Reference bsp_section_data_start from C yields "R_PPC_EMB_SDA21 relocation is in the wrong output section"

[Till Straumann]

I did that, too, but you have to know what you are doing.

This trick *only* works if you know that your symbol is
in the 'data' area and you want to avoid the compiler to
assume it to be in the short data area.

E.g., if you know our symbol is .text then you would declare
it as a function, of course.

Using a section __attribute__ is IMO preferable.

-- Till

On 05/16/2010 08:07 PM, Eric Norum wrote:
> I use the following trick to get at loader symbols (see the uC5282 BSP for examples).
>
> extern char RamSize[];
>
> Then to get the value:
> 	s = (uint32_t)RamSize;
>
> On 05/16/2010 05:41 AM, Peter Dufault wrote:
>    
>> This is in the MPC55XXEVB in the head, but it's a general question.
>>
>> I need to reference bsp_section_start from a routine that duplicates a program that's been running in RAM into the FLASH once it's been debugged.
>> I have this expression:
>>
>> extern void *bsp_section_text_end,
>>      *bsp_section_data_start,
>>      *bsp_section_data_end;
>>
>> ...
>>
>>      te = (uint32_t)&bsp_section_text_end;
>>      ds = (uint32_t)0x40000180; /* XXX Should be&bsp_section_data_start; but linker error */
>>      de = (uint32_t)&bsp_section_data_end;
>>      end = (te + ((de - ds) + 16))&~0x7;
>>
>> However, if I reference bsp_section_data_start in that instead of the hard-wired number I get this link error:
>>
>> /opt/rtems-4.10/lib/gcc/powerpc-rtems4.10/4.4.4/../../../../powerpc-rtems4.10/bin/ld: /home/dufault/work/scratch/peter_6600_dev/powerpcphycore_mpc5554rtems4.10/lib/libmpc55xx_misc.a(flash.o): the target (bsp_section_data_start) of a R_PPC_EMB_SDA21 relocation is in the wrong output section (.data)
>> /opt/rtems-4.10/lib/gcc/powerpc-rtems4.10/4.4.4/../../../../powerpc-rtems4.10/bin/ld: final link failed: Bad value
>> collect2: ld returned 1 exit status
>> make: *** [o-optimize/motobank.exe] Error 1
>>
>> Does anyone know how to fix this?  I've done some searches and don't know enough about the issues to solve it quickly.
>>
>>  From the name list:
>>
>> 40000180 D bsp_section_data_start
>> 40004ba0 G bsp_section_data_end
>> 000f5160 G bsp_section_text_end
>>
>> Peter
>> -----------------
>> Peter Dufault
>> HD Associates, Inc.      Software and System Engineering
>>
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>>
>>
>>      
>