浅析armlinux-setup_arch()->setup_arch()函数-最终

浅析armlinux-setup_arch()->setup_arch()函数-最终

文章来源:http://gliethttp.cublog.cn

建议首先参考《浅析armlinux2_4_19启动程序[head-armv.s文件]》与[http://gliethttp.cublog.cn]

《浅析setup_arch()函数tag_list的uboot[u-boot]由来》
《浅析armlinux-setup_arch()->setup_processor()函数1》
《浅析armlinux-setup_arch()->setup_machine()函数2 》
《浅析armlinux-setup_arch()->convert_to_tag_list()函数3 》
《浅析armlinux-setup_arch()->bootmem_init()函数4》
《浅析armlinux-setup_arch()->paging_init()函数5》
《浅析armlinux-seup_arch-alloc_bootmem_low_pages函数5-1》
《浅析armlinux-setup_arch()-memtable_init()函数5-2》
《浅析armlinux-setup_arch()-clear_mapping()函数5-2-1》
《浅析armlinux-setup_arch()-create_mapping()函数5-2-2》
《我看Buddy(伙伴)算法－为什么要有除2操作》
《浅析armlinux-paging_init()->at91rm9200_map_io()函数5-3》
《浅析armlinux-paging_init()->free_area_init_core()函数5-4》
《浅析armlinux-setup_arch()->request_standard_resources()函数6》
《浅析armlinux-setup_arch()->init_arch_irq()函数7》

//1.arch/arm/kernel/Setup.c->setup_arch()
void __init setup_arch(char **cmdline_p)
{
    struct tag *tags = (struct tag *)&init_tags;
    struct machine_desc *mdesc;
    char *from = default_command_line;

    ROOT_DEV = MKDEV(0, 255);//ROOT_DEV = 0xff;
//见《浅析armlinux-setup_arch()->setup_processor()函数1》[http://gliethttp.cublog.cn]
    setup_processor();
//见《浅析armlinux-setup_arch()->setup_machine(machine_arch_type)函数2》[http://gliethttp.cublog.cn]
    mdesc = setup_machine(machine_arch_type);//mdesc指向机器描述空间单元
//++++++++++++++
//arch/arm/mach-at91rm9200/Core.c
//位于.arch.info段
//MACHINE_START(AT91RM9200, "ATMEL AT91RM9200")//.nr = MACH_TYPE_##_type=MACH_TYPE_AT91RM9200=251
//与上面从u-boot传到r1中的一样[gliethttp]
//MAINTAINER("SAN People / ATMEL")
//BOOT_MEM(AT91_SDRAM_BASE, AT91C_BASE_SYS, AT91C_VA_BASE_SYS)
//BOOT_PARAMS(AT91_SDRAM_BASE + 0x100)//tag list存放的物理地址0x20000100[gliethttp]
//FIXUP(at91rm9200_fixup)
//MAPIO(at91rm9200_map_io)
//INITIRQ(at91rm9200_init_irq)
//MACHINE_END[gliethttp]
//--------------
    machine_name = mdesc->name;//machine_name="ATMEL AT91RM9200"

    if (mdesc->soft_reboot)//mdesc->soft_reboot初值为1
        reboot_setup("s");//分析见后

    if (mdesc->param_offset)//mdesc->param_offset=AT91_SDRAM_BASE + 0x100=物理地址0x20000100
        tags = phys_to_virt(mdesc->param_offset);//将tag list物理地址转换成虚拟地址,以便访问

    if (mdesc->fixup)//调用at91rm9200_fixup()修正函数,分析见后
        mdesc->fixup(mdesc, (struct param_struct *)tags,
             &from, &meminfo);
//很明显由bootloader[u-boot-1.1.5]传递到物理地址0x20000100处的参数是tag list结构[gliethttp]
    if (tags->hdr.tag != ATAG_CORE)
        convert_to_tag_list(tags);
//对于tag list的生成,请参考《浅析setup_arch()函数tag_list的uboot[u-boot]由来》[http://gliethttp.cublog.cn]

    if (tags->hdr.tag == ATAG_CORE) {
        if (meminfo.nr_banks != 0)//如果是tag list,那么如果系统已经创建了默认的meminfo.nr_banks
            squash_mem_tags(tags);//那么使用squash_mem_tags失效所有ATAG_MEM初始化的东东为ATAG_NONE,tag->hdr.size不变
        parse_tags(tags);
    }

    if (meminfo.nr_banks == 0) {//如果tag list中没有传递ATAG_MEM参数,那么采用编译时的默认配置值
        meminfo.nr_banks = 1;
        meminfo.bank[0].start = PHYS_OFFSET;//0x20000000
        meminfo.bank[0].size = MEM_SIZE;//32M
    }
//_text,_etext,_edata,_end参见arch/arm/vmlinux-armv.lds.in链接脚本
    init_mm.start_code = (unsigned long) &_text;
    init_mm.end_code = (unsigned long) &_etext;
    init_mm.end_data = (unsigned long) &_edata;
    init_mm.brk     = (unsigned long) &_end;

    memcpy(saved_command_line, from, COMMAND_LINE_SIZE);
    saved_command_line[COMMAND_LINE_SIZE-1] = '\0';//追0,防止非法字符串越界
//parse_cmdline,主要完成phys_initrd_start,phys_initrd_size和mem的解析,并将*cmdline_p=command_line全局量
    parse_cmdline(&meminfo, cmdline_p, from);
//将kernel自身和位图管理页占用的页对应的页位图置1,标识相应页已被占用
//将initrd占用的页对应的页位图置1,标识相应页已被占用[gliethttp]
    bootmem_init(&meminfo);
//清空页目录项,建立at91rm9200中断向量表空间和io寄存器空间从虚拟地址到物理地址的映射表
//建立map位图和page页管理空间,以及free_area.map位图管理空间等
    paging_init(&meminfo, mdesc);
    request_standard_resources(&meminfo, mdesc);//登记注册所有需要登记注册的cpu总线上的设备实体
    init_arch_irq = mdesc->init_irq;//中断初始化函数指针

#ifdef CONFIG_VT
#if defined(CONFIG_VGA_CONSOLE)
    conswitchp = &vga_con;//显示设备指针conswitchp指向vga_con设备
#elif defined(CONFIG_DUMMY_CONSOLE)//frambuffer选中后,就会使用dummy_con设备
    conswitchp = &dummy_con;//显示设备指针conswitchp指向dummy_con设备
#endif
#endif
}
//2.arch/arm/kernel/Process.c->reboot_setup()
static char reboot_mode = 'h';
int __init reboot_setup(char *str)
{
//reboot_mode将在machine_restart()系统重启时arch_reset()使用
    reboot_mode = str[0];//reboot_mode='s';
    return 1;
}
//3.arch/arm/mach-at91rm9200/Core.c->at91rm9200_fixup
static void __init at91rm9200_fixup(struct machine_desc *desc, struct param_struct *unused,
         char **cmdline, struct meminfo *mi)
{
#ifdef CONFIG_BLK_DEV_INITRD//CONFIG_BLK_DEV_INITRD = 1

//设置根目录为ramdisk
    ROOT_DEV = MKDEV(RAMDISK_MAJOR, 0);//0x100
//由make menuconfig产生CONFIG_BLK_DEV_RAM_SIZE = 15360k = 15M
    setup_ramdisk(1, 0, 0, CONFIG_BLK_DEV_RAM_SIZE);
//    setup_initrd(0xc0100000, 3*1024*1024);
#endif
}
void __init setup_ramdisk(int doload, int prompt, int image_start, unsigned int rd_sz)
{
#ifdef CONFIG_BLK_DEV_RAM
    extern int rd_size, rd_image_start, rd_prompt, rd_doload;
    rd_image_start = image_start;
    rd_prompt = prompt;
    rd_doload = doload;
    if (rd_sz)
        rd_size = rd_sz;//15M
#endif
}
//4.解析tag list中各个元素,进而改变内核全局量,来影响内核
//arch/arm/kernel/Setup.c->parse_tags()
static void __init parse_tags(const struct tag *t)
{
    for (; t->hdr.size; t = tag_next(t))
        if (!parse_tag(t))//解析该t
            printk(KERN_WARNING
                "Ignoring unrecognised tag 0x%08x\n",
                t->hdr.tag);
}
//5.arch/arm/kernel/Setup.c->parse_tag()
static int __init parse_tag(const struct tag *tag)
{
    extern struct tagtable __tagtable_begin, __tagtable_end;
    struct tagtable *t;
    for (t = &__tagtable_begin; t < &__tagtable_end; t++)
        if (tag->hdr.tag == t->tag) {
            t->parse(tag);
            break;
        }
    return t < &__tagtable_end;//找到匹配项,1;否则0
}
//arch/arm/vmlinux-armv.lds.in链接脚本中有如下定以
//...
//__tagtable_begin = .;
//*(.taglist)
//__tagtable_end = .;
//...
//在include/asm-arm/Setup.h中有如下定义
#define __tag __attribute__((unused, __section__(".taglist")))
#define __tagtable(tag, fn) \
static struct tagtable __tagtable_##fn __tag = { tag, fn }
__tagtable(ATAG_CORE, parse_tag_core);//ATAG_CORE解析函数parse_tag_core
__tagtable(ATAG_MEM, parse_tag_mem32);//ATAG_MEM解析函数parse_tag_mem32
__tagtable(ATAG_RAMDISK, parse_tag_ramdisk);//ATAG_RAMDISK解析函数parse_tag_ramdisk
__tagtable(ATAG_INITRD, parse_tag_initrd);//ATAG_INITRD解析函数parse_tag_initrd
__tagtable(ATAG_SERIAL, parse_tag_serialnr);//ATAG_SERIAL解析函数parse_tag_serialnr
__tagtable(ATAG_CMDLINE, parse_tag_cmdline);//ATAG_CMDLINE解析函数parse_tag_cmdline
......等