layout: post
tags: [STM32]
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文章目录
前言
这里以stm32f103为硬件平台，搭建了stm32f1系列的标准库，版本是V3.5,在路径标准库的源码路径下LibrariesCMSISCM3DeviceSupportSTSTM32F10xstartup包含了各个编译器或者说IDE的启动文件：
这些IDE分别是arm，gcc_ride7,iar,TrueSTUDIO,不过这不是关注的重点，本文主要分析startup_stm32f10x_md.s。
分析startup_stm32f10x_md.s
首先看一下arm文件夹下的文件，具体如下；
-ar--- 2011/3/10 10:52 15766 startup_stm32f10x_cl.s
-ar--- 2011/3/10 10:52 15503 startup_stm32f10x_hd.s
-ar--- 2011/3/10 10:52 15692 startup_stm32f10x_hd_vl.s
-ar--- 2011/3/10 10:52 12376 startup_stm32f10x_ld.s
-ar--- 2011/3/10 10:52 13656 startup_stm32f10x_ld_vl.s
-ar--- 2011/3/10 10:52 12765 startup_stm32f10x_md.s
-ar--- 2011/3/10 10:51 14073 startup_stm32f10x_md_vl.s
-ar--- 2011/3/10 10:51 15955 startup_stm32f10x_xl.s
这里可以看到文件最终加以区分的是xl,md_vl,md等等，这些需要根据芯片具体的容量不同进行选择；
下面看一下startup_stm32f10x_md.s的汇编代码另外一般用户的代码都是从main()函数开始的，但是在此之前，则有启动代码初始化化硬件环境，然后跳转到 c runtime lib的__main中，进行运行环境的初始化，包括栈，堆等等，最终跳转到用户的main函数中。这里没有找到c runtime lib的源码，着实有点遗憾。
在分析源码之前，有必要对部分汇编指令进行简单的了解，这里参考了《Cortex_M3权威指南》
汇编指令
EQU
将一个变量赋值，例如：Stack_Size EQU 0x00000400|
AREA
用于定义一个代码段或数据段,具体用法如：AREA 段名称 {,参数1} {,参数2}...
SPACE
用于申请一片内存空间但不赋初值，例如：Stack_Mem SPACE 0x00000400,分配1024字节的内存控制，感觉相当于malloc，Stack_Mem应该会该内存空间的首地址；
DCD
用于分配一片连续的字存储单元并用伪指令中指定的表达式初始化
PROC
该伪指令用于定义子程序，位置在子程序的开始处，它和ENDP分别表示子程序定义的开始和结束两者必须成对出现;
LDR
从存储器中加载字到一个寄存器中，Load Data to Register
常见的转移指令
B Label跳转到 Label 处对应的地址BX reg跳转到由寄存器 reg 给出的地址BL Label跳转到 Label 对应的地址，并且把跳转前的下条指令地址保存到 LRBLX reg跳转到由寄存器reg给出的地址，并根据 REG 的 LSB 切换处理器状态，还要把转移前的下条指令地址保存到 LR
LR（Link Register），连接寄存器的英文缩写，在ARM体系结构中LR的特殊用途有两种：
一是用来保存子程序返回地址；
二是当异常发生时，LR中保存的值等于异常发生时PC的值减4（或者减2），因此在各种异常模式下可以根据LR的值返回到异常发生前的相应位置继续执行。
源码分析
下面参考一下startup_stm32f10x_md.s的源码，进行分析一下。
;******************** (C) COPYRIGHT 2011 STMicroelectronics ********************
;* File Name : startup_stm32f10x_md.s
;* Author : MCD Application Team
;* Version : V3.5.0
;* Date : 11-March-2011
;* 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 >>>
;*******************************************************************************
; THE PRESENT FIRMWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS
; WITH CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE TIME.
; AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY DIRECT,
; INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING FROM THE
; CONTENT OF SUCH FIRMWARE AND/OR THE USE MADE BY CUSTOMERS OF THE CODING
; INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.
;*******************************************************************************
; 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 ;栈空间 1024 Bytes，1K的空间
;分配数据段，命名为`STACK`,数据段未初始化,可以读写
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 ;堆空间的配置，512 字节的空间
AREA HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem SPACE Heap_Size ;分配堆空间为 512字节
__heap_limit
PRESERVE8
THUMB
; Vector Table Mapped to Address 0 at Reset
;向量表映射到地址0x00000000
AREA RESET, DATA, READONLY
EXPORT __Vectors ;导出__Vectors符号，用于外部文件的使用
EXPORT __Vectors_End ;导出向量表的结束地址
EXPORT __Vectors_Size ;导出向量表的大小
;使用DCD为__initial_sp以及异常地址分配内存空间，存到向量表中
__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
; 外设的中断地址
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 ; 计算向量表大小
AREA |.text|, CODE, READONLY ; 分配代码段，只读
; 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)
; [WEAK]指令会优先使用外部的链接符号，但是没有原型，编译器也不会出现报错
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
;******************* (C) COPYRIGHT 2011 STMicroelectronics *****END OF FILE*****
主要做了这几个事情：
- 初始化堆栈内存空间；
- 设置
PC寄存器的地址指向Reset_Handler,即上电便运行复位程序； - 设置向量表，中断服务程序入口地址；
- 配置系统时钟,
SystemInit在main函数运行前就已经运行了； - 运行外部的函数，
LDR R0, =__main，将__main地址装载到R0寄存器并运行，__main在C库中，会初始化程序的C运行环境，最终调用用户的main函数；