Interface GDB with custom OS

[Christophe PLANAT <christophe dot planat at st dot com>]

Hi everybody,

I'm using GDB and searching how to interface GDB with a custom EMBEDDED
OS in a USER APPLICATION.

Question :
----------

Does the GDB thread control is dedicated to address MULTI-THREAD TARGETS

(such as multi-thread ISS) on which one may download any user program
(not threaded) - fig 1 ?

                OR

Does the GDB thread control is dedicated to address MULTI-THREAD
PROGRAMS downloaded in any ISS (not threaded) - fig 2 ?

fig 1 :
            |--|
|------|    |  |      |--------------------|
| GDB  |  thread API  | MULTI-THREADED ISS |<---- download (thru GDB)
|------|    |  |      | | th1 | th2 | ...  |      some not threaded user

            |--|      |--------------------|      pgm


fig 2 :
            |--|
|------|    |  |      |-----------------|
| GDB  |  thread API  |  Some  ISS      |<---- download (thru GDB)
|------|    |  |      |  (not threaded) |      MULTI-THREADED user pgm
            |--|      |-----------------|



Context for instance:
---------------------

A multi-threaded program uses an embedded kernel (say myos). The
processor is represented by a simulator (not threaded) targeted in GDB.

I analysed GDB 5.0 files concerning the thread control (thread.c,
gdbthread.h. and hpux-thread.c, nachos-thread.c  examples) but I don't
see how does the debugger (which controls the simulator) interfaces with

the OS kernel which is at the application level -- running on the
simulator (fig 2) ?

What I understand (is it true ?) :

GDB core uses internally a thread controller (thread.c). The user writes

an OS dependant file [for instance myos-thread.c] and primitivers
pointed by GDB core through the init_myos_thread_ops structure. Each
primitive may use OS dependant primitives listed in gdbthread.h.

But in this scheme, how does GDB interface with the embedded myos kernel

(fig 2) which is linked to the application program ? GDB (and ISS) are
not at the same level that myos kernel ?

Thanks a lot if you can help me on this very important subject.

Christophe Planat

--
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| Christophe PLANAT                 | Embedded Systems Technology    |
| Email : Christophe.Planat@st.com  | STMicroelectronics             |
| Phone : +33 04 76 92 68 82        | 850, rue Jean-Monnet           |
| Fax   : +33 04 76 92 50 94        | BP 16 - 38921 Crolles - France |
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