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Re: [PATCH] x86: correct UDn
On Wed, Nov 22, 2017 at 12:02 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 21.11.17 at 23:12, <hjl.tools@gmail.com> wrote:
>> On Mon, Nov 20, 2017 at 5:38 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>> --- a/opcodes/i386-opc.tbl
>>> +++ b/opcodes/i386-opc.tbl
>>> @@ -862,9 +862,12 @@ ud2, 0, 0xf0b, None, 2, Cpu186, No_bSuf|
>>> // alias for ud2
>>> ud2a, 0, 0xf0b, None, 2, Cpu186, No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
>>> // 2nd. official undefined instr.
>>> -ud1, 0, 0xfb9, None, 2, Cpu186, No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
>>> +ud1, 2, 0xfb9, None, 2, Cpu186, Modrm|No_bSuf|No_sSuf|No_ldSuf, { Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex|Disp8|Disp16|Disp32|Disp32S, Reg16|Reg32|Reg64 }
>>> // alias for ud1
>>> -ud2b, 0, 0xfb9, None, 2, Cpu186, No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
>>> +ud2b, 2, 0xfb9, None, 2, Cpu186, Modrm|No_bSuf|No_sSuf|No_ldSuf, { Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex|Disp8|Disp16|Disp32|Disp32S, Reg16|Reg32|Reg64 }
>>> +// 3rd official undefined instr
>>> +ud0, 0, 0xfff, None, 2, Cpu186,
>> No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
>>
>> Do we really need this? It will confuse disassembler.
>
> Well, it's officially documented by both Intel and AMD now. And I
> don't see why it would confuse the disassembler - neither does
> that one use the table here, nor is there anything in it (afaik)
> which would special case opcode 0f ff; are you perhaps mixing
> this up with opcode ff ff?
Disassembler expects the MODRM byte with 0xffff. Assembler may
accept "ud0" without operand. But it won't be what will be in the output
from disassembler.
>>> +ud0, 2, 0xfff, None, 2, CpuSSE4_2, Modrm|No_bSuf|No_sSuf|No_ldSuf, {
>> Reg16|Reg32|Reg64|Word|Dword|Qword|Unspecified|BaseIndex|Disp8|Disp16|Disp32|
>> Disp32S, Reg16|Reg32|Reg64 }
>>
>> Where does CpuSSE4_2 come from?
>
> It's the best I could come up with matching XED specifying this as
> the variant used from Nehalem onwards.
>
Can you try it on older machines?
--
H.J.