Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending

H. Peter Anvin
2008-03-03T17:53:51Z

Ingo Molnar wrote:
> * Klaus S. Madsen <ksm@hjernemadsen.org> wrote:
>
>> The following patch solves the segfault, by changing the mmap flags of
>> the video memory area, to allow execution. The patch is against
>> libx86-0.99 available from http://www.codon.org.uk/~mjg59/libx86/
>>
>> --- libx86-0.99/x86-common.c 2006-09-08 00:44:27.000000000 +0200
>> +++ libx86-0.99.new/x86-common.c 2008-03-01 10:08:25.000000000 +0100
>> @@ -232,7 +232,7 @@
>> }
>>
>> m = mmap((void *)0xa0000, 0x100000 - 0xa0000,
>> - PROT_READ | PROT_WRITE,
>> + PROT_READ | PROT_WRITE | PROT_EXEC,
>
> are you sure you ID-ed the right commit that broke things?
>
> while requiring PROT_EXEC is fine, breaking existing user-space apps
> over that is not fine. So are you absolutely sure that by reverting that
> PWT|PCD commit, s2ram again starts to work? That's utmost weird...
>
> perhaps there's some CPU bug that causes NX to _NOT_ work if only PCD is
> used (not PCD|PWT). Seems like a pretty unlikely scenario though.
>

It really does. What would be much more likely is that the PCD ->
(PCD|PWT) triggered something in the kernel proper.

-hpa