06.内核启动流程分析之内核启动

arch\arm\kernel

/*启动内核：bi_arch_number机器ID。参数存放的地址 bd->bi_boot_params*/
theKernel (0, bd->bi_arch_number, bd->bi_boot_params);

/**/
ENTRY(stext)
	msr	cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE @ ensure svc mode
						@ and irqs disabled
	mrc	p15, 0, r9, c0, c0		@ get processor id
	/*支持的处理器类型*/
	bl	__lookup_processor_type		@ r5=procinfo r9=cpuid
	movs	r10, r5				@ invalid processor (r5=0)?
	beq	__error_p			@ yes, error 'p'
	bl	__lookup_machine_type		@ r5=machinfo
	movs	r8, r5				@ invalid machine (r5=0)?
	beq	__error_a			@ yes, error 'a'
	bl	__create_page_tables

__lookup_machine_type:
	adr	r3, 3b              @ r3=3b的地址，物理地址
	/*	链接脚本
	__arch_info_begin = .;
			*(.arch.info.init)
		__arch_info_end = .;
	*/
	ldmia	r3, {r4, r5, r6}@ r4=“.”(.代表3b的虚拟地址) r5=__arch_info_begin r6=__arch_info_end
	sub	r3, r3, r4			@ get offset between virt&phys 虚拟地址物理地址的偏差
	add	r5, r5, r3			@ convert virt addresses to
	add	r6, r6, r3			@ physical address space
1:	ldr	r3, [r5, #MACHINFO_TYPE]	@ get machine type
	teq	r3, r1				@ matches loader number? 机器ID
	beq	2f				@ found
	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
	cmp	r5, r6
	blo	1b
	mov	r5, #0				@ unknown machine
2:	mov	pc, lr

/*linux-2.6.22.6\linux-2.6.22.6\include\asm-arm\mach\arch.h*/
/*定义两个结构体，把段强制设置成.arch.info.init*/
#define MACHINE_START(_type,_name)			\
static const struct machine_desc __mach_desc_##_type	\
 __used							\
 __attribute__((__section__(".arch.info.init"))) = {	\
	.nr		= MACH_TYPE_##_type,		\
	.name		= _name,
	
/*linux-2.6.22.6\linux-2.6.22.6\arch\arm\mach-s3c2440\Mach-smdk2440.c*/
MACHINE_START(S3C2440, "SMDK2440")
	/* Maintainer: Ben Dooks <ben@fluff.org> */
	.phys_io	= S3C2410_PA_UART,
	.io_pg_offst	= (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,
	.boot_params	= S3C2410_SDRAM_PA + 0x100,

	.init_irq	= s3c24xx_init_irq,
	.map_io		= smdk2440_map_io,
	.init_machine	= smdk2440_machine_init,
	.timer		= &s3c24xx_timer,
MACHINE_END

	bl	__create_page_tables

	adr	r4, __secondary_data
	ldmia	r4, {r5, r7, r13}		@ address to jump to after
	sub	r4, r4, r5			@ mmu has been enabled
	ldr	r4, [r7, r4]			@ get secondary_data.pgdir
	adr	lr, __enable_mmu		@ return address
	add	pc, r10, #PROCINFO_INITFUNC	@ initialise processor
						@ (return control reg)

b	start_kernel

/*启动流程
start_kernel
	setup_arch  解析UBOOT传入的启动参数
	setup_command_line   解析UBOOT传入的启动参数
	parse_early_param
		do_early_para
			从_setup_start到_setup_end,调用early函数
	unknown_bootoption
		obsolete_checksetup
			从_setup_start到_setup_end,调用early函数
	rest_init
		kernel_init
			prepare_namespace
				mount_root 挂载根文件系统
			init_post  执行应用程序
*/
	char * command_line;
	extern struct kernel_param __start___param[], __stop___param[];

	smp_setup_processor_id();

	/*
	 * Need to run as early as possible, to initialize the
	 * lockdep hash:
	 */
	unwind_init();
	lockdep_init();

	local_irq_disable();
	early_boot_irqs_off();
	early_init_irq_lock_class();

/*
 * Interrupts are still disabled. Do necessary setups, then
 * enable them
 */
	lock_kernel();
	tick_init();
	boot_cpu_init();
	page_address_init();
	printk(KERN_NOTICE);
	printk(linux_banner);
	setup_arch(&command_line);
	setup_command_line(command_line);
	unwind_setup();
	setup_per_cpu_areas();
	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */

	/*
	 * Set up the scheduler prior starting any interrupts (such as the
	 * timer interrupt). Full topology setup happens at smp_init()
	 * time - but meanwhile we still have a functioning scheduler.
	 */
	sched_init();
	/*
	 * Disable preemption - early bootup scheduling is extremely
	 * fragile until we cpu_idle() for the first time.
	 */
	preempt_disable();
	build_all_zonelists();
	page_alloc_init();
	printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
	parse_early_param();
	parse_args("Booting kernel", static_command_line, __start___param,
		   __stop___param - __start___param,
		   &unknown_bootoption);
	if (!irqs_disabled()) {
		printk(KERN_WARNING "start_kernel(): bug: interrupts were "
				"enabled *very* early, fixing it\n");
		local_irq_disable();
	}
	sort_main_extable();
	trap_init();
	rcu_init();
	init_IRQ();
	pidhash_init();
	init_timers();
	hrtimers_init();
	softirq_init();
	timekeeping_init();
	time_init();
	profile_init();
	if (!irqs_disabled())
		printk("start_kernel(): bug: interrupts were enabled early\n");
	early_boot_irqs_on();
	local_irq_enable();