分析Linux内核的启动过程

第一章环境

Ubuntu 14.10

Linux Kernel 3.18.6

第二章代码及调试过程

环境搭建与内核准备：

cd ~/LinuxKernel/
wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.18.6.tar.xz
xz -d linux-3.18.6.tar.xz
tar -xvf linux-3.18.6.tar
cd linux-3.18.6
make i386_defconfig
make 

cd ~/LinuxKernel/
mkdir rootfs
git clone  https://github.com/mengning/menu.git
cd menu
gcc -o init linktable.c menu.c test.c -m32 -static –lpthread
cd ../rootfs
cp ../menu/init ./
find . | cpio -o -Hnewc |gzip -9 > ../rootfs.img

cd ~/LinuxKernel/
qemu -kernel linux-3.18.6/arch/x86/boot/bzImage -initrd rootfs.img

又一次编译内核：

make menuconfig
kernel hacking—>
compile-time checks and compile options
[*] compile the kernel with debug info

開始调试：

qemu -kernel linux-3.18.6/arch/x86/boot/bzImage -initrd rootfs.img -s -S

同一时候另开一个窗体。执行GDB：

gdb
（gdb）file linux-3.18.6/vmlinux 
（gdb）target remote:1234 
（gdb）break start_kernel

(gdb)list

这一次代码就不贴出来了，在init/mian.c下，主要是代码太长。

http://codelab.shiyanlou.com/xref/linux-3.18.6/init/main.c

单击对应的链接能够找到引用的变量位置。我下载了几个。

这里打算分析:

cpu_startup_entry

page_address_init()

rest_init()

page_alloc_init()

trap_init()

tick_init()

profile_init()

key_init()

security_init()

buffer_init()

init_task 0号进程

run_init_process(const char *init_filename) 1号进程

0号进程init_task的结构：

#define INIT_TASK(tsk)	
{									
	.state		= 0,						
	.stack		= &init_thread_info,				
	.usage		= ATOMIC_INIT(2),				
	.flags		= PF_KTHREAD,					
	.prio		= MAX_PRIO-20,					
	.static_prio	= MAX_PRIO-20,					
	.normal_prio	= MAX_PRIO-20,					
	.policy		= SCHED_NORMAL,					
	.cpus_allowed	= CPU_MASK_ALL,					
	.nr_cpus_allowed= NR_CPUS,					
	.mm		= NULL,						
	.active_mm	= &init_mm,					
	.se		= {						
		.group_node 	= LIST_HEAD_INIT(tsk.se.group_node),	
	},								
	.rt		= {						
		.run_list	= LIST_HEAD_INIT(tsk.rt.run_list),	
		.time_slice	= RR_TIMESLICE,				
	},								
	.tasks		= LIST_HEAD_INIT(tsk.tasks),			
	INIT_PUSHABLE_TASKS(tsk)					
	INIT_CGROUP_SCHED(tsk)						
	.ptraced	= LIST_HEAD_INIT(tsk.ptraced),			
	.ptrace_entry	= LIST_HEAD_INIT(tsk.ptrace_entry),		
	.real_parent	= &tsk,						
	.parent		= &tsk,						
	.children	= LIST_HEAD_INIT(tsk.children),			
	.sibling	= LIST_HEAD_INIT(tsk.sibling),			
	.group_leader	= &tsk,						
	RCU_POINTER_INITIALIZER(real_cred, &init_cred),			
	RCU_POINTER_INITIALIZER(cred, &init_cred),			
	.comm		= INIT_TASK_COMM,				
	.thread		= INIT_THREAD,					
	.fs		= &init_fs,					
	.files		= &init_files,					
	.signal		= &init_signals,				
	.sighand	= &init_sighand,				
	.nsproxy	= &init_nsproxy,				
	.pending	= {						
		.list = LIST_HEAD_INIT(tsk.pending.list),		
		.signal = {{0}}},					
	.blocked	= {{0}},					
	.alloc_lock	= __SPIN_LOCK_UNLOCKED(tsk.alloc_lock),		
	.journal_info	= NULL,						
	.cpu_timers	= INIT_CPU_TIMERS(tsk.cpu_timers),		
	.pi_lock	= __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock),	
	.timer_slack_ns = 50000, /* 50 usec default slack */		
	.pids = {							
		[PIDTYPE_PID]  = INIT_PID_LINK(PIDTYPE_PID),		
		[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID),		
		[PIDTYPE_SID]  = INIT_PID_LINK(PIDTYPE_SID),		
	},								
	.thread_group	= LIST_HEAD_INIT(tsk.thread_group),		
	.thread_node	= LIST_HEAD_INIT(init_signals.thread_head),	
	INIT_IDS							
	INIT_PERF_EVENTS(tsk)						
	INIT_TRACE_IRQFLAGS						
	INIT_LOCKDEP							
	INIT_FTRACE_GRAPH						
	INIT_TRACE_RECURSION						
	INIT_TASK_RCU_PREEMPT(tsk)					
	INIT_TASK_RCU_TASKS(tsk)					
	INIT_CPUSET_SEQ(tsk)						
	INIT_RT_MUTEXES(tsk)						
	INIT_VTIME(tsk)							
}

第三章调试

设置断点：一共13个。

命令为：