Re: [Qemu-devel] log every write to register

[Sergey Smolov <smolov@ispras.ru>]

03.11.2015 20:29, Peter Crosthwaite пишет:
> On Tue, Nov 3, 2015 at 8:14 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
>> On 3 November 2015 at 13:17, Sergey Smolov <smolov@ispras.ru> wrote:
>>> I have a collection of ARMv8 register names. I need to add special logging
>>> mode to QEMU so that every time it is enabled, every write access to any of
>>> the specified registers will produce a new record to log, including register
>>> name and a value to be written.
>>>
>>> Is it possible to accomplish such a task? If yes, where shall I find
>>> functions that implement "writing to register" functionality?
>> This is difficult, because we don't have a single convenient
>> location which all register accesses go through. (General purpose
>> registers and some system registers will be optimised so that
>> accesses are made directly from JIT generated code.)
>>
> You may be able to hack the TCG generation functions to call out to
> helper context (which implements your log) on each op that updates
> your specific regs. It will kill performance though if those registers
> are hot.

Thank you for your answer!
Could you explain the idea in a more detailed way?
Which TCG generation functions should i hack for write-to-specific-regs 
logging?

Thanks in advance,
Sergey Smolov