up sigtrap handler in case we erroneously receive a trap. */
action.sa_flags = SA_SIGINFO | SA_NODEFER;
action.sa_sigaction = sigtrap_handler;
sigemptyset(&action.sa_mask);
if (sigaction(SIGTRAP, &action, NULL))
_exit((perror("sigaction failed"), 1));
/* Signal parent that we're starting to spin. */
if (write(STDOUT_FILENO, &val, sizeof(int)) == -1)
_exit((perror("write failed"), 1));
/* Should hang here until killed. */
while (!signal_count);
}
#define main test_main
TEST_HARNESS_MAIN
#undef main
int main(int argc, char *argv[])
{
if (!strcmp(argv[0], "exec_child")) {
exec_child();
return 1;
}
return test_main(argc, argv);
}
Codebase Browser
linux