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Visitor II
February 14, 2019
Solved

How to place Bootloader after Application in Flash

  • February 14, 2019
  • 2 replies
  • 2171 views

I wrote a Bootloader for my STM32F042k6 board that functions pretty well. On System Reset the Bootloader is launched and can later jump to the Application. That was great:). Now I wish to do the opposite in my Flash. I wish Launch my Bootloader at a start address other than 0x08000000 lets say at 0x08007000. When I do the modifications in the Linker Script the Programm cannot be debugged. In simple words I wish to place my bootloader at the end of my Flash. Without forget that the Bootloader is always the first Code to run after Reset. Thanks in advance for your help and comments Here is my Linker Script:

/* Entry Point */
ENTRY(Boot_Reset_Handler)
 
/* Highest address of the user mode stack */
_estack = 0x20001800; /* end of 6K RAM */
 
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0; /* required amount of heap */
_Min_Stack_Size = 0x80; /* required amount of stack */
 
/* Specify the memory areas */
MEMORY
{	
 BOOTLOADER (rx) : ORIGIN = 0x08007000, LENGTH = 4K	
 FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 28K 
 RAM (xrw) : ORIGIN = 0x200000C0, LENGTH = 6K - 192
 MEMORY_B1 (rx) : ORIGIN = 0x60000000, LENGTH = 0K
}
 
 
/* Define output sections */
SECTIONS
{
 /* The startup code goes first into BOOTLOADER */
 .isr_vector :
 {
 . = ALIGN(4);
 KEEP(*(.isr_vector)) /* Startup code */
 . = ALIGN(4);
 } >BOOTLOADER
 
 
 
 /* The program code and other data goes into BOOTLOADER */
 .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)
 
 KEEP (*(.init))
 KEEP (*(.fini))
 
 . = ALIGN(4);
 _etext = .; /* define a global symbols at end of code */
 } >BOOTLOADER
 
 /* Constant data goes into BOOTLOADER */
 .rodata :
 {
 . = ALIGN(4);
 *(.rodata) /* .rodata sections (constants, strings, etc.) */
 *(.rodata*) /* .rodata* sections (constants, strings, etc.) */
 . = ALIGN(4);
 } >BOOTLOADER
 
 .ARM.extab : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >BOOTLOADER
 .ARM : {
 __exidx_start = .;
 *(.ARM.exidx*)
 __exidx_end = .;
 } >BOOTLOADER
 
 .preinit_array :
 {
 PROVIDE_HIDDEN (__preinit_array_start = .);
 KEEP (*(.preinit_array*))
 PROVIDE_HIDDEN (__preinit_array_end = .);
 } >BOOTLOADER
 .init_array :
 {
 PROVIDE_HIDDEN (__init_array_start = .);
 KEEP (*(SORT(.init_array.*)))
 KEEP (*(.init_array*))
 PROVIDE_HIDDEN (__init_array_end = .);
 } >BOOTLOADER
 .fini_array :
 {
 PROVIDE_HIDDEN (__fini_array_start = .);
 KEEP (*(SORT(.fini_array.*)))
 KEEP (*(.fini_array*))
 PROVIDE_HIDDEN (__fini_array_end = .);
 } >BOOTLOADER
 
 /* used by the startup to initialize data */
 _sidata = LOADADDR(.data);
 
 /* Initialized data sections goes into RAM, load LMA copy after code */
 .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 AT> BOOTLOADER
 
 /* 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
 
 /* User_heap_stack section, used to check that there is enough RAM left */
 ._user_heap_stack :
 {
 . = ALIGN(4);
 PROVIDE ( end = . );
 PROVIDE ( _end = . );
 . = . + _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) }
}

    This topic has been closed for replies.
    Best answer by mcdino.5338840562911753E12

    Ive got the Solution. :) I forgot adding some Libraries.

    2 replies

    Graduate II
    February 14, 2019

    Get a better debugger.

    Make sure the bootloader​ code transfers control properly.

    Manage the relocation of the Vector Table to RAM​.

    Step the transition code to make sure it works and you understand the process.​

    Visitor II
    February 14, 2019

    From your point of view is my linker Script Ok? And where exactly should I do the relocation of the Vector Table? In the Main() of the Bootloader?

    When I placed the Bootloader at the Start Address( First Case 0x0800000 ) I had to do the relocation in the main() of the Application which started at 0x08000C00.

    Graduate II
    February 14, 2019

    Your boot loader takes an excessive amount of space, your app has next to no space, and the naming of sections could be more rational/consistent.

    I'm confused, why build for 0x08007000 when your application is at 0x08000C00?

    On this part the vector table must reside at address 0x00000000, this is normally achieved by mapping the BASE of FLASH (0x08000000) or RAM (0x20000000) there. In the RAM case you need to construct a copy of the vector table you have stored deeper in the FLASH (say 0x08007000 or 0x08000C00)

    Visitor II
    February 14, 2019

    Oh sorry I didnt take note that the bootloader was so small. Initially I reserved just 3Kb for it. My Hardware has just 32Kb of Flash ie from 0x08000000 - 0x0800 7FFF . lets forget about the bootloader stuff. Lets assume I want to write a LED Blink Application and I change the Address of the Flash from 0x08000000 (Standard) to 0x08000c00. What are the required steps?