On Apr 26 18:42, Alex Bennée wrote: > > Min-Yih Hsu <miny...@uci.edu> writes: > > > Hi Alex, > > > >> On Apr 23, 2021, at 8:44 AM, Alex Bennée <alex.ben...@linaro.org> wrote: > >> > >> > >> Min-Yih Hsu <miny...@uci.edu> writes: > >> > >>> Hi Alex and QEMU developers, > >>> > >>> Recently I was working with the TCG plugin. I found that > >>> `qemu_plugin_cb_flags` seems to reserve the functionality to > >>> read / write CPU register state, I'm wondering if you can share some > >>> roadmap or thoughts on this feature? > >> > >> I think reading the CPU register state is certainly on the roadmap, > >> writing registers presents a more philosophical question of if it opens > >> the way to people attempting a GPL bypass via plugins. However reading > >> registers would certainly be a worthwhile addition to the API. > > > > Interesting…I’ve never thought about this problem before. > > > >> > >>> Personally I see reading the CPU register state as (kind of) low-hanging > >>> fruit. The most straightforward way to implement > >>> it will be adding another function that can be called by insn_exec > >>> callbacks to read (v)CPU register values. What do you > >>> think about this? > >> > >> It depends on your definition of low hanging fruit ;-) > >> > >> Yes the implementation would be a simple helper which could be called > >> from a callback - I don't think we need to limit it to just insn_exec. I > >> think the challenge is proving a non-ugly API that works cleanly across > >> all the architectures. I'm not keen on exposing arbitrary gdb register > >> IDs to the plugins. > >> > >> There has been some discussion previously on the list which is probably > >> worth reviewing: > >> > >> Date: Mon, 7 Dec 2020 16:03:24 -0500 > >> From: Aaron Lindsay <aa...@os.amperecomputing.com> > >> Subject: Plugin Register Accesses > >> Message-ID: <X86YnHhHMpQBr2/G@strawberry.localdomain> > >> > >> But in short I think we need a new subsystem in QEMU where frontends can > >> register registers (sic) and then provide a common API for various > >> users. This common subsystem would then be the source of data for: > >> > >> - plugins > >> - gdbstub > >> - monitor (info registers) > >> - -d LOG_CPU logging > >> > >> If you are interested in tackling such a project I'm certainly happy to > >> provide pointers and review. > > > > Thank you! Yeah I’m definitely going to scratch a prototype for this > > register reading plugin interface. I’ll take a look at related email > > discussions. > > Awesome - please CC me on any patches you come up with (as well as > qemu-devel of course ;-).
I would love to be copied on any patches as well. I've wanted to look into doing this properly for some time now, but have not made time. -Aaron
