Merge branch 'bpf-show-precise-rejected-function-when-attaching-to-__noreturn-and-deny-list-functions'

KaFai Wan says:

====================
bpf: Show precise rejected function when attaching to __noreturn and deny list functions

Show precise rejected function when attaching fexit/fmod_ret to __noreturn
functions.
Add log for attaching tracing programs to functions in deny list.
Add selftest for attaching tracing programs to functions in deny list.
Migrate fexit_noreturns case into tracing_failure test suite.

changes:
v4:
- change tracing_deny case attaching function (Yonghong Song)
- add Acked-by: Yafang Shao and Yonghong Song

v3:
- add tracing_deny case into existing files (Alexei)
- migrate fexit_noreturns into tracing_failure
- change SOB
  https://lore.kernel.org/bpf/20250722153434.20571-1-kafai.wan@linux.dev/

v2:
- change verifier log message (Alexei)
- add missing Suggested-by
  https://lore.kernel.org/bpf/20250714120408.1627128-1-mannkafai@gmail.com/

v1:
 https://lore.kernel.org/all/20250710162717.3808020-1-mannkafai@gmail.com/
---
====================

Link: https://patch.msgid.link/20250724151454.499040-1-kafai.wan@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/verifier.c

@@ -23981,11 +23981,14 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 			return ret;
 	} else if (prog->type == BPF_PROG_TYPE_TRACING &&
 		   btf_id_set_contains(&btf_id_deny, btf_id)) {
+		verbose(env, "Attaching tracing programs to function '%s' is rejected.\n",
+			tgt_info.tgt_name);
 		return -EINVAL;
 	} else if ((prog->expected_attach_type == BPF_TRACE_FEXIT ||
 		   prog->expected_attach_type == BPF_MODIFY_RETURN) &&
 		   btf_id_set_contains(&noreturn_deny, btf_id)) {
-		verbose(env, "Attaching fexit/fmod_ret to __noreturn functions is rejected.\n");
+		verbose(env, "Attaching fexit/fmod_ret to __noreturn function '%s' is rejected.\n",
+			tgt_info.tgt_name);
 		return -EINVAL;
 	}
 

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

@@ -1,9 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <test_progs.h>
-#include "fexit_noreturns.skel.h"
-
-void test_fexit_noreturns(void)
-{
-	RUN_TESTS(fexit_noreturns);
-}

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

@@ -28,10 +28,62 @@ out:
 	tracing_failure__destroy(skel);
 }
 
+static void test_tracing_fail_prog(const char *prog_name, const char *exp_msg)
+{
+	struct tracing_failure *skel;
+	struct bpf_program *prog;
+	char log_buf[256];
+	int err;
+
+	skel = tracing_failure__open();
+	if (!ASSERT_OK_PTR(skel, "tracing_failure__open"))
+		return;
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+		goto out;
+
+	bpf_program__set_autoload(prog, true);
+	bpf_program__set_log_buf(prog, log_buf, sizeof(log_buf));
+
+	err = tracing_failure__load(skel);
+	if (!ASSERT_ERR(err, "tracing_failure__load"))
+		goto out;
+
+	ASSERT_HAS_SUBSTR(log_buf, exp_msg, "log_buf");
+out:
+	tracing_failure__destroy(skel);
+}
+
+static void test_tracing_deny(void)
+{
+	int btf_id;
+
+	/* __rcu_read_lock depends on CONFIG_PREEMPT_RCU */
+	btf_id = libbpf_find_vmlinux_btf_id("__rcu_read_lock", BPF_TRACE_FENTRY);
+	if (btf_id <= 0) {
+		test__skip();
+		return;
+	}
+
+	test_tracing_fail_prog("tracing_deny",
+			       "Attaching tracing programs to function '__rcu_read_lock' is rejected.");
+}
+
+static void test_fexit_noreturns(void)
+{
+	test_tracing_fail_prog("fexit_noreturns",
+			       "Attaching fexit/fmod_ret to __noreturn function 'do_exit' is rejected.");
+}
+
 void test_tracing_failure(void)
 {
 	if (test__start_subtest("bpf_spin_lock"))
 		test_bpf_spin_lock(true);
 	if (test__start_subtest("bpf_spin_unlock"))
 		test_bpf_spin_lock(false);
+	if (test__start_subtest("tracing_deny"))
+		test_tracing_deny();
+	if (test__start_subtest("fexit_noreturns"))
+		test_fexit_noreturns();
 }

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

@@ -1,15 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/bpf.h>
-#include <bpf/bpf_helpers.h>
-#include <bpf/bpf_tracing.h>
-#include "bpf_misc.h"
-
-char _license[] SEC("license") = "GPL";
-
-SEC("fexit/do_exit")
-__failure __msg("Attaching fexit/fmod_ret to __noreturn functions is rejected.")
-int BPF_PROG(noreturns)
-{
-	return 0;
-}

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

@@ -18,3 +18,15 @@ int BPF_PROG(test_spin_unlock, struct bpf_spin_lock *lock)
 {
 	return 0;
 }
+
+SEC("?fentry/__rcu_read_lock")
+int BPF_PROG(tracing_deny)
+{
+	return 0;
+}
+
+SEC("?fexit/do_exit")
+int BPF_PROG(fexit_noreturns)
+{
+	return 0;
+}