linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, Peter Oberparleiter <oberpar@linux.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Johannes Berg <johannes.berg@intel.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Kees Cook <keescook@chromium.org>, Marco Elver <elver@google.com>,
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] gcov,x86: Mark GCOV broken for x86
Date: Mon, 14 Jun 2021 18:20:18 +0200	[thread overview]
Message-ID: <20210614162018.GD68749@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKwvOd=PYrMnNOu060T3Z26RJriNXqu3iM85Daink4-BN__2sQ@mail.gmail.com>

On Mon, Jun 14, 2021 at 09:05:04AM -0700, Nick Desaulniers wrote:
> On Mon, Jun 14, 2021 at 3:17 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> >
> > As recently discovered, there is no function attribute to disable the
> > -fprofile-generate instrumentation. As such, GCOV is fundamentally
> > incompatible with architectures that rely on 'noinstr' for correctness.
> 
> Is there context for comment, or is this patch meant as a joke?

Only if you think recursion in exception entry code is funny.

noinstr *MUST* disable any and all compiler generated instrumentation,
currently it that isn't the case for -fprofile-gnerate, nor
-fprofile-arc.

Look for all the fun we had with KCOV back then. Luckily KCOV
instrumentation was trivial to patch out using objtool, so that's what
x86 is currently doing.

Luckily both compilers grew a __no_sanitize_coverage recently and we no
longer have to rely on objtool fixing up the compiler output for much
longer.

  https://lkml.kernel.org/r/20210527194448.3470080-1-elver@google.com

Now all we need is one more such attribute to kill -fprofile-* stuff.

  reply	other threads:[~2021-06-14 16:21 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14 10:17 Peter Zijlstra
2021-06-14 10:31 ` Marco Elver
2021-06-14 14:43 ` Peter Oberparleiter
2021-06-18 11:13   ` Peter Zijlstra
2021-06-21 13:53     ` Peter Oberparleiter
2021-06-14 16:05 ` Nick Desaulniers
2021-06-14 16:20   ` Peter Zijlstra [this message]
2021-06-14 18:05     ` Nick Desaulniers
2021-06-14 18:20       ` Borislav Petkov
2021-06-14 19:03         ` Nick Desaulniers
2021-06-14 19:28           ` Borislav Petkov
2021-06-14 18:31       ` Fangrui Song
2021-06-14 19:07         ` Peter Zijlstra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210614162018.GD68749@worktop.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=elver@google.com \
    --cc=johannes.berg@intel.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=oberpar@linux.ibm.com \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH] gcov,x86: Mark GCOV broken for x86' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).