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深入解析单片机STM32启动文件的汇编语言实现

1.简介

以前讲了固件库，从ST官网下载的固件库里面，有许多的启动文件（汇编语言写的.s文件）

启动文件 说明
startup_stm32f10x_ld.s Low Density 小容量
startup_stm32f10x_md.s Medium Density 中容量
startup_stm32f10x_hd.s High Density 高容量
startup_stm32f10x_xl.s Extra Large Density 超大容量
startup_stm32f10x_cl.s Connectivity line devices
startup_stm32f10x_ld_vl.s Low Density Value Line Devices
startup_stm32f10x_md_vl.s Medium Density Value Line Devices
startup_stm32f10x_hd_vl.s High Density Value Line Devices

这里我们就直接复制了一份启动文件来讲解一下，代码如下

;******************** (C) COPYRIGHT 2011 STMicroelectronics ********************
;* File Name          : startup_stm32f10x_md.s
;* Author             : MCD Application Team
;* Version            : V3.5.1
;* Date               : 08-September-2021
;* Description        : STM32F10x Medium Density Devices vector table for MDK-ARM 
;*                      toolchain.  
;*                      This module performs:
;*                      - Set the initial SP
;*                      - Set the initial PC == Reset_Handler
;*                      - Set the vector table entries with the exceptions ISR address
;*                      - Configure the clock system
;*                      - Branches to __main in the C library (which eventually
;*                        calls main()).
;*                      After Reset the CortexM3 processor is in Thread mode,
;*                      priority is Privileged, and the Stack is set to Main.
;* <<< Use Configuration Wizard in Context Menu >>>   
;*******************************************************************************
;*
;* Copyright (c) 2011 STMicroelectronics.
;* All rights reserved.
;*
;* This software is licensed under terms that can be found in the LICENSE file
;* in the root directory of this software component.
;* If no LICENSE file comes with this software, it is provided AS-IS.
;
;*******************************************************************************

; Amount of memory (in bytes) allocated for Stack
; Tailor this value to your application needs
; <h> Stack Configuration
;   <o> Stack Size (in Bytes) <0x0-0xFFFFFFFF:8>
; </h>

Stack_Size      EQU     0x00000400

                AREA    STACK, NOINIT, READWRITE, ALIGN=3
Stack_Mem       SPACE   Stack_Size
__initial_sp


; <h> Heap Configuration
;   <o>  Heap Size (in Bytes) <0x0-0xFFFFFFFF:8>
; </h>

Heap_Size       EQU     0x00000200

                AREA    HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem        SPACE   Heap_Size
__heap_limit

                PRESERVE8
                THUMB


; Vector Table Mapped to Address 0 at Reset
                AREA    RESET, DATA, READONLY
                EXPORT  __Vectors
                EXPORT  __Vectors_End
                EXPORT  __Vectors_Size

__Vectors       DCD     __initial_sp               ; Top of Stack
                DCD     Reset_Handler              ; Reset Handler
                DCD     NMI_Handler                ; NMI Handler
                DCD     HardFault_Handler          ; Hard Fault Handler
                DCD     MemManage_Handler          ; MPU Fault Handler
                DCD     BusFault_Handler           ; Bus Fault Handler
                DCD     UsageFault_Handler         ; Usage Fault Handler
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     SVC_Handler                ; SVCall Handler
                DCD     DebugMon_Handler           ; Debug Monitor Handler
                DCD     0                          ; Reserved
                DCD     PendSV_Handler             ; PendSV Handler
                DCD     SysTick_Handler            ; SysTick Handler

                ; External Interrupts
                DCD     WWDG_IRQHandler            ; Window Watchdog
                DCD     PVD_IRQHandler             ; PVD through EXTI Line detect
                DCD     TAMPER_IRQHandler          ; Tamper
                DCD     RTC_IRQHandler             ; RTC
                DCD     FLASH_IRQHandler           ; Flash
                DCD     RCC_IRQHandler             ; RCC
                DCD     EXTI0_IRQHandler           ; EXTI Line 0
                DCD     EXTI1_IRQHandler           ; EXTI Line 1
                DCD     EXTI2_IRQHandler           ; EXTI Line 2
                DCD     EXTI3_IRQHandler           ; EXTI Line 3
                DCD     EXTI4_IRQHandler           ; EXTI Line 4
                DCD     DMA1_Channel1_IRQHandler   ; DMA1 Channel 1
                DCD     DMA1_Channel2_IRQHandler   ; DMA1 Channel 2
                DCD     DMA1_Channel3_IRQHandler   ; DMA1 Channel 3
                DCD     DMA1_Channel4_IRQHandler   ; DMA1 Channel 4
                DCD     DMA1_Channel5_IRQHandler   ; DMA1 Channel 5
                DCD     DMA1_Channel6_IRQHandler   ; DMA1 Channel 6
                DCD     DMA1_Channel7_IRQHandler   ; DMA1 Channel 7
                DCD     ADC1_2_IRQHandler          ; ADC1_2
                DCD     USB_HP_CAN1_TX_IRQHandler  ; USB High Priority or CAN1 TX
                DCD     USB_LP_CAN1_RX0_IRQHandler ; USB Low  Priority or CAN1 RX0
                DCD     CAN1_RX1_IRQHandler        ; CAN1 RX1
                DCD     CAN1_SCE_IRQHandler        ; CAN1 SCE
                DCD     EXTI9_5_IRQHandler         ; EXTI Line 9..5
                DCD     TIM1_BRK_IRQHandler        ; TIM1 Break
                DCD     TIM1_UP_IRQHandler         ; TIM1 Update
                DCD     TIM1_TRG_COM_IRQHandler    ; TIM1 Trigger and Commutation
                DCD     TIM1_CC_IRQHandler         ; TIM1 Capture Compare
                DCD     TIM2_IRQHandler            ; TIM2
                DCD     TIM3_IRQHandler            ; TIM3
                DCD     TIM4_IRQHandler            ; TIM4
                DCD     I2C1_EV_IRQHandler         ; I2C1 Event
                DCD     I2C1_ER_IRQHandler         ; I2C1 Error
                DCD     I2C2_EV_IRQHandler         ; I2C2 Event
                DCD     I2C2_ER_IRQHandler         ; I2C2 Error
                DCD     SPI1_IRQHandler            ; SPI1
                DCD     SPI2_IRQHandler            ; SPI2
                DCD     USART1_IRQHandler          ; USART1
                DCD     USART2_IRQHandler          ; USART2
                DCD     USART3_IRQHandler          ; USART3
                DCD     EXTI15_10_IRQHandler       ; EXTI Line 15..10
                DCD     RTCAlarm_IRQHandler        ; RTC Alarm through EXTI Line
                DCD     USBWakeUp_IRQHandler       ; USB Wakeup from suspend
__Vectors_End

__Vectors_Size  EQU  __Vectors_End - __Vectors

                AREA    |.text|, CODE, READONLY

; Reset handler
Reset_Handler    PROC
                 EXPORT  Reset_Handler             [WEAK]
     IMPORT  __main
     IMPORT  SystemInit
                 LDR     R0, =SystemInit
                 BLX     R0
                 LDR     R0, =__main
                 BX      R0
                 ENDP

; Dummy Exception Handlers (infinite loops which can be modified)

NMI_Handler     PROC
                EXPORT  NMI_Handler                [WEAK]
                B       .
                ENDP
HardFault_Handler\
                PROC
                EXPORT  HardFault_Handler          [WEAK]
                B       .
                ENDP
MemManage_Handler\
                PROC
                EXPORT  MemManage_Handler          [WEAK]
                B       .
                ENDP
BusFault_Handler\
                PROC
                EXPORT  BusFault_Handler           [WEAK]
                B       .
                ENDP
UsageFault_Handler\
                PROC
                EXPORT  UsageFault_Handler         [WEAK]
                B       .
                ENDP
SVC_Handler     PROC
                EXPORT  SVC_Handler                [WEAK]
                B       .
                ENDP
DebugMon_Handler\
                PROC
                EXPORT  DebugMon_Handler           [WEAK]
                B       .
                ENDP
PendSV_Handler  PROC
                EXPORT  PendSV_Handler             [WEAK]
                B       .
                ENDP
SysTick_Handler PROC
                EXPORT  SysTick_Handler            [WEAK]
                B       .
                ENDP

Default_Handler PROC

                EXPORT  WWDG_IRQHandler            [WEAK]
                EXPORT  PVD_IRQHandler             [WEAK]
                EXPORT  TAMPER_IRQHandler          [WEAK]
                EXPORT  RTC_IRQHandler             [WEAK]
                EXPORT  FLASH_IRQHandler           [WEAK]
                EXPORT  RCC_IRQHandler             [WEAK]
                EXPORT  EXTI0_IRQHandler           [WEAK]
                EXPORT  EXTI1_IRQHandler           [WEAK]
                EXPORT  EXTI2_IRQHandler           [WEAK]
                EXPORT  EXTI3_IRQHandler           [WEAK]
                EXPORT  EXTI4_IRQHandler           [WEAK]
                EXPORT  DMA1_Channel1_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel2_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel3_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel4_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel5_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel6_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel7_IRQHandler   [WEAK]
                EXPORT  ADC1_2_IRQHandler          [WEAK]
                EXPORT  USB_HP_CAN1_TX_IRQHandler  [WEAK]
                EXPORT  USB_LP_CAN1_RX0_IRQHandler [WEAK]
                EXPORT  CAN1_RX1_IRQHandler        [WEAK]
                EXPORT  CAN1_SCE_IRQHandler        [WEAK]
                EXPORT  EXTI9_5_IRQHandler         [WEAK]
                EXPORT  TIM1_BRK_IRQHandler        [WEAK]
                EXPORT  TIM1_UP_IRQHandler         [WEAK]
                EXPORT  TIM1_TRG_COM_IRQHandler    [WEAK]
                EXPORT  TIM1_CC_IRQHandler         [WEAK]
                EXPORT  TIM2_IRQHandler            [WEAK]
                EXPORT  TIM3_IRQHandler            [WEAK]
                EXPORT  TIM4_IRQHandler            [WEAK]
                EXPORT  I2C1_EV_IRQHandler         [WEAK]
                EXPORT  I2C1_ER_IRQHandler         [WEAK]
                EXPORT  I2C2_EV_IRQHandler         [WEAK]
                EXPORT  I2C2_ER_IRQHandler         [WEAK]
                EXPORT  SPI1_IRQHandler            [WEAK]
                EXPORT  SPI2_IRQHandler            [WEAK]
                EXPORT  USART1_IRQHandler          [WEAK]
                EXPORT  USART2_IRQHandler          [WEAK]
                EXPORT  USART3_IRQHandler          [WEAK]
                EXPORT  EXTI15_10_IRQHandler       [WEAK]
                EXPORT  RTCAlarm_IRQHandler        [WEAK]
                EXPORT  USBWakeUp_IRQHandler       [WEAK]

WWDG_IRQHandler
PVD_IRQHandler
TAMPER_IRQHandler
RTC_IRQHandler
FLASH_IRQHandler
RCC_IRQHandler
EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
DMA1_Channel1_IRQHandler
DMA1_Channel2_IRQHandler
DMA1_Channel3_IRQHandler
DMA1_Channel4_IRQHandler
DMA1_Channel5_IRQHandler
DMA1_Channel6_IRQHandler
DMA1_Channel7_IRQHandler
ADC1_2_IRQHandler
USB_HP_CAN1_TX_IRQHandler
USB_LP_CAN1_RX0_IRQHandler
CAN1_RX1_IRQHandler
CAN1_SCE_IRQHandler
EXTI9_5_IRQHandler
TIM1_BRK_IRQHandler
TIM1_UP_IRQHandler
TIM1_TRG_COM_IRQHandler
TIM1_CC_IRQHandler
TIM2_IRQHandler
TIM3_IRQHandler
TIM4_IRQHandler
I2C1_EV_IRQHandler
I2C1_ER_IRQHandler
I2C2_EV_IRQHandler
I2C2_ER_IRQHandler
SPI1_IRQHandler
SPI2_IRQHandler
USART1_IRQHandler
USART2_IRQHandler
USART3_IRQHandler
EXTI15_10_IRQHandler
RTCAlarm_IRQHandler
USBWakeUp_IRQHandler

                B       .

                ENDP

                ALIGN

;*******************************************************************************
; User Stack and Heap initialization
;*******************************************************************************
                 IF      :DEF:__MICROLIB           
                
                 EXPORT  __initial_sp
                 EXPORT  __heap_base
                 EXPORT  __heap_limit
                
                 ELSE
                
                 IMPORT  __use_two_region_memory
                 EXPORT  __user_initial_stackheap
                 
__user_initial_stackheap

                 LDR     R0, =  Heap_Mem
                 LDR     R1, =(Stack_Mem + Stack_Size)
                 LDR     R2, = (Heap_Mem +  Heap_Size)
                 LDR     R3, = Stack_Mem
                 BX      LR

                 ALIGN

                 ENDIF

                 END

看见那么长的代码，不用慌，其实开头部分的注释就说明了，这个启动文件就做了如下的几个主要功能

This module performs:
- Set the initial SP                    //设置初始化堆栈空间
- Set the initial PC == Reset_Handler   //设置PC指针
- Set the vector table entries with the exceptions ISR address              //设置中断向量表
    - Configure the clock system                                            //设置系统时钟
    - Branches to __main in the C library (which eventually calls main()).  //进入C语言 main()

1.设置堆空间

Stack_Size      EQU     0x00000400                          ;定义Stack_Size 为 0x00000400 （1KB）

                AREA    STACK, NOINIT, READWRITE, ALIGN=3   ;定义一块的数据段或代码段，段名为STACK，不初始化，可读可写，8字节对齐
Stack_Mem       SPACE   Stack_Size                          ;分配一块名叫Stack_Mem空间，大小为Stack_Size（1KB），并初始化
__initial_sp                                                ;紧挨SPACE语句，表示栈的结束地址，即栈顶地址

EQU

伪指令的作用类似于 C 语言中的#define 用于为一个常量定义名称

指令格式：name EQU expr{,type}

name：要定义的常量的名称

expr：基于寄存器的地址值，程序中的标号，32位地址常量或32位常量

type：当expr为32位常量时，可用type指示expr表示的数据类型。如 CODE16、CODE32、DATA

AREA

伪指令用于定义一个代码段或数据段

指令格式：AREA section_name｛,attr｝{,attr}…

section_name：所定义的代码段或数据段的名称。
如果该名称是以数据开头的，则该名称必须用“|”括起来，如|1_datasec|。
还有一些代码段具有的约定的名称，如|text|表示C语言编译器产生的代码段或者与C语言库相关的代码段。

attr：该代码段或数据段的属性
属性 说明
DATA 定义为数据段
DODE 定义为代码段
NOINIT 本数据段仅仅保留了内存单元，而没有将各初始指写入内存单元，或者将内存单元值初始化为0
READONLY 指定本段为只读，代码段的默认属性为 READONLY
READWRITE 指定本段为可读可写，数据段的默认属性为 READWRITE
ALIGN = expr 默认的情况下，ELF的代码段和数据段是4字节对齐的，expr可以取0~31的数值，相应的对齐方为2expr字节对齐。如expr=3时为23 = 8字节对齐。对于代码段，expr不能为0或1

SPACE

用于分配一块内存单元，并用 0 初始化

指令格式：{label} SPACE expr

label：内存块起始地址标号

expr：所要分配的内存字节数

标号

__initial_sp 为标号

标号的使用取决于程序的需要，但是不被汇编程序识别，与指令系统无关。

有点类似于C语言中的goto语句中的标号，做为一个偏移。

2.设置栈空间

Heap_Size       EQU     0x00000200                          ;Heap_Size 为 0x00000200 （512B）

                AREA    HEAP, NOINIT, READWRITE, ALIGN=3    ;定义一块的数据段或代码段，段名为HEAP，不初始化，可读可写，8字节对齐
__heap_base                                                 ;堆的起始地址
Heap_Mem        SPACE   Heap_Size                           ;分配一块名叫Heap_Mem空间，大小为Heap_Size（1KB），并初始化
__heap_limit                                                ;堆的结束地址

                PRESERVE8                                   ;当前堆栈保持8字节对齐
                THUMB                                       ;兼容THUMB指令

PRESERVE8

伪指令指示当前文件保持堆栈为 8 字节对齐

THUMB

表示后面指令兼容THUMB指令。

THUBM 是ARM以前的指令集，16bit

THUMB-2 是现在Cortex-M系列的都使用指令集，32bit

THUMB 是兼容16位和32位的指令的超集

3.设置向量表

    AREA    RESET, DATA, READONLY   ;定义一块的数据段，段名为RESET，只读
    EXPORT  __Vectors               ;声明全局变量__Vectors
    EXPORT  __Vectors_End           ;声明全局变量__Vectors_End
    EXPORT  __Vectors_Size          ;声明全局变量__Vectors_Size

EXPORT

声明一个符号可以被其它文件引用，相当于声明了一个全局变量

指令格式：EXPORT symbol{[WEAK]}

symbol：要声明的符号名称
[WEAK]：声明优先使用其它的同名符

__Vectors       DCD     __initial_sp               ; Top of Stack 栈顶地址
                DCD     Reset_Handler              ; Reset Handler 默认程序上电复位从这里开始执行
                DCD     NMI_Handler                ; NMI Handler
                DCD     HardFault_Handler          ; Hard Fault Handler
                DCD     MemManage_Handler          ; MPU Fault Handler
                DCD     BusFault_Handler           ; Bus Fault Handler
                DCD     UsageFault_Handler         ; Usage Fault Handler
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     SVC_Handler                ; SVCall Handler
                DCD     DebugMon_Handler           ; Debug Monitor Handler
                DCD     0                          ; Reserved
                DCD     PendSV_Handler             ; PendSV Handler
                DCD     SysTick_Handler            ; SysTick Handler

                ; External Interrupts
                DCD     WWDG_IRQHandler            ; Window Watchdog
                DCD     PVD_IRQHandler             ; PVD through EXTI Line detect
                DCD     TAMPER_IRQHandler          ; Tamper
                DCD     RTC_IRQHandler             ; RTC
                DCD     FLASH_IRQHandler           ; Flash
                DCD     RCC_IRQHandler             ; RCC
                DCD     EXTI0_IRQHandler           ; EXTI Line 0
                DCD     EXTI1_IRQHandler           ; EXTI Line 1
                DCD     EXTI2_IRQHandler           ; EXTI Line 2
                DCD     EXTI3_IRQHandler           ; EXTI Line 3
                DCD     EXTI4_IRQHandler           ; EXTI Line 4
                DCD     DMA1_Channel1_IRQHandler   ; DMA1 Channel 1
                DCD     DMA1_Channel2_IRQHandler   ; DMA1 Channel 2
                DCD     DMA1_Channel3_IRQHandler   ; DMA1 Channel 3
                DCD     DMA1_Channel4_IRQHandler   ; DMA1 Channel 4
                DCD     DMA1_Channel5_IRQHandler   ; DMA1 Channel 5
                DCD     DMA1_Channel6_IRQHandler   ; DMA1 Channel 6
                DCD     DMA1_Channel7_IRQHandler   ; DMA1 Channel 7
                DCD     ADC1_2_IRQHandler          ; ADC1_2
                DCD     USB_HP_CAN1_TX_IRQHandler  ; USB High Priority or CAN1 TX
                DCD     USB_LP_CAN1_RX0_IRQHandler ; USB Low  Priority or CAN1 RX0
                DCD     CAN1_RX1_IRQHandler        ; CAN1 RX1
                DCD     CAN1_SCE_IRQHandler        ; CAN1 SCE
                DCD     EXTI9_5_IRQHandler         ; EXTI Line 9..5
                DCD     TIM1_BRK_IRQHandler        ; TIM1 Break
                DCD     TIM1_UP_IRQHandler         ; TIM1 Update
                DCD     TIM1_TRG_COM_IRQHandler    ; TIM1 Trigger and Commutation
                DCD     TIM1_CC_IRQHandler         ; TIM1 Capture Compare
                DCD     TIM2_IRQHandler            ; TIM2
                DCD     TIM3_IRQHandler            ; TIM3
                DCD     TIM4_IRQHandler            ; TIM4
                DCD     I2C1_EV_IRQHandler         ; I2C1 Event
                DCD     I2C1_ER_IRQHandler         ; I2C1 Error
                DCD     I2C2_EV_IRQHandler         ; I2C2 Event
                DCD     I2C2_ER_IRQHandler         ; I2C2 Error
                DCD     SPI1_IRQHandler            ; SPI1
                DCD     SPI2_IRQHandler            ; SPI2
                DCD     USART1_IRQHandler          ; USART1
                DCD     USART2_IRQHandler          ; USART2
                DCD     USART3_IRQHandler          ; USART3
                DCD     EXTI15_10_IRQHandler       ; EXTI Line 15..10
                DCD     RTCAlarm_IRQHandler        ; RTC Alarm through EXTI Line
                DCD     USBWakeUp_IRQHandler       ; USB Wakeup from suspend
__Vectors_End

__Vectors_Size  EQU  __Vectors_End - __Vectors

                AREA    |.text|, CODE, READONLY     ;定义一块的代码段，段名为|.text|，只读

当内核响应了一个发生的异常后，对应的异常服务程序就会被执行。为了决定异常服务程序的入口地址，内核就会使用向量表的方式查询，就像一个指针数组，每个下标表示一个异常，里面的值就是程序地址。因为复位后，寄存器的值为0，所以在0x0000 0000需要一张向量表，决定程序下一步的跳转，所以该表映射在0x0000 0000地址上

DCD

伪指令，用于分配一段字内存单元，并用伪指令中的expr初始化，分配的内存需要字对齐，一般可用来定义数据表格或其它常数

指令格式：{label} DCD expr{,expr}{,expr}…

label：内存块起始地址标号. 
expr：常数表达式或程序中的标号，内存分配字节数由expr个数决定

4.复位程序

Reset_Handler    PROC
                 EXPORT  Reset_Handler             [WEAK]   ;弱定义全局变量，如其他地方有定义，则不执行这个
     IMPORT  __main                                         ;告诉编译器，外部定义了这个__main
     IMPORT  SystemInit                                     ;告诉编译器，外部定义了这个SystemInit
                 LDR     R0, =SystemInit                    ;加载SystemInit程序地址到R0寄存器
                 BLX     R0                                 ;跳转到R0地址上执行程序
                 LDR     R0, =__main                        ;加载main程序地址到R0寄存器
                 BX      R0                                 ;跳转到R0地址上执行程序
                 ENDP

PROC ENDP

proc endp是定义子程序的伪指令，分别表示子程序定义的开始和结束两者必须成对出现。类似于C语言的｛｝

IMPORT

伪指令指示编译器当前的符号不是在本文件中定义的，而是在其他源文件中定义的，在本源文件中可能引用该符号。类似于C语言的外部声明extern

LDR

加载指令

指令格式：LDR{cond} Rd,<地址>

加载指定地址上的数据(字),放入Rd中

BLX

跳转指令

指令格式：BLX{cond} Rm

跳转到Rm指定的地址执行程序，并根据寄存器LES确定处理器状态，调整前把下条指令地址保存到LR

BX

跳转指令

指令格式：BX{cond} Rm

带状态切换的跳转指令，跳转到Rm指定的地址执行程序

5.中断服务

NMI_Handler     PROC
                EXPORT  NMI_Handler                [WEAK]
                B       .
                ENDP
HardFault_Handler\
                PROC
                EXPORT  HardFault_Handler          [WEAK]
                B       .
                ENDP
MemManage_Handler\
                PROC
                EXPORT  MemManage_Handler          [WEAK]
                B       .
                ENDP
BusFault_Handler\
                PROC
                EXPORT  BusFault_Handler           [WEAK]
                B       .
                ENDP
UsageFault_Handler\
                PROC
                EXPORT  UsageFault_Handler         [WEAK]
                B       .
                ENDP
SVC_Handler     PROC
                EXPORT  SVC_Handler                [WEAK]
                B       .
                ENDP
DebugMon_Handler\
                PROC
                EXPORT  DebugMon_Handler           [WEAK]
                B       .
                ENDP
PendSV_Handler  PROC
                EXPORT  PendSV_Handler             [WEAK]
                B       .
                ENDP
SysTick_Handler PROC
                EXPORT  SysTick_Handler            [WEAK]
                B       .
                ENDP

Default_Handler PROC

                EXPORT  WWDG_IRQHandler            [WEAK]
                EXPORT  PVD_IRQHandler             [WEAK]
                EXPORT  TAMPER_IRQHandler          [WEAK]
                EXPORT  RTC_IRQHandler             [WEAK]
                EXPORT  FLASH_IRQHandler           [WEAK]
                EXPORT  RCC_IRQHandler             [WEAK]
                EXPORT  EXTI0_IRQHandler           [WEAK]
                EXPORT  EXTI1_IRQHandler           [WEAK]
                EXPORT  EXTI2_IRQHandler           [WEAK]
                EXPORT  EXTI3_IRQHandler           [WEAK]
                EXPORT  EXTI4_IRQHandler           [WEAK]
                EXPORT  DMA1_Channel1_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel2_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel3_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel4_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel5_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel6_IRQHandler   [WEAK]
                EXPORT  DMA1_Channel7_IRQHandler   [WEAK]
                EXPORT  ADC1_2_IRQHandler          [WEAK]
                EXPORT  USB_HP_CAN1_TX_IRQHandler  [WEAK]
                EXPORT  USB_LP_CAN1_RX0_IRQHandler [WEAK]
                EXPORT  CAN1_RX1_IRQHandler        [WEAK]
                EXPORT  CAN1_SCE_IRQHandler        [WEAK]
                EXPORT  EXTI9_5_IRQHandler         [WEAK]
                EXPORT  TIM1_BRK_IRQHandler        [WEAK]
                EXPORT  TIM1_UP_IRQHandler         [WEAK]
                EXPORT  TIM1_TRG_COM_IRQHandler    [WEAK]
                EXPORT  TIM1_CC_IRQHandler         [WEAK]
                EXPORT  TIM2_IRQHandler            [WEAK]
                EXPORT  TIM3_IRQHandler            [WEAK]
                EXPORT  TIM4_IRQHandler            [WEAK]
                EXPORT  I2C1_EV_IRQHandler         [WEAK]
                EXPORT  I2C1_ER_IRQHandler         [WEAK]
                EXPORT  I2C2_EV_IRQHandler         [WEAK]
                EXPORT  I2C2_ER_IRQHandler         [WEAK]
                EXPORT  SPI1_IRQHandler            [WEAK]
                EXPORT  SPI2_IRQHandler            [WEAK]
                EXPORT  USART1_IRQHandler          [WEAK]
                EXPORT  USART2_IRQHandler          [WEAK]
                EXPORT  USART3_IRQHandler          [WEAK]
                EXPORT  EXTI15_10_IRQHandler       [WEAK]
                EXPORT  RTCAlarm_IRQHandler        [WEAK]
                EXPORT  USBWakeUp_IRQHandler       [WEAK]

WWDG_IRQHandler
PVD_IRQHandler
TAMPER_IRQHandler
RTC_IRQHandler
FLASH_IRQHandler
RCC_IRQHandler
EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
DMA1_Channel1_IRQHandler
DMA1_Channel2_IRQHandler
DMA1_Channel3_IRQHandler
DMA1_Channel4_IRQHandler
DMA1_Channel5_IRQHandler
DMA1_Channel6_IRQHandler
DMA1_Channel7_IRQHandler
ADC1_2_IRQHandler
USB_HP_CAN1_TX_IRQHandler
USB_LP_CAN1_RX0_IRQHandler
CAN1_RX1_IRQHandler
CAN1_SCE_IRQHandler
EXTI9_5_IRQHandler
TIM1_BRK_IRQHandler
TIM1_UP_IRQHandler
TIM1_TRG_COM_IRQHandler
TIM1_CC_IRQHandler
TIM2_IRQHandler
TIM3_IRQHandler
TIM4_IRQHandler
I2C1_EV_IRQHandler
I2C1_ER_IRQHandler
I2C2_EV_IRQHandler
I2C2_ER_IRQHandler
SPI1_IRQHandler
SPI2_IRQHandler
USART1_IRQHandler
USART2_IRQHandler
USART3_IRQHandler
EXTI15_10_IRQHandler
RTCAlarm_IRQHandler
USBWakeUp_IRQHandler

                B       .

                ENDP

                ALIGN

和复位程序相比，可知启动文件里面的这些中断复位程序都是空的，而真正相关的中断复位程序是需要我们在外部C文件编写实现的，如果外部没有实现相应的中断复位，发生了相关中断就会跳转这些空程序，循环死在这里

B

跳转指令，跳转到指定的地址执行程序

指令格式：B{cond} label

cond：条件

label：地址

6.堆栈初始化

 IF      :DEF:__MICROLIB                        ;同C语言的if
                
                 EXPORT  __initial_sp           ;声明全局变量__initial_sp
                 EXPORT  __heap_base            ;声明全局变量__heap_base
                 EXPORT  __heap_limit           ;声明全局变量__heap_limit
                
                 ELSE                           ;同C语言的else
                
                 IMPORT  __use_two_region_memory    ;外部定义__use_two_region_memory
                 EXPORT  __user_initial_stackheap   ;声明全局变量__user_initial_stackheap
                 
__user_initial_stackheap                                ;标号

                 LDR     R0, =  Heap_Mem                ;加载Heap_Mem到R0
                 LDR     R1, =(Stack_Mem + Stack_Size)  ;加载(Stack_Mem + Stack_Size)到R1
                 LDR     R2, = (Heap_Mem +  Heap_Size)  ;加载(Heap_Mem +  Heap_Size)到R2
                 LDR     R3, = Stack_Mem                ;加载Stack_Mem到R3
                 BX      LR                             ;跳转到LR寄存器

                 ALIGN                                  ;对齐

                 ENDIF                                  ;同C语言的endif

                 END                                    ;伪指令表示汇编源文件已结束

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