linux-kernel - Re: [patch 14/14] syslets: x86: optimized sys_umem

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Date:	Thu, 15 Feb 2007 21:23:00 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 14/14] syslets: x86: optimized sys_umem_add()

On Thu, Feb 15, 2007 at 05:52:59PM +0100, Ingo Molnar wrote:
> provide an optimized assembly version of sys_umem_add().

> --- linux.orig/arch/i386/lib/getuser.S
> +++ linux/arch/i386/lib/getuser.S

> +sys_umem_add:
> +	movl 0x4(%esp), %ecx			# uptr
> +	movl 0x8(%esp), %edx			# inc
> +
> +	cmpl $__PAGE_OFFSET, %ecx		# access_ok(uptr)
> +	jae bad_sys_umem_add
> +
> +1:	addl %edx, (%ecx)			# *uptr += inc
> +2:	movl (%ecx), %eax			# return *uptr
> +	ret
> +
> +bad_sys_umem_add:
> +	movl $-14, %eax

We have EFAULT for this. ;-)

> +	ret
> +
> +.section __ex_table,"a"
> +	.long 1b, bad_sys_umem_add
> +	.long 2b, bad_sys_umem_add
> +.previous

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