STM32 editing linker script

Question

In the STM32F767ZI reference manual, the memory organization is divided into:

FLASH, SRAM1, SRAM2, ITCM and DTCM, but in the linker script, the project is either stored into FLASH or RAM. I want to edit the linker script, so I can store data in a specific memory region.

I am trying to change it from:

MEMORY
{
 RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 512K
 FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 2048K
}

To this:

MEMORY
{
 ITCMRAM (xrw) : ORIGIN = 0x00000000, LENGTH = 16K
 DTCMRAM (xrw) : ORIGIN = 0x20000000, LENGTH = 128K
 RAM (xrw) : ORIGIN = 0x20020000, LENGTH = 368K
 SRAM (xrw) : ORIGIN = 0x2007C000, LENGTH = 16K
 FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 2048K
}

So I added in the sections this:

_sisram = LOADADDR(.sram);
.sram :
{
 . = ALIGN(4);
 _ssram = .; /* Create a global symbol at data start */
 (.sram) / .data sections */
 (.sram) /* .data* sections */
 . = ALIGN(4);
 _esram = .; /* Define a global symbol at data end */
} >SRAM AT> FLASH
_siitcm = LOADADDR(.itcm);
.itcm :
 . = ALIGN(4);
 _sitcm = .; /* Create a global symbol at data start */
 (.itcm) / .data sections */
 (.itcm) /* .data* sections */
 . = ALIGN(4);
 _eitcm = .; /* Define a global symbol at data end */
} >ITCMRAM AT> FLASH
_sidtcm = LOADADDR(.data);
.dtcm :
{
 . = ALIGN(4);
 _sdtcm = .; /* Create a global symbol at data start */
 (.dtcm) / .data sections */
 (.dtcm) /* .data* sections */
 . = ALIGN(4);
 _edtcm = .; /* Define a global symbol at data end */
} >DTCMRAM AT> FLASH

And then moved to the startup file.

First, I added the following:

.word _sisram
.word _ssram
.word _esram
.word _siitcm
.word _sitcm
.word _eitcm
.word _sidtcm
.word _sdtcm
.word _edtcm

And then the copy loop like this:

// SRAM
ldr r0, =_ssram
ldr r1, =_esram
ldr r2, =_sisram
movs r3, #0
b LoopCopySramInit
CopySramInit:
ldr r4, [r2, r3]
str r4, [r0, r3]
adds r3, r3, #4
LoopCopySramInit:
adds r4, r0, r3
cmp r4, r1
bcc CopySramInit
// ITCM
ldr r0, =_sitcm
ldr r1, =_eitcm
ldr r2, =_siitcm
movs r3, #0
b LoopCopyItcmInit
CopyItcmInit:
ldr r4, [r2, r3]
str r4, [r0, r3]
adds r3, r3, #4
LoopCopyItcmInit:
adds r4, r0, r3
cmp r4, r1
bcc CopyItcmInit
// DTCM
ldr r0, =_sdtcm
ldr r1, =_edtcm
ldr r2, =_sidtcm
movs r3, #0
b LoopCopyDtcmInit
CopyDtcmInit:
ldr r4, [r2, r3]
str r4, [r0, r3]
adds r3, r3, #4
LoopCopyDtcmInit:
adds r4, r0, r3
cmp r4, r1
bcc CopyDtcmInit

So I am basically copying what the mx did to the data section from flash memory to RAM, but when I run, I get this error:

undefined reference to `_ssram'

I tried to change it from .word to .extern, but still I get the same error.

What am I missing? Is there a better way to divide the RAM region to ITCM DTCM and RAM?

• 0___________: You probably do not link using this linker script. Check your build system.
• Faisal129: @0___________ Thank you for the reply, I did choose this linker from project properties. unless their is something more I should do?