MK64FN1M0xxx12_flash.ld链接文件解析

1.前言

本文主要对MK64FN1M0xxx12_flash.ld文件进行分析，以此来加深对链接文件的理解

2.文件详解

/*
** ###################################################################
**     Processors:          MK64FN1M0CAJ12
**                          MK64FN1M0VDC12
**                          MK64FN1M0VLL12
**                          MK64FN1M0VLQ12
**                          MK64FN1M0VMD12
**
**     Compiler:            GNU C Compiler
**     Reference manual:    K64P144M120SF5RM, Rev.2, January 2014
**     Version:             rev. 2.9, 2016-03-21
**     Build:               b170817
**
**     Abstract:
**         Linker file for the GNU C Compiler
**
**     Copyright 2016 Freescale Semiconductor, Inc.
**     Copyright 2016-2017 NXP
**     Redistribution and use in source and binary forms, with or without modification,
**     are permitted provided that the following conditions are met:
**
**     1. Redistributions of source code must retain the above copyright notice, this list
**       of conditions and the following disclaimer.
**
**     2. Redistributions in binary form must reproduce the above copyright notice, this
**       list of conditions and the following disclaimer in the documentation and/or
**       other materials provided with the distribution.
**
**     3. Neither the name of the copyright holder nor the names of its
**       contributors may be used to endorse or promote products derived from this
**       software without specific prior written permission.
**
**     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
**     ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
**     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
**     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
**     ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
**     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
**     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
**     ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
**     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
**     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
**
**     http:                 www.nxp.com
**     mail:                 support@nxp.com
**
** ###################################################################
*/

/* Entry Point */
NOTE:程序中第一条运行的指令被称为入口点entry point,可以使用ENTRY链接脚本命令设置entry point，参数是一个符号名：

有几种方法可以设置entry point,链接器会按照如下的顺序来try各种方法，只要任何一种方法成功则会停止：

• the ‘-e’ entry command-line option;
• the ENTRY(symbol) command in a linker script;
• the value of the symbol start, if defined;
• the address of the first byte of the ‘.text’ section, if present;
• The address 0

ENTRY(Reset_Handler)
/*

DEFINED(symbol)用于判断symbol在符号表中是否有定义，如果有定义则返回1否则返回0

*/ 
HEAP_SIZE = DEFINED(__heap_size__) ? __heap_size__ : 0x0400; STACK_SIZE = DEFINED(__stack_size__) ? __stack_size__ : 0x0400; /* Specify the memory areas */

/*定义内存区域的起始地址和长度*/
MEMORY
{
  m_interrupts          (RX)  : ORIGIN = 0x00000000, LENGTH = 0x00000400
  m_flash_config        (RX)  : ORIGIN = 0x00000400, LENGTH = 0x00000010
  m_text                (RX)  : ORIGIN = 0x00000410, LENGTH = 0x000FFBF0
  m_data                (RW)  : ORIGIN = 0x1FFF0000, LENGTH = 0x00010000
  m_data_2              (RW)  : ORIGIN = 0x20000000, LENGTH = 0x00030000
}

/* Define output sections */
SECTIONS
{
  /* The startup code goes first into internal flash */
  .interrupts :
  {
    . = ALIGN();
/*

isr_vector在start.S中定义：.section .isr_vector, "a"，按照MEMORY命令说明，isr_vector由于没有指定输出section,因此会创建与输入section同名的输出section，且会按照

isr_vector的属性放到合适的内存区域，此处KEEP是保证isr_vector的输出section不会被删除

*/
    KEEP(*(.isr_vector))     /* Startup code */
    . = ALIGN();
  } > m_interrupts

  .flash_config :
  {
    . = ALIGN();
    KEEP(*(.FlashConfig))    /* Flash Configuration Field (FCF) */
    . = ALIGN();
  } > m_flash_config

  /* The program code and other data goes into internal flash */
  .text :
  {
    . = ALIGN();
    *(.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();
  } > m_text

  .ARM.extab :
  {
    *(.ARM.extab* .gnu.linkonce.armextab.*)
  } > m_text

  .ARM :
  {
    __exidx_start = .;
    *(.ARM.exidx*)
    __exidx_end = .;
  } > m_text

 .ctors :
  {
    __CTOR_LIST__ = .;
    /* gcc uses crtbegin.o to find the start of
       the constructors, so we make sure it is
       first.  Because this is a wildcard, it
       doesn't matter if the user does not
       actually link against crtbegin.o; the
       linker won't look for a file to match a
       wildcard.  The wildcard also means that it
       doesn't matter which directory crtbegin.o
       is in.  */
    KEEP (*crtbegin.o(.ctors))
    KEEP (*crtbegin?.o(.ctors))
    /* We don't want to include the .ctor section from
       from the crtend.o file until after the sorted ctors.
       The .ctor section from the crtend file contains the
       end of ctors marker and it must be last */
    KEEP (*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors))
    KEEP (*(SORT(.ctors.*)))
    KEEP (*(.ctors))
    __CTOR_END__ = .;
  } > m_text

  .dtors :
  {
    __DTOR_LIST__ = .;
    KEEP (*crtbegin.o(.dtors))
    KEEP (*crtbegin?.o(.dtors))
    KEEP (*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors))
    KEEP (*(SORT(.dtors.*)))
    KEEP (*(.dtors))
    __DTOR_END__ = .;
  } > m_text

  .preinit_array :
  {
    PROVIDE_HIDDEN (__preinit_array_start = .);
    KEEP (*(.preinit_array*))
    PROVIDE_HIDDEN (__preinit_array_end = .);
  } > m_text

  .init_array :
  {
    PROVIDE_HIDDEN (__init_array_start = .);
    KEEP (*(SORT(.init_array.*)))
    KEEP (*(.init_array*))
    PROVIDE_HIDDEN (__init_array_end = .);
  } > m_text

  .fini_array :
  {
    PROVIDE_HIDDEN (__fini_array_start = .);
    KEEP (*(SORT(.fini_array.*)))
    KEEP (*(.fini_array*))
    PROVIDE_HIDDEN (__fini_array_end = .);
  } > m_text

  __etext = .;    /* define a global symbol at end of code */
  __DATA_ROM = .; /* Symbol is used by startup for data initialization */

  .data : AT(__DATA_ROM)
  {
    . = ALIGN();
    __DATA_RAM = .;
    __data_start__ = .;      /* create a global symbol at data start */
    *(.data)                 /* .data sections */
    *(.data*)                /* .data* sections */
    KEEP(*(.jcr*))
    . = ALIGN();
    __data_end__ = .;        /* define a global symbol at data end */
  } > m_data

  __DATA_END = __DATA_ROM + (__data_end__ - __data_start__);
  text_end = ORIGIN(m_text) + LENGTH(m_text);
  ASSERT(__DATA_END <= text_end, "region m_text overflowed with text and data")

  /* Uninitialized data section */
  .bss :
  {
    /* This is used by the startup in order to initialize the .bss section */
    . = ALIGN();
    __START_BSS = .;
    __bss_start__ = .;
    *(.bss)
    *(.bss*)
    *(COMMON)
    . = ALIGN();
    __bss_end__ = .;
    __END_BSS = .;
  } > m_data

  .heap :
  {
    . = ALIGN();
    __end__ = .;
    PROVIDE(end = .);
    __HeapBase = .;
    . += HEAP_SIZE;
    __HeapLimit = .;
    __heap_limit = .; /* Add for _sbrk */
  } > m_data_2

  .stack :
  {
    . = ALIGN();
    . += STACK_SIZE;
  } > m_data_2

  /* Initializes stack on the end of block */
  __StackTop   = ORIGIN(m_data_2) + LENGTH(m_data_2);
  __StackLimit = __StackTop - STACK_SIZE;
  PROVIDE(__stack = __StackTop);

  .ARM.attributes  : { *(.ARM.attributes) }

  ASSERT(__StackLimit >= __HeapLimit, "region m_data_2 overflowed with stack and heap")
}