Re: [PATCH] selftests/x86: Disable ldt_gdt_64 for now

From: Ingo Molnar
Date: Tue Jan 12 2016 - 05:45:58 EST



* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> On Mon, Jan 11, 2016 at 2:59 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> >
> > * Shuah Khan <shuahkh@xxxxxxxxxxxxxxx> wrote:
> >
> >> On 01/06/2016 12:51 PM, Andy Lutomirski wrote:
> >> > ldt_gdt.c relies on cross-cpu invalidation of SS to do one of its
> >> > tests. On 32-bit builds, this works fine, but on 64-bit builds, it
> >> > only works if the kernel has proper SS sigcontext handling for
> >> > 64-bit user programs.
> >> >
> >> > Since the SS fixes are currently reverted, restrict the test case to
> >> > 32 bits for now.
> >> >
> >> > In principle, I could change the test to use a different segment
> >> > register, but it would be messy: CS can't point to the LDT for
> >> > 64-bit code, and the other registers don't result in immediate
> >> > faults because they aren't reloaded on kernel -> user transitions.
> >> >
> >> > When we fix sigcontext (in 4.6?), we can revert this.
> >> >
> >> > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> >> > --
> >>
> >> Andy,
> >>
> >> This patch didn't apply to linux-kselftest next.
> >> It probably has to go through x86.
> >
> > It doesn't apply to -tip either. Andy, which tree is this against?
>
> Oops, it applies on top of a new self-test that I forgot to send. I
> send a v2 that should be better. I'll send the new selftest out as
> well once -tip catches up with all the vdso patches.

Ok, sounds great!

Thanks,

Ingo