How can Gcc work with itcm of stm32h7x

when i use the ITCM of stm32h743,in linkscript,i add new section as:

  _sitcm_addr = LOADADDR(.ItcmRam);
  _svtor_addr = LOADADDR(.isr_vector);
  _vtor_size = 0x400; /*SIZEOF (.isr_vector)*/
  .ItcmRam :
  {
    . = _vtor_size;    /*reserved for vector table*/
    . = ALIGN(4);     
    _sitcm = .;        /* create a global symbol at ITCM start */
    *(.ItcmRam);       /* ram_itcm */
    . = ALIGN(4);
    _eitcm = .;        /* define a global symbol at ITCM end */
  } >ITCMRAM AT> FLASH
    

where ITCMRAM in memory

MEMORY
{
DTCMRAM (xrw)      : ORIGIN = 0x20000000, LENGTH = 128K
RAM_D1 (xrw)      : ORIGIN = 0x24000000, LENGTH = 512K
RAM_D2 (xrw)      : ORIGIN = 0x30000000, LENGTH = 288K
RAM_D3 (xrw)      : ORIGIN = 0x38000000, LENGTH = 64K
ITCMRAM (xrw)      : ORIGIN = 0x00000000, LENGTH = 64K
FLASH (rx)      : ORIGIN = 0x8000000, LENGTH = 2048K
}

in startup file ,i copy .ItcmRam section content in flash to itcm ram after .bss section,like this

CopyItcmInit:
  ldr  r3, =_sitcm_addr
  ldr  r3, [r3, r1]
  str  r3, [r0, r1]
  adds  r1, r1, #4

LoopCopyItcmInit:
  ldr  r0, =_sitcm
  ldr  r3, =_eitcm
  adds  r2, r0, r1
  cmp  r2, r3
  bcc  CopyItcmInit

in source file ,i make some function in ItcmRam section like

void TestItcm(void) __attribute__((section(".ItcmRam")));

in main(){

TestBF();

TestItcm();

TestAF()

}

it works right that can go into the function TestItcm,but then can not get back to main to run the next TestAf function

in the TestItcm function ,it works correctly untill  return , and not retrun to main instead of into "HardFault_Handler".

IS there some method to use stm32h7x's itcm ram with GCC? thanks!