[PATCH bpf-next v5 2/2] selftests/bpf: Augment send_signal test with remote signaling

Puranjay Mohan
2024-10-16T08:42:20Z

Add testcases to test bpf_send_signal_task(). In these new test cases,
the main process triggers the BPF program and the forked process
receives the signals. The target process's signal handler receives a
cookie from the bpf program.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
.../selftests/bpf/prog_tests/send_signal.c | 133 +++++++++++++-----
.../bpf/progs/test_send_signal_kern.c | 35 ++++-
2 files changed, 130 insertions(+), 38 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c b/tools/testing/selftests/bpf/prog_tests/send_signal.c
index 6cc69900b3106..1aed94ec14efb 100644
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -8,17 +8,25 @@ static int sigusr1_received;

static void sigusr1_handler(int signum)
{
- sigusr1_received = 1;
+ sigusr1_received = 8;
+}
+
+static void sigusr1_siginfo_handler(int s, siginfo_t *i, void *v)
+{
+ sigusr1_received = (int)(long long)i->si_value.sival_ptr;
}

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;
+ struct sigaction sa;
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;
@@ -39,11 +47,14 @@ 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");
+ if (remote) {
+ sa.sa_sigaction = sigusr1_siginfo_handler;
+ sa.sa_flags = SA_RESTART | SA_SIGINFO;
+ ASSERT_NEQ(sigaction(SIGUSR1, &sa, NULL), -1, "sigaction");
+ } else {
+ ASSERT_NEQ(signal(SIGUSR1, sigusr1_handler), SIG_ERR, "signal");
+ }

close(pipe_c2p[0]); /* close read */
close(pipe_p2c[1]); /* close write */
@@ -52,10 +63,12 @@ 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");
@@ -66,20 +79,25 @@ 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';
- ASSERT_EQ(sigusr1_received, 1, "sigusr1_received");
+ buf[0] = sigusr1_received;
+
+ ASSERT_EQ(sigusr1_received, 8, "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");
+ if (!remote)
+ ASSERT_OK(setpriority(PRIO_PROCESS, 0, old_prio), "setpriority");

close(pipe_c2p[1]);
close(pipe_p2c[0]);
@@ -93,6 +111,17 @@ 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 +129,12 @@ 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 +152,30 @@ 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"))
@@ -133,7 +185,7 @@ static void test_send_signal_common(struct perf_event_attr *attr,
goto disable_pmu;
}

- ASSERT_EQ(buf[0], '2', "incorrect result");
+ ASSERT_EQ(buf[0], 8, "incorrect result");

/* notify child safe to exit */
ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");
@@ -142,18 +194,21 @@ 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 +217,10 @@ 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 +246,35 @@ 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 92354cd720440..176a355e30624 100644
--- a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
@@ -1,27 +1,50 @@
// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Facebook
-#include <linux/bpf.h>
+#include <vmlinux.h>
#include <linux/version.h>
#include <bpf/bpf_helpers.h>

-__u32 sig = 0, pid = 0, status = 0, signal_thread = 0;
+struct task_struct *bpf_task_from_pid(int pid) __ksym;
+void bpf_task_release(struct task_struct *p) __ksym;
+int bpf_send_signal_task(struct task_struct *task, int sig, enum pid_type type, u64 value) __ksym;
+
+__u32 sig = 0, pid = 0, status = 0, signal_thread = 0, target_pid = 0;

static __always_inline int bpf_send_signal_test(void *ctx)
{
+ struct task_struct *target_task = NULL;
int ret;
+ u64 value;

if (status != 0 || pid == 0)
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 (target_pid) {
+ target_task = bpf_task_from_pid(target_pid);
+ if (!target_task)
+ return 0;
+ value = 8;
+ }
+
+ if (signal_thread) {
+ if (target_pid)
+ ret = bpf_send_signal_task(target_task, sig, PIDTYPE_PID, value);
+ else
+ ret = bpf_send_signal_thread(sig);
+ } else {
+ if (target_pid)
+ ret = bpf_send_signal_task(target_task, sig, PIDTYPE_TGID, value);
+ else
+ ret = bpf_send_signal(sig);
+ }
if (ret == 0)
status = 1;
}

+ if (target_task)
+ bpf_task_release(target_task);
+
return 0;
}

--
2.40.1