linux-kernel - Re: [PATCH 4/5] uprobes: Introduce copy_to

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Message-ID: <20130325103126.GE8163@bandura.brq.redhat.com>
Date:	Mon, 25 Mar 2013 11:31:26 +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 4/5] uprobes: Introduce copy_to_page()

On Sun, Mar 24, 2013 at 07:21:22PM +0100, Oleg Nesterov wrote:
> Extract the kmap_atomic/memcpy/kunmap_atomic code from
> xol_get_insn_slot() into the new simple helper, copy_to_page().
> It will have more users soon.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/events/uprobes.c |   14 ++++++++------
>  1 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index e5d479f..9d943f7 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -180,6 +180,13 @@ static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, in
>  	kunmap_atomic(kaddr);
>  }
>  
> +static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
> +{
> +	void *kaddr = kmap_atomic(page);
> +	memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
> +	kunmap_atomic(kaddr);
> +}
> +
>  static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
>  {
>  	uprobe_opcode_t old_opcode;
> @@ -1204,9 +1211,7 @@ static unsigned long xol_take_insn_slot(struct xol_area *area)
>  static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
>  {
>  	struct xol_area *area;
> -	unsigned long offset;
>  	unsigned long xol_vaddr;
> -	void *vaddr;
>  
>  	area = get_xol_area();
>  	if (!area)
> @@ -1217,10 +1222,7 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
>  		return 0;
>  
>  	/* Initialize the slot */
> -	offset = xol_vaddr & ~PAGE_MASK;
> -	vaddr = kmap_atomic(area->page);
> -	memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
> -	kunmap_atomic(vaddr);
> +	copy_to_page(area->page, xol_vaddr, uprobe->arch.insn, MAX_UINSN_BYTES);
>  	/*
>  	 * We probably need flush_icache_user_range() but it needs vma.
>  	 * This should work on supported architectures too.
> -- 
> 1.5.5.1
> 

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