Commit b5cc46cd authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

selftests/bpf: Fix spurious test failures in core_retro selftest 



core_retro selftest uses BPF program that's triggered on sys_enter
system-wide, but has no protection from some unrelated process doing syscall
while selftest is running. This leads to occasional test failures with
unexpected PIDs being returned. Fix that by filtering out all processes that
are not test_progs process.

Fixes: fcda189a ("selftests/bpf: Add test relying only on CO-RE and no recent kernel features")
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200731204957.2047119-1-andriin@fb.com
parent 5a6b1a20

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

+6 −2
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ 


void test_core_retro(void)

{

	int err, zero = 0, res, duration = 0;

	int err, zero = 0, res, duration = 0, my_pid = getpid();

	struct test_core_retro *skel;



	/* load program */
@@ -14,6 +14,10 @@ void test_core_retro(void) 
	if (CHECK(!skel, "skel_load", "skeleton open/load failed\n"))

		goto out_close;



	err = bpf_map_update_elem(bpf_map__fd(skel->maps.exp_tgid_map), &zero, &my_pid, 0);

	if (CHECK(err, "map_update", "failed to set expected PID: %d\n", errno))

		goto out_close;



	/* attach probe */

	err = test_core_retro__attach(skel);

	if (CHECK(err, "attach_kprobe", "err %d\n", err))
@@ -26,7 +30,7 @@ void test_core_retro(void) 
	if (CHECK(err, "map_lookup", "failed to lookup result: %d\n", errno))

		goto out_close;



	CHECK(res != getpid(), "pid_check", "got %d != exp %d\n", res, getpid());

	CHECK(res != my_pid, "pid_check", "got %d != exp %d\n", res, my_pid);



out_close:

	test_core_retro__destroy(skel);

tools/testing/selftests/bpf/progs/test_core_retro.c

+13 −0
Original line number Diff line number Diff line
@@ -8,6 +8,13 @@ struct task_struct { 
	int tgid;

} __attribute__((preserve_access_index));



struct {

	__uint(type, BPF_MAP_TYPE_ARRAY);

	__uint(max_entries, 1);

	__type(key, int);

	__type(value, int);

} exp_tgid_map SEC(".maps");



struct {

	__uint(type, BPF_MAP_TYPE_ARRAY);

	__uint(max_entries, 1);
@@ -21,6 +28,12 @@ int handle_sys_enter(void *ctx) 
	struct task_struct *task = (void *)bpf_get_current_task();

	int tgid = BPF_CORE_READ(task, tgid);

	int zero = 0;

	int real_tgid = bpf_get_current_pid_tgid() >> 32;

	int *exp_tgid = bpf_map_lookup_elem(&exp_tgid_map, &zero);



	/* only pass through sys_enters from test process */

	if (!exp_tgid || *exp_tgid != real_tgid)

		return 0;



	bpf_map_update_elem(&results, &zero, &tgid, 0);