* The entry of Xen's exception handler
@ 2012-10-02 20:51 Xinxin Jin
2012-10-02 21:23 ` Andrew Cooper
2012-10-02 21:30 ` Keir Fraser
0 siblings, 2 replies; 3+ messages in thread
From: Xinxin Jin @ 2012-10-02 20:51 UTC (permalink / raw)
To: Xen-devel
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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?
Thanks,
--
Xinxin
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: The entry of Xen's exception handler
2012-10-02 20:51 The entry of Xen's exception handler Xinxin Jin
@ 2012-10-02 21:23 ` Andrew Cooper
2012-10-02 21:30 ` Keir Fraser
1 sibling, 0 replies; 3+ messages in thread
From: Andrew Cooper @ 2012-10-02 21:23 UTC (permalink / raw)
To: xen-devel
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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: The entry of Xen's exception handler
2012-10-02 20:51 The entry of Xen's exception handler Xinxin Jin
2012-10-02 21:23 ` Andrew Cooper
@ 2012-10-02 21:30 ` Keir Fraser
1 sibling, 0 replies; 3+ messages in thread
From: Keir Fraser @ 2012-10-02 21:30 UTC (permalink / raw)
To: Xinxin Jin, Xen-devel
On 02/10/2012 21:51, "Xinxin Jin" <xinxinjin89@gmail.com> 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?
Otherwise handle_exception would not know which type of exception it was
handling, would it.
-- Keir
> Thanks,
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-10-02 21:23 ` Andrew Cooper
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