FreeRTOS 第二课：启动文件分析_freertos vector table

1. 简介：

对 stm32f103 工程的分析，需要从启动文件开始

2. 固件库中 stm32f103 的启动文件：

文件的名字：startup_stm32f10xhd.s 

前边是段的声明

    MODULE  ?cstartup
        
        ;; Forward declaration of sections.
        SECTION CSTACK:DATA:NOROOT(3)

        SECTION .intvec:CODE:NOROOT(2)

        EXTERN  __iar_program_start
        EXTERN  SystemInit        
        PUBLIC  __vector_table

【1】MODULE 控制指令是用来标记 modules 源码的开始和结束，后边的 ?cstartup 是模块的名字，此文档的最后的 END 表明模块的结束

【2】SECTION 指令是声明段，一个段不能同时包含 public symbol 和 pubweak symbol ，模块只有在相同的名字的模块没有被链接进来的时候才会被链接进来。

    语法格式：SECTION section:type [flag] [(align)]

        align，是用于指定地址对齐到 2^align，他的取值是 0 到 30

        flag，取值NOROOT、ROOT、REORDER、NOREORDER，默认是ROOT，NOROOT表示如果这个段中的符号没有被引用，将会被连接器舍弃，即可被优化。ROOT表示不可被优化。REORDER表示开始一个新的名字是 section 的段（section），NOREORDER表示开始一个新的名字为 section 的片段（fragment），多个片段组成一个段（section）

        type，memory 的类型，取值是 CODE、CONST、DATA

        section，段的名字

【3】EXTERN 用导入其他模块的 symbol（符号）

【4】PUBLIC 导出 symbol（符号）

        DATA
       
__vector_table
        DCD     sfe(CSTACK)
        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 & ADC2
        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
        DCD     TIM8_BRK_IRQHandler       ; TIM8 Break
        DCD     TIM8_UP_IRQHandler        ; TIM8 Update
        DCD     TIM8_TRG_COM_IRQHandler   ; TIM8 Trigger and Commutation
        DCD     TIM8_CC_IRQHandler        ; TIM8 Capture Compare
        DCD     ADC3_IRQHandler           ; ADC3
        DCD     FSMC_IRQHandler           ; FSMC
        DCD     SDIO_IRQHandler           ; SDIO
        DCD     TIM5_IRQHandler           ; TIM5
        DCD     SPI3_IRQHandler           ; SPI3
        DCD     UART4_IRQHandler          ; UART4
        DCD     UART5_IRQHandler          ; UART5
        DCD     TIM6_IRQHandler           ; TIM6
        DCD     TIM7_IRQHandler           ; TIM7
        DCD     DMA2_Channel1_IRQHandler  ; DMA2 Channel1
        DCD     DMA2_Channel2_IRQHandler  ; DMA2 Channel2
        DCD     DMA2_Channel3_IRQHandler  ; DMA2 Channel3
        DCD     DMA2_Channel4_5_IRQHandler ; DMA2 Channel4 & Channel5
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

【1】DATA 表示下边中的标签是 32 位的标签，THUMB 表示下边的标签是 16 位的标签，所谓的标签是 地址的别名，不占用代码空间，给编译器看的

【2】 DCD 是数据定义或者 重定位指令，为的是定义一个值，或者保留 memory，DCD 别名是 DC32，用于声明一个 32 位的常量，这部分是中断向量表的内容，需要注意的是，他们的顺序不能改变，此部分会放到 flash 的最开始部分，当系统启动的时候会加载前另个地址，第一个地址是 c 程序的栈的栈顶地址，第二个地址是向量表的开始地址，中断发生时会根据向量表的首地址和偏移量来找到程序的入口

【3】sfe 指令作用是返回栈的结尾，因为栈的增长方向是反方向的

;;
;; Default interrupt handlers.
;;
        THUMB

        PUBWEAK Reset_Handler
        SECTION .text:CODE:REORDER(2)
Reset_Handler
        LDR     R0, =SystemInit
        BLX     R0
        LDR     R0, =__iar_program_start
        BX      R0
               
        PUBWEAK NMI_Handler
        SECTION .text:CODE:REORDER(1)
NMI_Handler
        B NMI_Handler

        PUBWEAK HardFault_Handler
        SECTION .text:CODE:REORDER(1)
HardFault_Handler
        B HardFault_Handler

        PUBWEAK MemManage_Handler
        SECTION .text:CODE:REORDER(1)
MemManage_Handler
        B MemManage_Handler

        PUBWEAK BusFault_Handler
        SECTION .text:CODE:REORDER(1)
BusFault_Handler
        B BusFault_Handler

        PUBWEAK UsageFault_Handler
        SECTION .text:CODE:REORDER(1)
UsageFault_Handler
        B UsageFault_Handler

        PUBWEAK SVC_Handler
        SECTION .text:CODE:REORDER(1)
SVC_Handler
        B SVC_Handler

        PUBWEAK DebugMon_Handler
        SECTION .text:CODE:REORDER(1)
DebugMon_Handler
        B DebugMon_Handler

        PUBWEAK PendSV_Handler
        SECTION .text:CODE:REORDER(1)
PendSV_Handler
        B PendSV_Handler

        PUBWEAK SysTick_Handler
        SECTION .text:CODE:REORDER(1)
SysTick_Handler
        B SysTick_Handler

        PUBWEAK WWDG_IRQHandler
        SECTION .text:CODE:REORDER(1)
WWDG_IRQHandler
        B WWDG_IRQHandler

        PUBWEAK PVD_IRQHandler
        SECTION .text:CODE:REORDER(1)
PVD_IRQHandler
        B PVD_IRQHandler

        PUBWEAK TAMPER_IRQHandler
        SECTION .text:CODE:REORDER(1)
TAMPER_IRQHandler
        B TAMPER_IRQHandler

        PUBWEAK RTC_IRQHandler
        SECTION .text:CODE:REORDER(1)
RTC_IRQHandler
        B RTC_IRQHandler

        PUBWEAK FLASH_IRQHandler
        SECTION .text:CODE:REORDER(1)
FLASH_IRQHandler
        B FLASH_IRQHandler

        PUBWEAK RCC_IRQHandler
        SECTION .text:CODE:REORDER(1)
RCC_IRQHandler
        B RCC_IRQHandler

        PUBWEAK EXTI0_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI0_IRQHandler
        B EXTI0_IRQHandler

        PUBWEAK EXTI1_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI1_IRQHandler
        B EXTI1_IRQHandler

        PUBWEAK EXTI2_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI2_IRQHandler
        B EXTI2_IRQHandler

        PUBWEAK EXTI3_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI3_IRQHandler
        B EXTI3_IRQHandler

        PUBWEAK EXTI4_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI4_IRQHandler
        B EXTI4_IRQHandler

        PUBWEAK DMA1_Channel1_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel1_IRQHandler
        B DMA1_Channel1_IRQHandler

        PUBWEAK DMA1_Channel2_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel2_IRQHandler
        B DMA1_Channel2_IRQHandler

        PUBWEAK DMA1_Channel3_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel3_IRQHandler
        B DMA1_Channel3_IRQHandler

        PUBWEAK DMA1_Channel4_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel4_IRQHandler
        B DMA1_Channel4_IRQHandler

        PUBWEAK DMA1_Channel5_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel5_IRQHandler
        B DMA1_Channel5_IRQHandler

        PUBWEAK DMA1_Channel6_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel6_IRQHandler
        B DMA1_Channel6_IRQHandler

        PUBWEAK DMA1_Channel7_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA1_Channel7_IRQHandler
        B DMA1_Channel7_IRQHandler

        PUBWEAK ADC1_2_IRQHandler
        SECTION .text:CODE:REORDER(1)
ADC1_2_IRQHandler
        B ADC1_2_IRQHandler

        PUBWEAK USB_HP_CAN1_TX_IRQHandler
        SECTION .text:CODE:REORDER(1)
USB_HP_CAN1_TX_IRQHandler
        B USB_HP_CAN1_TX_IRQHandler

        PUBWEAK USB_LP_CAN1_RX0_IRQHandler
        SECTION .text:CODE:REORDER(1)
USB_LP_CAN1_RX0_IRQHandler
        B USB_LP_CAN1_RX0_IRQHandler

        PUBWEAK CAN1_RX1_IRQHandler
        SECTION .text:CODE:REORDER(1)
CAN1_RX1_IRQHandler
        B CAN1_RX1_IRQHandler

        PUBWEAK CAN1_SCE_IRQHandler
        SECTION .text:CODE:REORDER(1)
CAN1_SCE_IRQHandler
        B CAN1_SCE_IRQHandler

        PUBWEAK EXTI9_5_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI9_5_IRQHandler
        B EXTI9_5_IRQHandler

        PUBWEAK TIM1_BRK_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM1_BRK_IRQHandler
        B TIM1_BRK_IRQHandler

        PUBWEAK TIM1_UP_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM1_UP_IRQHandler
        B TIM1_UP_IRQHandler

        PUBWEAK TIM1_TRG_COM_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM1_TRG_COM_IRQHandler
        B TIM1_TRG_COM_IRQHandler

        PUBWEAK TIM1_CC_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM1_CC_IRQHandler
        B TIM1_CC_IRQHandler

        PUBWEAK TIM2_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM2_IRQHandler
        B TIM2_IRQHandler

        PUBWEAK TIM3_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM3_IRQHandler
        B TIM3_IRQHandler

        PUBWEAK TIM4_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM4_IRQHandler
        B TIM4_IRQHandler

        PUBWEAK I2C1_EV_IRQHandler
        SECTION .text:CODE:REORDER(1)
I2C1_EV_IRQHandler
        B I2C1_EV_IRQHandler

        PUBWEAK I2C1_ER_IRQHandler
        SECTION .text:CODE:REORDER(1)
I2C1_ER_IRQHandler
        B I2C1_ER_IRQHandler

        PUBWEAK I2C2_EV_IRQHandler
        SECTION .text:CODE:REORDER(1)
I2C2_EV_IRQHandler
        B I2C2_EV_IRQHandler

        PUBWEAK I2C2_ER_IRQHandler
        SECTION .text:CODE:REORDER(1)
I2C2_ER_IRQHandler
        B I2C2_ER_IRQHandler

        PUBWEAK SPI1_IRQHandler
        SECTION .text:CODE:REORDER(1)
SPI1_IRQHandler
        B SPI1_IRQHandler

        PUBWEAK SPI2_IRQHandler
        SECTION .text:CODE:REORDER(1)
SPI2_IRQHandler
        B SPI2_IRQHandler

        PUBWEAK USART1_IRQHandler
        SECTION .text:CODE:REORDER(1)
USART1_IRQHandler
        B USART1_IRQHandler

        PUBWEAK USART2_IRQHandler
        SECTION .text:CODE:REORDER(1)
USART2_IRQHandler
        B USART2_IRQHandler

        PUBWEAK USART3_IRQHandler
        SECTION .text:CODE:REORDER(1)
USART3_IRQHandler
        B USART3_IRQHandler

        PUBWEAK EXTI15_10_IRQHandler
        SECTION .text:CODE:REORDER(1)
EXTI15_10_IRQHandler
        B EXTI15_10_IRQHandler

        PUBWEAK RTCAlarm_IRQHandler
        SECTION .text:CODE:REORDER(1)
RTCAlarm_IRQHandler
        B RTCAlarm_IRQHandler

        PUBWEAK USBWakeUp_IRQHandler
        SECTION .text:CODE:REORDER(1)
USBWakeUp_IRQHandler
        B USBWakeUp_IRQHandler

        PUBWEAK TIM8_BRK_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM8_BRK_IRQHandler
        B TIM8_BRK_IRQHandler

        PUBWEAK TIM8_UP_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM8_UP_IRQHandler
        B TIM8_UP_IRQHandler

        PUBWEAK TIM8_TRG_COM_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM8_TRG_COM_IRQHandler
        B TIM8_TRG_COM_IRQHandler

        PUBWEAK TIM8_CC_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM8_CC_IRQHandler
        B TIM8_CC_IRQHandler

        PUBWEAK ADC3_IRQHandler
        SECTION .text:CODE:REORDER(1)
ADC3_IRQHandler
        B ADC3_IRQHandler

        PUBWEAK FSMC_IRQHandler
        SECTION .text:CODE:REORDER(1)
FSMC_IRQHandler
        B FSMC_IRQHandler

        PUBWEAK SDIO_IRQHandler
        SECTION .text:CODE:REORDER(1)
SDIO_IRQHandler
        B SDIO_IRQHandler

        PUBWEAK TIM5_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM5_IRQHandler
        B TIM5_IRQHandler

        PUBWEAK SPI3_IRQHandler
        SECTION .text:CODE:REORDER(1)
SPI3_IRQHandler
        B SPI3_IRQHandler

        PUBWEAK UART4_IRQHandler
        SECTION .text:CODE:REORDER(1)
UART4_IRQHandler
        B UART4_IRQHandler

        PUBWEAK UART5_IRQHandler
        SECTION .text:CODE:REORDER(1)
UART5_IRQHandler
        B UART5_IRQHandler

        PUBWEAK TIM6_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM6_IRQHandler
        B TIM6_IRQHandler

        PUBWEAK TIM7_IRQHandler
        SECTION .text:CODE:REORDER(1)
TIM7_IRQHandler
        B TIM7_IRQHandler

        PUBWEAK DMA2_Channel1_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA2_Channel1_IRQHandler
        B DMA2_Channel1_IRQHandler

        PUBWEAK DMA2_Channel2_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA2_Channel2_IRQHandler
        B DMA2_Channel2_IRQHandler

        PUBWEAK DMA2_Channel3_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA2_Channel3_IRQHandler
        B DMA2_Channel3_IRQHandler

        PUBWEAK DMA2_Channel4_5_IRQHandler
        SECTION .text:CODE:REORDER(1)
DMA2_Channel4_5_IRQHandler
        B DMA2_Channel4_5_IRQHandler
        
        
        END

【1】THUMB 表明下边是 thumb 指令

【2】Reset_Handler 在开机或者复位的时候执行

    R0 = SystemInit

    跳转到 SystemInit 函数，并将处理器切换到 thumb 状态

    R0 = __iar_program_start

    跳转到 __iar_program_start 函数，状态也是切换到 thumb 状态

【3】此处的 __iar_program_start 在程序中找不到是因为它已经被封装到了 IAR 自带的C库启动代码中了，当我们编译的时候，在项目属性的 linker，library中勾选了 Automatic runtime library ，就告诉了编译器用库中的 __iar_program_start ，具体实现了什么，我们可以查看 IAR 工具为我们提供的源码，具体路径在 IAR 安装目录下的 arm\src\lib\thumb ，我们可以看到有的文件分别的提供了 汇编代码和 c 代码。

其中的 cstartup_M.s 文件中有

#pragma required=__vector_table
void __iar_program_start( void )
{
  __iar_init_core();
  __iar_init_vfp();
  __cmain();
}

【1】此段的程序中前两个函数是弱函数，在工程共没有定义

【2】__cmain 函数作用是初始化段和底层硬件，最后调用main

至此，库文件中的启动文件先分析到这里

3. FreeRTOS 中的汇编代码：

当 FreeRTOS 和 stm32 移植好后，会用到 FreeRTOS 中的源码文件 portasm.s 中的函数

xPortPendSVHandler 函数：

xPortPendSVHandler:
	mrs r0, psp
	isb
	ldr	r3, =pxCurrentTCB  /* 获取当前任务的控制块（TCB）指针. */
	ldr	r2, [r3]

	stmdb r0!, {r4-r11}  /* 保存 R4-R11 到该任务的堆栈. */
	str r0, [r2]	     /* 将最后的堆栈指针保存到任务控制块的 pxTopOfStack. */

	stmdb sp!, {r3, r14}
	mov r0, #configMAX_SYSCALL_INTERRUPT_PRIORITY /* 关闭中断 */
	msr basepri, r0
	dsb
	isb
	bl vTaskSwitchContext /* 切换任务上下文，pxCurrentTCB 已指向新的任务 */
	mov r0, #0
	msr basepri, r0
	ldmia sp!, {r3, r14}

	ldr r1, [r3]  /* 恢复新任务的上下文到各寄存器 */
	ldr r0, [r1]		/* The first item in pxCurrentTCB is the task top of stack. */
	ldmia r0!, {r4-r11}	/* Pop the registers. */
	msr psp, r0
	isb
	bx r14

【1】这个函数的功能是请求切换任务

【2】任务切换的示意图如下：

vPortSVCHandler 函数：直接切换任务用于vPortStartFirstTask第一次启动任务时初始化堆栈和各寄存器

vPortSVCHandler:
	/* Get the location of the current TCB. */
	ldr	r3, =pxCurrentTCB
	ldr r1, [r3]
	ldr r0, [r1]
	/* Pop the core registers. */
	ldmia r0!, {r4-r11}
	msr psp, r0
	isb
	mov r0, #0
	msr	basepri, r0
	orr r14, r14, #13
	bx r14

函数：启动第一个任务的汇编实现

vPortStartFirstTask
	/* Use the NVIC offset register to locate the stack. */
	ldr r0, =0xE000ED08 /* 向量表偏移量寄存器 (VTOR) */
	ldr r0, [r0]
	ldr r0, [r0]
	/* Set the msp back to the start of the stack. */
	msr msp, r0 /* 将堆栈地址保存到主堆栈指针msp中 */
	/* Call SVC to start the first task, ensuring interrupts are enabled. */
	cpsie i /* 触发SVC软中断，由vPortSVCHandler()完成第一个任务的具体切换工作 */
	cpsie f
	dsb
	isb
	svc 0

【1】此部分参照 (伟研科技 http://www.gzweiyan.com) 资料

【2】内核调度器启动的流程如下：