Compiler: TI arm linker ALIAS keyword and section's address

Regarding the ALIAS problem ... Please show an example.  Be sure to include the exact text of the error message.

Guy Mardiks said:

i can not give as a section's binding address an expression like (0x1000 + 5) even though it is a constant and i can only enter actual numbers. why is that? 

It is a limitation on the parsing capability of the linker.  In some contexts, like a value assigned to symbol, expressions are allowed.  In other contexts, only well defined constants are allowed.

Thanks and regards,

-George

ALIAS example and errors:

MEMORY

{

ALIAS

{

         MEM1 (RWIX): org = (0)

         MEM3 (RWIX): org = (0x55020000)

   } len = (0x4000)

}

SECTIONS

{

   GROUP (GROUP1)

   {

    .sec_group1 : {}

   } >  MEM1

   .another_sec : {} > MEM1

}

The Errors:

error #10433-D: ALIAS'ed memory range, MEM1, may only be used for run placement and not for load placement for "GROUP1".

error #10433-D: ALIAS'ed memory range, MEM1, may only be used for run placement and not for load placement for ".another_sec".

If  removing the ALIAS there are no issues.

Thanks

Guy

Guy,

The linker ALIAS feature is intended for use with the Cortex-M4's SRAM mapping feature where the on-chip SRAM is mapped from both the SRAM memory region to the CODE memory region.  This is due to the device's separate instruction and data buses.

The use case supported is for running functions from RAM.  ie for performance reasons.

It requires that you use copy tables to load code to the alias'ed region.  The linker then ensures during placement that any placements to SRAM_DATA do not collide with those used to load code for SRAM_CODE.

Please see below example:

//task1.c
#include <stdio.h>
void toggle(void)
{ printf("alias placement succeeded for ramfunc toggle\n"); }

//main.c
#include <cpy_tbl.h>
extern void toggle();
void main(void)
{
    extern COPY_TABLE _task1_copy_table;
    copy_in(&_task1_copy_table);
    toggle();
}


MEMORY
{
    MAIN       (RX) : origin = 0x00000020, length = 0x0000FFFF
    ALIAS
    {
       SRAM_CODE  (RWX): origin = 0x00030000
       SRAM_DATA  (RW) : origin = 0x00040000
    } length = 0x0000F000
}
SECTIONS
{
    GROUP
    {
       .task1: { task1.obj(.text) }
    } load = MAIN, run = SRAM_CODE, table(_task1_copy_table)
    .text   :   > MAIN
    .const  :   > MAIN
    .cinit  :   > MAIN
    .pinit  :   > MAIN
    .data   :   > 0x00040000
    .bss    :   > SRAM_DATA
    .sysmem :   > SRAM_DATA
    .stack  :   > SRAM_DATA (HIGH)
}

Thanks and Regards,
Greg

Hello, Thanks.
I might be misunderstanding something as it does not feel very useful - cant i do the same by just allocate DATA and CODE to the same region and you'll have no problems of collisions. if you want different names for data and CODE you can just define another name as the one define on MEMORY (which will be similar to gnu MEM_ALIAS)
i would have thought it would enable to actually define different regions which each can be used separately but the linker will know they are the same physical space: i.e for M4 since the RAM region is NX , there is need to use the AMMU to map it to an executable region so after AMMU you'll have two different regions that are the same space - it would have been useful if the ALIAS would have helped with that.

Thanks for letting me know that it does no function as i thought (and as could be understood from the document).
maybe you'll consider to update this feature so it will be as it sounds.

Regards
Guy