[PATCH v3 10/10] x86-64: Intel64 adjustments for insns dealing with far pointers

[Jan Beulich]

On 20.01.2020 14:42, H.J. Lu wrote:
> On Mon, Jan 20, 2020 at 2:12 AM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> On 17.01.2020 19:06, H.J. Lu wrote:
>>> On Fri, Jan 17, 2020 at 3:48 AM Jan Beulich <jbeulich@suse.com> wrote:
>>>>
>>>> On 16.01.2020 21:24,  H.J. Lu  wrote:
>>>>> We should improve gas documentation.  The current far branches
>>>>> work fine.  Why bother to add new far branches without giving
>>>>> developer a clue how to use them?
>>>>
>>>> That's the subject of CPU documentation, not that of any assembler.
>>>> The current far branches "work fine" as far as they're being made
>>>> accessible (encodable) by gas. The 64-bit forms Intel CPUs support
>>>> didn't work fine at all (because one had to use hand crafted REX.W
>>>> prefixes), as per Andrew's bug report. There's no difference here
>>>> to the prior work you did to support the Intel64 / AMD64
>>>> differences for certain other insns - you've simply made gas
>>>> capable of properly encoding them in a vendor dependent manner.
>>>> You didn't accompany this with any documentation explaining "how
>>>> to use" these. If, retroactively, you think this should have been
>>>> accompanied by such documentation, may I ask that you add such,
>>>
>>> Yes, it is not very obvious how to use them, we should add some
>>> documentation.   Which one do you have in mind?
>>
>> All which currently have the Intel64 or AMD64 attribute. If all
>> present ones had extra documentation, then (as said) it would be
>> more obvious that _and_ what documentation needs/wants adding
>> for ones covered anew.
> 
> Let's start with one first.  Please name one.

CALL r/m (and then naturally also JMP r/m).

(There aren't this many yet, the other ones being CALL disp,
JMP disp, SYSENTER, and SYSEXIT.)

Jan