linux-kernel - Re: [PATCH] objtool: Fix stack overflow in validate

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Message-ID: <20251203193741.2be672de@pumpkin>
Date: Wed, 3 Dec 2025 19:37:41 +0000
From: David Laight <david.laight.linux@...il.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>, Peter
 Zijlstra <peterz@...radead.org>, Alexandre Chartre
 <alexandre.chartre@...cle.com>, Linus Torvalds
 <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] objtool: Fix stack overflow in validate_branch()

On Wed, 3 Dec 2025 20:15:19 +0100
Ingo Molnar <mingo@...nel.org> wrote:

> * Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> 
> > On Wed, Dec 03, 2025 at 10:54:19AM -0800, Josh Poimboeuf wrote:  
> > > Keep in mind this is a worst case function for objtool: KASAN with tons
> > > of memory accesses.  The vast majority of functions won't come anywhere
> > > near that level of recursion.  
> > 
> > And BTW, supporting that further, the max recursion depth on vmlinux.o
> > on a defconfig kernel is showing 162.  
> 
> That's mostly immaterial - 'make allmodconfig' is not some esoteric
> test, it's one of the most common testing methods by developers and CI
> projects ... For example I use allmodconfig builds for every commit I
> write or apply.

Both allmodconfig and allyesconfig should probably manage to disable KASAN.
Apart from building faster, the object files will be more realistic.

I'm not sure how to make that work though.
Could you have an ALLYESCONFIG config option that only 'all yes' will set and
then make KASAN depend on !ALLYESCONFIG

	David

> 
> Thanks,
> 
> 	Ingo