What does gdb stub need for thread aware debugging on embedded system?

What does gdb stub need for thread aware debugging on embedded system?

[John Carter]

I'm looking to get thread aware debugging running on our "sparc-alike"
Leon II processor.

Unlike the usual sparc stub, I cannot get thread information from
Solaris as we're not running solaris on this device.

If I understand things correctly, getting gdb working should just be a
matter of tying gdb/sparc-stub.c to our serial ports by defining
   extern void putDebugChar();	/* write a single character      */
   extern int getDebugChar();	/* read and return a single char */

Grepping through that code the word "thread" doesn't occur.

What I'm missing is how does gdb get information about threads from
the devices OS to gdb running on the desktop.

Any pointers to the right bit of documentation / code would be most
welcome.




John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter@tait.co.nz
New Zealand

Re: What does gdb stub need for thread aware debugging on embedded system?

[Michael Snyder]

On Mon, 2008-06-16 at 12:09 +1200, John Carter wrote:
> I'm looking to get thread aware debugging running on our "sparc-alike"
> Leon II processor.
> 
> Unlike the usual sparc stub, I cannot get thread information from
> Solaris as we're not running solaris on this device.
> 
> If I understand things correctly, getting gdb working should just be a
> matter of tying gdb/sparc-stub.c to our serial ports by defining
>    extern void putDebugChar();	/* write a single character      */
>    extern int getDebugChar();	/* read and return a single char */
> 
> Grepping through that code the word "thread" doesn't occur.
> 
> What I'm missing is how does gdb get information about threads from
> the devices OS to gdb running on the desktop.
> 
> Any pointers to the right bit of documentation / code would be most
> welcome.

At the time that that code was written, threads were very far from 
the minds of people who wrote remote gdb stubs!

Look at gdbserver -- it has support for threads.

Re: What does gdb stub need for thread aware debugging on embedded system?

[Daniel Jacobowitz]

On Sun, Jun 15, 2008 at 05:19:59PM -0700, Michael Snyder wrote:
> At the time that that code was written, threads were very far from 
> the minds of people who wrote remote gdb stubs!

Yeah.  While sparc-stub.c is a valid example, keep in mind that it is
a very old one.  There's been a tremendous amount of change in the
remote protocol since then, including in the threads area (see
e.g. the description of vCont in the remote protocol documentation,
which is in the GDB manual).

-- 
Daniel Jacobowitz
CodeSourcery