Re: [RFC PATCH] bpf: s390: add JIT support for multi-function programs

[Ilya Leoshkevich <iii@linux.ibm.com>]

> Am 27.08.2019 um 16:21 schrieb Yauheni Kaliuta <yauheni.kaliuta@redhat.com>:
> 
> Hi, Ilya!
> 
>>>>>> On Tue, 27 Aug 2019 15:46:43 +0200, Ilya Leoshkevich  wrote:
> 
>>> Am 27.08.2019 um 15:21 schrieb Ilya Leoshkevich <iii@linux.ibm.com>:
>>> 
>>>> Am 26.08.2019 um 20:20 schrieb Yauheni Kaliuta <yauheni.kaliuta@redhat.com>:
>>>> 
>>>> test_verifier (5.3-rc6):
>>>> 
>>>> without patch:
>>>> Summary: 1501 PASSED, 0 SKIPPED, 47 FAILED
>>>> 
>>>> with patch:
>>>> Summary: 1540 PASSED, 0 SKIPPED, 8 FAILED
>>> 
>>> Are you per chance running with a testsuite patch like this one?
>>> 
>>> --- a/tools/testing/selftests/bpf/test_verifier.c
>>> +++ b/tools/testing/selftests/bpf/test_verifier.c
>>> @@ -846,7 +846,7 @@ static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
>>> tmp, &size_tmp, &retval, NULL);
>>> if (unpriv)
>>> set_admin(false);
>>> -	if (err && errno != 524/*ENOTSUPP*/ && errno != EPERM) {
>>> +	if (err && errno != EPERM) {
>>> printf("Unexpected bpf_prog_test_run error ");
>>> return err;
>>> }
>>> 
>>> Without it, all the failures appear to be masked for me.
> 
>> Hmm, I'm sorry, I thought about it a bit more, and the patch I
>> posted above doesn't make any sense, because the failures you
>> fixed are during load, and not run time.
> 
>> Now I think you are using CONFIG_BPF_JIT_ALWAYS_ON for your
>> testing, is that right? If yes, it would be nice to mention
> 
> Right.
> 
>> this in the commit message.
> 
> Sure. Should I post non-RFC v2 or wait for some more comments?

So far I only spotted a minor issue:

+		if (ret < 0)
+			return ret;

Right now bpf_jit_insn returns 0 or -1, but bpf_jit_get_func_addr
returns 0 or -errno. This does not affect anything in the end, but just
to be uniform, maybe return -1 here or -EINVAL in the default: branch?


I don't see any other obvious problems with the patch, but I'd like to
take some time to understand how exactly some parts of it work before
acking it. So I think it's fine to post a non-RFC version.