[PATCH] x86: Warn .insn instruction with length > 15 bytes

[Jan Beulich]

On 06.02.2024 12:36, H.J. Lu wrote:
> On Tue, Feb 6, 2024 at 12:19 AM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> On 05.02.2024 21:00, H.J. Lu wrote:
>>> Change .insn instruction with length > 15 bytes from error to warning.
>>
>> Thanks for doing this. FTAOD though - it addresses only half of my
>> concern. Besides .insn (where the concern was of general nature) I
>> also use
>>
>>         bextr   eax, fs:[eax*4], 0x11223344
>>         xacquire lock add qword ptr gs:[eax*8], 0x11223344
>>
>> in testing of my own disassembler library. I expect to continue to
>> be able to avoid using .insn (and even more so .byte) when assembling
>> this code. IOW there will still need to be a way to also override
>> the defaulting to as_bad() when not using .insn.
> 
> We issue a warning when something is wrong in input, but still manage
> to generate an instruction.   This is an error case.

I disagree. It was a warning until you changed it (without me really
agreeing), and some hypothetical vendor could come and lift the limit,
on precisely the basis that there are legal encodings exceeding it. I'm
okay if this can be forced to be an error, but I continue to think that
it ought to be a warning only by default.

Jan