bpf: Implement bpf_get_attach_cookie() for tracing programs.

Implement bpf_get_attach_cookie() for fentry, fexit, and fmod_ret
tracing programs.  The cookie is from the bpf_prog from the program ID
of the current BPF program.

Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>

kernel/trace/bpf_trace.c

@@ -1084,6 +1084,26 @@ static const struct bpf_func_proto bpf_get_attach_cookie_proto_pe = {
 	.arg1_type	= ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_get_attach_cookie_tracing, void *, ctx)
+{
+	const struct bpf_prog *prog;
+	int off = get_trampo_var_off(ctx, BPF_TRAMP_F_PROG_ID);
+
+	if (off < 0)
+		return 0;
+
+	prog = (const struct bpf_prog *)((u64 *)ctx)[-off];
+
+	return prog->aux->cookie;
+}
+
+static const struct bpf_func_proto bpf_get_attach_cookie_proto_tracing = {
+	.func		= bpf_get_attach_cookie_tracing,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
 {
 #ifndef CONFIG_X86
@@ -1708,6 +1728,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_ret_proto : NULL;
 	case BPF_FUNC_get_func_arg_cnt:
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_func_arg_cnt_proto : NULL;
+	case BPF_FUNC_get_attach_cookie:
+		return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto_tracing : NULL;
 	default:
 		fn = raw_tp_prog_func_proto(func_id, prog);
 		if (!fn && prog->expected_attach_type == BPF_TRACE_ITER)

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

@@ -231,6 +231,61 @@ static void pe_subtest(struct test_bpf_cookie *skel)
 	bpf_link__destroy(link);
 }
 
+static void tracing_subtest(struct test_bpf_cookie *skel)
+{
+	__u64 cookie;
+	__u32 duration = 0, retval;
+	int prog_fd;
+	int fentry_fd = -1, fexit_fd = -1, fmod_ret_fd = -1;
+
+	skel->bss->fentry_res = 0;
+	skel->bss->fexit_res = 0;
+
+	cookie = 0x100000;
+	prog_fd = bpf_program__fd(skel->progs.fentry_test1);
+	if (!ASSERT_GE(prog_fd, 0, "fentry.prog_fd"))
+		return;
+	fentry_fd = bpf_raw_tracepoint_cookie_open(NULL, prog_fd, cookie);
+	if (!ASSERT_GE(fentry_fd, 0, "fentry.open"))
+		return;
+
+	cookie = 0x200000;
+	prog_fd = bpf_program__fd(skel->progs.fexit_test1);
+	if (!ASSERT_GE(prog_fd, 0, "fexit.prog_fd"))
+		goto cleanup;
+	fexit_fd = bpf_raw_tracepoint_cookie_open(NULL, prog_fd, cookie);
+	if (!ASSERT_GE(fexit_fd, 0, "fexit.open"))
+		goto cleanup;
+
+	cookie = 0x300000;
+	prog_fd = bpf_program__fd(skel->progs.fmod_ret_test);
+	if (!ASSERT_GE(prog_fd, 0, "fmod_ret.prog_fd"))
+		goto cleanup;
+	fmod_ret_fd = bpf_raw_tracepoint_cookie_open(NULL, prog_fd, cookie);
+	if (!ASSERT_GE(fmod_ret_fd, 0, "fmod_ret.opoen"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.fentry_test1);
+	bpf_prog_test_run(prog_fd, 1, NULL, 0,
+			  NULL, NULL, &retval, &duration);
+
+	prog_fd = bpf_program__fd(skel->progs.fmod_ret_test);
+	bpf_prog_test_run(prog_fd, 1, NULL, 0,
+			  NULL, NULL, &retval, &duration);
+
+	ASSERT_EQ(skel->bss->fentry_res, 0x100000, "fentry_res");
+	ASSERT_EQ(skel->bss->fexit_res, 0x200000, "fexit_res");
+	ASSERT_EQ(skel->bss->fmod_ret_res, 0x300000, "fmod_ret_res");
+
+cleanup:
+	if (fentry_fd >= 0)
+		close(fentry_fd);
+	if (fexit_fd >= 0)
+		close(fexit_fd);
+	if (fmod_ret_fd >= 0)
+		close(fmod_ret_fd);
+}
+
 void test_bpf_cookie(void)
 {
 	struct test_bpf_cookie *skel;
@@ -249,6 +304,8 @@ void test_bpf_cookie(void)
 		tp_subtest(skel);
 	if (test__start_subtest("perf_event"))
 		pe_subtest(skel);
+	if (test__start_subtest("tracing"))
+		tracing_subtest(skel);
 
 	test_bpf_cookie__destroy(skel);
 }

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

@@ -14,6 +14,9 @@ int uprobe_res;
 int uretprobe_res;
 int tp_res;
 int pe_res;
+int fentry_res;
+int fexit_res;
+int fmod_ret_res;
 
 static void update(void *ctx, int *res)
 {
@@ -82,4 +85,25 @@ int handle_pe(struct pt_regs *ctx)
 	return 0;
 }
 
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(fentry_test1, int a)
+{
+	update(ctx, &fentry_res);
+	return 0;
+}
+
+SEC("fexit/bpf_fentry_test1")
+int BPF_PROG(fexit_test1, int a, int ret)
+{
+	update(ctx, &fexit_res);
+	return 0;
+}
+
+SEC("fmod_ret/bpf_modify_return_test")
+int BPF_PROG(fmod_ret_test, int _a, int *_b, int _ret)
+{
+	update(ctx, &fmod_ret_res);
+	return 1234;
+}
+
 char _license[] SEC("license") = "GPL";