SDK: nRF5SDK
Toolchain: ARM GCC
Hello,
I have some devices out in the field using nRF52840s, using the non-SoftDevice bootloader, and a custom mechanism for reading updates that I've downloaded to the flash remotely.
In our application, I'd like to start using a NOLOAD section of RAM, by altering the linker script.
However, I'm unsure of what guarantees I can make about how the bootloader will alter the RAM? Given that I can't remotely flash on a new bootloader with a linker script that respects by NOLOAD section.
Given that I have the bootloader code, and linker script, is there anyway I can analyse the memory addresses and determine if there's a portion of RAM which the bootloader defintely won't be initing or messing with, and thus I'm safe to use as a "NOLOAD" section in my application code?
Attached are the bootloader linker script and common linker script in case you don't have the SDK available to you
Thanks,
Joshua
/* Linker script to configure memory regions. */
SEARCH_DIR(.)
GROUP(-lgcc -lc -lnosys)
MEMORY
{
FLASH (rx) : ORIGIN = 0xf4000, LENGTH = 0x0A000
RAM (rwx) : ORIGIN = 0x20000008, LENGTH = 0x3FFF8
uicr_bootloader_start_address (r) : ORIGIN = 0x10001014, LENGTH = 0x4
bootloader_settings_page (r) : ORIGIN = 0x000FF000, LENGTH = 0x1000
uicr_mbr_params_page (r) : ORIGIN = 0x10001018, LENGTH = 0x4
mbr_params_page (r) : ORIGIN = 0x000FE000, LENGTH = 0x1000
}
SECTIONS
{
. = ALIGN(4);
.uicr_bootloader_start_address :
{
PROVIDE(__start_uicr_bootloader_start_address = .);
KEEP(*(SORT(.uicr_bootloader_start_address*)))
PROVIDE(__stop_uicr_bootloader_start_address = .);
} > uicr_bootloader_start_address
. = ALIGN(4);
.bootloader_settings_page(NOLOAD) :
{
PROVIDE(__start_bootloader_settings_page = .);
KEEP(*(SORT(.bootloader_settings_page*)))
PROVIDE(__stop_bootloader_settings_page = .);
} > bootloader_settings_page
. = ALIGN(4);
.uicr_mbr_params_page :
{
PROVIDE(__start_uicr_mbr_params_page = .);
KEEP(*(SORT(.uicr_mbr_params_page*)))
PROVIDE(__stop_uicr_mbr_params_page = .);
} > uicr_mbr_params_page
. = ALIGN(4);
.mbr_params_page(NOLOAD) :
{
PROVIDE(__start_mbr_params_page = .);
KEEP(*(SORT(.mbr_params_page*)))
PROVIDE(__stop_mbr_params_page = .);
} > mbr_params_page
}
SECTIONS
{
. = ALIGN(4);
.mem_section_dummy_ram :
{
}
.fs_data :
{
PROVIDE(__start_fs_data = .);
KEEP(*(.fs_data))
PROVIDE(__stop_fs_data = .);
} > RAM
.log_dynamic_data :
{
PROVIDE(__start_log_dynamic_data = .);
KEEP(*(SORT(.log_dynamic_data*)))
PROVIDE(__stop_log_dynamic_data = .);
} > RAM
.log_filter_data :
{
PROVIDE(__start_log_filter_data = .);
KEEP(*(SORT(.log_filter_data*)))
PROVIDE(__stop_log_filter_data = .);
} > RAM
} INSERT AFTER .data;
SECTIONS
{
.mem_section_dummy_rom :
{
}
.crypto_data :
{
PROVIDE(__start_crypto_data = .);
KEEP(*(SORT(.crypto_data*)))
PROVIDE(__stop_crypto_data = .);
} > FLASH
.nrf_queue :
{
PROVIDE(__start_nrf_queue = .);
KEEP(*(.nrf_queue))
PROVIDE(__stop_nrf_queue = .);
} > FLASH
.dfu_trans :
{
PROVIDE(__start_dfu_trans = .);
KEEP(*(SORT(.dfu_trans*)))
PROVIDE(__stop_dfu_trans = .);
} > FLASH
.log_const_data :
{
PROVIDE(__start_log_const_data = .);
KEEP(*(SORT(.log_const_data*)))
PROVIDE(__stop_log_const_data = .);
} > FLASH
.nrf_balloc :
{
PROVIDE(__start_nrf_balloc = .);
KEEP(*(.nrf_balloc))
PROVIDE(__stop_nrf_balloc = .);
} > FLASH
.log_backends :
{
PROVIDE(__start_log_backends = .);
KEEP(*(SORT(.log_backends*)))
PROVIDE(__stop_log_backends = .);
} > FLASH
} INSERT AFTER .text
SECTIONS
{
.noinit (NOLOAD) :
{
. = ALIGN(4);
__noinit_start__ = .;
*(.noinit*)
__noinit_end__ = .;
} > PD
}
INCLUDE "nrf_common.ld"
/* Linker script for Nordic Semiconductor nRF5 devices
*
* Version: Sourcery G++ 4.5-1
* Support: https://support.codesourcery.com/GNUToolchain/
*
* Copyright (c) 2007, 2008, 2009, 2010 CodeSourcery, Inc.
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice is included verbatim in any distributions. No written agreement,
* license, or royalty fee is required for any of the authorized uses.
* Modifications to this software may be copyrighted by their authors
* and need not follow the licensing terms described here, provided that
* the new terms are clearly indicated on the first page of each file where
* they apply.
*/
OUTPUT_FORMAT ("elf32-littlearm", "elf32-bigarm", "elf32-littlearm")
/* Linker script to place sections and symbol values. Should be used together
* with other linker script that defines memory regions FLASH and RAM.
* It references following symbols, which must be defined in code:
* Reset_Handler : Entry of reset handler
*
* It defines following symbols, which code can use without definition:
* __exidx_start
* __exidx_end
* __etext
* __data_start__
* __preinit_array_start
* __preinit_array_end
* __init_array_start
* __init_array_end
* __fini_array_start
* __fini_array_end
* __data_end__
* __bss_start__
* __bss_end__
* __end__
* end
* __HeapLimit
* __StackLimit
* __StackTop
* __stack
*/
ENTRY(Reset_Handler)
SECTIONS
{
.text :
{
KEEP(*(.Vectors))
*(.text*)
KEEP(*(.init))
KEEP(*(.fini))
/* .ctors */
*crtbegin.o(.ctors)
*crtbegin?.o(.ctors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
*(SORT(.ctors.*))
*(.ctors)
/* .dtors */
*crtbegin.o(.dtors)
*crtbegin?.o(.dtors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
*(SORT(.dtors.*))
*(.dtors)
*(.rodata*)
*(.eh_frame*)
. = ALIGN(4);
} > FLASH
.ARM.extab :
{
*(.ARM.extab* .gnu.linkonce.armextab.*)
. = ALIGN(4);
} > FLASH
__exidx_start = .;
.ARM.exidx :
{
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
. = ALIGN(4);
} > FLASH
__exidx_end = .;
__etext = .;
.data : AT (__etext)
{
__data_start__ = .;
*(vtable)
*(.data*)
. = ALIGN(4);
/* preinit data */
PROVIDE_HIDDEN (__preinit_array_start = .);
*(.preinit_array)
PROVIDE_HIDDEN (__preinit_array_end = .);
. = ALIGN(4);
/* init data */
PROVIDE_HIDDEN (__init_array_start = .);
*(SORT(.init_array.*))
*(.init_array)
PROVIDE_HIDDEN (__init_array_end = .);
. = ALIGN(4);
/* finit data */
PROVIDE_HIDDEN (__fini_array_start = .);
*(SORT(.fini_array.*))
*(.fini_array)
PROVIDE_HIDDEN (__fini_array_end = .);
*(.jcr)
. = ALIGN(4);
/* All data end */
__data_end__ = .;
} > RAM
.bss :
{
. = ALIGN(4);
__bss_start__ = .;
*(.bss*)
*(COMMON)
. = ALIGN(4);
__bss_end__ = .;
} > RAM
.heap (COPY):
{
__end__ = .;
end = __end__;
*(.heap*)
__HeapLimit = .;
} > RAM
/* .stack_dummy section doesn't contains any symbols. It is only
* used for linker to calculate size of stack sections, and assign
* values to stack symbols later */
.stack_dummy (COPY):
{
*(.stack*)
} > RAM
/* Set stack top to end of RAM, and stack limit move down by
* size of stack_dummy section */
__StackTop = ORIGIN(RAM) + LENGTH(RAM);
__StackLimit = __StackTop - SIZEOF(.stack_dummy);
PROVIDE(__stack = __StackTop);
/* Check if data + heap + stack exceeds RAM limit */
ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed with stack")
}
