linux-kernel - Re: [GIT pull] x86 vdso updates

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Date:	Sun, 29 May 2011 16:39:47 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Lutomirski <luto@....edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT pull] x86 vdso updates

Ingo Molnar writes:
 > 
 > * Andrew Lutomirski <luto@....edu> wrote:
 > 
 > > On Fri, May 27, 2011 at 7:36 AM, Andrew Lutomirski <luto@....edu> wrote:
 > > > 3. Add int 0xcc and use it from vgettimeofday.  It will SIGSEGV if
 > > > called from a user address (so it has no risk of ever becoming ABI)
 > > > and it will do gettimeofday if called from the right address.  (I like
...
 > > Make it a real syscall but with extra constraints.  It would have the
 > > same calling convention as the syscall instruction, but it would turn
 > > into SIGKILL if the calling address isn't in the VSYSCALL page

This will make things difficult for user-space dynamic binary instrumentation
applications, since these normally execute generated code at different
addresses than the original code.

Is there a safe fallback for this particular vsyscall?

/Mikael
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