[PATCH bpf-next v2] bpf: Return -ENOTSUPP if calls are not allowed in non-JITed programs

[Tiezhu Yang]

If CONFIG_BPF_JIT_ALWAYS_ON is not set and bpf_jit_enable is 0, there
exist 6 failed tests.

  [root@linux bpf]# echo 0 > /proc/sys/net/core/bpf_jit_enable
  [root@linux bpf]# echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled
  [root@linux bpf]# ./test_verifier | grep FAIL
  #106/p inline simple bpf_loop call FAIL
  #107/p don't inline bpf_loop call, flags non-zero FAIL
  #108/p don't inline bpf_loop call, callback non-constant FAIL
  #109/p bpf_loop_inline and a dead func FAIL
  #110/p bpf_loop_inline stack locations for loop vars FAIL
  #111/p inline bpf_loop call in a big program FAIL
  Summary: 768 PASSED, 15 SKIPPED, 6 FAILED

The test log shows that callbacks are not allowed in non-JITed programs,
interpreter doesn't support them yet, thus these tests should be skipped
if jit is disabled, just return -ENOTSUPP instead of -EINVAL for pseudo
calls in fixup_call_args().

With this patch:

  [root@linux bpf]# echo 0 > /proc/sys/net/core/bpf_jit_enable
  [root@linux bpf]# echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled
  [root@linux bpf]# ./test_verifier | grep FAIL
  Summary: 768 PASSED, 21 SKIPPED, 0 FAILED

Additionally, as Eduard suggested, return -ENOTSUPP instead of -EINVAL
for the other three places where "non-JITed" is used in error messages
to keep consistent.

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---

v2:
  -- rebase on the latest bpf-next tree.
  -- return -ENOTSUPP instead of -EINVAL for the other three places
     where "non-JITed" is used in error messages to keep consistent.
  -- update the patch subject and commit message.

 kernel/bpf/verifier.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d5f4ff1eb235..99558a5186b2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8908,7 +8908,7 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
 			goto error;
 		if (env->subprog_cnt > 1 && !allow_tail_call_in_subprogs(env)) {
 			verbose(env, "tail_calls are not allowed in non-JITed programs with bpf-to-bpf calls\n");
-			return -EINVAL;
+			return -ENOTSUPP;
 		}
 		break;
 	case BPF_FUNC_perf_event_read:
@@ -19069,14 +19069,14 @@ static int fixup_call_args(struct bpf_verifier_env *env)
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
 	if (has_kfunc_call) {
 		verbose(env, "calling kernel functions are not allowed in non-JITed programs\n");
-		return -EINVAL;
+		return -ENOTSUPP;
 	}
 	if (env->subprog_cnt > 1 && env->prog->aux->tail_call_reachable) {
 		/* When JIT fails the progs with bpf2bpf calls and tail_calls
 		 * have to be rejected, since interpreter doesn't support them yet.
 		 */
 		verbose(env, "tail_calls are not allowed in non-JITed programs with bpf-to-bpf calls\n");
-		return -EINVAL;
+		return -ENOTSUPP;
 	}
 	for (i = 0; i < prog->len; i++, insn++) {
 		if (bpf_pseudo_func(insn)) {
@@ -19084,7 +19084,7 @@ static int fixup_call_args(struct bpf_verifier_env *env)
 			 * have to be rejected, since interpreter doesn't support them yet.
 			 */
 			verbose(env, "callbacks are not allowed in non-JITed programs\n");
-			return -EINVAL;
+			return -ENOTSUPP;
 		}
 
 		if (!bpf_pseudo_call(insn))
-- 
2.42.0