[PATCH] x86: Add __sigsetjmp_cancel and __setjmp_cancel

[Florian Weimer]

* H. J. Lu:

> On Thu, Mar 29, 2018 at 10:34 AM, Florian Weimer <fw@deneb.enyo.de> wrote:
>> * H. J. Lu:
>>
>>> Here is the updated patch.  OK for master?
>>
>> If you want to backport this into Fedora 28, you will have to avoid
>> new symbol versions.
>
> Should we revisit my patch to extend struct pthread_unwind_buf:
>
> https://sourceware.org/ml/libc-alpha/2018-02/msg00291.html
>
> This patch doesn't introduce the new symbol version.

That patch will require recompiling a subset of static libraries in
Fedora 28 to avoid crashes once CET is enabled.  Which should be
doable at a technical level, but takes resources away from other work,
obviously.

My preference still is a solution where we shift the stored signal
mask to make room for the shadow stack data in CET mode (for maximum
compatibility).  But I expect that Carlos will review your patch.