Re: [PATCH bpf-next] bpf: Disable -Wmissing-declarations for globally-linked kfuncs

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 8/16/23 8:48 PM, Alexei Starovoitov wrote:
On Wed, Aug 16, 2023 at 8:38 PM Yonghong Song <yonghong.song@xxxxxxxxx> 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@xxxxxxxxx/

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?





[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux