From: Matthieu Baerts <matttbe@kernel.org>
To: Eduard Zingerman <eddyz87@gmail.com>,
ihor.solodrai@linux.dev, alan.maguire@oracle.com
Cc: bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
Andrii Nakryiko <andrii@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, Shuah Khan <shuah@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>
Subject: Re: [PATCH bpf] selftests/bpf: fix implicit-function-declaration errors
Date: Sat, 4 Oct 2025 10:51:36 +0200 [thread overview]
Message-ID: <8b49ca48-ff6b-40ed-8322-e0c9791d1d17@kernel.org> (raw)
In-Reply-To: <d108d59be611a63c73303347d07fe0ba5f2b74b7.camel@gmail.com>
Hi Eduard,
On 04/10/2025 01:37, Eduard Zingerman wrote:
> On Fri, 2025-10-03 at 17:24 +0200, Matthieu Baerts (NGI0) wrote:
>> When trying to build the latest BPF selftests, with a debug kernel
>> config, Pahole 1.30 and CLang 20.1.8 (and GCC 15.2), I got these errors:
>>
>> progs/dynptr_success.c:579:9: error: call to undeclared function 'bpf_dynptr_slice'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>> 579 | data = bpf_dynptr_slice(&ptr, 0, NULL, 1);
>> | ^
>> progs/dynptr_success.c:579:9: note: did you mean 'bpf_dynptr_size'?
>> .virtme/build-debug-btf//tools/include/vmlinux.h:120280:14: note: 'bpf_dynptr_size' declared here
>> 120280 | extern __u32 bpf_dynptr_size(const struct bpf_dynptr *p) __weak __ksym;
>> | ^
>> progs/dynptr_success.c:579:7: error: incompatible integer to pointer conversion assigning to '__u64 *' (aka 'unsigned long long *') from 'int' [-Wint-conversion]
>> 579 | data = bpf_dynptr_slice(&ptr, 0, NULL, 1);
>> | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> progs/dynptr_success.c:596:9: error: call to undeclared function 'bpf_dynptr_slice'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>> 596 | data = bpf_dynptr_slice(&ptr, 0, NULL, 10);
>> | ^
>> progs/dynptr_success.c:596:7: error: incompatible integer to pointer conversion assigning to 'char *' from 'int' [-Wint-conversion]
>> 596 | data = bpf_dynptr_slice(&ptr, 0, NULL, 10);
>> | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> I don't have these errors without the debug kernel config from
>> kernel/configs/debug.config. With the debug kernel, bpf_dynptr_slice()
>> is not declared in vmlinux.h. It is declared there without debug.config.
>>
>> The fix is similar to what is done in dynptr_fail.c which is also using
>> bpf_dynptr_slice(): bpf_kfuncs.h is now included.
>>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>> ---
>
> I can reproduce similar issue when including
> kernel/configs/debug.config with my regular dev config, but for
> different functions: bpf_rcu_read_{un,}lock().
Thank you for having checked! I also had issues with these functions on
my side, when testing on top of 'net'.
> However, this is not a way to fix this.
> Kfuncs are not supposed to just disappear from DWARF.
Indeed. But strange it was fine before. Or fine without debug.config.
Cheers,
Matt
--
Sponsored by the NGI0 Core fund.
prev parent reply other threads:[~2025-10-04 8:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-03 15:24 [PATCH bpf] selftests/bpf: fix implicit-function-declaration errors Matthieu Baerts (NGI0)
2025-10-03 23:37 ` Eduard Zingerman
2025-10-04 3:08 ` Ihor Solodrai
2025-10-04 3:19 ` Ihor Solodrai
2025-10-04 8:52 ` Matthieu Baerts
2025-10-04 8:51 ` Matthieu Baerts [this message]
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