Subject: [PATCHv2 bpf 1/3] selftests/bpf: Shuffle cookies symbols in kprobe multi test

From: Jiri Olsa <[email-masked]>
Date: Mon, 6 Jun 2022 20:47:29 +0200

There's a kernel bug that causes cookies to be misplaced and
the reason we did not catch this with this test is that we
provide bpf_fentry_test* functions already sorted by name.

Shuffling function bpf_fentry_test2 deeper in the list and
keeping the current cookie values as before will trigger
the bug.

The kernel fix is coming in following changes.

Acked-by: Song Liu <[email-masked]>
Signed-off-by: Jiri Olsa <[email-masked]>
---
 .../selftests/bpf/prog_tests/bpf_cookie.c     | 78 +++++++++----------
 .../selftests/bpf/progs/kprobe_multi.c        | 24 +++---
 2 files changed, 51 insertions(+), 51 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
index 83ef55e3caa4..2974b44f80fa 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
@@ -121,24 +121,24 @@ static void kprobe_multi_link_api_subtest(void)
 })
 
 	GET_ADDR("bpf_fentry_test1", addrs[0]);
-	GET_ADDR("bpf_fentry_test2", addrs[1]);
-	GET_ADDR("bpf_fentry_test3", addrs[2]);
-	GET_ADDR("bpf_fentry_test4", addrs[3]);
-	GET_ADDR("bpf_fentry_test5", addrs[4]);
-	GET_ADDR("bpf_fentry_test6", addrs[5]);
-	GET_ADDR("bpf_fentry_test7", addrs[6]);
+	GET_ADDR("bpf_fentry_test3", addrs[1]);
+	GET_ADDR("bpf_fentry_test4", addrs[2]);
+	GET_ADDR("bpf_fentry_test5", addrs[3]);
+	GET_ADDR("bpf_fentry_test6", addrs[4]);
+	GET_ADDR("bpf_fentry_test7", addrs[5]);
+	GET_ADDR("bpf_fentry_test2", addrs[6]);
 	GET_ADDR("bpf_fentry_test8", addrs[7]);
 
 #undef GET_ADDR
 
-	cookies[0] = 1;
-	cookies[1] = 2;
-	cookies[2] = 3;
-	cookies[3] = 4;
-	cookies[4] = 5;
-	cookies[5] = 6;
-	cookies[6] = 7;
-	cookies[7] = 8;
+	cookies[0] = 1; /* bpf_fentry_test1 */
+	cookies[1] = 2; /* bpf_fentry_test3 */
+	cookies[2] = 3; /* bpf_fentry_test4 */
+	cookies[3] = 4; /* bpf_fentry_test5 */
+	cookies[4] = 5; /* bpf_fentry_test6 */
+	cookies[5] = 6; /* bpf_fentry_test7 */
+	cookies[6] = 7; /* bpf_fentry_test2 */
+	cookies[7] = 8; /* bpf_fentry_test8 */
 
 	opts.kprobe_multi.addrs = (const unsigned long *) &addrs;
 	opts.kprobe_multi.cnt = ARRAY_SIZE(addrs);
@@ -149,14 +149,14 @@ static void kprobe_multi_link_api_subtest(void)
 	if (!ASSERT_GE(link1_fd, 0, "link1_fd"))
 		goto cleanup;
 
-	cookies[0] = 8;
-	cookies[1] = 7;
-	cookies[2] = 6;
-	cookies[3] = 5;
-	cookies[4] = 4;
-	cookies[5] = 3;
-	cookies[6] = 2;
-	cookies[7] = 1;
+	cookies[0] = 8; /* bpf_fentry_test1 */
+	cookies[1] = 7; /* bpf_fentry_test3 */
+	cookies[2] = 6; /* bpf_fentry_test4 */
+	cookies[3] = 5; /* bpf_fentry_test5 */
+	cookies[4] = 4; /* bpf_fentry_test6 */
+	cookies[5] = 3; /* bpf_fentry_test7 */
+	cookies[6] = 2; /* bpf_fentry_test2 */
+	cookies[7] = 1; /* bpf_fentry_test8 */
 
 	opts.kprobe_multi.flags = BPF_F_KPROBE_MULTI_RETURN;
 	prog_fd = bpf_program__fd(skel->progs.test_kretprobe);
@@ -181,12 +181,12 @@ static void kprobe_multi_attach_api_subtest(void)
 	struct kprobe_multi *skel = NULL;
 	const char *syms[8] = {
 		"bpf_fentry_test1",
-		"bpf_fentry_test2",
 		"bpf_fentry_test3",
 		"bpf_fentry_test4",
 		"bpf_fentry_test5",
 		"bpf_fentry_test6",
 		"bpf_fentry_test7",
+		"bpf_fentry_test2",
 		"bpf_fentry_test8",
 	};
 	__u64 cookies[8];
@@ -198,14 +198,14 @@ static void kprobe_multi_attach_api_subtest(void)
 	skel->bss->pid = getpid();
 	skel->bss->test_cookie = true;
 
-	cookies[0] = 1;
-	cookies[1] = 2;
-	cookies[2] = 3;
-	cookies[3] = 4;
-	cookies[4] = 5;
-	cookies[5] = 6;
-	cookies[6] = 7;
-	cookies[7] = 8;
+	cookies[0] = 1; /* bpf_fentry_test1 */
+	cookies[1] = 2; /* bpf_fentry_test3 */
+	cookies[2] = 3; /* bpf_fentry_test4 */
+	cookies[3] = 4; /* bpf_fentry_test5 */
+	cookies[4] = 5; /* bpf_fentry_test6 */
+	cookies[5] = 6; /* bpf_fentry_test7 */
+	cookies[6] = 7; /* bpf_fentry_test2 */
+	cookies[7] = 8; /* bpf_fentry_test8 */
 
 	opts.syms = syms;
 	opts.cnt = ARRAY_SIZE(syms);
@@ -216,14 +216,14 @@ static void kprobe_multi_attach_api_subtest(void)
 	if (!ASSERT_OK_PTR(link1, "bpf_program__attach_kprobe_multi_opts"))
 		goto cleanup;
 
-	cookies[0] = 8;
-	cookies[1] = 7;
-	cookies[2] = 6;
-	cookies[3] = 5;
-	cookies[4] = 4;
-	cookies[5] = 3;
-	cookies[6] = 2;
-	cookies[7] = 1;
+	cookies[0] = 8; /* bpf_fentry_test1 */
+	cookies[1] = 7; /* bpf_fentry_test3 */
+	cookies[2] = 6; /* bpf_fentry_test4 */
+	cookies[3] = 5; /* bpf_fentry_test5 */
+	cookies[4] = 4; /* bpf_fentry_test6 */
+	cookies[5] = 3; /* bpf_fentry_test7 */
+	cookies[6] = 2; /* bpf_fentry_test2 */
+	cookies[7] = 1; /* bpf_fentry_test8 */
 
 	opts.retprobe = true;
 
diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi.c b/tools/testing/selftests/bpf/progs/kprobe_multi.c
index 93510f4f0f3a..08f95a8155d1 100644
--- a/tools/testing/selftests/bpf/progs/kprobe_multi.c
+++ b/tools/testing/selftests/bpf/progs/kprobe_multi.c
@@ -54,21 +54,21 @@ static void kprobe_multi_check(void *ctx, bool is_return)
 
 	if (is_return) {
 		SET(kretprobe_test1_result, &bpf_fentry_test1, 8);
-		SET(kretprobe_test2_result, &bpf_fentry_test2, 7);
-		SET(kretprobe_test3_result, &bpf_fentry_test3, 6);
-		SET(kretprobe_test4_result, &bpf_fentry_test4, 5);
-		SET(kretprobe_test5_result, &bpf_fentry_test5, 4);
-		SET(kretprobe_test6_result, &bpf_fentry_test6, 3);
-		SET(kretprobe_test7_result, &bpf_fentry_test7, 2);
+		SET(kretprobe_test2_result, &bpf_fentry_test2, 2);
+		SET(kretprobe_test3_result, &bpf_fentry_test3, 7);
+		SET(kretprobe_test4_result, &bpf_fentry_test4, 6);
+		SET(kretprobe_test5_result, &bpf_fentry_test5, 5);
+		SET(kretprobe_test6_result, &bpf_fentry_test6, 4);
+		SET(kretprobe_test7_result, &bpf_fentry_test7, 3);
 		SET(kretprobe_test8_result, &bpf_fentry_test8, 1);
 	} else {
 		SET(kprobe_test1_result, &bpf_fentry_test1, 1);
-		SET(kprobe_test2_result, &bpf_fentry_test2, 2);
-		SET(kprobe_test3_result, &bpf_fentry_test3, 3);
-		SET(kprobe_test4_result, &bpf_fentry_test4, 4);
-		SET(kprobe_test5_result, &bpf_fentry_test5, 5);
-		SET(kprobe_test6_result, &bpf_fentry_test6, 6);
-		SET(kprobe_test7_result, &bpf_fentry_test7, 7);
+		SET(kprobe_test2_result, &bpf_fentry_test2, 7);
+		SET(kprobe_test3_result, &bpf_fentry_test3, 2);
+		SET(kprobe_test4_result, &bpf_fentry_test4, 3);
+		SET(kprobe_test5_result, &bpf_fentry_test5, 4);
+		SET(kprobe_test6_result, &bpf_fentry_test6, 5);
+		SET(kprobe_test7_result, &bpf_fentry_test7, 6);
 		SET(kprobe_test8_result, &bpf_fentry_test8, 8);
 	}
 
-- 
2.35.3