From: Daniel Borkmann <daniel@iogearbox.net>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Yaniv Agman <yanivagman@gmail.com>, bpf <bpf@vger.kernel.org>,
Yonghong Song <yhs@fb.com>
Subject: Re: libbpf error: unknown register name 'r0' in asm
Date: Fri, 9 Oct 2020 20:41:16 +0200 [thread overview]
Message-ID: <ece9975d-717c-a868-be51-c97aeae8e011@iogearbox.net> (raw)
In-Reply-To: <CAEf4Bza4KFJ_j7vmg-x_Zinp0PUM-zmWYHMq_y+2zWmX485sBQ@mail.gmail.com>
On 10/9/20 8:35 PM, Andrii Nakryiko wrote:
> On Fri, Oct 9, 2020 at 11:21 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>> On 10/9/20 8:09 PM, Yaniv Agman wrote:
>>> בתאריך יום ו׳, 9 באוק׳ 2020 ב-20:39 מאת Daniel Borkmann
>>> <daniel@iogearbox.net>:
>>>>
>>>> On 10/9/20 6:56 PM, Yaniv Agman wrote:
>>>>> בתאריך יום ו׳, 9 באוק׳ 2020 ב-19:27 מאת Daniel Borkmann
>>>>> <daniel@iogearbox.net>:
>>>>>>
>>>>>> [ Cc +Yonghong ]
>>>>>>
>>>>>> On 10/9/20 6:05 PM, Yaniv Agman wrote:
>>>>>>> Pulling the latest changes of libbpf and compiling my application with it,
>>>>>>> I see the following error:
>>>>>>>
>>>>>>> ../libbpf/src//root/usr/include/bpf/bpf_helpers.h:99:10: error:
>>>>>>> unknown register name 'r0' in asm
>>>>>>> : "r0", "r1", "r2", "r3", "r4", "r5");
>>>>>>>
>>>>>>> The commit which introduced this change is:
>>>>>>> 80c7838600d39891f274e2f7508b95a75e4227c1
>>>>>>>
>>>>>>> I'm not sure if I'm doing something wrong (missing include?), or this
>>>>>>> is a genuine error
>>>>>>
>>>>>> Seems like your clang/llvm version might be too old.
>>>>>
>>>>> I'm using clang 10.0.1
>>>>
>>>> Ah, okay, I see. Would this diff do the trick for you?
>>>
>>> Yes! Now it compiles without any problems!
>>
>> Great, thx, I'll cook proper fix and check with clang6 as Yonghong mentioned.
>
> Am I the only one confused here?... Yonghong said it should be
> supported as early as clang 6, Yaniv is using Clang 10 and is still
> getting this error. Let's figure out what's the problem before adding
> unnecessary checks.
>
> I think it's not the clang_major check that helped, rather __bpf__
> check. So please hold off on the fix, let's get to the bottom of this
> first.
I don't see confusion here (maybe other than which minimal clang/llvm version
libbpf should support). If we do `#if __clang_major__ >= 6 && defined(__bpf__)`
for the final patch, then this means that user passed clang -target bpf and
the min supported version for inline assembly was there, otherwise we fall back
to bpf_tail_call. In Yaniv's case, he probably had native target with -emit-llvm
and then used llc invocation.
>>>> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
>>>> index 2bdb7d6dbad2..31e356831fcf 100644
>>>> --- a/tools/lib/bpf/bpf_helpers.h
>>>> +++ b/tools/lib/bpf/bpf_helpers.h
>>>> @@ -72,6 +72,7 @@
>>>> /*
>>>> * Helper function to perform a tail call with a constant/immediate map slot.
>>>> */
>>>> +#if __clang_major__ >= 10 && defined(__bpf__)
>>>> static __always_inline void
>>>> bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
>>>> {
>>>> @@ -98,6 +99,9 @@ bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
>>>> :: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot)
>>>> : "r0", "r1", "r2", "r3", "r4", "r5");
>>>> }
>>>> +#else
>>>> +# define bpf_tail_call_static bpf_tail_call
>>>> +#endif /* __clang_major__ >= 10 && __bpf__ */
>>>>
>>>> /*
>>>> * Helper structure used by eBPF C program
>>
next prev parent reply other threads:[~2020-10-09 18:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 16:05 libbpf error: unknown register name 'r0' in asm Yaniv Agman
2020-10-09 16:27 ` Daniel Borkmann
2020-10-09 16:56 ` Yaniv Agman
2020-10-09 17:39 ` Daniel Borkmann
2020-10-09 18:09 ` Yaniv Agman
2020-10-09 18:21 ` Daniel Borkmann
2020-10-09 18:33 ` Yaniv Agman
2020-10-09 18:39 ` Andrii Nakryiko
2020-10-09 19:32 ` Yaniv Agman
2020-10-09 19:53 ` Andrii Nakryiko
2020-10-09 20:24 ` Yaniv Agman
2020-10-12 20:03 ` Andrii Nakryiko
2020-10-12 21:48 ` Yaniv Agman
2020-10-12 22:16 ` Andrii Nakryiko
2020-10-09 18:35 ` Andrii Nakryiko
2020-10-09 18:41 ` Daniel Borkmann [this message]
2020-10-09 18:59 ` Andrii Nakryiko
2020-10-09 19:08 ` Yonghong Song
2020-10-09 19:33 ` Yaniv Agman
2020-10-09 19:58 ` Daniel Borkmann
2020-10-21 9:43 ` Yaniv Agman
2020-10-21 17:18 ` Daniel Borkmann
2020-10-21 19:33 ` Yaniv Agman
2020-10-09 17:41 ` Yonghong Song
2020-10-09 18:03 ` Andrii Nakryiko
2020-10-09 18:12 ` Yaniv Agman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ece9975d-717c-a868-be51-c97aeae8e011@iogearbox.net \
--to=daniel@iogearbox.net \
--cc=andrii.nakryiko@gmail.com \
--cc=bpf@vger.kernel.org \
--cc=yanivagman@gmail.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).