linux-kernel - Re: [PATCH] selftests/x86: Disable ldt_gdt

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Date:	Tue, 12 Jan 2016 11:45:44 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Shuah Khan <shuahkh@....samsung.com>,
	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests/x86: Disable ldt_gdt_64 for now


* Andy Lutomirski <luto@...capital.net> wrote:

> On Mon, Jan 11, 2016 at 2:59 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Shuah Khan <shuahkh@....samsung.com> 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@...nel.org>
> >> > --
> >>
> >> 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