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

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Date:   Thu, 22 Jun 2023 23:18:27 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "szabolcs.nagy@....com" <szabolcs.nagy@....com>,
        "Lutomirski, Andy" <luto@...nel.org>
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Subject: Re: [PATCH v9 23/42] Documentation/x86: Add CET shadow stack
 description

On Thu, 2023-06-22 at 17:42 +0100, szabolcs.nagy@....com wrote:
> the downside is that longjmp across makecontext needs a
> separate solution then which implies that all shstk needs
> a detectable token at the end of the shstk.. so again
> something that we have to get right now and cannot add
> later.)

This sounds like some scheme to search for a token on another stack,
which if so, you haven't elaborated on.

I'm not going to be able to contribute on this thread much over the
next week, but if you think you know to solve problems which have
remained unsolved for years, please spell out the solutions.

I'd also appreciate if you could spell out exactly which:
 - ucontext
 - signal
 - longjmp
 - custom library stack switching

patterns you think shadow stack should support working together.
Because even after all these mails, I'm still not sure exactly what you
are trying to achieve.