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Add kselftest to test that remove_on_exec removes inherited events from child tasks. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210408103605.1676875-9-elver@google.com
261 lines
6.4 KiB
C
261 lines
6.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Test for remove_on_exec.
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*
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* Copyright (C) 2021, Google LLC.
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*/
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#define _GNU_SOURCE
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/* We need the latest siginfo from the kernel repo. */
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#include <sys/types.h>
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#include <asm/siginfo.h>
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#define __have_siginfo_t 1
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#define __have_sigval_t 1
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#define __have_sigevent_t 1
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#define __siginfo_t_defined
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#define __sigval_t_defined
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#define __sigevent_t_defined
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#define _BITS_SIGINFO_CONSTS_H 1
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#define _BITS_SIGEVENT_CONSTS_H 1
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <linux/perf_event.h>
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#include <pthread.h>
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#include <signal.h>
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#include <sys/ioctl.h>
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#include <sys/syscall.h>
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#include <unistd.h>
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#include "../kselftest_harness.h"
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static volatile int signal_count;
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static struct perf_event_attr make_event_attr(void)
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{
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struct perf_event_attr attr = {
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.type = PERF_TYPE_HARDWARE,
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.size = sizeof(attr),
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.config = PERF_COUNT_HW_INSTRUCTIONS,
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.sample_period = 1000,
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.exclude_kernel = 1,
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.exclude_hv = 1,
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.disabled = 1,
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.inherit = 1,
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/*
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* Children normally retain their inherited event on exec; with
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* remove_on_exec, we'll remove their event, but the parent and
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* any other non-exec'd children will keep their events.
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*/
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.remove_on_exec = 1,
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.sigtrap = 1,
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};
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return attr;
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}
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static void sigtrap_handler(int signum, siginfo_t *info, void *ucontext)
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{
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if (info->si_code != TRAP_PERF) {
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fprintf(stderr, "%s: unexpected si_code %d\n", __func__, info->si_code);
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return;
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}
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signal_count++;
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}
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FIXTURE(remove_on_exec)
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{
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struct sigaction oldact;
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int fd;
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};
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FIXTURE_SETUP(remove_on_exec)
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{
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struct perf_event_attr attr = make_event_attr();
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struct sigaction action = {};
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signal_count = 0;
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/* Initialize sigtrap handler. */
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action.sa_flags = SA_SIGINFO | SA_NODEFER;
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action.sa_sigaction = sigtrap_handler;
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sigemptyset(&action.sa_mask);
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ASSERT_EQ(sigaction(SIGTRAP, &action, &self->oldact), 0);
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/* Initialize perf event. */
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self->fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
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ASSERT_NE(self->fd, -1);
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}
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FIXTURE_TEARDOWN(remove_on_exec)
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{
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close(self->fd);
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sigaction(SIGTRAP, &self->oldact, NULL);
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}
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/* Verify event propagates to fork'd child. */
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TEST_F(remove_on_exec, fork_only)
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{
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int status;
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pid_t pid = fork();
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if (pid == 0) {
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ASSERT_EQ(signal_count, 0);
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ASSERT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
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while (!signal_count);
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_exit(42);
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}
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while (!signal_count); /* Child enables event. */
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EXPECT_EQ(waitpid(pid, &status, 0), pid);
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EXPECT_EQ(WEXITSTATUS(status), 42);
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}
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/*
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* Verify that event does _not_ propagate to fork+exec'd child; event enabled
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* after fork+exec.
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*/
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TEST_F(remove_on_exec, fork_exec_then_enable)
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{
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pid_t pid_exec, pid_only_fork;
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int pipefd[2];
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int tmp;
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/*
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* Non-exec child, to ensure exec does not affect inherited events of
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* other children.
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*/
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pid_only_fork = fork();
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if (pid_only_fork == 0) {
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/* Block until parent enables event. */
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while (!signal_count);
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_exit(42);
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}
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ASSERT_NE(pipe(pipefd), -1);
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pid_exec = fork();
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if (pid_exec == 0) {
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ASSERT_NE(dup2(pipefd[1], STDOUT_FILENO), -1);
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close(pipefd[0]);
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execl("/proc/self/exe", "exec_child", NULL);
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_exit((perror("exec failed"), 1));
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}
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close(pipefd[1]);
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ASSERT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Child is running. */
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/* Wait for exec'd child to start spinning. */
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EXPECT_EQ(read(pipefd[0], &tmp, sizeof(int)), sizeof(int));
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EXPECT_EQ(tmp, 42);
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close(pipefd[0]);
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/* Now we can enable the event, knowing the child is doing work. */
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EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
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/* If the event propagated to the exec'd child, it will exit normally... */
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usleep(100000); /* ... give time for event to trigger (in case of bug). */
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EXPECT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Should still be running. */
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EXPECT_EQ(kill(pid_exec, SIGKILL), 0);
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/* Verify removal from child did not affect this task's event. */
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tmp = signal_count;
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while (signal_count == tmp); /* Should not hang! */
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/* Nor should it have affected the first child. */
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EXPECT_EQ(waitpid(pid_only_fork, &tmp, 0), pid_only_fork);
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EXPECT_EQ(WEXITSTATUS(tmp), 42);
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}
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/*
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* Verify that event does _not_ propagate to fork+exec'd child; event enabled
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* before fork+exec.
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*/
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TEST_F(remove_on_exec, enable_then_fork_exec)
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{
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pid_t pid_exec;
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int tmp;
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EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
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pid_exec = fork();
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if (pid_exec == 0) {
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execl("/proc/self/exe", "exec_child", NULL);
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_exit((perror("exec failed"), 1));
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}
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/*
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* The child may exit abnormally at any time if the event propagated and
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* a SIGTRAP is sent before the handler was set up.
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*/
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usleep(100000); /* ... give time for event to trigger (in case of bug). */
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EXPECT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Should still be running. */
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EXPECT_EQ(kill(pid_exec, SIGKILL), 0);
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/* Verify removal from child did not affect this task's event. */
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tmp = signal_count;
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while (signal_count == tmp); /* Should not hang! */
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}
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TEST_F(remove_on_exec, exec_stress)
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{
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pid_t pids[30];
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int i, tmp;
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for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++) {
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pids[i] = fork();
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if (pids[i] == 0) {
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execl("/proc/self/exe", "exec_child", NULL);
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_exit((perror("exec failed"), 1));
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}
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/* Some forked with event disabled, rest with enabled. */
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if (i > 10)
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EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
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}
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usleep(100000); /* ... give time for event to trigger (in case of bug). */
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for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++) {
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/* All children should still be running. */
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EXPECT_EQ(waitpid(pids[i], &tmp, WNOHANG), 0);
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EXPECT_EQ(kill(pids[i], SIGKILL), 0);
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}
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/* Verify event is still alive. */
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tmp = signal_count;
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while (signal_count == tmp);
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}
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/* For exec'd child. */
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static void exec_child(void)
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{
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struct sigaction action = {};
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const int val = 42;
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/* Set up sigtrap handler in case we erroneously receive a trap. */
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action.sa_flags = SA_SIGINFO | SA_NODEFER;
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action.sa_sigaction = sigtrap_handler;
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sigemptyset(&action.sa_mask);
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if (sigaction(SIGTRAP, &action, NULL))
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_exit((perror("sigaction failed"), 1));
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/* Signal parent that we're starting to spin. */
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if (write(STDOUT_FILENO, &val, sizeof(int)) == -1)
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_exit((perror("write failed"), 1));
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/* Should hang here until killed. */
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while (!signal_count);
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}
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#define main test_main
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TEST_HARNESS_MAIN
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#undef main
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int main(int argc, char *argv[])
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{
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if (!strcmp(argv[0], "exec_child")) {
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exec_child();
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return 1;
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}
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return test_main(argc, argv);
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}
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