tools/testing/selftests/bpf/prog_tests/send_signal.c

// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
#include <sys/time.h>
#include <sys/resource.h>
#include "test_send_signal_kern.skel.h"

static int sigusr1_received;

static void sigusr1_handler(int signum)
{
	sigusr1_received = 1;
}

static void test_send_signal_common(struct perf_event_attr *attr,
				    bool signal_thread)
{
	struct test_send_signal_kern *skel;
	int pipe_c2p[2], pipe_p2c[2];
	int err = -1, pmu_fd = -1;
	char buf[256];
	pid_t pid;

	if (!ASSERT_OK(pipe(pipe_c2p), "pipe_c2p"))
		return;

	if (!ASSERT_OK(pipe(pipe_p2c), "pipe_p2c")) {
		close(pipe_c2p[0]);
		close(pipe_c2p[1]);
		return;
	}

	pid = fork();
	if (!ASSERT_GE(pid, 0, "fork")) {
		close(pipe_c2p[0]);
		close(pipe_c2p[1]);
		close(pipe_p2c[0]);
		close(pipe_p2c[1]);
		return;
	}

	if (pid == 0) {
		int old_prio;
		volatile int j = 0;

		/* install signal handler and notify parent */
		ASSERT_NEQ(signal(SIGUSR1, sigusr1_handler), SIG_ERR, "signal");

		close(pipe_c2p[0]); /* close read */
		close(pipe_p2c[1]); /* close write */

		/* boost with a high priority so we got a higher chance
		 * that if an interrupt happens, the underlying task
		 * is this process.
		 */
		errno = 0;
		old_prio = getpriority(PRIO_PROCESS, 0);
		ASSERT_OK(errno, "getpriority");
		ASSERT_OK(setpriority(PRIO_PROCESS, 0, -20), "setpriority");

		/* notify parent signal handler is installed */
		ASSERT_EQ(write(pipe_c2p[1], buf, 1), 1, "pipe_write");

		/* make sure parent enabled bpf program to send_signal */
		ASSERT_EQ(read(pipe_p2c[0], buf, 1), 1, "pipe_read");

		/* wait a little for signal handler */
		for (int i = 0; i < 1000000000 && !sigusr1_received; i++)
			j /= i + j + 1;

		buf[0] = sigusr1_received ? '2' : '0';
		ASSERT_EQ(sigusr1_received, 1, "sigusr1_received");
		ASSERT_EQ(write(pipe_c2p[1], buf, 1), 1, "pipe_write");

		/* wait for parent notification and exit */
		ASSERT_EQ(read(pipe_p2c[0], buf, 1), 1, "pipe_read");

		/* restore the old priority */
		ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), "setpriority");

		close(pipe_c2p[1]);
		close(pipe_p2c[0]);
		exit(0);
	}

	close(pipe_c2p[1]); /* close write */
	close(pipe_p2c[0]); /* close read */

	skel = test_send_signal_kern__open_and_load();
	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
		goto skel_open_load_failure;

	if (!attr) {
		err = test_send_signal_kern__attach(skel);
		if (!ASSERT_OK(err, "skel_attach")) {
			err = -1;
			goto destroy_skel;
		}
	} else {
		pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1 /* cpu */,
				 -1 /* group id */, 0 /* flags */);
		if (!ASSERT_GE(pmu_fd, 0, "perf_event_open")) {
			err = -1;
			goto destroy_skel;
		}

		skel->links.send_signal_perf =
			bpf_program__attach_perf_event(skel->progs.send_signal_perf, pmu_fd);
		if (!ASSERT_OK_PTR(skel->links.send_signal_perf, "attach_perf_event"))
			goto disable_pmu;
	}

	/* wait until child signal handler installed */
	ASSERT_EQ(read(pipe_c2p[0], buf, 1), 1, "pipe_read");

	/* trigger the bpf send_signal */
	skel->bss->signal_thread = signal_thread;
	skel->bss->sig = SIGUSR1;
	skel->bss->pid = pid;

	/* notify child that bpf program can send_signal now */
	ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");

	/* wait for result */
	err = read(pipe_c2p[0], buf, 1);
	if (!ASSERT_GE(err, 0, "reading pipe"))
		goto disable_pmu;
	if (!ASSERT_GT(err, 0, "reading pipe error: size 0")) {
		err = -1;
		goto disable_pmu;
	}

	ASSERT_EQ(buf[0], '2', "incorrect result");

	/* notify child safe to exit */
	ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");

disable_pmu:
	close(pmu_fd);
destroy_skel:
	test_send_signal_kern__destroy(skel);
skel_open_load_failure:
	close(pipe_c2p[0]);
	close(pipe_p2c[1]);
	wait(NULL);
}

static void test_send_signal_tracepoint(bool signal_thread)
{
	test_send_signal_common(NULL, signal_thread);
}

static void test_send_signal_perf(bool signal_thread)
{
	struct perf_event_attr attr = {
		.sample_period = 1,
		.type = PERF_TYPE_SOFTWARE,
		.config = PERF_COUNT_SW_CPU_CLOCK,
	};

	test_send_signal_common(&attr, signal_thread);
}

static void test_send_signal_nmi(bool signal_thread)
{
	struct perf_event_attr attr = {
		.sample_period = 1,
		.type = PERF_TYPE_HARDWARE,
		.config = PERF_COUNT_HW_CPU_CYCLES,
	};
	int pmu_fd;

	/* Some setups (e.g. virtual machines) might run with hardware
	 * perf events disabled. If this is the case, skip this test.
	 */
	pmu_fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */,
			 -1 /* cpu */, -1 /* group_fd */, 0 /* flags */);
	if (pmu_fd == -1) {
		if (errno == ENOENT) {
			printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n",
			       __func__);
			test__skip();
			return;
		}
		/* Let the test fail with a more informative message */
	} else {
		close(pmu_fd);
	}

	test_send_signal_common(&attr, signal_thread);
}

void test_send_signal(void)
{
	if (test__start_subtest("send_signal_tracepoint"))
		test_send_signal_tracepoint(false);
	if (test__start_subtest("send_signal_perf"))
		test_send_signal_perf(false);
	if (test__start_subtest("send_signal_nmi"))
		test_send_signal_nmi(false);
	if (test__start_subtest("send_signal_tracepoint_thread"))
		test_send_signal_tracepoint(true);
	if (test__start_subtest("send_signal_perf_thread"))
		test_send_signal_perf(true);
	if (test__start_subtest("send_signal_nmi_thread"))
		test_send_signal_nmi(true);
}