[edk2-devel] Does anyone know the definition of EFI_SYSTEM_CONTEXT_X64.Gdtr[2] and EFI_SYSTEM_CONTEXT_X64.Idtr[2]

[Andrew Fish via groups.io]

> On Jun 3, 2020, at 5:37 PM, Michael D Kinney <michael.d.kinney at intel.com> wrote:
> 
> Hi Andrew,
> 
> Are you referring to the order the fields are filled in by the C code
> before the x86 instruction is executed?  I do not think that matters.
> 

Mike,

The instructions point to a blob of data that is not UINTN aligned. These register point to a limit then base address. If you execute the instruction you get 2 bytes of limit and 4 or 8 bytes of data. But Idtr[0] is base and Intro[1] is limit, so reversed from the instruction order. What defines index 0 vs. index 1 data contents?

Thanks,

Andrew Fish

> Thanks,
> 
> Mike
> 
>> -----Original Message-----
>> From: devel at edk2.groups.io <devel at edk2.groups.io> On
>> Behalf Of Andrew Fish via groups.io
>> Sent: Wednesday, June 3, 2020 4:39 PM
>> To: edk2-devel-groups-io <devel at edk2.groups.io>
>> Subject: [edk2-devel] Does anyone know the definition of
>> EFI_SYSTEM_CONTEXT_X64.Gdtr[2] and
>> EFI_SYSTEM_CONTEXT_X64.Idtr[2]
>> 
>> The x86 instructions do limit then base, but the code is
>> storing base, then limit. Does anyone remember if this
>> is properly defined some place?
>> 
>> Thanks,
>> 
>> Andrew Fish
>> 
> 
> 
> 
> 


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