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Re: [PATCH 2/2] x86-64/swapcontext: Restore the pointer into %rdx after syscall
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: "Carlos O'Donell" <carlos at redhat dot com>
- Cc: Florian Weimer <fweimer at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Wed, 2 May 2018 06:35:12 -0700
- Subject: Re: [PATCH 2/2] x86-64/swapcontext: Restore the pointer into %rdx after syscall
- References: <20180426121744.GB30766@intel.com> <09599cf2-6eca-1052-1788-35dd3b2e5225@redhat.com> <CAMe9rOr35ZeLd09es4WeBgd1pej2B89VLFYcs9WwJ9zKPjPJNg@mail.gmail.com> <8a034d00-37ca-5752-064b-778af4aef718@redhat.com>
On Tue, May 1, 2018 at 9:46 PM, Carlos O'Donell <carlos@redhat.com> wrote:
> On 04/29/2018 06:08 PM, H.J. Lu wrote:
>> On Sun, Apr 29, 2018 at 2:10 PM, Florian Weimer <fweimer@redhat.com> wrote:
>>> On 04/26/2018 02:17 PM, H.J. Lu wrote:
>>>>
>>>> + /* Restore destroyed register into RDX which is preserved by
>>>> + the syscall. */
>>>> + movq %r12, %rdx
>>>
>>>
>>> Again, this comment does not make sense without the other upcoming changes.
>>>
>>
>> Here is the patch to use it:
>>
>> https://github.com/hjl-tools/glibc/commit/182ce0987aada98b2d606276d4aa4fbd2527031b
>
> If we are doing a "flag-day" enable for ucontext, is there
> any reason not to add additional space today that can be
> used in the future?
That is a good idea. I added 4 words for CET. We can add another 8
or 16 words.
--
H.J.