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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	x86@kernel.org, llvm@lists.linux.dev,
	linux-sparse@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel test robot <lkp@intel.com>,
	Nathan Chancellor <nathan@kernel.org>
Subject: Re: [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__
Date: Tue, 18 Jan 2022 15:01:20 -0800	[thread overview]
Message-ID: <20220118230120.pivvson7qekfiqic@treble> (raw)
In-Reply-To: <20220118192256.jzk5dnceeusq7x7u@treble>

On Tue, Jan 18, 2022 at 11:22:59AM -0800, Josh Poimboeuf wrote:
> On Sun, Jan 16, 2022 at 02:32:59PM +0100, Borislav Petkov wrote:
> > so I like the local label and how it is more readable this way.
> > 
> > So, provided the memory clobber works (I wonder here if Josh has some
> > concrete failing cases which could be tested with your version) and
> > after the nitpicks have been addressed
> > 
> > Acked-by: Borislav Petkov <bp@suse.de>
> 
> I think Nick was already able to recreate the original issue.  I'll run
> it through some more testing.
> 
> I wanted to make this change years ago, but couldn't because of legacy
> toolchains.  Here's hoping this is the final solution for those @#$%^
> macros.
> 
> Boris, thanks for looping Nick in, I should have done so to begin with.

Apparently this patch isn't going to work after all :-(

  https://lkml.kernel.org/r/202201190632.lhlaiCBk-lkp@intel.com

With the two WARN_ONs in media_request_object_complete(), GCC apparently
considers the two reachable() asm statements as duplicates, and it
removes the second one.

-- 
Josh


  reply	other threads:[~2022-01-18 23:01 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-14  1:05 [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__ Nick Desaulniers
2022-01-14 21:58 ` Nathan Chancellor
2022-01-16 13:32 ` Borislav Petkov
2022-01-18 19:22   ` Josh Poimboeuf
2022-01-18 23:01     ` Josh Poimboeuf [this message]
2022-01-18 23:33       ` Borislav Petkov
2022-01-19  0:03         ` Josh Poimboeuf
2022-01-19 10:01           ` Borislav Petkov
2022-01-24 23:26       ` Nick Desaulniers
2022-01-24 23:38         ` Nick Desaulniers
2022-01-25 18:49           ` Borislav Petkov
2022-01-25 23:31         ` Segher Boessenkool
2022-01-26  0:59           ` Nick Desaulniers
2022-01-26  2:12             ` Nick Desaulniers
2022-01-26 11:13               ` Segher Boessenkool
2022-01-31 20:45           ` Nick Desaulniers
2022-01-31 22:13             ` Segher Boessenkool

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