linux-kernel - Re: [PATCH v7 3.2-rc2 9/30] uprobes: Background page replacement.

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Date:	Fri, 25 Nov 2011 15:54:46 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...k.frob.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Stephen Wilson <wilsons@...rt.ca>
Subject: Re: [PATCH v7 3.2-rc2 9/30] uprobes: Background page replacement.

On Fri, 2011-11-18 at 16:38 +0530, Srikar Dronamraju wrote:
> +static int read_opcode(struct mm_struct *mm, unsigned long vaddr,
> +                                               uprobe_opcode_t *opcode)
> +{
> +       struct page *page;
> +       void *vaddr_new;
> +       int ret;
> +
> +       ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
> +       if (ret <= 0)
> +               return ret;
> +
> +       lock_page(page);
> +       vaddr_new = kmap_atomic(page);
> +       vaddr &= ~PAGE_MASK;

BUG_ON(vaddr + uprobe_opcode_sz >= PAGE_SIZE);

> +       memcpy(opcode, vaddr_new + vaddr, uprobe_opcode_sz);
> +       kunmap_atomic(vaddr_new);
> +       unlock_page(page);
> +       put_page(page);         /* we did a get_user_pages in the beginning */
> +       return 0;
> +} 

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