Message-ID: <CAP-5=fUdZRbCp+2ghEUdp+qJ1BuMDuTtw9R+dFAaom+3oqQV_g@mail.gmail.com>
Date: Mon, 4 Nov 2024 14:03:28 -0800
From: Ian Rogers <irogers@...gle.com>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Arnd Bergmann <arnd@...db.de>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Mickaël Salaün <mic@...ikod.net>, 
	Günther Noack <gnoack@...gle.com>, 
	Christian Brauner <brauner@...nel.org>, guoren <guoren@...nel.org>, 
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>, 
	James Clark <james.clark@...aro.org>, Mike Leach <mike.leach@...aro.org>, 
	Leo Yan <leo.yan@...ux.dev>, Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	linux-security-module@...r.kernel.org, bpf@...r.kernel.org, 
	"linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>, linux-arm-kernel@...ts.infradead.org, 
	linux-doc@...r.kernel.org
Subject: Re: [PATCH RFT 00/16] perf tools: Use generic syscall scripts for all archs

On Mon, Nov 4, 2024 at 1:32 PM Charlie Jenkins <charlie@...osinc.com> wrote:
>
> On Mon, Nov 04, 2024 at 10:13:18PM +0100, Arnd Bergmann wrote:
> > On Mon, Nov 4, 2024, at 22:06, Charlie Jenkins wrote:
> > > Standardize the generation of syscall headers around syscall tables.
> > > Previously each architecture independently selected how syscall headers
> > > would be generated, or would not define a way and fallback onto
> > > libaudit. Convert all architectures to use a standard syscall header
> > > generation script and allow each architecture to override the syscall
> > > table to use if they do not use the generic table.
> > >
> > > As a result of these changes, no architecture will require libaudit, and
> > > so the fallback case of using libaudit is removed by this series.
> > >
> > > Testing:
> > >
> > > I have tested that the syscall mappings of id to name generation works
> > > as expected for every architecture, but I have only validated that perf
> > > trace compiles and runs as expected on riscv, arm64, and x86_64.
> > >
> > > Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> >
> > Thanks for doing this, I had plans to do this myself, but hadn't
> > completed that bit so far. I'm travelling at the moment, so I'm
> > not sure I have time to look at it in enough detail this week.
> >
> > One problem I ran into doing this previously was the incompatible
> > format of the tables for x86 and s390, which have conflicting
> > interpretations of what the '-' character means. It's possible
> > that this is only really relevant for the in-kernel table,
> > not the version in tools.
> >
>
> I don't think that is an issue for this usecase because the only
> information that is taken from the syscall table is the number and the
> name of the syscall. '-' doesn't appear in either of these columns!

This is cool stuff. An area that may not be immediately apparent for
improvement is that the x86-64 build only has access to the 64-bit
syscall table. Perhaps all the syscall tables should always be built
and then at runtime the architecture of the perf.data file, etc. used
to choose the appropriate one. The cleanup to add an ELF host #define
could help with this:
https://lore.kernel.org/linux-perf-users/20241017002520.59124-1-irogers@google.com/

Ultimately I'd like to see less arch code as it inherently makes cross
platform worker harder. That doesn't impact this work which I'm happy
to review.

Thanks,
Ian

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