Need help in figuring out the flow of RTEMS codes

[Sebastian Huber]

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.