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

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Date: Wed, 23 Dec 2015 16:11:22 -0800
From: Tony Lindgren <tony@...mide.com>
To: Nicolas Pitre <nicolas.pitre@...aro.org>
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

* Nicolas Pitre <nicolas.pitre@...aro.org> [151223 13:45]:
> 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.

Thanks hey some assembly fun for the holidays :) I also need to check what
all gets relocated to SRAM here.

In any case, seems like the $subject patch is too intrusive for v4.5 at
this point.

Regards,

Tony

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