Re: [PATCH] Adding ability to change disassembler syntax in TCG plugins

[Richard Henderson <richard.henderson@linaro.org>]

On 2/15/23 19:04, Mikhail Tyutin wrote:
>> On 2/15/23 18:17, Mikhail Tyutin wrote:
>>> ping
>>>
>>> patchew link:
>>> https://patchew.org/QEMU/7d17f0cbb5ed4c90bbadd3992429006f@yadro.com/
>>>
>>> 10.02.2023 18:24, Mikhail Tyutin wrote:
>>>> This patch adds new function qemu_plugin_insn_disas_with_syntax() that allows TCG
>>>> plugins to get disassembler string with non-default syntax if it wants to.
>>>>
>>>> Signed-off-by: Mikhail Tyutin <m.tyutin@yadro.com>
>>
>> Why?
>>
>> It's certainly not very generic, exposing a disassembly quirk for exactly one guest
>> architecture.  I mean, you could just as easily link your plugin directly to libcapstone
>> via qemu_plugin_insn_data().
>>
>>
>> r~
>   
> I agree it can be done outside of Qemu using another disassembler library. However,
> there are few reasons to do it in Qemu from architecture standpoint:
> 
> 1. To have a single place of instruction decoding logic. TCG has to decode guest instructions
> anyway. If plugins add another decoder, it causes double work and prone to errors (however
> current implementation does double decode work anyway). For example, TCG might support
> new instruction which is not available in external decoder yet.
> 
> 2. Under the hood Qemu uses different implementations of decoder (in addition to capstone)
> which is not exposed in public interface. If there is a need to configure its output, proposed
> API allows that as well.
> 
> 3. If multiple plugins want to use another disassembler syntax, they have to share
> implementation as utility function.

What's all this got to do with preferring intel over at&t syntax?
I still think it's a generally useless switch.


r~