linux-kernel - Re: [PATCH v2 09/10] perf trace: Collect augmented data using BPF

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Message-ID: <ZsibWgNtUUSLEbd5@x1>
Date: Fri, 23 Aug 2024 11:23:22 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Howard Chu <howardchu95@...il.com>
Cc: adrian.hunter@...el.com, irogers@...gle.com, jolsa@...nel.org,
	kan.liang@...ux.intel.com, namhyung@...nel.org,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 09/10] perf trace: Collect augmented data using BPF

On Fri, Aug 23, 2024 at 10:42:21AM -0300, Arnaldo Carvalho de Melo wrote:
> On Fri, Aug 23, 2024 at 10:38:21AM -0300, Arnaldo Carvalho de Melo wrote:
> > On Fri, Aug 23, 2024 at 10:24:09AM -0300, Arnaldo Carvalho de Melo wrote:
> > > On Thu, Aug 15, 2024 at 09:36:25AM +0800, Howard Chu wrote:
> > > > +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
> > > > @@ -427,7 +538,8 @@ int sys_enter(struct syscall_enter_args *args)
> > > >  	 * "!raw_syscalls:unaugmented" that will just return 1 to return the
> > > >  	 * unaugmented tracepoint payload.
> > > >  	 */
> > > > -	bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
> > > > +	if (augment_sys_enter(args, &augmented_args->args))
> > > > +		bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
> > > 
> > > We shouldn't do that, instead we keep doing
> > > 
> > > 	bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
> > > 
> > > And userspace will setup the syscalls_sys_enter map adding the generic
> > > pointer collector (augment_sys_enter) for syscalls that have pointers
> > > _and_ are not serviced by a pre-existing, specialized handler, this way
> > > we keep the ones we have already and that already take into account
> > > pretty printing network addresses based on the network family, knows how
> > > to pretty print flags (the perf_event_open, etc).
> > > 
> > > I'll try to do this now.
> > 
> > So, step by step, first this, and then hook it to the syscalls that:
> > 
> > 1) have a pointer to collect and no handler, i.e. as a last step in
> > assigning the functions to be tail called from the syscalls BPF map.
> > 

Sorry, I'm wrong, we can use the generic collector and just in userspace
wire it up to the more specialized pretty printer :-)

- Arnaldo