Re: [PATCH 07/11] unpaged: COW on VM_UNPAGED

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, 18 Nov 2005, David S. Miller wrote:
> 
> The recent vbetool suspend-from-ram datapoint shows that it might be
> important that the BIOS data area is application local,
> ie. MAP_PRIVATE.  Ie. it works only if the writes are not performed
> to the real BIOS data page.

Interesting.  I haven't dared reach that conclusion yet.

> If true, that means the MAP_PRIVATE+VM_UNPAGED case has legit users.
> Although, such applications could just copy the interrupt vector plus
> BIOS data area into an anonymously mapped region and have the vm86
> execution work off that instead of the /dev/mem mapping.

Yes, they could indeed.  Would save the kernel contortions.

> So, just to make sure this all adds up, a PROT_WRITE+MAP_PRIVATE
> mapping of /dev/mem results in any pages written to being COW'd.
> Right?

Yes, in everything before 2.6.15-rc1, and again with my patches.

> It is a good question as to which cases doing stuff like this want to
> make modifications to the real BIOS data area, and which ones do not.
> Aparently vbetool does not.

Hugh
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux