Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS to %ss

Brian Gerst
2015-04-23T11:11:55Z

On Thu, Apr 23, 2015 at 5:56 AM, Borislav Petkov <bp@alien8.de> wrote:
> On Thu, Apr 23, 2015 at 11:20:56AM +0200, Denys Vlasenko wrote:
>> * what if %ss before syscall was NOT the usual value of 0x2b, but some
>> other segment, not the typical 0-base, 0xffffffff limit 32-bit expand-up one?
>> Not restoring proper %ss would not go well.
>> [but then, Intel CPUs work, and old code worked....]
>
> Have we run the exact same reproducer on Intel already?
>
> Brian, can you run the same thing on an Intel box, if you haven't done
> so already?
>
> Thanks.

Tested it on a Intel(R) Core(TM)2 Duo CPU T6400 @ 2.00GHz and cannot
reproduce it there. Note that on Intel CPUs, we use the sysenter VDSO
but return with sysret.

--
Brian Gerst