linux-kernel - Re: [PATCH bpf-next v6 3/3] selftests/bpf: Skip callback tests if jit is disabled in test

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Date: Tue, 23 Jan 2024 11:34:54 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Eduard Zingerman <eddyz87@...il.com>,
 John Fastabend <john.fastabend@...il.com>, Jiri Olsa <jolsa@...nel.org>,
 Hou Tao <houtao@...weicloud.com>, Song Liu <song@...nel.org>,
 bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v6 3/3] selftests/bpf: Skip callback tests if jit
 is disabled in test_verifier



On 01/23/2024 09:08 AM, Andrii Nakryiko wrote:
> On Sun, Jan 21, 2024 at 11:57 PM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>>
>> If CONFIG_BPF_JIT_ALWAYS_ON is not set and bpf_jit_enable is 0, there
>> exist 6 failed tests.

..

>>         if (expected_ret == ACCEPT || expected_ret == VERBOSE_ACCEPT) {
>> +               if (fd_prog < 0 && saved_errno == EINVAL && jit_disabled) {
>> +                       for (i = 0; i < prog_len; i++, prog++) {
>> +                               if (!insn_is_pseudo_func(prog))
>> +                                       continue;
>> +                               printf("SKIP (callbacks are not allowed in non-JITed programs)\n");
>> +                               skips++;
>> +                               goto close_fds;
>> +                       }
>> +               }
>
> Wouldn't it be better to add an explicit flag to those tests to mark
> that they require JIT enabled, instead of trying to derive this from
> analysing their BPF instructions?

Maybe something like this, add test flag F_NEEDS_JIT_ENABLED in
bpf_loop_inline.c, check the flag and jit_disabled at the beginning
of do_test_single(), no need to check fd_prog, saved_errno and the other
conditions, the patch #2 can be removed too.

If you are OK with the following changes, I will send v7 later.

----->8-----

diff --git a/tools/testing/selftests/bpf/test_verifier.c 
b/tools/testing/selftests/bpf/test_verifier.c
index 1a09fc34d093..c65915188d7c 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -67,6 +67,7 @@

  #define F_NEEDS_EFFICIENT_UNALIGNED_ACCESS     (1 << 0)
  #define F_LOAD_WITH_STRICT_ALIGNMENT           (1 << 1)
+#define F_NEEDS_JIT_ENABLED                    (1 << 2)

  /* need CAP_BPF, CAP_NET_ADMIN, CAP_PERFMON to load progs */
  #define ADMIN_CAPS (1ULL << CAP_NET_ADMIN |    \
@@ -74,6 +75,7 @@
                     1ULL << CAP_BPF)
  #define UNPRIV_SYSCTL "kernel/unprivileged_bpf_disabled"
  static bool unpriv_disabled = false;
+static bool jit_disabled;
  static int skips;
  static bool verbose = false;
  static int verif_log_level = 0;
@@ -1524,6 +1526,13 @@ static void do_test_single(struct bpf_test *test, 
bool unpriv,
         __u32 pflags;
         int i, err;

+       if ((test->flags & F_NEEDS_JIT_ENABLED) && jit_disabled) {
+               printf("SKIP (callbacks are not allowed in non-JITed 
programs)\n");
+               skips++;
+               sched_yield();
+               return;
+       }
+
         fd_prog = -1;
         for (i = 0; i < MAX_NR_MAPS; i++)
                 map_fds[i] = -1;
@@ -1844,6 +1853,8 @@ int main(int argc, char **argv)
                 return EXIT_FAILURE;
         }

+       jit_disabled = !is_jit_enabled();
+
         /* Use libbpf 1.0 API mode */
         libbpf_set_strict_mode(LIBBPF_STRICT_ALL);

diff --git a/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c 
b/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c
index a535d41dc20d..59125b22ae39 100644
--- a/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c
+++ b/tools/testing/selftests/bpf/verifier/bpf_loop_inline.c
@@ -57,6 +57,7 @@
         .expected_insns = { PSEUDO_CALL_INSN() },
         .unexpected_insns = { HELPER_CALL_INSN() },
         .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+       .flags = F_NEEDS_JIT_ENABLED,
         .result = ACCEPT,
         .runs = 0,
         .func_info = { { 0, MAIN_TYPE }, { 12, CALLBACK_TYPE } },
@@ -90,6 +91,7 @@
         .expected_insns = { HELPER_CALL_INSN() },
         .unexpected_insns = { PSEUDO_CALL_INSN() },
         .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+       .flags = F_NEEDS_JIT_ENABLED,
         .result = ACCEPT,
         .runs = 0,
         .func_info = { { 0, MAIN_TYPE }, { 16, CALLBACK_TYPE } },
@@ -127,6 +129,7 @@
         .expected_insns = { HELPER_CALL_INSN() },
         .unexpected_insns = { PSEUDO_CALL_INSN() },
         .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+       .flags = F_NEEDS_JIT_ENABLED,
         .result = ACCEPT,
         .runs = 0,
         .func_info = {
@@ -165,6 +168,7 @@
         .expected_insns = { PSEUDO_CALL_INSN() },
         .unexpected_insns = { HELPER_CALL_INSN() },
         .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+       .flags = F_NEEDS_JIT_ENABLED,
         .result = ACCEPT,
         .runs = 0,
         .func_info = {
@@ -235,6 +239,7 @@
         },
         .unexpected_insns = { HELPER_CALL_INSN() },
         .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+       .flags = F_NEEDS_JIT_ENABLED,
         .result = ACCEPT,
         .func_info = {
                 { 0, MAIN_TYPE },
@@ -252,6 +257,7 @@
         .unexpected_insns = { HELPER_CALL_INSN() },
         .result = ACCEPT,
         .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+       .flags = F_NEEDS_JIT_ENABLED,
         .func_info = { { 0, MAIN_TYPE }, { 16, CALLBACK_TYPE } },
         .func_info_cnt = 2,
         BTF_TYPES

Thanks,
Tiezhu