svn commit: r226343 - head/sys/vm

[Kostik Belousov]

On Thu, Oct 13, 2011 at 11:30:12AM -0700, Marcel Moolenaar wrote:
>
> On Oct 13, 2011, at 11:20 AM, Kostik Belousov wrote:
>
> > The two commits removed NX support for .data/.bss for 32bit binaries
> > Thon amd64. is is too unfortunate. Can we claim that only old
> > Thbinaries need this hack ?
>
> I don't know. When did our ABI for i386 change to have NX by default?
I think it changed de-facto when NX appears to be supported by hardware.
In other words, PF_R->PF_X was always considered a coincident, and not
a promise.

I think we can claim that the moment FreeBSD gained PAE support, it happen.

I would suggest to add a sysctl, say kern.elf32.readable_nx, with
the values:
0 - strictly follow segment permissions
1 - PF_R implies PF_X if p_osrel < 600000
2 - PF_R always implied PF_X
for 32bit binaries.
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