Re: frysk-core/frysk proc/BankRegister.java proc/C ...

[Andrew Cagney <cagney@redhat.com>]

Phil Muldoon wrote:
> Andrew Cagney wrote:
>> Phil Muldoon wrote:
>>> Andrew,
>>>
>>> I know this work is ongoing, so should I sit tight regarding the 
>>> FIXME notifications? I'm not sure how to fix the gpr registers 
>>> access. If it is work ongoing, I'll just wait until you give the 
>>> signal with an explanation regarding how a Task accesses it's own 
>>> registers.
>>>
>> The function to look at is Task.accessRegister(Register register,int 
>> offset, int length, byte[] buffer, int start, boolean write) which 
>> will does a direct/raw byte copy of the data into a buffer.
>>
>> However, yes, perhaps hold off a little until I've got all the 
>> register code in frysk.proc resolved.
>> Andrew
>>
>
> Ok will do, will wait and see. As a rhetorical question, what is wrong 
> with task.getSomeRegisterFunctionName("eax") as a general helper function?

The only place where a String->Register lookup (e.g., "eax" -> 
frysk.isa.IA32Registers.EAX) is needed is in the expression evaluator 
where it interprets << $eax >>.  Every where else constant object, such 
as frysk.isa.IA32Registers.EAX can be used: these objects are efficient 
(better with HashMap) and second having defined constants prevents typos 
such as a register being called "foo" in one place and "fos" in a second.

> Why do I need to know (ptrace buffer?) offset and length to access a 
> register? Is this because register access is being move to the task 
> from the ISA? Just trying to get a sense of where this refactor is going.
>

I'm not sure what you mean, the offset/length are for within the 
specified register, and start is an offset into the byte buffer.  Two 
things change: tThe code that implements register accesses isn't being 
moved to the task; but the way to access registers is now simpler, contrast:
    Task.getRegister(IA32Register.XIP)
with:
    Task.getIsa().getBankRegister("xip").getRegister(task)
the internals, though cleaned up will still be very similar.

Andrew


> Regards
>
> Phil
>