selftests/bpf: Add case to test bpf_in_interrupt()

Add a timer test case to test 'bpf_in_interrupt()'.

cd tools/testing/selftests/bpf
./test_progs -t timer_interrupt
462     timer_interrupt:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20250903140438.59517-3-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/timer.c b/tools/testing/selftests/bpf/prog_tests/timer.c
index d66687f1ee6a..049efb5e7823 100644
--- a/tools/testing/selftests/bpf/prog_tests/timer.c
+++ b/tools/testing/selftests/bpf/prog_tests/timer.c
@@ -3,6 +3,7 @@
 #include <test_progs.h>
 #include "timer.skel.h"
 #include "timer_failure.skel.h"
+#include "timer_interrupt.skel.h"
 
 #define NUM_THR 8
 
@@ -95,3 +96,32 @@ void serial_test_timer(void)
 
 	RUN_TESTS(timer_failure);
 }
+
+void test_timer_interrupt(void)
+{
+	struct timer_interrupt *skel = NULL;
+	int err, prog_fd;
+	LIBBPF_OPTS(bpf_test_run_opts, opts);
+
+	skel = timer_interrupt__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "timer_interrupt__open_and_load"))
+		return;
+
+	err = timer_interrupt__attach(skel);
+	if (!ASSERT_OK(err, "timer_interrupt__attach"))
+		goto out;
+
+	prog_fd = bpf_program__fd(skel->progs.test_timer_interrupt);
+	err = bpf_prog_test_run_opts(prog_fd, &opts);
+	if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
+		goto out;
+
+	usleep(50);
+
+	ASSERT_EQ(skel->bss->in_interrupt, 0, "in_interrupt");
+	if (skel->bss->preempt_count)
+		ASSERT_NEQ(skel->bss->in_interrupt_cb, 0, "in_interrupt_cb");
+
+out:
+	timer_interrupt__destroy(skel);
+}