linux-kernel - Re: [PATCH] x86/asm/entry/64: better check for canonical address

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Message-ID: <CALCETrUf3GeNZ8DajRyhJSttpoCoNFV_VHHbNPqJsMArgJdGGg@mail.gmail.com>
Date:	Tue, 21 Apr 2015 11:08:42 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/asm/entry/64: better check for canonical address

On Tue, Apr 21, 2015 at 9:27 AM, Denys Vlasenko <dvlasenk@...hat.com> wrote:
> This change makes the check exact (no more false positives
> on "negative" addresses).

Acked-by: Andy Lutomirski <luto@...nel.org>

I'll take a full implementation of what Intel says over probably
unmeasurable performance.  If anyone in the AMD camp really cared, we
could add X86_BUG_SYSRET_NEEDS_CANONICAL_RCX and use alternatives to
patch this out on AMD.  I doubt this would buy us much.

--Andy
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