stm32g070 execute code in ram

/*
******************************************************************************
**
** @file : LinkerScript.ld
**
** @author : Auto-generated by STM32CubeIDE
**
** @brief : Linker script for STM32G070CBTx Device from STM32G0 series
** 128Kbytes FLASH
** 36Kbytes 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
**
** Copyright (c) 2022 STMicroelectronics.
** All rights reserved.
**
** This software is licensed under terms that can be found in the LICENSE file
** in the root directory of this software component.
** If no LICENSE file comes with this software, it is provided AS-IS.
**
******************************************************************************
*/
 
/* 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 = 0x400 ; /* required amount of heap */
_Min_Stack_Size = 0x800 ; /* required amount of stack */
 
/* Memories definition */
MEMORY
{
 RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 36K
 FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 128K
}
 
/* Sections */
SECTIONS
{
 /* The startup code into "RAM" Rom type memory */
 .isr_vector :
 {
 . = ALIGN(4);
 KEEP(*(.isr_vector)) /* Startup code */
 . = ALIGN(4);
 } >RAM
 
 /* 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)
 *(.RamFunc) /* .RamFunc sections */
 *(.RamFunc*) /* .RamFunc* sections */
 
 KEEP (*(.init))
 KEEP (*(.fini))
 
 . = ALIGN(4);
 _etext = .; /* define a global symbols at end of code */
 } >RAM
 
 /* Constant data into "FLASH" Rom type memory */
 .rodata :
 {
 . = ALIGN(4);
 *(.rodata) /* .rodata sections (constants, strings, etc.) */
 *(.rodata*) /* .rodata* sections (constants, strings, etc.) */
 . = ALIGN(4);
 } >RAM
 
 .ARM.extab : {
 . = ALIGN(4);
 *(.ARM.extab* .gnu.linkonce.armextab.*)
 . = ALIGN(4);
 } >RAM
 
 .ARM : {
 . = ALIGN(4);
 __exidx_start = .;
 *(.ARM.exidx*)
 __exidx_end = .;
 . = ALIGN(4);
 } >RAM
 
 .preinit_array :
 {
 . = ALIGN(4);
 PROVIDE_HIDDEN (__preinit_array_start = .);
 KEEP (*(.preinit_array*))
 PROVIDE_HIDDEN (__preinit_array_end = .);
 . = ALIGN(4);
 } >RAM
 
 .init_array :
 {
 . = ALIGN(4);
 PROVIDE_HIDDEN (__init_array_start = .);
 KEEP (*(SORT(.init_array.*)))
 KEEP (*(.init_array*))
 PROVIDE_HIDDEN (__init_array_end = .);
 . = ALIGN(4);
 } >RAM
 
 .fini_array :
 {
 . = ALIGN(4);
 PROVIDE_HIDDEN (__fini_array_start = .);
 KEEP (*(SORT(.fini_array.*)))
 KEEP (*(.fini_array*))
 PROVIDE_HIDDEN (__fini_array_end = .);
 . = ALIGN(4);
 } >RAM
 
 /* 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 */
 
 . = ALIGN(4);
 _edata = .; /* define a global symbol at data end */
 
 } >RAM
 
 /* 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
 
 /* Remove information from the compiler libraries */
 /DISCARD/ :
 {
 libc.a ( * )
 libm.a ( * )
 libgcc.a ( * )
 }
 
 .ARM.attributes 0 : { *(.ARM.attributes) }
}

linker script

>stm32cube mx just generate flash.ld linker script. So I create my own ram.ld linker script

It is unusual to link an app in RAM because it is volatile, which means its content disappears on a power-cycle.

>i modify system_stm32g0xx.c to point the entry point to sram

Ok your linker script puts your vector table, .text, .rodata, .data etc in RAM.

But does your GDB reset after loading your code in RAM?

Check RM0454 section 2.5 about boot modes. If you have not configured your option bytes to boot from internal SRAM (0x20000000), you will need to modify your debug configuration's startup script to ensure your debug session starts execution at your Reset_Handler address in RAM.

Do you actually need to boot from SRAM or is this a learning exercise? Can you share the rationale please?