[PATCH bpf-next 2/4] selftests/bpf: Run the patch list tests with bpf_jit_harden off

[Qiliang Yuan]

The patch list tests compare the xlated insns of their progs, and
patch_list/line_and_func_info and patch_list/poke_descriptor look at
the line info and the poke descriptors of a prog. They run serially,
because other tests change net.core.bpf_jit_harden.

They don't set the sysctl themselves, though. When it is 2 at the
start, constant blinding rewrites the progs: 8 of the
verifier_patch_list tests and patch_list/line_and_func_info fail, and
patch_list/poke_descriptor passes with no poke descriptor to check:

  XLATED:
  ...
  5: r12 = -360925233
  6: r12 ^= -360925238
  7: if r1 > r12 goto pc+3
  ...
  #719/1   verifier_patch_list/patch list: forward jumps to and over patched insns:FAIL
  ...
  test_line_and_func_info:FAIL:fn_1001 unexpected fn_1001: got FALSE

Set the sysctl to 0 while verifier_patch_list and the first two
subtests of patch_list run, and restore it afterwards, the way
patch_list/classic_filter does.

Fixes: 67d4d0b73c29 ("selftests/bpf: Test jumps around patched instructions")
Fixes: d86e6695cb2f ("selftests/bpf: Test the tables that follow patched and removed instructions")
Reported-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Closes: https://lore.kernel.org/bpf/DMKHZS5B5CNO.186F6YH1T6YU4@xxxxxxxxx/
Signed-off-by: Qiliang Yuan <odys.yuan@xxxxxxxxx>
---
 tools/testing/selftests/bpf/prog_tests/patch_list.c | 10 +++++++++-
 tools/testing/selftests/bpf/prog_tests/verifier.c   | 17 +++++++++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/patch_list.c b/tools/testing/selftests/bpf/prog_tests/patch_list.c
index 127ed58cfc39d..43bd8a4428060 100644
--- a/tools/testing/selftests/bpf/prog_tests/patch_list.c
+++ b/tools/testing/selftests/bpf/prog_tests/patch_list.c
@@ -243,14 +243,22 @@ static void test_classic_filter(void)
 
 /*
  * Serial: the xlated code is another one and there are no poke descriptors
- * while another test sets bpf_jit_harden, and classic_filter sets it.
+ * while another test sets bpf_jit_harden, and classic_filter sets it. Keep
+ * the sysctl at 0 for the subtests that need the code unblinded.
  */
 void serial_test_patch_list(void)
 {
+	const char *harden = "/proc/sys/net/core/bpf_jit_harden";
+	char old[16] = {};
+
+	if (sysctl_set_or_fail(harden, old, "0"))
+		return;
 	if (test__start_subtest("line_and_func_info"))
 		test_line_and_func_info();
 	if (test__start_subtest("poke_descriptor"))
 		test_poke_descriptor();
+	sysctl_set_or_fail(harden, NULL, old);
+
 	if (test__start_subtest("classic_filter"))
 		test_classic_filter();
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 99f0551c8b592..1108fd5e4d162 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -6,6 +6,7 @@
 #include "arena_noarena.skel.h"
 #include "arena_kfunc_jit.skel.h"
 #include "cap_helpers.h"
+#include "sysctl_helpers.h"
 #include "cb_refs.skel.h"
 #include "verifier_aggregate_arg.skel.h"
 #include "verifier_aggregate_ret.skel.h"
@@ -288,8 +289,20 @@ void test_verifier_netfilter_ctx(void)        { RUN(verifier_netfilter_ctx); }
 void test_verifier_netfilter_retcode(void)    { RUN(verifier_netfilter_retcode); }
 void test_verifier_bpf_fastcall(void)         { RUN(verifier_bpf_fastcall); }
 void test_verifier_or_jmp32_k(void)           { RUN(verifier_or_jmp32_k); }
-/* Serial: the xlated code is another one while another test sets bpf_jit_harden */
-void serial_test_verifier_patch_list(void)    { RUN(verifier_patch_list); }
+/*
+ * Run serially with bpf_jit_harden at 0: blinding changes the xlated insns that
+ * the tests compare, and other tests set the sysctl.
+ */
+void serial_test_verifier_patch_list(void)
+{
+	const char *harden = "/proc/sys/net/core/bpf_jit_harden";
+	char old[16] = {};
+
+	if (sysctl_set_or_fail(harden, old, "0"))
+		return;
+	RUN(verifier_patch_list);
+	sysctl_set_or_fail(harden, NULL, old);
+}
 void test_verifier_percpu_addr(void)          { RUN(verifier_percpu_addr); }
 void test_verifier_precision(void)            { RUN(verifier_precision); }
 void test_verifier_prevent_map_lookup(void)   { RUN(verifier_prevent_map_lookup); }

-- 
2.43.0