linux-kernel - Re: [PATCH 0/6] generic relative extable support

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Message-ID: <568AB6C0.4060502@zytor.com>
Date:	Mon, 04 Jan 2016 10:15:28 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:	linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
	linux-s390@...r.kernel.org, x86@...nel.org, mingo@...hat.com,
	schwidefsky@...ibm.com, mattst88@...il.com,
	ink@...assic.park.msu.ru, rth@...ddle.net, tony.luck@...el.com,
	fenghua.yu@...el.com, catalin.marinas@....com, will.deacon@....com,
	arnd@...db.de, akpm@...ux-foundation.org, mark.rutland@....com,
	marc.zyngier@....com
Subject: Re: [PATCH 0/6] generic relative extable support

On 01/04/2016 03:20 AM, Heiko Carstens wrote:
> On Sun, Jan 03, 2016 at 05:05:51PM +0100, Ard Biesheuvel wrote:
>> There are currently four architectures (x86, ia64, alpha and s390) whose
>> user-access exception tables are relative to the table entry address rather
>> than absolute. Each of these architectures has its own search_extable() and
>> sort_extable() implementation, which are not only mostly identical to each
>> other, but also deviate very little from the generic absolute implementations
>> in lib/extable.c that they override.
>>
>> So before making arm64 the fifth architecture that reimplements this, let's
>> refactor the existing code so that all of these architectures use common code
>> for searching and sorting the relative extables. Archs may set
>> ARCH_HAS_RELATIVE_EXTABLE to indicate that the table consists of a pair of
>> relative ints, and may define swap_ex_entry_fixup() if the fixup member needs
>> special treatment in the swapping step of the sorting routine (such as alpha).
>>
>> Note that the s390 patch applies on top of the following patch:
>>
>>   http://article.gmane.org/gmane.linux.kernel/2117036
>>
>> which fixes a bug I spotted while working on this code. Since that probably
>> needs to go to -stable, I broke it out and posted it separately.
>>
>> Ard Biesheuvel (6):
>>   extable: add support for relative extables to search and sort routines
>>   alpha/extable: use generic search and sort routines
>>   s390/extable: use generic search and sort routines
>>   x86/extable: use generic search and sort routines
>>   ia64/extable: use generic search and sort routines
>>   arm64: switch to relative exception tables
> 
> For the s390 bits:
> 
> Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>
> 

For the x86 bits:

Acked-by: H. Peter Anvin <hpa@...ux.intel.com>

*However*, please see my comment about generalizing _ASM_EXTABLE() for
the non-x86 architectures.

	-hpa

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