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From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Daney <david.s.daney@gmail.com>,
	David Daney <ddaney.cavm@gmail.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org, Michal Marek <mmarek@suse.cz>,
	linux-kernel@vger.kernel.org, linux-mips@linux-mips.org,
	Andrew Morton <akpm@linux-foundation.org>,
	David Daney <david.daney@cavium.com>
Subject: Re: [PATCH v1 1/5] scripts: Add sortextable to sort the kernel's exception table.
Date: Thu, 19 Apr 2012 20:42:47 -0700	[thread overview]
Message-ID: <4F90DB37.9080702@zytor.com> (raw)
In-Reply-To: <CA+55aFyijf43qSu3N9nWHEBwaGbb7T2Oq9A=9EyR=Jtyqfq_cQ@mail.gmail.com>

On 04/19/2012 08:31 PM, Linus Torvalds wrote:
> On Thu, Apr 19, 2012 at 8:17 PM, David Daney <david.s.daney@gmail.com> wrote:
>>
>> I hadn't considered that the image was relocatable.  Our MIPS kernels never
>> have relocations.
>>
>> I am working on a version of this that handles the relocations.  It
>> shouldn't be too difficult.
> 
> It might be better to just make the rule be that we don't have
> relocations there - make everything relative to the start of the code
> segment or something.
> 
> On x86, we already use that _ASM_EXTABLE() macro to hide the
> differences between x86-64 and x86-32. So it should be be somewhat
> easy to make that same macro make it relative to the code start, and
> at the same time also make the exception table perhaps be two 32-bit
> words rather than two pointers.
> 
> So it would shrink the exception table and avoid relocations at the
> same time. Win-win. No?
> 

I don't think we can get _ASM_EXTABLE() to do that work for us, because
we'd need to subtract symbols from two different sections.  We would
need the postprocessing tool to take care this, but guess what, we can
do exactly that (and then, as I mentioned, just zero out the relocation
section.)

	-hpa





  reply	other threads:[~2012-04-20  3:44 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-19 21:59 [PATCH v2 0/5] Speed booting by sorting exception tables at build time David Daney
2012-04-19 21:59 ` [PATCH v1 1/5] scripts: Add sortextable to sort the kernel's exception table David Daney
2012-04-20  0:20   ` [tip:x86/extable] scripts: Add sortextable to sort the kernel' s " tip-bot for David Daney
2012-04-20  1:44   ` [PATCH v1 1/5] scripts: Add sortextable to sort the kernel's " H. Peter Anvin
2012-04-20  3:17     ` David Daney
2012-04-20  3:31       ` Linus Torvalds
2012-04-20  3:42         ` H. Peter Anvin [this message]
2012-04-20  4:49           ` H. Peter Anvin
2012-04-20  4:54             ` H. Peter Anvin
2012-04-20 21:55         ` [tip:x86/extable] x86, extable: Use .pushsection ... . popsection for _ASM_EXTABLE() tip-bot for H. Peter Anvin
2012-04-20 21:56         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/ia32/ia32entry.S tip-bot for H. Peter Anvin
2012-04-20 21:57         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/kernel/entry_32.S tip-bot for H. Peter Anvin
2012-04-20 21:58         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/kernel/entry_64.S tip-bot for H. Peter Anvin
2012-04-20 21:58         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/kernel/test_rodata.c tip-bot for H. Peter Anvin
2012-04-20 21:59         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/checksum_32.S tip-bot for H. Peter Anvin
2012-04-20 22:00         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/copy_user_64.S tip-bot for H. Peter Anvin
2012-04-20 22:01         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/ copy_user_nocache_64.S tip-bot for H. Peter Anvin
2012-04-20 22:02         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/csum-copy_64.S tip-bot for H. Peter Anvin
2012-04-20 22:03         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/getuser.S tip-bot for H. Peter Anvin
2012-04-20 22:03         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/putuser.S tip-bot for H. Peter Anvin
2012-04-20 22:04         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/lib/usercopy_32.c tip-bot for H. Peter Anvin
2012-04-20 22:05         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/um/checksum_32.S tip-bot for H. Peter Anvin
2012-04-20 22:06         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/xen/xen-asm_32.S tip-bot for H. Peter Anvin
2012-04-20 22:07         ` [tip:x86/extable] x86, extable: Remove the now-unused __ASM_EX_SEC macros tip-bot for H. Peter Anvin
2012-04-20 22:08         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/include/asm/kvm_host .h tip-bot for H. Peter Anvin
2012-04-20 22:08         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/include/asm/xsave.h tip-bot for H. Peter Anvin
2012-04-21  0:16         ` [tip:x86/extable] x86, extable: Remove open-coded exception table entries in arch/x86/ia32/ia32entry.S tip-bot for H. Peter Anvin
2012-04-21  0:17         ` [tip:x86/extable] x86, extable: Add _ASM_EXTABLE_EX() macro tip-bot for H. Peter Anvin
2012-04-21  1:16         ` [tip:x86/extable] x86, extable: Disable presorted exception table for now tip-bot for H. Peter Anvin
2012-04-21  1:17         ` [tip:x86/extable] x86, extable: Switch to relative exception table entries tip-bot for H. Peter Anvin
2012-04-20 14:59   ` [PATCH v1 1/5] scripts: Add sortextable to sort the kernel's exception table Sam Ravnborg
2012-04-20 16:49     ` David Daney
2012-04-19 21:59 ` [PATCH v2 2/5] extable: Skip sorting if sorted at build time David Daney
2012-04-20  0:21   ` [tip:x86/extable] " tip-bot for David Daney
2012-04-19 21:59 ` [PATCH v2 3/5] kbuild/extable: Hook up sortextable into the build system David Daney
2012-04-20  0:22   ` [tip:x86/extable] " tip-bot for David Daney
2012-04-20 15:02   ` [PATCH v2 3/5] " Sam Ravnborg
2012-04-19 21:59 ` [PATCH v2 4/5] MIPS: Select BUILDTIME_EXTABLE_SORT David Daney
2012-04-20  0:23   ` [tip:x86/extable] " tip-bot for David Daney
2012-04-19 21:59 ` [PATCH v2 5/5] x86: " David Daney
2012-04-20  0:23   ` [tip:x86/extable] " tip-bot for David Daney

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