Re: Protected Objects and Interrupt Handlers

[Simon Wright <simon@pushface.org>]

Simon Wright <simon@pushface.org> writes:

> Tero Koskinen <tero.koskinen@iki.fi> writes:
>
>> For example in the normal case, you can have all the startup code in C
>> (or in Ada, which is then exported to C)
>
> Actually, very little even needs exporting to C! I had one that I've
> given convention Asm (it's invoked by the linker script), but I'm not at
> all sure it needs it.
>
> Mind you,
>
>    procedure Program_Initialization
>    with
>      Export,
>      Convention => Asm,
>      External_Name => "program_initialization",
>      No_Return;
>    pragma Machine_Attribute (Program_Initialization, "naked");
>
>    procedure Program_Initialization is
>    begin
>       --  _estack: the first address after the top of stack space
>       System.Machine_Code.Asm ("ldr sp, =_estack", Volatile => True);
>       Complete_Program_Initialization;
>    end Program_Initialization;
>
> probably isn't going to cause much trouble anyway.

The thinking behind that little bit of asm was that the SAM3X8E has a
bootstrap loader in (a separate section of) FLASH, and a reset mode that
uses it, and you can mistakenly leave the MCU in bootstrap mode, and thi
should recover it .. but I'm now pretty sure it desn't.

Corrent work, on STM32F429I, manages an Ada startup with two assembler
instructions (dsb, isb to flush the caches after enabling the FPU).