ARM 链接脚本分析
分析连接脚本的语法规则
/* ----------------------------------------------------------------------------
* Memory linker description
* ------------------------------------------------------------------------- */
MEMORY
{
/* ROM区，只读， 起始地址0x00000000, 长度4K */
ROM (r) : ORIGIN = 0x00000000, LENGTH = 4K
/* FLASH区， 读，写，可执行， 起始地址0x00100000, 长度380K*/
FLASH (xrw) : ORIGIN = 0x00100000, LENGTH = 380K
/* PRAM , 32K */
PRAM (xrw) : ORIGIN = 0x00200000, LENGTH = 32K
DRAM (xrw) : ORIGIN = 0x20000000, LENGTH = 24K
DRAM_DSP (xrw) : ORIGIN = 0x20006000, LENGTH = 48K
DRAM_BB (xrw) : ORIGIN = 0x20012000, LENGTH = 16K
}
/* ----------------------------------------------------------------------------
* Stack related defines and provided variables
* ------------------------------------------------------------------------- */
/* 计算stack的地址 */
__stack = ORIGIN(DRAM) + LENGTH(DRAM);
/* 全局变量__stack, c语言可以应用 */
PROVIDE ( __stack = __stack ) ;
/*
* Default stack sizes.
* These are used by the startup in order to allocate stacks
* for the different modes.
*/
__Main_Stack_Size = 1024 ;
PROVIDE ( _Main_Stack_Size = __Main_Stack_Size ) ;
__Main_Stack_Limit = __stack - __Main_Stack_Size ;
PROVIDE ( _Main_Stack_Limit = __Main_Stack_Limit ) ;
/* ----------------------------------------------------------------------------
* Heap related defines and provided variables
* ------------------------------------------------------------------------- */
PROVIDE ( __Heap_Begin__ = __noinit_end__ ) ;
PROVIDE ( __Heap_Limit__ = __stack - __Main_Stack_Size ) ;
/*
* The entry point is informative, for debuggers and simulators,
* since the Cortex-M vector points to it anyway.
*/
/* 指定可执行文件的起始代码段是Reset_Handler */
ENTRY(Reset_Handler)
/*
* As is the VTOR register, we refer to it in startup documentation
*/
__VTOR = 0xE000ED08;
/* ----------------------------------------------------------------------------
* Section definitions
* ------------------------------------------------------------------------- */
SECTIONS
{
/*
* For Cortex-M devices, the beginning of the startup code is stored in
* the .interrupt_vector section, which goes to FLASH
*/
/* DEFINED判断括号内的__app_rom_start，是否在全局符号表内，并且定义了，是就返回1，否返回0
* 再根据DEFINED结果进行判断__rom_start的值，是__app_rom_start，还是ORIGIN(FLASH)
*/
__rom_start = DEFINED(__app_rom_start) ? __app_rom_start : ORIGIN(FLASH);
/* 计算image的大小 */
__image_size = __data_init__ + SIZEOF(.data) - __rom_start;
/* .text代码段, 保存在FLASH中，FLASH起始地址0x0010000*/
.text __rom_start :
{
/* 四字节对齐 */
. = ALIGN(4);
/* 强制链接器保留一些特定的section */
KEEP(*(.interrupt_vector))
/*
* This section is here to store the startup code immediately after
* the interrupt vectors, as required by the program ROM.
*/
/* 所有文件的reset段，都放在interrupt_vector段后面 */
*(.reset)
/*
* FOTA BootLoader descriptor
*/
*(.rodata.fota.image-size)
KEEP(*(.rodata.fota.build-id))
/*
* FOTA version descriptor
*/
/* 所有的.rodata.boot.version section 放到.text section里面*/
*(.rodata.boot.version)
/* Pre-initialization Code */
. = ALIGN(4);
PROVIDE_HIDDEN (__preinit_array_start__ = .);
/* System initialization and the platform initialization (if present)
* should be first */
KEEP(*(.preinit_array_sysinit .preinit_array_sysinit.*))
KEEP(*(.preinit_array_platform .preinit_array_platform.*))
/* Pre-initialization functions (to be executed before C++
* constructors are run) */
KEEP(*(.preinit_array .preinit_array.*))
PROVIDE_HIDDEN (__preinit_array_end__ = .);
/* Initialization Code */
. = ALIGN(4);
PROVIDE_HIDDEN (__init_array_start__ = .);
KEEP(*(SORT(.init_array.*)))
KEEP(*(.init_array))
PROVIDE_HIDDEN (__init_array_end__ = .);
/*
* The program code is stored in the .text section,
* which goes to FLASH.
*/
. = ALIGN(4);
/* 所有的文件的.text section*/
*(.text .text.*) /* all remaining code */
/* 所有文件的.rodata section */
*(.rodata .rodata.*) /* read-only data (constants) */
. = ALIGN(4);
__dsp_start__ = . ;
KEEP(*(.dsp .dsp.*)) /* all remaining DSP code */
__dsp_end__ = . ;
/* 四字节对齐 */
. = ALIGN(4);
/* .text全部链接到FLASH里面,Flash是前面MEMORY里面定义的，起始地址是0x00100000 */
} >FLASH
/*
* This address is used by the startup code to
* initialize the .data section.
*/
. = ALIGN(4);
/* 将定位符号'.'的值赋给__data_init */
/* 也就是说__data_init__放在.text段的后面 */
__data_init__ = .;
/* Place the SystemClock variable needed for CMSIS in a place that is
* compatible with the ROM's placement of this variable so that the
* variable can be used by CMSIS and the ROM's flash write libary */
.systemclock (NOLOAD) :
{
. = ALIGN(4);
KEEP(*(.systemclock))
/* 保存到DRAM中 */
} > DRAM
/*
* 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.
*/
/* 查看__app_ram_start是否定义，并给__ram_start赋值 */
__ram_start = DEFINED(__app_ram_start) ? __app_ram_start : .;
/* .data数据段 */
/* AT表示加载地址或者存储地址,指程序编译之后存放的地址,一般在ROM或者FLASH中 */
/* 运行的时候，从AT指定的地址__data_init__中赋值到_ram_start中运行 */
/* 从FLASH中复制到RAM里面运行 */
.data __ram_start : AT ( __data_init__ )
{
. = ALIGN(4);
/* This is used by the startup code to initialize the .data section */
__data_start__ = . ;
*(.data_begin .data_begin.*)
*(.data .data.*)
*(.data_end .data_end.*)
. = ALIGN(4);
/* This is used by the startup code to initialize the .data section */
__data_end__ = . ;
} >DRAM
/*
* The uninitialized data section. NOLOAD is used to avoid
* the "section `.bss' type changed to PROGBITS" warning
*/
/* .bss未初始化的数据段, 存放在DRAM中 */
.bss (NOLOAD) :
{
. = ALIGN(4);
__bss_start__ = .; // 把__bss_start_段赋值当前位置，bss段的起始位置
*(.bss_begin .bss_begin.*) // 所有的bss_begin和bss_begin.*段放到bss里面
*(.bss .bss.*) // 所有文件的.bss和.bss.*段放在bss_begin，bss_begin.*后面
*(COMMON) // COMMON放在.bss，.bss.*后面
*(.bss_end .bss_end.*) // 所有文件的.bss_end, .bss_end.* 放在COMMON后面
. = ALIGN(4);
__bss_end__ = .; // 把__bss_end__段赋值为当前位置，结束位置
} >DRAM
.noinit (NOLOAD) :
{
. = ALIGN(4);
__noinit_start__ = .;
*(.noinit .noinit.*)
. = ALIGN(4) ;
__noinit_end__ = .;
} > DRAM
/* Check if there is enough space to allocate the main stack */
._stack (NOLOAD) :
{
. = ALIGN(4);
. = . + __Main_Stack_Size ; // 计算栈的大小放到DRAM中
. = ALIGN(4);
} >DRAM
}
