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From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	"linux-tip-commits@vger.kernel.org" 
	<linux-tip-commits@vger.kernel.org>
Subject: Re: [tip:x86/kaslr] x86, kaslr: Provide randomness functions
Date: Mon, 11 Nov 2013 20:58:53 +0100	[thread overview]
Message-ID: <20131111195852.GA17408@gmail.com> (raw)
In-Reply-To: <52813334.2040405@zytor.com>


* H. Peter Anvin <hpa@zytor.com> wrote:

> On 11/11/2013 11:37 AM, Kees Cook wrote:
> > On Mon, Nov 11, 2013 at 11:27 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> >> On 11/11/2013 10:20 AM, Ingo Molnar wrote:
> >>>
> >>> Why aren't the 3 sources of entropy XOR-ed together?
> >>
> >> Note we don't want to poke i8254 if we have any other sources, as the
> >> i8254 may not be present on newer systems and in some other cases not
> >> safe to touch.  We can XOR in the TSC with RDRAND although it seems a
> >> bit odd.
> > 
> > I await the final decision! :)
> > 
> 
> Use the i8254 if and only if nothing else is available, it isn't safe to
> touch on some newer systems.

I concur - the i8254 is probably also a low entry source, given that this 
all runs early bootup.

In any case there's no excuse for not mixing RDRAND and RDTSC entropy.

Thanks,

	Ingo

  reply	other threads:[~2013-11-11 19:59 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-11  0:18 [PATCH v8 0/6] Kernel base address randomization Kees Cook
2013-10-11  0:18 ` [kernel-hardening] " Kees Cook
2013-10-11  0:18 ` [PATCH v8 1/6] x86, boot: move CPU flags out of cpucheck Kees Cook
2013-10-11  0:18   ` [kernel-hardening] " Kees Cook
2013-10-13 12:01   ` [tip:x86/kaslr] x86, boot: Move " tip-bot for Kees Cook
2013-10-13 12:02   ` [tip:x86/kaslr] x86, boot: Rename get_flags() and check_flags() to *_cpuflags() tip-bot for H. Peter Anvin
2013-10-11  0:18 ` [PATCH v8 2/6] x86, kaslr: return location from decompress_kernel Kees Cook
2013-10-11  0:18   ` [kernel-hardening] " Kees Cook
2013-10-13 12:01   ` [tip:x86/kaslr] x86, kaslr: Return " tip-bot for Kees Cook
2013-10-11  0:18 ` [PATCH v8 3/6] x86, kaslr: provide randomness functions Kees Cook
2013-10-11  0:18   ` [kernel-hardening] " Kees Cook
2013-10-13 12:01   ` [tip:x86/kaslr] x86, kaslr: Provide " tip-bot for Kees Cook
2013-11-11 18:20     ` Ingo Molnar
2013-11-11 18:31       ` Ingo Molnar
2013-11-11 19:32         ` Kees Cook
2013-11-11 19:37           ` H. Peter Anvin
2013-11-11 20:07             ` Ingo Molnar
2013-11-11 20:11               ` Kees Cook
2013-11-11 20:16                 ` H. Peter Anvin
2013-11-11 19:27       ` H. Peter Anvin
2013-11-11 19:37         ` Kees Cook
2013-11-11 19:42           ` H. Peter Anvin
2013-11-11 19:58             ` Ingo Molnar [this message]
2013-11-11 20:04               ` H. Peter Anvin
2013-11-11 20:09                 ` Ingo Molnar
2013-11-13 18:16       ` Pavel Machek
2013-11-13 18:40         ` H. Peter Anvin
2013-11-13 23:23           ` Pavel Machek
2013-11-13 23:25             ` H. Peter Anvin
2013-10-11  0:18 ` [PATCH v8 4/6] x86, kaslr: select random position from e820 maps Kees Cook
2013-10-11  0:18   ` [kernel-hardening] " Kees Cook
2013-10-13 12:01   ` [tip:x86/kaslr] x86, kaslr: Select " tip-bot for Kees Cook
2013-10-11  0:18 ` [PATCH v8 5/6] x86, kaslr: report kernel offset on panic Kees Cook
2013-10-11  0:18   ` [kernel-hardening] " Kees Cook
2013-10-13 12:01   ` [tip:x86/kaslr] x86, kaslr: Report " tip-bot for Kees Cook
2013-10-11  0:18 ` [PATCH v8 6/6] x86, kaslr: raise max positions to 1GiB on x86_64 Kees Cook
2013-10-11  0:18   ` [kernel-hardening] " Kees Cook
2013-10-13 12:02   ` [tip:x86/kaslr] x86, kaslr: Raise the maximum virtual address to -1 GiB " tip-bot for Kees Cook

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