From: Omar Sandoval <osandov@osandov.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, linux-debuggers@vger.kernel.org,
kernel-team@fb.com
Subject: Re: [PATCH] x86/unwind/orc: add ELF section with ORC version number
Date: Fri, 9 Jun 2023 16:17:39 -0700 [thread overview]
Message-ID: <ZIOzE4f2xr9CCA45@telecaster> (raw)
In-Reply-To: <20230609224803.275vqw345utsusah@treble>
On Fri, Jun 09, 2023 at 03:48:03PM -0700, Josh Poimboeuf wrote:
> On Fri, Jun 09, 2023 at 03:24:38PM -0700, Omar Sandoval wrote:
> > > Though, instead of
> > > using an incrementing version, Peter had the idea to hash the struct,
> > > like:
> > >
> > > awk '/^struct orc_entry {$/ { p=1 } p { print } /^}/ { p=0 }' arch/x86/include/asm/orc_types.h | sha1sum
> > >
> > > That way we don't have to remember to bump the version number, and it
> > > would be more resilient to partial backports in distros.
> > >
> > > Would something like that work for you?
> >
> > Any sort of unique identifier works for me. One thing that the proposed
> > hash wouldn't catch is if ORC_REG_* or ORC_TYPE_* are ever renumbered
> > (i.e., the meanings of existing values change). It also wouldn't catch
> > if something about the .orc_unwind_ip section changed. But assuming
> > changes like that would be much rarer, it could be handled manually by
> > bumping a "salt" for the hash. E.g., by adding 'BEGIN { print <SALT> }'
> > to the awk script:
> >
> > awk 'BEGIN { print 1 } /^struct orc_entry {$/ { p=1 } p { print } /^}/ { p=0 }' arch/x86/include/asm/orc_types.h | sha1sum
> >
> > I'll defer to you guys whether it's easier to remember to bump a version
> > everytime or only in those rare cases.
>
> I think I'd prefer only bumping it in the rare cases, because we're
> going to end up forgetting either way ;-)
>
> To catch REG/TYPE changes, we could forego awk and just hash the whole
> file, the only downside being that it might introduce unnecessary
> changes if we change a comment or something. But the file changes
> rarely enough.
>
> Or we could tweak the awk to also print ORC_{REG,TYPE}_* pretty easily.
Printing ORC_{REG,TYPE}_* should cover almost everything, and if there's
anything not covered, it can be handled manually, so that sounds good to
me. I'll draft a patch doing that.
Thanks,
Omar
prev parent reply other threads:[~2023-06-09 23:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-08 22:38 [PATCH] x86/unwind/orc: add ELF section with ORC version number Omar Sandoval
2023-06-09 22:04 ` Josh Poimboeuf
2023-06-09 22:24 ` Omar Sandoval
2023-06-09 22:48 ` Josh Poimboeuf
2023-06-09 23:17 ` Omar Sandoval [this message]
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