[patch 5/8] Doc for agent

[Yao Qi]

On 02/11/2012 12:28 AM, Pedro Alves wrote:
>> > The reasons for this kind of design are,
>> > 
>> >   #1.  agent, inferior and debugger (GDB or GDBserver) are running
>> > on the same machine, so protocol doesn't to have to handle machine
>> > difference, such as endianess, word size, etc.  Binary copy should
>> > work fine.
> Nope, that's not true at all.  Several architectures can run in
> different modes (x86 32-bit/64-bit; arm/thumbx big/little/mixed; mips; ppc, etc.).
> Several architectures have more than one ABI.  We can have e.g., a 64-bit
> gdbserver controlling a 32-bit process on x86.  You can have a gdbserver controlling
> an inferior that's running a different endianness on some machines.
> 

I agree that the process of GDB/GDBserver and process of inferior have
differences on ABI, word-size, except endianess.  I can't find an
example that two processes on the same machine have different endianess.
 I google'ed a while, and find some processors such as ARM, PowerPC, and
Itanium have such capability to change endian mode on runtime, but seems
not widely used.  Do we need to consider this case here?

> The current IPA has the limitation that fast tracepoints only work if the
> inferior has the same arch/abi as gdbserver.  If we're adding a new IPC,
> and an IPA v2, let's not repeat the mistake.
> 

Pedro, thanks for your input.  I'll post the agent protocol draft later.

-- 
Yao (齐尧)