linux-kernel - Re: [PATCH v9 23/42] Documentation/x86: Add CET shadow stack description

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Message-ID: <c7df57a7489ff555fc531d19a5a4a689f6f99a7c.camel@intel.com>
Date:   Wed, 21 Jun 2023 23:15:30 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v9 23/42] Documentation/x86: Add CET shadow stack
 description

On Wed, 2023-06-21 at 16:05 -0700, H.J. Lu wrote:
> > Which makes me think if we did want to make a more compatible
> > longjmp()
> > a better the way to do it might be an arch_prctl that emits a token
> > at
> > the current SSP. This would be loosening up the security somewhat
> > (have
> > to be an opt-in), but less so then enabling WRSS. But it would also
> > be
> > way simpler, work for all cases (I think), and be faster (maybe?)
> > than
> > INCSSPing through a bunch of stacks.
> 
> Since longjmp isn't required to be called after setjmp, leaving a
> restore
> token doesn't work when longjmp isn't called.

Oh good point. Hmm.