Why linker section accepts load memory adress but we have to load manually

[SeyyedMohammad]

We have to manually load data to virtual memory adres VMA from Load Memory Adress LMA. But linker also requires the LMA. Look:

.fastcode :
  {
	  . = ALIGN(4);
	  _sfastcode = .;
	  *(.fastcode)
	  . = ALIGN(4);
	  *(.fastcode*)
	  . = ALIGN(4);
	/*  *arm_cortexM7lfdp_math.a:arm_fir_f32.o(.text*)*/
	  *arm_cortexM7lfdp_math.a:arm_*.o(.text*)
	  . = ALIGN(4);
	  _efastcode = .;
  } >ITCMRAM AT> FLASH

There you can see FLASH shows the load adress but we must initiate data in the startup:

ldr r0, =_sfastcode
 ldr r1, =_efastcode
 ldr r2, =_sifastcode
 movs r3, #0
 b LoopCopyFastcodeInit
 
CopyFastcodeInit:
 ldr r4, [r2, r3]
 str r4, [r0, r3]
 adds r3, r3, #4
 
LoopCopyFastcodeInit:
 adds r4, r0, r3
 cmp r4, r1
 bcc CopyFastcodeInit

Then relly there is no action happen by feeding ITCMRAM to LMA?

[KnarfB · Accepted solution]

The linker script requires the LMA such that a .bin file can be generated for example. Also in an .elf file must be enough information such that a loader can load that stuff into the flash for persistent storage.

In your above script, a line

_sifastcode = LOADADDR(.fastcode);

is not shown which will provide the .fastcode LMA in a symbol for your copy loop.

The linker itself will not generate code, just may provide symbols for your code.

See also https://sourceware.org/binutils/docs/ld/index.html

hth

KnarfB