linux-kernel - Re: [PATCH] lib/dma-debug: check for vmalloc buffers used with the DMA-API

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Date:	Tue, 18 Sep 2012 15:18:42 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Jan Luebbe <jlu@...gutronix.de>
CC:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lib/dma-debug: check for vmalloc buffers used with the
 DMA-API

On Mon, Sep 03, 2012 at 01:00:04PM +0200, Jan Luebbe wrote:
> Signed-off-by: Jan Luebbe <jlu@...gutronix.de>
> ---
> I'm not sure why we don't check for high memory, is there any problem
> with this approach?
> 
>  lib/dma-debug.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index 66ce414..7d60ff0 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -944,6 +944,9 @@ static void check_for_illegal_area(struct device *dev, void *addr, unsigned long
>  	if (overlap(addr, len, _text, _etext) ||
>  	    overlap(addr, len, __start_rodata, __end_rodata))
>  		err_printk(dev, NULL, "DMA-API: device driver maps memory from kernel text or rodata [addr=%p] [len=%lu]\n", addr, len);
> +	if (is_vmalloc_or_module_addr(addr) ||
> +	    is_vmalloc_or_module_addr(addr+len))
> +		err_printk(dev, NULL, "DMA-API: device driver maps memory from vmalloc or module address range [addr=%p] [len=%lu]\n", addr, len);

Hmm, this only checks whether the start or end+1 address is in the
vmalloc/module range. I think it is better to check for overlap against
VMALLOC_START/END and do a seperate overlap check for MODULES_VADDR and
MODULES_END when needed.

Thanks,

	Joerg

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