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

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Message-ID: <ZJP664odSJC+tGzT@arm.com>
Date:   Thu, 22 Jun 2023 08:40:27 +0100
From:   "szabolcs.nagy@....com" <szabolcs.nagy@....com>
To:     "H.J. Lu" <hjl.tools@...il.com>,
        "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

The 06/21/2023 16:02, H.J. Lu wrote:
> On Wed, Jun 21, 2023 at 11:54 AM Edgecombe, Rick P
> <rick.p.edgecombe@...el.com> wrote:
> > HJ, can you link your patch that makes it extensible and we can clear
> > this up? Maybe the issue extends beyond fnon-call-exceptions, but that
> > is where I reproduced it.
> 
> Here is the patch:
> 
> https://gitlab.com/x86-gcc/gcc/-/commit/aab4c24b67b5f05b72e52a3eaae005c2277710b9

ok i don't see how this is related to fnon-call-exceptions..

but it is wrong if the shstk is ever discontinous even though the
shstk format would allow that. this was my original point in this
thread: with current unwinder code you cannot add altshstk later.
and no, introducing new binary markings and rebuild the world just
for altshstk is not OK. so we have to decide now if we want alt
shstk in the future or not, i gave reasons why we would want it.