linux-kernel - Re: [PATCH] debug: fix WARN_ON

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Date:   Sat, 15 Jul 2017 08:26:34 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Mike Galbraith <efault@....de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] debug: fix WARN_ON_ONCE() for modules

On Sat, Jul 15, 2017 at 08:29:57AM +0200, Mike Galbraith wrote:
> On Sat, 2017-07-15 at 00:10 -0500, Josh Poimboeuf wrote:
> > 
> > The bug table was made writable for vmlinux, which relies on
> > vmlinux.lds.S and vmlinux.lds.h for laying out the sections.  However,
> > it wasn't made writable for modules, which rely on the ELF section
> > header flags.
> 
> It seems vmlinux sort of relies on your fix too.  objdump did show
> vmlinux __bug_table as being READONLY, but that (lie) is now gone.

Yeah, those ELF bits are ignored by the kernel.  It sets its own
protections during boot, e.g. mark_rodata_ro().

-- 
Josh