Add kselftest to test that remove_on_exec removes inherited events from
child tasks.
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
---
v3:
* Fix for latest libc signal.h.
v2:
* Add patch to series.
---
.../testing/selftests/perf_events/.gitignore | 1 +
tools/testing/selftests/perf_events/Makefile | 2 +-
.../selftests/perf_events/remove_on_exec.c | 260 ++++++++++++++++++
3 files changed, 262 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/perf_events/remove_on_exec.c
diff --git a/tools/testing/selftests/perf_events/.gitignore b/tools/testing/selftests/perf_events/.gitignore
index 4dc43e1bd79c..790c47001e77 100644
--- a/tools/testing/selftests/perf_events/.gitignore
+++ b/tools/testing/selftests/perf_events/.gitignore
@@ -1,2 +1,3 @@
# SPDX-License-Identifier: GPL-2.0-only
sigtrap_threads
+remove_on_exec
diff --git a/tools/testing/selftests/perf_events/Makefile b/tools/testing/selftests/perf_events/Makefile
index 973a2c39ca83..fcafa5f0d34c 100644
--- a/tools/testing/selftests/perf_events/Makefile
+++ b/tools/testing/selftests/perf_events/Makefile
@@ -2,5 +2,5 @@
CFLAGS += -Wl,-no-as-needed -Wall -I../../../../usr/include
LDFLAGS += -lpthread
-TEST_GEN_PROGS := sigtrap_threads
+TEST_GEN_PROGS := sigtrap_threads remove_on_exec
include ../lib.mk
diff --git a/tools/testing/selftests/perf_events/remove_on_exec.c b/tools/testing/selftests/perf_events/remove_on_exec.c
new file mode 100644
index 000000000000..5814611a1dc7
--- /dev/null
+++ b/tools/testing/selftests/perf_events/remove_on_exec.c
@@ -0,0 +1,260 @@
+// 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);
+}
--
2.31.0.208.g409f899ff0-goog
