Re: [RFC][PATCH] linux-2.6.2-rc2_vsyscall-gtod_B1.patch

[Jamie Lokier <jamie _at_ xxxxxxxxxxxxx>]

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 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?

If the answer is no, then btw we were talking about i386 until you joined in. :)
The "sysenter" instruction is definitely mapped into userspace there.

-- Jamie

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