From: Peter Zijlstra <peterz@infradead•org>
To: Naveen N Rao <naveen@kernel•org>
Cc: linux-kernel@vger•kernel.org, Nicholas Piggin <npiggin@gmail•com>,
Sathvika Vasireddy <sv@linux•ibm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux•ibm.com>,
linuxppc-dev@lists•ozlabs.org,
Josh Poimboeuf <jpoimboe@kernel•org>
Subject: Re: [RFC PATCH v1 1/3] Revert "powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto"
Date: Tue, 20 Jun 2023 09:10:05 +0200 [thread overview]
Message-ID: <20230620071005.GR4253@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1687237941.1wok7iiqm0.naveen@kernel.org>
On Tue, Jun 20, 2023 at 10:51:25AM +0530, Naveen N Rao wrote:
> Christophe Leroy wrote:
> > This reverts commit 1e688dd2a3d6759d416616ff07afc4bb836c4213.
> >
> > That commit aimed at optimising the code around generation of
> > WARN_ON/BUG_ON but this leads to a lot of dead code erroneously
> > generated by GCC.
> >
> > text data bss dec hex filename
> > 9551585 3627834 224376 13403795 cc8693 vmlinux.before
> > 9535281 3628358 224376 13388015 cc48ef vmlinux.after
> >
> > Once this change is reverted, in a standard configuration (pmac32 +
> > function tracer) the text is reduced by 16k which is around 1.7%
>
> Aneesh recently reported a build failure due to the use of 'asm goto' in
> WARN_ON(). We were able to root-cause it to the use of 'asm goto' with two
> config options: CONFIG_CC_OPTIMIZE_FOR_SIZE and
> CONFIG_DEBUG_SECTION_MISMATCH.
FWIW;
I recently had clang-powerpc report a very dodgy build error that was
due to a combination of these asm-goto and the usage of __cleanup__.
For some reason the label of the asm-goto crossed over the __cleanup__
variable declaration -- which is not valid, but also was completely
insane for that's not what the code called for.
https://lkml.kernel.org/r/20230610082005.GB1370249@hirez.programming.kicks-ass.net
But in my book that's a compiler issue, not a kernel issue and I'd be
hesitant to pull the asm-goto use just for that.
next prev parent reply other threads:[~2023-06-20 7:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-16 13:47 [RFC PATCH v1 0/3] powerpc/objtool: First step towards uaccess validation (v1) Christophe Leroy
2023-06-16 13:47 ` [RFC PATCH v1 1/3] Revert "powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto" Christophe Leroy
2023-06-20 5:21 ` Naveen N Rao
2023-06-20 7:10 ` Peter Zijlstra [this message]
2023-06-16 13:47 ` [RFC PATCH v1 2/3] powerpc: Mark all .S files invalid for objtool Christophe Leroy
2023-06-20 6:04 ` Naveen N Rao
2023-06-20 6:15 ` Christophe Leroy
2023-06-20 6:40 ` Naveen N Rao
2023-06-16 13:47 ` [RFC PATCH v1 3/3] powerpc: WIP draft support to objtool check Christophe Leroy
2023-06-16 14:43 ` Peter Zijlstra
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