Re: [arm-gnu] not a gnu question per se, but related (linker script help)

[42Bastian <list-bastian.schick@xxxxxxxxxxx>]

Am 30.04.2010 05:16, schrieb Andrew Kohlsmith (mailing lists account):
> Good evening,

:-) Depends, morning here in Germany.

> In order to isolate bootloader changes from affecting the application's ability 
> to use bootloader functions, I'm thinking of creating a jump table much the 
> same as the ARM's exception table. The idea is certainly not new; I know from 
> my ancient history that the Commodore 64 used the same idea to provide a fixed 
> set of addresses for functions.
> 
> Is there a slick way of creating this jump table using the linker? Do I just 
> create a section in my boot.s file, populate it with branch instructions to the 
> functions, and then use PROVIDE() statements in the linker? Is there a better 
> way? This is all thumb code, and I know that branches in thumb are limited to 
> 2kB, so maybe I should be using an ARM jump table instead since the bootloader 
> functions can occupy anything in the first 4k of Flash? Should I be looking at 
> this differently?

I would do the following:
1) Place all shared functions at the end of the bootloader section
2) Create a table of addresses at a well know place. (Either linker, or a
small assembly file).
3) In you application, let a function-pointer array point to this place.
4) Call the functions via function pointers.

-- 
42Bastian
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