Need help in figuring out the flow of RTEMS codes

[Gedare Bloom]

On Fri, May 29, 2020 at 1:59 AM Richi Dubey <richidubey at gmail.com> wrote:
>
> This makes sense. Thanks a lot!
>
>
> On Fri, May 29, 2020 at 1:18 PM Sebastian Huber
> <sebastian.huber at embedded-brains.de> wrote:
> >
> > Hello Richi,
> >
> > On 29/05/2020 09:36, Richi Dubey wrote:
> > > Hii,
> > >
> > > I had a small doubt about all the source code/procedures that a code
> > > goes through. Where can I read more about it? For instance, when I am
> > > debugging smpschededf02.exe with gdb, It starts  with
> > > bsps/sparc/shared/start/start.S, line 107(Why did it start with
> > > start.s?) and the last line of this file is:
> > >
> > >   mov     %g0, %o0                ! command line
> > >          call    SYM(boot_card)          ! does not return
> > >           sub     %sp, 0x60, %sp         ! room for boot_card to save args
> > >
> > > After this it starts executing bsps/shared/start/bootcard.c: line 53 .
> > > How did this happen? Is it because of call? If yes, why was sub
> > > executed(in gdb) before executing code from bootcard.c?
> > >
> > > I hope I am not trying to going too deep into this. I just want to
> > > have a overall picture of how a code gets executed.
> >
> > if you want to learn how code executes at processor level, then I would
> > recommend to work with an ARM (Qemu) or RISC-V (SIS, Qemu) simulator.
> > These are the currently most relevant architectures. SPARC is a dead
> > architecture and it has some peculiarities which were a nice idea in the
> > 1980s.
> >
> > > This is necessary
> > > for writing your own code in RTEMS, right?
> > It helps, but it is not necessary.
+1

This is quirky assembly stuff. Your project should not require writing
assembly, but it is helpful if you can start to learn how to read it
for debugging.

If you know a different assembly language, you might try to set up an
environment with that target and use it for low-level debugging
purposes. Mostly though, gdb should take care of translating the
executing lines to source linkage, so you would only face trouble when
debugging assembly source like this. As Sebastian mentioned, if you
don't know an assembly language, your time is better spent to learn a
modern widely used one.

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