From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: The entry of Xen's exception handler
Date: Tue, 2 Oct 2012 22:23:05 +0100
Message-ID: <506B5B39.4010205@citrix.com>
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On 02/10/2012 21:51, Xinxin Jin wrote:
> Hi, I am trying to understand the exception handler of Xen. In
> xen/arch/x86/x86_64/entry.S, the entry of the page fault handler is :
>
> ENTRY(page_fault)
>         movl  $TRAP_page_fault,4(%rsp)
>         jmp   handle_exception
>
> Here I did not get why to put the exception vector ($TRAP_page_fault)
> to stack before calling handle_exception?

This is so every single exception fills in its cpu_user_regs with the
correct trap, so the C code an distinguish if its needs to.  (See
current.h for the structures which get filled in)

~Andrew

>
> Thanks,
>
> -- 
> Xinxin
>