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. Best, -Min > >> >> Thank you >> -Min > > > -- > Alex Bennée
