[Xen-devel] Re: [RFC, PATCH 7/24] i386 Vmi memory hole

[Chris Wright <chrisw@xxxxxxxxxxxx>]

* Zachary Amsden (zach@xxxxxxxxxx) wrote:
> >+       DEFINE(VSYSCALL_BASE, (PAGE_OFFSET - 2*PAGE_SIZE));
> 
> Ok, I'm confused.  What fixed math?

Sorry, bad choice of words.  From above, the VYSYCALL_BASE is known
at compile time (in asm-offsets.h).  So the SYSENTER_RETURN is still
fixed addr.  For execshield it's truly dynamic, so you get something
like this instead of the constant SYSENTER_RETURN:

-       pushl $SYSENTER_RETURN
+       pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)

thanks,
-chris

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