selftests/bpf: Verify no warning when close fexit link

Add a test to verify that there's no WARNING when detaching fexit link by
following the repro steps of previous commit.

Without the fix, the WARNING could be triggered by this test.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20260722151909.69142-3-leon.hwang@linux.dev
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
index c66037162da5..c5c9d6c359bb 100644
--- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
+++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
@@ -13,6 +13,8 @@
 #include "tailcall_cgrp_storage.skel.h"
 #include "tailcall_sleepable.skel.h"
 #include "tailcall_callback.skel.h"
+#include "tailcall_bpf2bpf2.skel.h"
+#include "tailcall_bpf2bpf_fexit.skel.h"
 
 /* test_tailcall_1 checks basic functionality by patching multiple locations
  * in a single program for a single tail call slot with nop->jmp, jmp->nop
@@ -1907,6 +1909,50 @@ static void test_tailcall_callback(void)
 	RUN_TESTS(tailcall_callback);
 }
 
+static void test_tailcall_bpf2bpf_fexit_links(void)
+{
+	struct tailcall_bpf2bpf_fexit *skel1 = NULL, *skel2 = NULL;
+	struct tailcall_bpf2bpf2 *skel_tc;
+	int err, prog_fd;
+
+	skel_tc = tailcall_bpf2bpf2__open_and_load();
+	if (!ASSERT_OK_PTR(skel_tc, "tailcall_bpf2bpf2__open_and_load"))
+		return;
+
+	skel1 = tailcall_bpf2bpf_fexit__open();
+	if (!ASSERT_OK_PTR(skel1, "tailcall_bpf2bpf_fexit__open"))
+		goto out;
+
+	prog_fd = bpf_program__fd(skel_tc->progs.classifier_0);
+	err = bpf_program__set_attach_target(skel1->progs.fexit, prog_fd, "subprog_tail");
+	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+		goto out;
+
+	err = tailcall_bpf2bpf_fexit__load(skel1);
+	if (!ASSERT_OK(err, "tailcall_bpf2bpf_fexit__load"))
+		goto out;
+
+	skel1->links.fexit = bpf_program__attach_trace(skel1->progs.fexit);
+	if (!ASSERT_OK_PTR(skel1->links.fexit, "bpf_program__attach_trace"))
+		goto out;
+
+	skel2 = tailcall_bpf2bpf_fexit__open();
+	if (!ASSERT_OK_PTR(skel2, "tailcall_bpf2bpf_fexit__open"))
+		goto out;
+
+	err = bpf_program__set_attach_target(skel2->progs.fexit, prog_fd, "subprog_tail");
+	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
+		goto out;
+
+	err = tailcall_bpf2bpf_fexit__load(skel2);
+	ASSERT_OK(err, "tailcall_bpf2bpf_fexit__load");
+
+out:
+	tailcall_bpf2bpf_fexit__destroy(skel1);
+	tailcall_bpf2bpf_fexit__destroy(skel2);
+	tailcall_bpf2bpf2__destroy(skel_tc);
+}
+
 void test_tailcalls(void)
 {
 	if (test__start_subtest("tailcall_1"))
@@ -1974,4 +2020,6 @@ void test_tailcalls(void)
 	if (test__start_subtest("tailcall_cgrp_storage_no_storage_bridge"))
 		test_tailcall_cgrp_storage_no_storage_bridge();
 	test_tailcall_callback();
+	if (test__start_subtest("tailcall_bpf2bpf_fexit_links"))
+		test_tailcall_bpf2bpf_fexit_links();
 }