linux-kernel - Re: What exactly do 32-bit x86 exceptions push on the stack in the CS slot?

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Message-ID: <20161123085640.GA7601@gmail.com>
Date:   Wed, 23 Nov 2016 09:57:27 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Matthew Whitehead <tedheadster@...il.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        George Spelvin <linux@...izon.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>
Subject: Re: What exactly do 32-bit x86 exceptions push on the stack in the
 CS slot?


* Andy Lutomirski <luto@...capital.net> wrote:

> The SDM says:
> 
> If the source operand is an immediate of size less than the operand size, a 
> sign-extended value is pushed on the stack. If the source operand is a segment 
> register (16 bits) and the operand size is 64-bits, a zero- extended value is 
> pushed on the stack; if the operand size is 32-bits, either a zero-extended 
> value is pushed on the stack or the segment selector is written on the stack 
> using a 16-bit move. For the last case, all recent Core and Atom processors 
> perform a 16-bit move, leaving the upper portion of the stack location 
> unmodified.
> 
> This makes me think that even new processors are quirky.

Oh well ...

Thanks,

	Ingo