Re: [PATCH 1/1] perf build: Require at least clang 16.0.6 to build BPF skeletons

[James Clark]

On 12/09/2024 15:50, Arnaldo Carvalho de Melo wrote:
> On Thu, Sep 12, 2024 at 03:40:32PM +0100, James Clark wrote:
> > On 11/09/2024 13:24, Arnaldo Carvalho de Melo wrote:
> > > Howard reported problems using perf features that use BPF:
>
> > >     perf $ clang -v
> > >     Debian clang version 15.0.6
> > >     Target: x86_64-pc-linux-gnu
> > >     Thread model: posix
> > >     InstalledDir: /bin
> > >     Found candidate GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
> > >     Selected GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
> > >     Candidate multilib: .;@m64
> > >     Selected multilib: .;@m64
> > >     perf $ ./perf trace -e write --max-events=1
> > >     libbpf: prog 'sys_enter_rename': BPF program load failed: Permission denied
> > >     libbpf: prog 'sys_enter_rename': -- BEGIN PROG LOAD LOG --
> > >     0: R1=ctx() R10=fp0
> > >
> > > But it works with:
> > >
> > >     perf $ clang -v
> > >     Debian clang version 16.0.6 (15~deb12u1)
> > >     Target: x86_64-pc-linux-gnu
> > >     Thread model: posix
> > >     InstalledDir: /bin
> > >     Found candidate GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
> > >     Selected GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
> > >     Candidate multilib: .;@m64
> > >     Selected multilib: .;@m64
> > >     perf $ ./perf trace -e write --max-events=1
> > >          0.000 ( 0.009 ms): gmain/1448 write(fd: 4, buf: \1\0\0\0\0\0\0\0, count: 8)                         = 8 (kworker/0:0-eve)
> > >     perf $
> > >
> > > So lets make that the required version, if you happen to have a slightly
> > > older version where this work, please report so that we can adjust the
> > > minimum required version.
>   
> > I wasn't able to reproduce the issue with either of these versions. But I
> > suppose it could be an issue with only 15.0.6.
>
> Interesting, that complicates things, probably the best way then is to
> try to build it, if it fails, mention that 15.0.6 is known to be
> problematic and suggest working versions?
>
> - Arnaldo
>   

I'll try to build it and see. But Ubuntu 22 only has clang 11 to 15 so 
making 16 the minimum could be an issue.