Zephyr OS 汇编阶段是怎样的

今天就跟大家聊聊有关Zephyr OS 汇编阶段是怎样的，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。

Zephyr OS 内核篇：系统启动 - 汇编阶段

汇编阶段

/* * Copyright (c) 2013-2014 Wind River Systems, Inc. * * SPDX-License-Identifier: Apache-2.0 *//** * @file * @brief Reset handler * * Reset handler that prepares the system for running C code. */#include #include #include #include #include #include "vector_table.h"_ASM_FILE_PROLOGUEGTEXT(__reset)GTEXT(memset)GDATA(_interrupt_stack)/** * * @brief Reset vector * * Ran when the system comes out of reset. The processor is in thread mode with * privileged level. At this point, the main stack pointer (MSP) is already * pointing to a valid area in SRAM. * * Locking interrupts prevents anything but NMIs and hard faults from * interrupting the CPU. A default NMI handler is already in place in the * vector table, and the boot code should not generate hard fault, or we're in * deep trouble. * * We want to use the process stack pointer (PSP) instead of the MSP, since the * MSP is to be set up to point to the one-and-only interrupt stack during later * boot. That would not be possible if in use for running C code. * * When these steps are completed, jump to _PrepC(), which will finish setting * up the system for running C code. * * @return N/A */SECTION_SUBSEC_FUNC(TEXT,_reset_section,__reset)/* * The entry point is located at the __reset symbol, which * is fetched by a XIP image playing the role of a bootloader, which jumps to * it, not through the reset vector mechanism. Such bootloaders might want to * search for a __start symbol instead, so create that alias here. */SECTION_SUBSEC_FUNC(TEXT,_reset_section,__start)    /* lock interrupts: will get unlocked when switch to main task */#if defined(CONFIG_ARMV6_M)    cpsid i#elif defined(CONFIG_ARMV7_M)    /**     直接将中断优先级 _EXC_IRQ_DEFAULT_PRIO 写入中断屏蔽寄存器 BASEPRI     所有优先级高于 _EXC_IRQ_DEFAULT_PRIO 的中断都会被屏蔽    */    movs.n r0, #_EXC_IRQ_DEFAULT_PRIO    msr BASEPRI, r0#else#error Unknown ARM architecture#endif /* CONFIG_ARMV6_M */#ifdef CONFIG_WDOG_INIT    /* board-specific watchdog initialization is necessary */    bl _WdogInit#endif#ifdef CONFIG_INIT_STACKS    /**      初始化中断栈空间，在汇编里面使用寄存器传递参数，     r0 对应于 memset 的第一个参数     r1 对应于 memset 的第二个参数     r2 对应于 memset 的第三个参数     注意到，栈空间的初始化值是 0xaa，而不是 0x0。用于堆栈溢出检测    */    ldr r0, =_interrupt_stack    ldr r1, =0xaa    ldr r2, =CONFIG_ISR_STACK_SIZE    bl memset#endif    /*     * Set PSP and use it to boot without using MSP, so that it     * gets set to _interrupt_stack during nanoInit().     */    ldr r0, =_interrupt_stack    ldr r1, =CONFIG_ISR_STACK_SIZE    adds r0, r0, r1    msr PSP, r0    movs.n r0, #2 /* switch to using PSP (bit1 of CONTROL reg) */    msr CONTROL, r0    b _PrepC#if defined(CONFIG_SOC_TI_LM3S6965_QEMU)GTEXT(_do_software_reboot)SECTION_FUNC(TEXT,_do_software_reboot)        eors r0, r0        /* move exception table back to 0 */        ldr r1, =0xe000e000        str r0, [r1, #0xd08] /* VTOR */        ldr r0, [r0, #4]        bx r0GTEXT(_force_exit_one_nested_irq)SECTION_FUNC(TEXT,_force_exit_one_nested_irq)        ldr r0, =_SCS_ICSR_RETTOBASE        ldr r1, =_SCS_ICSR        ldr r1, [r1]        ands.w r0, r1        /*         *  If Z flag is set, we are nested, so un-nest one level and get back to         *  this function to unwind the next level; else, exit the last interrupt         *  by jumping to reboot code.         */        ittee eq                ldreq lr, =0xfffffff1                ldreq r2, =_force_exit_one_nested_irq                ldrne lr, =0xfffffffd                ldrne r2, =_do_software_reboot        ldr ip, =_interrupt_stack        add.w ip, #(___esf_t_SIZEOF * 2) /* enough for a stack frame */        ldr r1, =0xfffffffe        and.w r2, r1        str r2, [ip, #(6 * 4)]        ldr r2, =0x01000000        str r2, [ip, #(7 * 4)]        ite eq                moveq sp, ip                msrne PSP, ip        bx lr#endif

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