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RAM Section allocated by Linker

WesC

I don’t know what all the XML syntax is, or what program processes the flash_placement.xml file, or what form the output is in, so I don’t know if I have to do exactly what is suggested, or if we can tweak it.

 I suggested to create a RAM section at a specific location and size in the Flash_placement.xml file:

                <ProgramSection alignment="4" keep="Yes" load="No" name=".myram_RAM_section" start="0x20006000" size="0x2000" />

 

I am hoping I can create a RAM section whose location and size are determined by the linker, and by what I place in it.

Can i do something like this?

                <ProgramSection alignment="4" keep="Yes" load="No" name=".cnfig_data" address_symbol="__start_cnfig_data" end_symbol="__stop_cnfig_data" />

 

Is there syntax that will let me specify a maximum size for the “.cnfig_data” RAM section?

 If not, I might still be OK, because I believe I can reference the “__start_cnfig_data” and “__stop_cnfig_data” symbols in C, right?

 If so, I can calculate the size and ASSERT and/or set an alarm if it exceeds 4096.

 I am also worried about a group of sectors that may expect to be contiguous, so I put my new sector AFTER that grouping that starts with name “.nrf_sections_run” and ends with name “.nrf_sections_run_end”.

 

I attached my modified flash_placement.xml file. It hasn’t been executed yet – I really want to get it right the first time, and then run it as my only change, with only one variable assigned to that new section.

 

<!DOCTYPE Linker_Placement_File>
<Root name="Flash Section Placement">
  <MemorySegment name="FLASH" start="$(FLASH_PH_START)" size="$(FLASH_PH_SIZE)">
    <ProgramSection load="no" name=".reserved_flash" start="$(FLASH_PH_START)" size="$(FLASH_START)-$(FLASH_PH_START)" />
    <ProgramSection alignment="0x100" load="Yes" name=".vectors" start="$(FLASH_START)" />
    <ProgramSection alignment="4" load="Yes" name=".init" />
    <ProgramSection alignment="4" load="Yes" name=".init_rodata" />
    <ProgramSection alignment="4" load="Yes" name=".text" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".sdh_soc_observers" inputsections="*(SORT(.sdh_soc_observers*))" address_symbol="__start_sdh_soc_observers" end_symbol="__stop_sdh_soc_observers" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".sdh_ble_observers" inputsections="*(SORT(.sdh_ble_observers*))" address_symbol="__start_sdh_ble_observers" end_symbol="__stop_sdh_ble_observers" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".pwr_mgmt_data" inputsections="*(SORT(.pwr_mgmt_data*))" address_symbol="__start_pwr_mgmt_data" end_symbol="__stop_pwr_mgmt_data" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".sdh_req_observers" inputsections="*(SORT(.sdh_req_observers*))" address_symbol="__start_sdh_req_observers" end_symbol="__stop_sdh_req_observers" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".sdh_state_observers" inputsections="*(SORT(.sdh_state_observers*))" address_symbol="__start_sdh_state_observers" end_symbol="__stop_sdh_state_observers" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".sdh_stack_observers" inputsections="*(SORT(.sdh_stack_observers*))" address_symbol="__start_sdh_stack_observers" end_symbol="__stop_sdh_stack_observers" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".nrf_queue" inputsections="*(.nrf_queue*)" address_symbol="__start_nrf_queue" end_symbol="__stop_nrf_queue" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".nrf_balloc" inputsections="*(.nrf_balloc*)" address_symbol="__start_nrf_balloc" end_symbol="__stop_nrf_balloc" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".cli_command" inputsections="*(.cli_command*)" address_symbol="__start_cli_command" end_symbol="__stop_cli_command" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".crypto_data" inputsections="*(SORT(.crypto_data*))" address_symbol="__start_crypto_data" end_symbol="__stop_crypto_data" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".log_const_data" inputsections="*(SORT(.log_const_data*))" address_symbol="__start_log_const_data" end_symbol="__stop_log_const_data" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".log_backends" inputsections="*(SORT(.log_backends*))" address_symbol="__start_log_backends" end_symbol="__stop_log_backends" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".nrf_sections" address_symbol="__start_nrf_sections" />
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".cli_sorted_cmd_ptrs"  inputsections="*(.cli_sorted_cmd_ptrs*)" runin=".cli_sorted_cmd_ptrs_run"/>
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".fs_data"  inputsections="*(.fs_data*)" runin=".fs_data_run"/>
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".log_dynamic_data"  inputsections="*(SORT(.log_dynamic_data*))" runin=".log_dynamic_data_run"/>
    <ProgramSection alignment="4" keep="Yes" load="Yes" name=".log_filter_data"  inputsections="*(SORT(.log_filter_data*))" runin=".log_filter_data_run"/>
    <ProgramSection alignment="4" load="Yes" name=".dtors" />
    <ProgramSection alignment="4" load="Yes" name=".ctors" />
    <ProgramSection alignment="4" load="Yes" name=".rodata" />
    <ProgramSection alignment="4" load="Yes" name=".ARM.exidx" address_symbol="__exidx_start" end_symbol="__exidx_end" />
    <ProgramSection alignment="4" load="Yes" runin=".fast_run" name=".fast" />
    <ProgramSection alignment="4" load="Yes" runin=".data_run" name=".data" />
    <ProgramSection alignment="4" load="Yes" runin=".tdata_run" name=".tdata" />
  </MemorySegment>
  <MemorySegment name="RAM1" start="$(RAM_PH_START)" size="$(RAM_PH_SIZE)">
    <ProgramSection load="no" name=".reserved_ram" start="$(RAM_PH_START)" size="$(RAM_START)-$(RAM_PH_START)" />
    <ProgramSection alignment="0x100" load="No" name=".vectors_ram" start="$(RAM_START)" address_symbol="__app_ram_start__"/>
    <ProgramSection alignment="4" keep="Yes" load="No" name=".nrf_sections_run" address_symbol="__start_nrf_sections_run" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".cli_sorted_cmd_ptrs_run" address_symbol="__start_cli_sorted_cmd_ptrs" end_symbol="__stop_cli_sorted_cmd_ptrs" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".fs_data_run" address_symbol="__start_fs_data" end_symbol="__stop_fs_data" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".log_dynamic_data_run" address_symbol="__start_log_dynamic_data" end_symbol="__stop_log_dynamic_data" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".log_filter_data_run" address_symbol="__start_log_filter_data" end_symbol="__stop_log_filter_data" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".nrf_sections_run_end" address_symbol="__end_nrf_sections_run" />
    <ProgramSection alignment="4" keep="Yes" load="No" name=".cnfig_data" address_symbol="__start_cnfig_data" end_symbol="__stop_cnfig_data" />
    <ProgramSection alignment="4" load="No" name=".fast_run" />
    <ProgramSection alignment="4" load="No" name=".data_run" />
    <ProgramSection alignment="4" load="No" name=".tdata_run" />
    <ProgramSection alignment="4" load="No" name=".bss" />
    <ProgramSection alignment="4" load="No" name=".tbss" />
    <ProgramSection alignment="4" load="No" name=".non_init" />
    <ProgramSection alignment="4" size="__HEAPSIZE__" load="No" name=".heap" />
    <ProgramSection alignment="8" size="__STACKSIZE__" load="No" place_from_segment_end="Yes" name=".stack"  address_symbol="__StackLimit" end_symbol="__StackTop"/>
    <ProgramSection alignment="8" size="__STACKSIZE_PROCESS__" load="No" name=".stack_process" />
  </MemorySegment>
</Root>

  • 0

    Hi,

    This thread on the Segger forum shows how to place data at a specific location (both in flash and RAM). That does not show how to specify size, but it is described in the linker documentation here.

  • 0

    How do I set an upper limit on the size of the section in order to prevent linking when the config data area gets larger than 4096?

     the  “size” attribute won’t work for this application because it sets the size of the section being created to a fixed value.

    I hope this doesn’t confuse things, but this is how I do it for the GNU linker (ld) in a .ld file:

       /*///////////////////////////////////////////////////////////////////////////*/
   /* .cnfig_data must fit into one flash block (4K) including the 2-byte CRC-16 */
   /*///////////////////////////////////////////////////////////////////////////*/
   .cnfig_data :
   {
                _start_of_cnfig_data = .;
                *(.cnfig_data)
                *(.cnfig_data.*)
                _end_of_cnfig_data = .;
   } > SRAM1

   _size_of_cnfig_data = _end_of_cnfig_data - _start_of_cnfig_data;
   ASSERT( _size_of_cnfig_data <= 4094, ".cnfig_data cannot exceed 4094 bytes")

   /*///////////////////////////////////////////////////////////////////////////*/

  • 0 in reply to WesC

    Ah, I see. I have not been able to find an answer to that. Have you tried asking Segger (either private support or on their forum)? I would expect they should be able to answer quickly.

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