Re: x86_64: Fix double fault stack setup

[Andrew Cooper <andrew.cooper3@citrix.com>]

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On 24/05/12 19:04, Keir Fraser wrote:
> On 24/05/2012 16:28, "Andrew Cooper" <andrew.cooper3@citrix.com> wrote:
>
>> Ah yes - how silly of me.  I misread the manual when checking that fact,
>> but this was an INT 08 experiment.  I really should have checked with a
>> ud2 as well.
>>
>> That is a bit awkward.
>>
>> Do we actually care about this error from an INT 08?  I suppose we could
>> check under rip for 0xcd 0x08, but then the same argument would apply to
>> all other exceptions which may push an error onto the stack.
>>
>> Do we care however that entry_vector is not being set correctly?  I cant
>> see anything on the current codepath which uses it, but it doesn't
>> preclude someone adding code in the future.
> It would be a simple one-line patch and make that entry point consistent
> with all other exception-handling entry points. So I'm in favour of it.
>
>  -- Keir

Ok - attached.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com


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# HG changeset patch
# Parent 69c3ae25bb1ddcb0ea44b7566d36d34e9d6a70aa
x86_64: Record entry vector for double faults.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff -r 69c3ae25bb1d xen/arch/x86/x86_64/entry.S
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -595,6 +595,7 @@ ENTRY(spurious_interrupt_bug)
         jmp   handle_exception
 
 ENTRY(double_fault)
+        movl $TRAP_double_fault,4(%rsp)
         SAVE_ALL
         movq  %rsp,%rdi
         call  do_double_fault

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