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List:       linux-alpha
Subject:    Re: [PATCH v2 resend 6/6] arm64: switch to relative exception tables
From:       Andrew Morton <akpm () linux-foundation ! org>
Date:       2016-01-27 19:46:11
Message-ID: 20160127114611.25531afcfabf03febc134b48 () linux-foundation ! org
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On Wed, 27 Jan 2016 20:39:23 +0100 Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> On 27 January 2016 at 20:35, Andrew Morton <akpm@linux-foundation.org> wrote:
> > On Wed, 27 Jan 2016 11:55:23 +0100 Ard Biesheuvel <ard.biesheuvel@linaro.org> \
> > wrote: 
> > > Instead of using absolute addresses for both the exception location
> > > and the fixup, use offsets relative to the exception table entry values.
> > > Not only does this cut the size of the exception table in half, it is
> > > also a prerequisite for KASLR, since absolute exception table entries
> > > are subject to dynamic relocation, which is incompatible with the sorting
> > > of the exception table that occurs at build time.
> > > 
> > > This patch also introduces the _ASM_EXTABLE preprocessor macro (which
> > > exists on x86 as well) and its _asm_extable assembly counterpart, as
> > > shorthands to emit exception table entries.
> > 
> > checkpatch speaketh truth:
> > 
> > ERROR: #define of 'ARCH_HAS_RELATIVE_EXTABLE' is wrong - use Kconfig variables or \
> > standard guards instead #113: FILE: arch/arm64/include/asm/uaccess.h:56:
> 
> That may be true, but it extends an established pattern of #defines in
> the various uaccess.h versions, i.e., ARCH_HAS_SORT_EXTABLE, and
> ARCH_HAS_SEARCH_EXTABLE

True.  But now we have two things to fix, not one ;)

Whatever.  Later.
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