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

[Mikhail Tyutin]

> On 2/15/23 19:04, Mikhail Tyutin wrote:
> >> On 2/15/23 18:17, Mikhail Tyutin wrote:
> >>> ping
> >>>
> >>> patchew link:
> >>> 7d17f0cbb5ed4c90bbadd3992429006f@yadro.com/">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~

Linux-world prefers AT&T style, Windows-world prefers Intel style for x86_64 
ISA. That causes
a lot of pain for developers and tools that have to compare and parse assembler 
texts. If you have
to work on different hosts, you would better use one style for both.