linux-kernel - Re: [PATCH 5/5] uprobes: Change write_opcode() to use copy

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Message-ID: <20130325103136.GF8163@bandura.brq.redhat.com>
Date:	Mon, 25 Mar 2013 11:31:36 +0100
From:	Anton Arapov <anton@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Josh Stone <jistone@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	adrian.m.negreanu@...el.com, Torsten.Polle@....de
Subject: Re: [PATCH 5/5] uprobes: Change write_opcode() to use copy_*page()

On Sun, Mar 24, 2013 at 07:21:25PM +0100, Oleg Nesterov wrote:
> Change write_opcode() to use copy_highpage() + copy_to_page()
> and simplify the code.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/events/uprobes.c |   12 ++----------
>  1 files changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 9d943f7..72f03d4 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -232,7 +232,6 @@ static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
>  			uprobe_opcode_t opcode)
>  {
>  	struct page *old_page, *new_page;
> -	void *vaddr_old, *vaddr_new;
>  	struct vm_area_struct *vma;
>  	int ret;
>  
> @@ -253,15 +252,8 @@ retry:
>  
>  	__SetPageUptodate(new_page);
>  
> -	/* copy the page now that we've got it stable */
> -	vaddr_old = kmap_atomic(old_page);
> -	vaddr_new = kmap_atomic(new_page);
> -
> -	memcpy(vaddr_new, vaddr_old, PAGE_SIZE);
> -	memcpy(vaddr_new + (vaddr & ~PAGE_MASK), &opcode, UPROBE_SWBP_INSN_SIZE);
> -
> -	kunmap_atomic(vaddr_new);
> -	kunmap_atomic(vaddr_old);
> +	copy_highpage(new_page, old_page);
> +	copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
>  
>  	ret = anon_vma_prepare(vma);
>  	if (ret)
> -- 
> 1.5.5.1
> 

Acked-by: Anton Arapov <anton@...hat.com>
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