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

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Message-ID: <t2kjptjbjxngetngckmammsvhmg2kh7v4hrblkswhypbk66h2p@qq3bnyyji63v>
Date: Wed, 3 Dec 2025 15:53:37 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	Nathan Chancellor <nathan@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Alexandre Chartre <alexandre.chartre@...cle.com>, David Laight <david.laight.linux@...il.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] objtool: Fix stack overflow in validate_branch()

On Wed, Dec 03, 2025 at 08:15:19PM +0100, Ingo Molnar 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.

FWIW, here are some numbers from a clang allmodconfig build:

vmlinux.o max recursion: 1,017

modules max recursion:
- mean: 69
- median: 41
- max: 7,165

-- 
Josh