linux-kernel - Re: [PATCH v2] ARM: mm: flip priority of CONFIG_DEBUG

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Message-ID: <alpine.LFD.2.20.1512231637110.3603@knanqh.ubzr>
Date:	Wed, 23 Dec 2015 16:45:16 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Tony Lindgren <tony@...mide.com>
cc:	Laura Abbott <labbott@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	kernel-hardening@...ts.openwall.com,
	linux-arm-kernel@...ts.infradead.org,
	Laura Abbott <labbott@...oraproject.org>
Subject: Re: [PATCH v2] ARM: mm: flip priority of CONFIG_DEBUG_RODATA

On Wed, 23 Dec 2015, Tony Lindgren wrote:

> Hi,
> 
> * Laura Abbott <labbott@...hat.com> [151223 12:31]:
> > 
> > Looks like a case similar to Geert's
> > 
> >         adr     r7, kick_counter
> > wait_dll_lock_timed:
> >         ldr     r4, wait_dll_lock_counter
> >         add     r4, r4, #1
> >         str     r4, [r7, #wait_dll_lock_counter - kick_counter]
> >         ldr     r4, sdrc_dlla_status
> >         /* Wait 20uS for lock */
> >         mov     r6, #8
> > 
> > 
> > kick_counter and wait_dll_lock_counter are in the text section which is marked read only.
> > They need to be moved to the data section along with a few other variables from what I
> > can tell (maybe those are read only?).
> 
> Thanks for looking, yeah so it seem.
> 
> > I suspect this is going to be a common issue with suspend/resume code paths since those
> > are hand written assembly.
> 
> Yes I suspect we have quite a few cases like this.

We fixed a bunch of similar issues where code was located in the .data 
section for ease of use from assembly code.  See commit b4e61537 and 
d0776aff for example.


Nicolas
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