Re: [PATCH bpf-next 1/2] libbpf: Extend BPF_KSYSCALL documentation

[Jiri Olsa <olsajiri@gmail.com>]

On Sat, Jul 23, 2022 at 04:03:43AM +0200, Ilya Leoshkevich wrote:
> Explicitly list known quirks.
> Mention that socket-related syscalls can be invoked via socketcall().
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  tools/lib/bpf/bpf_tracing.h | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
> index f4d3e1e2abe2..9d2feab7d903 100644
> --- a/tools/lib/bpf/bpf_tracing.h
> +++ b/tools/lib/bpf/bpf_tracing.h
> @@ -523,10 +523,16 @@ static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
>   * Original struct pt_regs * context is preserved as 'ctx' argument. This might
>   * be necessary when using BPF helpers like bpf_perf_event_output().
>   *
> - * At the moment BPF_KSYSCALL does not handle all the calling convention
> - * quirks for mmap(), clone() and compat syscalls transparrently. This may or
> - * may not change in the future. User needs to take extra measures to handle
> - * such quirks explicitly, if necessary.
> + * At the moment BPF_KSYSCALL does not transparently handle all the calling
> + * convention quirks for the following syscalls:
> + *
> + * - mmap(): __ARCH_WANT_SYS_OLD_MMAP.
> + * - clone(): CLONE_BACKWARDS, CLONE_BACKWARDS2 and CLONE_BACKWARDS3.

nit, these could have CONFIG_ prefix to make it more
obvious it's config options

jirka

> + * - socket-related syscalls: __ARCH_WANT_SYS_SOCKETCALL.
> + * - compat syscalls.
> + *
> + * This may or may not change in the future. User needs to take extra measures
> + * to handle such quirks explicitly, if necessary.
>   *
>   * This macro relies on BPF CO-RE support and virtual __kconfig externs.
>   */
> -- 
> 2.35.3
>