Dormant Linker Subsection

Chia-Ning Wang said:

 I was wondering if it's possible to declare custom linker sections and turn them on/off as needed.

Yes.  Here is how I would do it.  

First, compile with the option --gen_func_subsections.  This causes every function to be placed in input sections with names like .text:name_of_function.  Consult your compiler manual for the precise details.  In your linker command file, you can make use of the preprocessing feature to do something like ...

SECTIONS
{
    #ifdef SPECIAL_LINK
    special_section 
    {
        .text:one_function
        .text_two_function
        /* and so on */
    } > SPECIAL_MEMORY_RANGE
    #endif

    .text > RAM
    /* other sections here */
}

If the preprocessor symbol SPECIAL_LINK is defined, then those functions are collected into the output section special_section and allocated to the SPECIAL_MEMORY_RANGE.  If SPECIAL_LINK is not defined, those those functions become part of the .text output section, and are allocated to RAM.

Thanks and regards,

-George