Messages in this thread | | | Date | Wed, 16 Aug 2023 23:08:29 -0700 | Subject | Re: [PATCH bpf-next] bpf: Disable -Wmissing-declarations for globally-linked kfuncs | From | Yonghong Song <> |
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On 8/16/23 8:48 PM, Alexei Starovoitov wrote: > On Wed, Aug 16, 2023 at 8:38 PM Yonghong Song <yonghong.song@linux.dev> wrote: >> >> >> >> On 8/16/23 8:06 AM, David Vernet wrote: >>> We recently got an lkp warning about missing declarations, as in e.g. >>> [0]. This warning is largely redundant with -Wmissing-prototypes, which >>> we already disable for kfuncs that have global linkage and are meant to >>> be exported in BTF, and called from BPF programs. Let's also disable >>> -Wmissing-declarations for kfuncs. For what it's worth, I wasn't able to >>> reproduce the warning even on W <= 3, so I can't actually be 100% sure >>> this fixes the issue. >>> >>> [0]: https://lore.kernel.org/all/202308162115.Hn23vv3n-lkp@intel.com/ >> >> Okay, I just got a similar email to [0] which complains >> bpf_obj_new_impl, ..., bpf_cast_to_kern_ctx >> missing declarations. >> >> In the email, the used compiler is >> compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0 >> >> Unfortunately, I did not have gcc-7 to verify this. >> Also, what is the minimum gcc version kernel supports? 5.1? > > pahole and BTF might be broken in such old GCC too. > Maybe we should add: > config BPF_SYSCALL > depends on GCC_VERSION >= 90000 || CLANG_VERSION >= 130000
Do you remember what kind of issues pahole/BTF have for < 9.0 gcc and < 13.0 clang?
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