Question
Linker Script , optimisation
Posted on February 28, 2014 at 15:05
Hello,
I would like to be sure I understand the linker script that I am using. My main question is : the code is it copy to RAM before to be executed? I think It's not the case, because the code is .text section, that is just copy to FLASH with >FLASH. (the linker script is a copy from ST source + some modifications )
/*
*****************************************************************************
**
** File : stm32_mdp.ld
**
** Abstract : Linker script for stm32l1xx_mdp Device
**
** 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.
**
** (c)Copyright Atollic AB.
** You may use this file as-is or modify it according to the needs of your
** project. Distribution of this file (unmodified or modified) is not
** permitted. Atollic AB permit registered Atollic TrueSTUDIO(R) users the
** rights to distribute the assembled, compiled & linked contents of this
** file as part of an application binary file, provided that it is built
** using the Atollic TrueSTUDIO(R) toolchain.
**
*****************************************************************************
*/
/* Entry Point */
ENTRY(Reset_Handler)
/* Highest address of the user mode stack */
_estack = 0x20008000; /* end of 32K RAM */
__ICFEDIT_region_RAM_end__ = _estack;
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0; /* required amount of heap */
_Min_Stack_Size = 0x200; /* required amount of stack */
/* Specify the memory areas */
MEMORY
{
FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 256K /*- 0x3000*/
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 32K
MEMORY_B1 (rx) : ORIGIN = 0x60000000, LENGTH = 0K
}
/* Define output sections */
SECTIONS
{
/* The startup code goes first into FLASH */
.isr_vector :
{
. = ALIGN(4);
KEEP(*(.isr_vector)) /* Startup code */
. = ALIGN(4);
} >FLASH
/* The version number is placed before the beginning of code */
.nb_version :
{
. = ALIGN(4);
KEEP(*(.nb_version)) /* KEEP the variable even if not referenced */
. = ALIGN(4);
} >FLASH
/* The program code and other data goes into FLASH */
.text :
{
. = ALIGN(4);
_stext = .; /* define a global symbols at start of code */
*(.text) /* .text sections (code) */
*(.text*) /* .text* sections (code) */
*(.rodata) /* .rodata sections (constants, strings, etc.) */
*(.rodata*) /* .rodata* sections (constants, strings, etc.) */
*(.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
__checksum = _stext;
__end_of_code = _etext;
.ARM.extab : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >FLASH
.ARM : {
__exidx_start = .;
*(.ARM.exidx*)
__exidx_end = .;
} >FLASH
.preinit_array :
{
PROVIDE_HIDDEN (__preinit_array_start = .);
KEEP (*(.preinit_array*))
PROVIDE_HIDDEN (__preinit_array_end = .);
} >FLASH
.init_array :
{
PROVIDE_HIDDEN (__init_array_start = .);
KEEP (*(SORT(.init_array.*)))
KEEP (*(.init_array*))
PROVIDE_HIDDEN (__init_array_end = .);
} >FLASH
.fini_array :
{
PROVIDE_HIDDEN (__fini_array_start = .);
KEEP (*(.fini_array*))
KEEP (*(SORT(.fini_array.*)))
PROVIDE_HIDDEN (__fini_array_end = .);
} >FLASH
/* used by the startup to initialize data */
_sidata = .;
/* Initialized data sections goes into RAM, load LMA copy after code */
.data : AT ( _sidata )
{
. = 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
__ICFEDIT_region_RAM_end__ = _edata; /* used to check the RAM used */
/* Uninitialized data section */
. = ALIGN(4);
.bss :
{
/* This is used by the startup in order to initialize the .bss secion */
_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
PROVIDE ( end = _ebss );
PROVIDE ( _end = _ebss );
/* User_heap_stack section, used to check that there is enough RAM left */
._user_heap_stack :
{
. = ALIGN(4);
. = . + _Min_Heap_Size;
. = . + _Min_Stack_Size;
. = ALIGN(4);
} >RAM
/* MEMORY_bank1 section, code must be located here explicitly */
/* Example: extern int foo(void) __attribute__ ((section (''.mb1text''))); */
.memory_b1_text :
{
*(.mb1text) /* .mb1text sections (code) */
*(.mb1text*) /* .mb1text* sections (code) */
*(.mb1rodata) /* read-only data (constants) */
*(.mb1rodata*)
} >MEMORY_B1
/* Remove information from the standard libraries */
/DISCARD/ :
{
libc.a ( * )
libm.a ( * )
libgcc.a ( * )
}
.ARM.attributes 0 : { *(.ARM.attributes) }
}
.section .text.Reset_Handler
.weak Reset_Handler
.type Reset_Handler, %function
Reset_Handler:
/* Copy the data segment initializers from flash to SRAM */
movs r1, #0
b LoopCopyDataInit
CopyDataInit:
ldr r3, =_sidata
ldr r3, [r3, r1]
str r3, [r0, r1]
adds r1, r1, #4
LoopCopyDataInit:
ldr r0, =_sdata
ldr r3, =_edata
adds r2, r0, r1
cmp r2, r3
bcc CopyDataInit
ldr r2, =_sbss
b LoopFillZerobss
/* Zero fill the bss segment. */
FillZerobss:
movs r3, #0
str r3, [r2], #4
LoopFillZerobss:
ldr r3, = _ebss
cmp r2, r3
bcc FillZerobss
/* Call the application's entry point.*/
bl main
bx lr
.size Reset_Handler, .-Reset_Handler