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

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Date:	Mon, 11 Jan 2016 17:25:06 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Ingo Molnar <mingo@...nel.org>
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

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.

--Andy