circuitpython/ports/atmel-samd/boards/samd51x18-bootloader-external-flash.ld
Jeff Epler 5eb9f9d060 atmel-samd: Fix rebooting to bootloader
Commit efbf08266b moved _estack in order to ensure 8-byte alignment
of the stack, but the address of _bootloader_dbl_tap must remain
right at the end of SRAM.

I verified by reading the source that the 4-byte-aligned address is
used for all samd21 / samd51 boards in
adafruit/circuitpython@efbf08266b.  However, I only tested on
trinket_m0.

Closes: #739
2018-04-03 21:40:10 -05:00

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/*
GNU linker script for SAMD51x18 (256K flash, 128K RAM)
*/
/* Specify the memory areas */
MEMORY
{
/* Leave 16KiB for the bootloader. */
FLASH (rx) : ORIGIN = 0x00000000 + 16K, LENGTH = 256K - 16K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 128K
}
/* top end of the stack */
/* stack must be double-word (8 byte) aligned */
_estack = ORIGIN(RAM) + LENGTH(RAM) - 8;
_bootloader_dbl_tap = ORIGIN(RAM) + LENGTH(RAM) - 4;
/* define output sections */
SECTIONS
{
/* The program code and other data goes into FLASH */
.text :
{
. = ALIGN(4);
_sfixed = .;
KEEP(*(.vectors)) /* isr vector table */
*(.text) /* .text sections (code) */
*(.text*) /* .text* sections (code) */
*(.rodata) /* .rodata sections (constants, strings, etc.) */
*(.rodata*) /* .rodata* sections (constants, strings, etc.) */
. = ALIGN(4);
} >FLASH
.ARM.exidx :
{
*(.ARM.exidx*)
*(.gnu.linkonce.armexidx.*)
_etext = .; /* define a global symbol at end of code */
_sidata = .; /* start of .data section */
} > FLASH
/* This is the initialized data section
The program executes knowing that the data is in the RAM
but the loader puts the initial values in the FLASH (inidata).
It is one task of the startup to copy the initial values from FLASH to RAM. */
.data : AT ( _sidata )
{
. = ALIGN(4);
_srelocate = .; /* create a global symbol at data start; used by startup code in order to initialise the .data section in RAM */
*(.ramfunc)
*(.ramfunc*)
*(.data) /* .data sections */
*(.data*) /* .data* sections */
. = ALIGN(4);
_erelocate = .; /* define a global symbol at data end; used by startup code in order to initialise the .data section in RAM */
} >RAM
/* Uninitialized data section */
.bss :
{
. = ALIGN(4);
_sbss = .;
_szero = .; /* define a global symbol at bss start; used by startup code */
*(.bss)
*(.bss*)
*(COMMON)
. = ALIGN(4);
_ezero = .; /* define a global symbol at bss end; used by startup code */
_ebss = .;
} >RAM
/* this just checks there is enough RAM for a minimal stack */
.stack :
{
. = ALIGN(4);
. = . + 2K; /* Reserve a minimum of 2K for the stack. */
. = ALIGN(4);
} >RAM
.ARM.attributes 0 : { *(.ARM.attributes) }
}