[PATCH bpf-next 2/2] selftests/bpf: Augment send_signal test with remote signaling

[Puranjay Mohan]

Add testcases to test bpf_send_signal_pid/tgid(). In these new test cases,
the main process triggers the BPF program and the forked process
receives the signals.

Signed-off-by: Puranjay Mohan <puranjay@xxxxxxxxxx>
---
 .../selftests/bpf/prog_tests/send_signal.c    | 110 +++++++++++++-----
 .../bpf/progs/test_send_signal_kern.c         |  17 ++-
 2 files changed, 95 insertions(+), 32 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c b/tools/testing/selftests/bpf/prog_tests/send_signal.c
index 6cc69900b310..a8392dfc69e2 100644
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -12,13 +12,15 @@ static void sigusr1_handler(int signum)
 }
 
 static void test_send_signal_common(struct perf_event_attr *attr,
-				    bool signal_thread)
+				    bool signal_thread, bool remote)
 {
 	struct test_send_signal_kern *skel;
 	int pipe_c2p[2], pipe_p2c[2];
 	int err = -1, pmu_fd = -1;
+	volatile int j = 0;
 	char buf[256];
 	pid_t pid;
+	int old_prio;
 
 	if (!ASSERT_OK(pipe(pipe_c2p), "pipe_c2p"))
 		return;
@@ -39,9 +41,6 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 	}
 
 	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");
 
@@ -52,10 +51,12 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 		 * 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");
+		if (!remote) {
+			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");
@@ -66,9 +67,12 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 		/* wait a little for signal handler */
 		for (int i = 0; i < 1000000000 && !sigusr1_received; i++) {
 			j /= i + j + 1;
-			if (!attr)
-				/* trigger the nanosleep tracepoint program. */
-				usleep(1);
+			if (remote)
+				sleep(1);
+			else
+				if (!attr)
+					/* trigger the nanosleep tracepoint program. */
+					usleep(1);
 		}
 
 		buf[0] = sigusr1_received ? '2' : '0';
@@ -79,7 +83,8 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 		ASSERT_EQ(read(pipe_p2c[0], buf, 1), 1, "pipe_read");
 
 		/* restore the old priority */
-		ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), "setpriority");
+		if (!remote)
+			ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), "setpriority");
 
 		close(pipe_c2p[1]);
 		close(pipe_p2c[0]);
@@ -93,6 +98,17 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
 		goto skel_open_load_failure;
 
+	/* boost with a high priority so we got a higher chance
+	 * that if an interrupt happens, the underlying task
+	 * is this process.
+	 */
+	if (remote) {
+		errno = 0;
+		old_prio = getpriority(PRIO_PROCESS, 0);
+		ASSERT_OK(errno, "getpriority");
+		ASSERT_OK(setpriority(PRIO_PROCESS, 0, -20), "setpriority");
+	}
+
 	if (!attr) {
 		err = test_send_signal_kern__attach(skel);
 		if (!ASSERT_OK(err, "skel_attach")) {
@@ -100,8 +116,12 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 			goto destroy_skel;
 		}
 	} else {
-		pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1 /* cpu */,
-				 -1 /* group id */, 0 /* flags */);
+		if (!remote)
+			pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1 /* cpu */,
+					 -1 /* group id */, 0 /* flags */);
+		else
+			pmu_fd = syscall(__NR_perf_event_open, attr, getpid(), -1 /* cpu */,
+					 -1 /* group id */, 0 /* flags */);
 		if (!ASSERT_GE(pmu_fd, 0, "perf_event_open")) {
 			err = -1;
 			goto destroy_skel;
@@ -119,11 +139,30 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 	/* trigger the bpf send_signal */
 	skel->bss->signal_thread = signal_thread;
 	skel->bss->sig = SIGUSR1;
-	skel->bss->pid = pid;
+	if (!remote) {
+		skel->bss->target_pid = 0;
+		skel->bss->pid = pid;
+	} else {
+		skel->bss->target_pid = pid;
+		skel->bss->pid = getpid();
+	}
 
 	/* notify child that bpf program can send_signal now */
 	ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");
 
+	/* For the remote test, the BPF program is triggered from this
+	 * process but the other process/thread is signaled.
+	 */
+	if (remote) {
+		if (!attr) {
+			for (int i = 0; i < 10; i++)
+				usleep(1);
+		} else {
+			for (int i = 0; i < 100000000; i++)
+				j /= i + 1;
+		}
+	}
+
 	/* wait for result */
 	err = read(pipe_c2p[0], buf, 1);
 	if (!ASSERT_GE(err, 0, "reading pipe"))
@@ -142,18 +181,21 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 	close(pmu_fd);
 destroy_skel:
 	test_send_signal_kern__destroy(skel);
+	/* restore the old priority */
+	if (remote)
+		ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), "setpriority");
 skel_open_load_failure:
 	close(pipe_c2p[0]);
 	close(pipe_p2c[1]);
 	wait(NULL);
 }
 
-static void test_send_signal_tracepoint(bool signal_thread)
+static void test_send_signal_tracepoint(bool signal_thread, bool remote)
 {
-	test_send_signal_common(NULL, signal_thread);
+	test_send_signal_common(NULL, signal_thread, remote);
 }
 
-static void test_send_signal_perf(bool signal_thread)
+static void test_send_signal_perf(bool signal_thread, bool remote)
 {
 	struct perf_event_attr attr = {
 		.freq = 1,
@@ -162,10 +204,10 @@ static void test_send_signal_perf(bool signal_thread)
 		.config = PERF_COUNT_SW_CPU_CLOCK,
 	};
 
-	test_send_signal_common(&attr, signal_thread);
+	test_send_signal_common(&attr, signal_thread, remote);
 }
 
-static void test_send_signal_nmi(bool signal_thread)
+static void test_send_signal_nmi(bool signal_thread, bool remote)
 {
 	struct perf_event_attr attr = {
 		.sample_period = 1,
@@ -191,21 +233,35 @@ static void test_send_signal_nmi(bool signal_thread)
 		close(pmu_fd);
 	}
 
-	test_send_signal_common(&attr, signal_thread);
+	test_send_signal_common(&attr, signal_thread, remote);
 }
 
 void test_send_signal(void)
 {
 	if (test__start_subtest("send_signal_tracepoint"))
-		test_send_signal_tracepoint(false);
+		test_send_signal_tracepoint(false, false);
 	if (test__start_subtest("send_signal_perf"))
-		test_send_signal_perf(false);
+		test_send_signal_perf(false, false);
 	if (test__start_subtest("send_signal_nmi"))
-		test_send_signal_nmi(false);
+		test_send_signal_nmi(false, false);
 	if (test__start_subtest("send_signal_tracepoint_thread"))
-		test_send_signal_tracepoint(true);
+		test_send_signal_tracepoint(true, false);
 	if (test__start_subtest("send_signal_perf_thread"))
-		test_send_signal_perf(true);
+		test_send_signal_perf(true, false);
 	if (test__start_subtest("send_signal_nmi_thread"))
-		test_send_signal_nmi(true);
+		test_send_signal_nmi(true, false);
+
+	/* Signal remote thread and thread group */
+	if (test__start_subtest("send_signal_tracepoint_remote"))
+		test_send_signal_tracepoint(false, true);
+	if (test__start_subtest("send_signal_perf_remote"))
+		test_send_signal_perf(false, true);
+	if (test__start_subtest("send_signal_nmi_remote"))
+		test_send_signal_nmi(false, true);
+	if (test__start_subtest("send_signal_tracepoint_thread_remote"))
+		test_send_signal_tracepoint(true, true);
+	if (test__start_subtest("send_signal_perf_thread_remote"))
+		test_send_signal_perf(true, true);
+	if (test__start_subtest("send_signal_nmi_thread_remote"))
+		test_send_signal_nmi(true, true);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
index 92354cd72044..fd6c055377ae 100644
--- a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
@@ -4,7 +4,7 @@
 #include <linux/version.h>
 #include <bpf/bpf_helpers.h>
 
-__u32 sig = 0, pid = 0, status = 0, signal_thread = 0;
+__u32 sig = 0, pid = 0, status = 0, signal_thread = 0, target_pid = 0;
 
 static __always_inline int bpf_send_signal_test(void *ctx)
 {
@@ -14,10 +14,17 @@ static __always_inline int bpf_send_signal_test(void *ctx)
 		return 0;
 
 	if ((bpf_get_current_pid_tgid() >> 32) == pid) {
-		if (signal_thread)
-			ret = bpf_send_signal_thread(sig);
-		else
-			ret = bpf_send_signal(sig);
+		if (signal_thread) {
+			if (target_pid != 0)
+				ret = bpf_send_signal_pid(sig, target_pid);
+			else
+				ret = bpf_send_signal_thread(sig);
+		} else {
+			if (target_pid != 0)
+				ret = bpf_send_signal_tgid(sig, target_pid);
+			else
+				ret = bpf_send_signal(sig);
+		}
 		if (ret == 0)
 			status = 1;
 	}
-- 
2.40.1