Kernel启动流程源码解析 6 setup_arch

一 setup_arch

setup_arch顾名思义就是架构相关的初始化函数，这里选取arm64结构进行分析。

1.0 setup_arch

定义在arch/arm64/kernel/setup.c中

void __init setup_arch(char **cmdline_p)

{

    setup_processor(); // 检测处理器类型,并初始化处理器相关的底层变量

    setup_machine_fdt(__fdt_pointer); // 获取device tree信息，并设置一些device tree相关全局变量信息

    init_mm.start_code = (unsigned long) _text; // 记录kernel代码段的虚拟启始地址

    init_mm.end_code   = (unsigned long) _etext; // 记录kernel代码段的虚拟结束地址

    init_mm.end_data   = (unsigned long) _edata; // 记录kernel数据段的虚拟结束地址

    init_mm.brk       = (unsigned long) _end; // brk指向kernel全部段的虚拟结束地址

    *cmdline_p = boot_command_line; // 将boot_command_line的地址保存到start_kernel局部指针变量cmdline_p中

    parse_early_param(); // 解析需要'早期'处理的启动参数用

    arm64_memblock_init(); // 初始化memblock，用于引导阶段的内存管理

    paging_init(); // 初始化分页机制

    request_standard_resources(); // 申请内核代码段和数据段内存资源

    unflatten_device_tree(); // DTB转换成节点是device_node的树状结构

    psci_init(); // Power State Coordination Interface，和多核启动相关，暂时没有用到

    cpu_logical_map(0) = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;

    cpu_read_bootcpu_ops(); // 获取cpu0的enable method

#ifdef CONFIG_SMP

    smp_init_cpus(); // 获取除cpu0外的其他cpu信息，并将它们设为possible状态

    smp_build_mpidr_hash(); // 生成MPIDR（cpu id） hash

#endif

#ifdef CONFIG_VT // 虚拟终端

#if defined(CONFIG_VGA_CONSOLE)

    conswitchp = &vga_con;

#elif defined(CONFIG_DUMMY_CONSOLE)

    conswitchp = &dummy_con;

#endif

#endif

}

1.1 setup_processor

定义在arch/arm64/kernel/setup.c中

static void __init setup_processor(void)

{

    struct cpu_info *cpu_info;

    /*

     * locate processor in the list of supported processor

     * types.  The linker builds this table for us from the

     * entries in arch/arm/mm/proc.S

     */

    cpu_info = lookup_processor_type(read_cpuid_id());

    if (!cpu_info) {

        printk("CPU configuration botched (ID %08x), unable to continue.\n",

               read_cpuid_id());

        while (1);

    }

    cpu_name = cpu_info->cpu_name;

    printk("CPU: %s [%08x] revision %d\n",

           cpu_name, read_cpuid_id(), read_cpuid_id() & 15);

    sprintf(init_utsname()->machine, "aarch64");

    elf_hwcap = 0;

}

struct cpu_info cpu_table[] = {

    {

        .cpu_id_val = 0x000f0000,

        .cpu_id_mask    = 0x000f0000,

        .cpu_name   = "AArch64 Processor",

        .cpu_setup  = __cpu_setup,

    },

    { /* Empty */ },

};

1.2 setup_machine_fdt

定义在arch/arm64/kernel/setup.c中

static void __init setup_machine_fdt(phys_addr_t dt_phys)

{

    struct boot_param_header *devtree;

    unsigned long dt_root;

    /* Check we have a non-NULL DT pointer */

    if (!dt_phys) {

        early_print("\n"

            "Error: NULL or invalid device tree blob\n"

            "The dtb must be 8-byte aligned and passed in the first 512MB of memory\n"

            "\nPlease check your bootloader.\n");

        while (true)

            cpu_relax();

    }

    devtree = phys_to_virt(dt_phys);

    /* Check device tree validity */

    if (be32_to_cpu(devtree->magic) != OF_DT_HEADER) {

        early_print("\n"

            "Error: invalid device tree blob at physical address 0x%p (virtual address 0x%p)\n"

            "Expected 0x%x, found 0x%x\n"

            "\nPlease check your bootloader.\n",

            dt_phys, devtree, OF_DT_HEADER,

            be32_to_cpu(devtree->magic));

        while (true)

            cpu_relax();

    }

    initial_boot_params = devtree; // 全局变量initial_boot_params保存dev