linux-kernel - Re: [PATCH] x86/shstk: Enable shadow stack for x32

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Date: Fri, 22 Mar 2024 14:07:27 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "hjl.tools@...il.com" <hjl.tools@...il.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH] x86/shstk: Enable shadow stack for x32

On Fri, 2024-03-15 at 07:34 -0700, H.J. Lu wrote:
> > How many people do you think will use this?

I'm concerned that the only use of this will ever be exercise via the
glibc unit tests, but will still require work to support.

> > 
> > I would have thought it would require more changes for basic x32
> 
> This is all needed.
> 
> > operation. What was the testing exactly?
> 
> I configured x32 glibc with --enable-cet, build glibc and
> run all glibc tests with shadow stack enabled.  There are
> no regressions.  I verified that shadow stack is enabled
> via /proc/pid/status.

The shadow stack is supposed to be mapped above 4G, so how is this
supposed to work for x32?