使用LiteOS Studio揭秘LiteOS在STM32上如何运行

Reset_Handler:
  cpsid i
  ldr   sp, =_estack      /* set stack pointer */
/* Copy the vector_ram segment initializers from flash to SRAM */
  movs  r1, #0
  b  LoopCopyVectorInit
CopyVectorInit:
  ldr   r3, =_si_liteos_vector_data
  ldr   r3, [r3, r1]
  str   r3, [r0, r1]
  adds   r1, r1, #4
LoopCopyVectorInit:
  ldr   r0, =_s_liteos_vector
  ldr   r3, =_e_liteos_vector
  adds   r2, r0, r1
  cmp   r2, r3
  bcc   CopyVectorInit
/* Copy the data segment initializers from flash to SRAM */
  movs  r1, #0
  b  LoopCopyDataInit
CopyDataInit:
  ldr  r3, =_sidata
  ldr  r3, [r3, r1]
  str  r3, [r0, r1]
  adds  r1, r1, #4
LoopCopyDataInit:
  ldr  r0, =_sdata
  ldr  r3, =_edata
  adds  r2, r0, r1
  cmp  r2, r3
  bcc  CopyDataInit
  ldr  r2, =_sbss
  b  LoopFillZerobss
/* Zero fill the bss segment. */
FillZerobss:
  movs  r3, #0
  str  r3, [r2], #4
LoopFillZerobss:
  ldr  r3, = _ebss
  cmp  r2, r3
  bcc  FillZerobss
/* Call the clock system initialization function.*/
  bl  SystemInit
/* Call static constructors */
/*    bl __libc_init_array */
/* Call the application's entry point.*/
  bl  main
  bx  lr

INT32 main(VOID)
{
    HardwareInit();
    PRINT_RELEASE("\n********Hello Huawei LiteOS********\n"
                  "\nLiteOS Kernel Version : %s\n"
                  "build data : %s %s\n\n"
                  "**********************************\n",
                  HW_LITEOS_KERNEL_VERSION_STRING, __DATE__, __TIME__);
    UINT32 ret = OsMain();
    if (ret != LOS_OK) {
        return LOS_NOK;
    }
    OsStart();
    return 0;
}

LITE_OS_SEC_TEXT_INIT UINT32 OsMain(VOID)
{
    UINT32 ret;
#ifdef LOSCFG_EXC_INTERACTION
    ret = OsMemExcInteractionInit((UINTPTR)&__bss_end);
    if (ret != LOS_OK) {
        return ret;
    }
#endif
    /* 初始化动态内存池 */
    ret = OsMemSystemInit((UINTPTR)&__bss_end + g_excInteractMemSize);
    if (ret != LOS_OK) {
        return ret;
    }
    /*
     * 配置最大支持的任务个数、信号量个数、互斥锁个数、
     * 队列个数以及软件定时器个数，设置g_sysClock和
     * g_tickPerSecond全局变量
     */
    OsRegister();
#ifdef LOSCFG_SHELL_LK
    OsLkLoggerInit(NULL);
#endif
#ifdef LOSCFG_SHELL_DMESG
    ret = OsDmesgInit();
    if (ret != LOS_OK) {
        return ret;
    }
#endif
/*
 * 初始化硬中断，此后LiteOS就会接管系统的中断，
 * 使用中断前需要先注册中断并使能
 */
    OsHwiInit();
    /*
     * 设置中断向量的中断处理函数，包括
     * Hard Fault硬件故障中断、
     * Non Maskable Interrupt不可屏蔽中断（NMI）、
     * Memory Management内存管理中断、
     * Bus Fault 总线故障中断、
     * Usage Fault使用故障中断、
     * SVCall利用SVC指令调用系统服务的中断
     */
    ArchExcInit();
    ret = OsTickInit(GET_SYS_CLOCK(), LOSCFG_BASE_CORE_TICK_PER_SECOND);
    if (ret != LOS_OK) {
        return ret;
    }
#ifdef LOSCFG_PLATFORM_UART_WITHOUT_VFS
    uart_init();
#ifdef LOSCFG_SHELL
    extern int uart_hwiCreate(void); /* HuaWeiChange */
    uart_hwiCreate();
#endif /* LOSCFG_SHELL */
#endif /* LOSCFG_PLATFORM_UART_WITHOUT_VFS */
    /*
     * 初始化任务链表包括任务的排序链表，
     * 初始化优先级消息队列链表（用于管理不同优先级任务）
     */
    ret = OsTaskInit();
    if (ret != LOS_OK) {
        PRINT_ERR("OsTaskInit error\n");
        return ret;
    }
#ifdef LOSCFG_KERNEL_TRACE
    ret = LOS_TraceInit(NULL, LOS_TRACE_BUFFER_SIZE);
    if (ret != LOS_OK) {
        PRINT_ERR("LOS_TraceInit error\n");
        return ret;
    }
#endif
/*
 * 初始化任务监视器
 */
#ifdef LOSCFG_BASE_CORE_TSK_MONITOR
    OsTaskMonInit();
#endif
/*
 * OsIpcInit包括初始化消息队列链表、互斥锁链表和信号量链表
 */
    ret = OsIpcInit();
    if (ret != LOS_OK) {
        return ret;
    }
    /*
     * CPUP should be inited before first task creation which depends on the semaphore
     * when LOSCFG_KERNEL_SMP_TASK_SYNC is enabled. So don't change this init sequence
     * if not necessary. The sequence should be like this:
     * 1. OsIpcInit
     * 2. OsCpupInit -> has first task creation
     * 3. other inits have task creation
     */
#ifdef LOSCFG_KERNEL_CPUP
    ret = OsCpupInit();
    if (ret != LOS_OK) {
        PRINT_ERR("OsCpupInit error\n");
        return ret;
    }
#endif
/*
 * OsSwtmrInit对软件定时器和其在percpu上的排序链表进行初始化，
 * 并初始化定期器处理函数的内存池，同时还会创建软件定时器
 * 的消息队列和定时器任务
 */
#ifdef LOSCFG_BASE_CORE_SWTMR
    ret = OsSwtmrInit();
    if (ret != LOS_OK) {
        return ret;
    }
#endif
#ifdef LOSCFG_KERNEL_SMP
    (VOID)OsMpInit();
#endif
#ifdef LOSCFG_KERNEL_DYNLOAD
    ret = OsDynloadInit();
    if (ret != LOS_OK) {
        return ret;
    }
#endif
#if defined(LOSCFG_HW_RANDOM_ENABLE) || defined (LOSCFG_DRIVERS_RANDOM)
    random_alg_context.ra_init_alg(NULL);
    run_harvester_iterate(NULL);
#endif
/* 创建空闲任务 */
    ret = OsIdleTaskCreate();
    if (ret != LOS_OK) {
        return ret;
    }
#ifdef LOSCFG_KERNEL_RUNSTOP
    ret = OsWowWriteFlashTaskCreate();
    if (ret != LOS_OK) {
        return ret;
    }
#endif
#ifdef LOSCFG_DRIVERS_BASE
    ret = OsDriverBaseInit();
    if (ret != LOS_OK) {
        return ret;
    }
#ifdef LOSCFG_COMPAT_LINUX
    (VOID)do_initCalls(LEVEL_ARCH);
#endif
#endif
#ifdef LOSCFG_KERNEL_PERF
    ret = LOS_PerfInit(NULL, LOS_PERF_BUFFER_SIZE);
    if (ret != LOS_OK) {
        return ret;
    }
#endif
/*
 * LOSCFG_PLATFORM_OSAPPINIT宏默认已经在.config、menuconfig.h中定义。
 * OsAppInit创建了一个名为“app_Task”的任务，该任务处理函数为
 * app_init，任务优先级为10；
 * OsTestInit创建了一个名为“IT_TST_IN”的任务，该任务处理函数为
 * TestTaskEntry，任务优先级为25。该函数暂时没有开源。
 */
#ifdef LOSCFG_PLATFORM_OSAPPINIT
    ret = osAppInit();
#else /* LOSCFG_TEST */
    ret = OsTestInit();
#endif
    if (ret != LOS_OK) {
        return ret;
    }

    return LOS_OK;
}

LITE_OS_SEC_TEXT_INIT VOID OsStart(VOID)
{
    LosTaskCB *taskCB = NULL;
 /* 获取当前执行任务的CPU ID，STM32F769是单核芯片，cpuid为0 */
    UINT32 cpuid = ArchCurrCpuid();
    /*
     * 配置Tick中断向量，其中断处理函数为OsTickHandler。
     * 初始化System Tick Timer及其中断，并启动此Timer。
     * 计数器会产生周期性中断
     */ 
    OsTickStart();
    LOS_SpinLock(&g_taskSpin);
    /* 获取最高优先级任务队列中的第一个任务，赋给taskCB */
    taskCB = OsGetTopTask();
#ifdef LOSCFG_KERNEL_SMP
    /*
     * attention: current cpu needs to be set, in case first task deletion
     * may fail because this flag mismatch with the real current cpu.
     */
    taskCB->currCpu = (UINT16)cpuid;
#endif
    /* 设置32位的调度flag，第CPU ID位设置为1 */
    OS_SCHEDULER_SET(cpuid);
    PRINTK("cpu %u entering scheduler\n", cpuid);
    /*
     * 调度g_runTask即taskCB任务，OsStartToRun函数
     * 定义在los_dispatch.S汇编文件中
     */
    OsStartToRun(taskCB);
}