Re: [Qemu-devel] [RFC] Disassembler options going forward

[Peter Maydell]

On 14 February 2013 21:10, Richard Henderson <address@hidden> wrote:
> The only options I can see going forward are
>
>  1) Provide a configure time option to link to the "system" libopcodes.
>  2) Use someone else's (bsd licensed?) disassember.
>  3) Rearrange relevant translators so that they can disassemble and
>     not translate.
>
> The complete solution could be a combination of all three.

4) Since we only do disassembly for debug logging, have our debug
logging just log hex, with postprocessing by a script that runs
objdump or something

> To me, option (1) means that qemu the project is not "infecting" the
> binary with GPLv3, but requiring the user to make that choice.  Which
> seems fine; those that have moral objections to v3 can simply not use
> that configure option.  It's a bit awkward that most distributions don't
> package up libopcodes for install, but if you manually build binutils
> you'll have it done.

I'm not hugely convinced by the idea of "here's a configure switch
to produce binaries you can't legally distribute".

> I hope we'll all agree that option (3) is not ideal, since having a
> separate disassembler works as a check against the translator.  However,
> for odd parts that will never be a host it's not a totally unreasonable
> solution, as it at least provides *some* disassembly.
>
> As for option (2), I'm not even sure what to suggest.  I suppose there's
> some part of LLVM that does textual disassembly.  Whether we want to
> drag that in as a submodule or just require it to be installed and
> notice it at configure time, I have no opinion.  But because of the odd
> parts, (2) can't be the only option.

I had a look at the LLVM disassembler the other day. From a quick
glance it seems like LLVM drives the disassembler off a generalised
machine description language (which it also uses for various other
things), so getting the disassemblers would also require us to
pull in quite a bit of LLVM infrastructure for parsing the machine
descriptions. It didn't look particularly easy, but this is just
from 15 minutes browsing a source tree, so if anybody more LLVM
aware here has an opinion do say.

> But most of all I think we should have a plan.

Agreed.

-- PMM