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From: Ingo Molnar <mingo@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Hector Marco-Gisbert <hecmargi@upv.es>,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>,
	Jan-Simon <dl9pf@gmx.de>,
	linux-fsdevel@vger.kernel.org, kees Cook <keescook@chromium.org>,
	Ismael Ripoll <iripoll@disca.upv.es>
Subject: Re: [PATCH] mm/x86: AMD Bulldozer ASLR fix
Date: Sun, 29 Mar 2015 10:51:22 +0200	[thread overview]
Message-ID: <20150329085122.GA25177@gmail.com> (raw)
In-Reply-To: <20150327144438.GA3254@pd.tnic>


* Borislav Petkov <bp@alien8.de> wrote:

> From: Hector Marco-Gisbert <hecmargi@upv.es>
> Date: Fri, 27 Mar 2015 12:38:21 +0100
> Subject: [PATCH] x86/mm: Improve AMD Bulldozer ASLR fix
> 
> The ASLR implementation needs to special-case AMD F15h processors by
> clearing out bits [14:12] of the virtual address in order to avoid I$
> cross invalidations and thus performance penalty for certain workloads.
> For details, see:
> 
>   dfb09f9b7ab0 ("x86, amd: Avoid cache aliasing penalties on AMD family 15h")
> 
> This special case reduces the mmapped files entropy by eight.

s/reduces the mmapped file's entropy by 3 bits

Which does:

 - a grammar fix

 - measure it in bits, as later on we are talking about randomness in 
   bits as well.

Btw., does this limitation affect both executable and non-executable 
mmap()s? Because data mmap()s don't need this I$ related workaround, 
right? So we could relax it for data-mmap()s?

Thanks,

	Ingo

  parent reply	other threads:[~2015-03-29  8:51 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-24 18:00 [PATCH] mm/x86: AMD Bulldozer ASLR fix Hector Marco-Gisbert
2015-03-24 19:15 ` Borislav Petkov
2015-03-25 18:29   ` Hector Marco
2015-03-25 18:36   ` Hector Marco-Gisbert
2015-03-26 19:08     ` Borislav Petkov
2015-03-27 11:38       ` Hector Marco-Gisbert
2015-03-27 12:14         ` Ingo Molnar
2015-03-27 12:35           ` Borislav Petkov
2015-03-27 14:44         ` Borislav Petkov
2015-03-27 15:06           ` Hector Marco-Gisbert
2015-03-28 13:10           ` Kees Cook
2015-03-29  8:51           ` Ingo Molnar [this message]
2015-03-29  9:53             ` Borislav Petkov
2015-03-31  7:59               ` Ingo Molnar
2015-03-31 12:37         ` [tip:x86/mm] x86/mm: Improve AMD Bulldozer ASLR workaround tip-bot for Hector Marco-Gisbert

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