2011-02-06 10:30:31

by Bodo Eggert

[permalink] [raw]
Subject: Re: [PATCH] NX protection for kernel data : fix 32 bits S3 suspend

H. Peter Anvin <[email protected]> wrote:

> In static_protections() we have:
>
>> /*
>> * The BIOS area between 640k and 1Mb needs to be executable for
>> * PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
>> */

I don't think the CGA/MDA/VGA graphics memory areas should be executable,
and I doubt execute access to these areas is required - is it?

0xA000:0000 might be a BIOS area, if it is, you don't have a VGA and the
ROM will be exactly 64K. 0xB800 and 0xB000 SHOULD NOT be a ROM, nobody dared
to use it (I don't remember exactly where ROMs are searched).
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2011-02-06 23:33:23

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH] NX protection for kernel data : fix 32 bits S3 suspend

On 02/06/2011 02:30 AM, Bodo Eggert wrote:
> H. Peter Anvin <[email protected]> wrote:
>
>> In static_protections() we have:
>>
>>> /*
>>> * The BIOS area between 640k and 1Mb needs to be executable for
>>> * PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
>>> */
>
> I don't think the CGA/MDA/VGA graphics memory areas should be executable,
> and I doubt execute access to these areas is required - is it?
>
> 0xA000:0000 might be a BIOS area, if it is, you don't have a VGA and the
> ROM will be exactly 64K. 0xB800 and 0xB000 SHOULD NOT be a ROM, nobody dared
> to use it (I don't remember exactly where ROMs are searched).


0xA0000..0xBFFFF can be ROM if you don't have a VGA card; this is new in
PCI 3.x IIRC. However, in legacy systems you will not have ROM in this
area.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.