bpf: Add bpf_jit_supports_fsession()

The added fsession does not prevent running on those architectures, that
haven't added fsession support.

For example, try to run fsession tests on arm64:

test_fsession_basic:PASS:fsession_test__open_and_load 0 nsec
test_fsession_basic:PASS:fsession_attach 0 nsec
check_result:FAIL:test_run_opts err unexpected error: -14 (errno 14)

In order to prevent such errors, add bpf_jit_supports_fsession() to guard
those architectures.

Fixes: 2d419c4 ("bpf: add fsession support")
Acked-by: Puranjay Mohan <puranjay@kernel.org>
Tested-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260131144950.16294-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Asphaltt

arch/x86/net/bpf_jit_comp.c

@@ -4112,3 +4112,8 @@ bool bpf_jit_supports_timed_may_goto(void)
 {
 	return true;
 }
+
+bool bpf_jit_supports_fsession(void)
+{
+	return true;
+}

include/linux/filter.h

@@ -1167,6 +1167,7 @@ bool bpf_jit_supports_arena(void);
 bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena);
 bool bpf_jit_supports_private_stack(void);
 bool bpf_jit_supports_timed_may_goto(void);
+bool bpf_jit_supports_fsession(void);
 u64 bpf_arch_uaddress_limit(void);
 void arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp), void *cookie);
 u64 arch_bpf_timed_may_goto(void);

kernel/bpf/core.c

@@ -3144,6 +3144,11 @@ bool __weak bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)
 	return false;
 }
 
+bool __weak bpf_jit_supports_fsession(void)
+{
+	return false;
+}
+
 u64 __weak bpf_arch_uaddress_limit(void)
 {
 #if defined(CONFIG_64BIT) && defined(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE)

kernel/bpf/verifier.c

@@ -24828,6 +24828,11 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 	case BPF_TRACE_FENTRY:
 	case BPF_TRACE_FEXIT:
 	case BPF_TRACE_FSESSION:
+		if (prog->expected_attach_type == BPF_TRACE_FSESSION &&
+		    !bpf_jit_supports_fsession()) {
+			bpf_log(log, "JIT does not support fsession\n");
+			return -EOPNOTSUPP;
+		}
 		if (!btf_type_is_func(t)) {
 			bpf_log(log, "attach_btf_id %u is not a function\n",
 				btf_id);

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

@@ -29,8 +29,16 @@ static void test_fsession_basic(void)
 	struct fsession_test *skel = NULL;
 	int err;
 
-	skel = fsession_test__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "fsession_test__open_and_load"))
+	skel = fsession_test__open();
+	if (!ASSERT_OK_PTR(skel, "fsession_test__open"))
+		return;
+
+	err = fsession_test__load(skel);
+	if (err == -EOPNOTSUPP) {
+		test__skip();
+		goto cleanup;
+	}
+	if (!ASSERT_OK(err, "fsession_test__load"))
 		goto cleanup;
 
 	err = fsession_test__attach(skel);
@@ -47,8 +55,16 @@ static void test_fsession_reattach(void)
 	struct fsession_test *skel = NULL;
 	int err;
 
-	skel = fsession_test__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "fsession_test__open_and_load"))
+	skel = fsession_test__open();
+	if (!ASSERT_OK_PTR(skel, "fsession_test__open"))
+		return;
+
+	err = fsession_test__load(skel);
+	if (err == -EOPNOTSUPP) {
+		test__skip();
+		goto cleanup;
+	}
+	if (!ASSERT_OK(err, "fsession_test__load"))
 		goto cleanup;
 
 	/* first attach */
@@ -94,6 +110,10 @@ static void test_fsession_cookie(void)
 	bpf_program__set_autoload(skel->progs.test6, false);
 
 	err = fsession_test__load(skel);
+	if (err == -EOPNOTSUPP) {
+		test__skip();
+		goto cleanup;
+	}
 	if (!ASSERT_OK(err, "fsession_test__load"))
 		goto cleanup;
 
@@ -111,10 +131,6 @@ static void test_fsession_cookie(void)
 
 void test_fsession_test(void)
 {
-#if !defined(__x86_64__)
-	test__skip();
-	return;
-#endif
 	if (test__start_subtest("fsession_test"))
 		test_fsession_basic();
 	if (test__start_subtest("fsession_reattach"))