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Date: Tue, 3 Feb 2004 19:34:58 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Jamie Lokier <jamie@shareable.org>
Cc: Ulrich Drepper <drepper@redhat.com>, john stultz <johnstul@us.ibm.com>,
       lkml <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH] linux-2.6.2-rc2_vsyscall-gtod_B1.patch
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On Tue, Feb 03, 2004 at 06:23:10PM +0000, Jamie Lokier wrote:
> Andrea Arcangeli wrote:
> > vsyscalls will never execute anything like execve. They can at most
> > modify userspace memory a fixed address, so if the userspace isn't
> > fixed, then nothing can be done with a vsyscall.
> 
> Are we talking about the same x86_64?

I did, I don't think it worth to backport to i386 btw.

> 
> I see this in arch/x86_64/vsyscall.S:
> 
> __kernel_vsyscall:
> .LSTART_vsyscall:
> 	push	%ebp
> .Lpush_ebp:
> 	movl	%ecx, %ebp
> 	syscall
> 
> Is that page not mapped into userspace?

this code wasn't there last time I worked on it, it's not in 2.4 either.
I assume it's mapped in userspace, but I'm unsure why it's necessary. I
need to think more about it to understand why such code is there and how
can it be removed. I was taking about the .c file not this new .S one.