Re: [PATCH V5] x86: NX protection for kernel data

[Siarhei Liakh]

>> I'd be surprised if anything ever did; this is the *kernel* mapping of
>> the first megabyte, not some userspace mapping....
>
> APM, BIOS32, EDD, PnPBIOS ..
>
> However except for APM (which isn't generally needed on NX capable
> devices or found on them) none of them are usually on critical paths
> because EDD is just grovelling around sort of stuff, and BIOS32 isn't
> generally used by the kernel anyway so could probably cope with flipping
> the permissions on the low 1 MB each call.

Actually, I have posted a patch to fix RW+X problem with BIOS32 some
time ago. See my submission to LKML (and subsequent discussion) on Jul
19 2009 "[PATCH] x86: Reducing footprint of BIOS32 service mappings".

Nevertheless, that 1MB area is on my "to do" list, and I will be
patching it sooner or later (assuming I get my patches tested well
enough to get them accepted).
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