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Re: RFC: Shadow Stack support in glibc

On Fri, 9 Jun 2017, H.J. Lu wrote:

> On Fri, Jun 9, 2017 at 4:32 AM, Florian Weimer <fweimer@redhat.com> wrote:
> > On 06/09/2017 01:28 PM, H.J. Lu wrote:
> >> Yes,  99% of codes just need to recompile.  If context functions
> >> are used or jmpbuf is used independently of setjmp/longjmp,
> >> enabling is needed.
> >
> > Would you please clarify if the size of the type jmp_buf changes in the
> > new compilation mode?
> >
> 
> jmp_buf size will be increased unconditionally in glibc whose <setjmp.h>
> has

Previous experience (the s390 change in 2.19, reverted in 2.20) showed 
that changing jmp_buf size, even with symbol versioning, is very 
problematic.  jmp_buf gets embedded in types involved in the ABIs of 
third-party libraries such as libpng.

-- 
Joseph S. Myers
joseph@codesourcery.com
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