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In-Reply-To: <1429633649-20169-1-git-send-email-dvlasenk@redhat.com>
References: <1429633649-20169-1-git-send-email-dvlasenk@redhat.com>
From: Andy Lutomirski <luto@amacapital.net>
Date: Tue, 21 Apr 2015 11:08:42 -0700
Message-ID: <CALCETrUf3GeNZ8DajRyhJSttpoCoNFV_VHHbNPqJsMArgJdGGg@mail.gmail.com>
Subject: Re: [PATCH] x86/asm/entry/64: better check for canonical address
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>, Will Drewry <wad@chromium.org>,
        Kees Cook <keescook@chromium.org>, X86 ML <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Apr 21, 2015 at 9:27 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
> This change makes the check exact (no more false positives
> on "negative" addresses).

Acked-by: Andy Lutomirski <luto@kernel.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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