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