Re: [PATCH 1/2] perf trace augmented_syscalls.bpf: Move the renameat augmenter to renameat2, temporarily

[Ian Rogers]

On Fri, Sep 6, 2024 at 12:50 PM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> While trying to shape Howard Chu's generic BPF augmenter transition into
> the codebase I got stuck with the renameat2 syscall.
>
> Until I noticed that the attempt at reusing augmenters were making it
> use the 'openat' syscall augmenter, that collect just one string syscall
> arg, for the 'renameat2' syscall, that takes two strings.
>
> So, for the moment, just to help in this transition period, since
> 'renameat2' is what is used these days in the 'mv' utility, just make
> the BPF collector be associated with the more widely used syscall,
> hopefully the transition to Howard's generic BPF augmenter will cure
> this, so get this out of the way for now!

Should any of this be captured in a comment next to the code?

> So now we still have that odd "reuse", but for something we're not
> testing so won't get in the way anymore:
>
>   root@number:~# rm -f 987654 ; touch 123456 ; perf trace -vv -e rename* mv 123456 987654 |& grep renameat
>   Reusing "openat" BPF sys_enter augmenter for "renameat"
>        0.000 ( 0.079 ms): mv/1158612 renameat2(olddfd: CWD, oldname: "123456", newdfd: CWD, newname: "987654", flags: NOREPLACE) = 0
>   root@number:~#
>
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Howard Chu <howardchu95@xxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Cc: Alan Maguire <alan.maguire@xxxxxxxxxx>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> ---
>  tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> index 0acbd74e8c760956..0f9bd2690d4e5295 100644
> --- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> @@ -260,8 +260,8 @@ int sys_enter_rename(struct syscall_enter_args *args)
>         return augmented__output(args, augmented_args, len);
>  }
>
> -SEC("tp/syscalls/sys_enter_renameat")
> -int sys_enter_renameat(struct syscall_enter_args *args)
> +SEC("tp/syscalls/sys_enter_renameat2")
> +int sys_enter_renameat2(struct syscall_enter_args *args)
>  {
>         struct augmented_args_payload *augmented_args = augmented_args_payload();
>         const void *oldpath_arg = (const void *)args->args[1],
> --
> 2.46.0
>