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

[matthieu castet]

H. Peter Anvin a écrit :
> On 02/07/2011 11:59 AM, castet.matthieu@xxxxxxx wrote:
> > For .39 I hope we could remove most of the RWX rights after init (This means
> > make low memory trampoline NX or !RW).
> > This should be possible on :
> > - 32 bit if wakeup use trampoline_32 [1] that doesn't enable paging in low
> > memory (can be NX)
> > - trampoline_64 need fix to support NX on data section. It tries to read data
> > section before enabling NX. A possible fix is to use its own page table [2]. And
> > the kernel one can be NX.
>
> No, you're really barking down the wrong path on this.  The trampoline
> code is tiny; I don't think it is really worth trying to NX-ify it.  The
Even if the trampoline is tiny, a hole is a hole.

The trampoline code job is to jump from low memory (realmode) to somewhere in kernel text.
Why should we enable paging or use kernel page table for doing that ?

> additional complexity caused by not being able to execute in this space
> will really damage some other incoming code, so it isn't an option as
> far as I'm concerned.
What do you plan to add that won't be compatible with that ?


Matthieu

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