linux-kernel - Re: [PATCH v4 09/10] x86-64: Randomize int 0xcc magic al values at boot

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Date:	Tue, 31 May 2011 12:10:40 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Jesper Juhl <jj@...osbits.net>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Jan Beulich <JBeulich@...ell.com>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	Mikael Pettersson <mikpe@...uu.se>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v4 09/10] x86-64: Randomize int 0xcc magic al values at boot

On Tue, May 31, 2011 at 11:56 AM, Andrew Lutomirski <luto@....edu> wrote:
> We could scrap int 0xcc entirely and emulate on page fault, but that
> is slower and has other problems (like breaking anything that thinks
> it can look at a call target in a binary and dereference that
> address).
>
> Here's a possibly dumb/evil idea:
>
> Put real syscalls in the vsyscall page but mark the page NX.  Then
> emulate the vsyscalls on the PF_INSTR fault when userspace jumps to
> the correct address but send SIGSEGV for the wrong address.
>
> Down side: it's even more complexity for the same silly case.

Scratch that.  It's incompatible with keeping time() fast for now.

>
> --Andy
>
>>
>> Thanks,
>>
>>        Ingo
>>
>
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