Allocate user defined section on FLASH with constant value

[SSeo.17]

I'm using STM32F427.

I want to declare the variable as a custom section and use it in a specific address area on the MCU FLASH.

I change the *.ld file, declare that the variables are assigned to the designated section, so the compile becomes normal, and when I check the *.lst file and *.map file, I can confirm that they are assigned normally.

However, in the Memory Regions window of Build Analyzer on CubeIDE, the usage of the custom section is displayed as 0%.

(In the attached image CCMRAM and FLSHOPT region)

And it is not possible to check the variable value of the designated area during the actual Debug.

How can I solve this problem?

Please give me some advice.

Thank you.

Best regards.

[Javier1]

>>And it is not possible to check the variable value of the designated area during the actual Debug.

why not?

i am able to see any part of the ram/flash i want at any given time during debugging.

You could try also to connect your chip to stCUBEprogrammer and dump or explore the entire flash content of your STM32F427.

Could you show us how did you defined the region in your .ld script?

[SSeo.17]

I attach the .ld file.

/*

******************************************************************************

**

** @file    : LinkerScript.ld

**

** @author   : Auto-generated by STM32CubeIDE

**

** @brief    : Linker script for STM32F427ZGTx Device from STM32F4 series

**           1024Kbytes FLASH

**           64Kbytes CCMRAM

**           192Kbytes RAM

**

**        Set heap size, stack size and stack location according

**        to application requirements.

**

**        Set memory bank area and size if external memory is used

**

** Target   : STMicroelectronics STM32

**

** Distribution: The file is distributed as is, without any warranty

**        of any kind.

**

******************************************************************************

** @attention

**

** <h2><center>&copy; Copyright (c) 2021 STMicroelectronics.

** All rights reserved.</center></h2>

**

** This software component is licensed by ST under BSD 3-Clause license,

** the "License"; You may not use this file except in compliance with the

** License. You may obtain a copy of the License at:

**            opensource.org/licenses/BSD-3-Clause

**

******************************************************************************

*/

/* Entry Point */

ENTRY(Reset_Handler)

/* Highest address of the user mode stack */

_estack = ORIGIN(RAM) + LENGTH(RAM); /* end of "RAM" Ram type memory */

_Min_Heap_Size = 0x200 ; /* required amount of heap */

_Min_Stack_Size = 0x400 ; /* required amount of stack */

/* Memories definition */

MEMORY

{

 CCMRAM (xrw) : ORIGIN = 0x10000000,  LENGTH = 64K

 RAM   (xrw) : ORIGIN = 0x20000000,  LENGTH = 192K

 BKPRAM (rw) : ORIGIN = 0x40024000,  LENGTH = 4K

/*FLASH  (rx) : ORIGIN = 0x08000000,  LENGTH = 1024K */

 FLSHOPT (rx) : ORIGIN = 0x080E0000,  LENGTH = 128K /* option data repository on flash */

 FLASH  (rx) : ORIGIN = 0x08000000,  LENGTH = 896K

}

/* Sections */

SECTIONS

{

 /* The startup code into "FLASH" Rom type memory */

 .isr_vector :

 {

  . = ALIGN(4);

  KEEP(*(.isr_vector)) /* Startup code */

  . = ALIGN(4);

 } >FLASH

 /* The program code and other data into "FLASH" Rom type memory */

 .text :

 {

  . = ALIGN(4);

  *(.text)      /* .text sections (code) */

  *(.text*)     /* .text* sections (code) */

  *(.glue_7)     /* glue arm to thumb code */

  *(.glue_7t)    /* glue thumb to arm code */

  *(.eh_frame)

  KEEP (*(.init))

  KEEP (*(.fini))

  . = ALIGN(4);

  _etext = .;    /* define a global symbols at end of code */

 } >FLASH

 /* Constant data into "FLASH" Rom type memory */

 .rodata :

 {

  . = ALIGN(4);

  *(.rodata)     /* .rodata sections (constants, strings, etc.) */

  *(.rodata*)    /* .rodata* sections (constants, strings, etc.) */

  . = ALIGN(4);

 } >FLASH

 .ARM.extab  : {

  . = ALIGN(4);

  *(.ARM.extab* .gnu.linkonce.armextab.*)

  . = ALIGN(4);

 } >FLASH

 .ARM : {

  . = ALIGN(4);

  __exidx_start = .;

  *(.ARM.exidx*)

  __exidx_end = .;

  . = ALIGN(4);

 } >FLASH

 .preinit_array   :

 {

  . = ALIGN(4);

  PROVIDE_HIDDEN (__preinit_array_start = .);

  KEEP (*(.preinit_array*))

  PROVIDE_HIDDEN (__preinit_array_end = .);

  . = ALIGN(4);

 } >FLASH

 .init_array :

 {

  . = ALIGN(4);

  PROVIDE_HIDDEN (__init_array_start = .);

  KEEP (*(SORT(.init_array.*)))

  KEEP (*(.init_array*))

  PROVIDE_HIDDEN (__init_array_end = .);

  . = ALIGN(4);

 } >FLASH

 .fini_array :

 {

  . = ALIGN(4);

  PROVIDE_HIDDEN (__fini_array_start = .);

  KEEP (*(SORT(.fini_array.*)))

  KEEP (*(.fini_array*))

  PROVIDE_HIDDEN (__fini_array_end = .);

  . = ALIGN(4);

 } >FLASH

 /* Used by the startup to initialize data */

 _sidata = LOADADDR(.data);

 /* Initialized data sections into "RAM" Ram type memory */

 .data :

 {

  . = ALIGN(4);

  _sdata = .;    /* create a global symbol at data start */

  *(.data)      /* .data sections */

  *(.data*)     /* .data* sections */

  *(.RamFunc)    /* .RamFunc sections */

  *(.RamFunc*)    /* .RamFunc* sections */

  . = ALIGN(4);

  _edata = .;    /* define a global symbol at data end */

 } >RAM AT> FLASH

 /* --------------------------------------- */

 /* Option data flash area <20220206 seosh> */

 .Sect_FlashOpt :

 {

. = ALIGN(4);

KEEP ( *(.Sect_FlashOpt))

*(.Sect_FlashOpt*)

. = ALIGN(4);

 } >FLSHOPT

 _siccmram = LOADADDR(.ccmram);

 /* CCM-RAM section

 *

 * IMPORTANT NOTE!

 * If initialized variables will be placed in this section,

 * the startup code needs to be modified to copy the init-values.

 */

 .ccmram :

 {

  . = ALIGN(4);

  _sccmram = .;    /* create a global symbol at ccmram start */

  KEEP(*(.ccmram))

  *(.ccmram*)

  . = ALIGN(4);

  _eccmram = .;    /* create a global symbol at ccmram end */

/* } >CCMRAM AT> FLASH */

 } >CCMRAM

 /* Uninitialized data section into "RAM" Ram type memory */

 . = ALIGN(4);

 .bss :

 {

  /* This is used by the startup in order to initialize the .bss section */

  _sbss = .;     /* define a global symbol at bss start */

  __bss_start__ = _sbss;

  *(.bss)

  *(.bss*)

  *(COMMON)

  . = ALIGN(4);

  _ebss = .;     /* define a global symbol at bss end */

  __bss_end__ = _ebss;

 } >RAM

 /* User_heap_stack section, used to check that there is enough "RAM" Ram type memory left */

 ._user_heap_stack :

 {

  . = ALIGN(8);

  PROVIDE ( end = . );

  PROVIDE ( _end = . );

  . = . + _Min_Heap_Size;

  . = . + _Min_Stack_Size;

  . = ALIGN(8);

 } >RAM

 /* --------------------------------------- */

 /* Error bank area <20220206 seosh> */

 /* .Sect_ErrBank : */

 .Sect_ErrBank (NOLOAD):

 {

  . = ALIGN(4);

  KEEP ( *(.Sect_ErrBank))

  *(.Sect_ErrBank*)

  . = ALIGN(4);

 } >BKPRAM

 /* Remove information from the compiler libraries */

 /DISCARD/ :

 {

  libc.a ( * )

  libm.a ( * )

  libgcc.a ( * )

 }

 .ARM.attributes 0 : { *(.ARM.attributes) }

}

[SSeo.17]

I declared the variables in the assembly source, and the section was just declared without any option as follows.

.section .Sect_FlashOpt

This part was changed as follows to solve the memory section allocation problem.

.section .Sect_FlashOpt,"a",%progbits