HELP with linker script!!!

[Vincent Rubiolo]

Hello Nick,

Thanks for this informative reply. There is something I am wondering 
about using the gcc attributes to put variables or functions : how to 
control the section flags of these new sections?

I know I can use objcopy with the --set-section-flags to tweak section 
flags to my liking. I was wondering how gcc was settings these flags : 
for your '.cached_bss' section, it may have the NOBITS flag set but does 
gcc know that, for instance, the NOBITS flag will have to be set?

As for Pieter problem, the crt0.c will surely rely on special symbols 
like __heap_start or __stack_start (set by the linker script) to detect 
and set the start of heap and stack.
You are also encouraged to use the MEMORY keyword that Nick mentioned : 
it make things clearer. However, it may not suit you if you have 
sections that have dynamic addresses/sizes i.e computed from say, the 
previous section' size (you will then have to rely on the computation 
capabilities of the ld script).

Regards,

Vincent

Nick Clifton wrote:
[...]
> your application then it is easy.  Simply use the:
> 
>   __attribute__((section(".cached_bss")))
> 
> feature of GCC to annotate all of those variables which you want to be 
> placed into the cacheable RAM, and then make sure that your linker 
> script assigns the .cached_bss to the cacheable RAM memory region. Easy! 
> :-)
> 
>   MEMORY
>   {
>      cachableRAM : org = 0x100, len = 0x200
>      uncacheRAM:   org = 0x3000, len = 0x40000
>   }
> 
>   SECTIONS
>   {
>      [...other sections...]
> 
>      .cached_bss : { *(.cached_bss) } > cachableRAM;
>      .bss : { *(.bss) } > uncacheRAM;
> 
>      [...other sections...]
>   }
> 
> Cheers
>   Nick

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