实验12 Linux内核启动分析.doc

实验12 Linux内核启动分析 实验目的 就boot.s和head.s了解Linux启动的部分工程 实验步骤 下载源码 分析源码 源码分析结果 head.s # head.s contains the 32-bit startup code. # Two L3 task multitasking. The code of tasks are in kernel area, # just like the Linux. The kernel code is located at 0x10000. ;头文件包含32位的启动代码 ;两个L3 分配多个任务,就像linux,它的任务代码在核心区域 ;核心代码在0x10000的地址上 SCRN_SEL = 0x18 TSS0_SEL = 0x20 LDT0_SEL = 0x28 TSS1_SEL = 0X30 LDT1_SEL = 0x38 ;将代码段和数据段的地址设为0x10 ;lss传送目标指针，将目标指针内容送入 ;LSS DI,string ;把段地址:偏移地址存到SS:DI. .text startup_32: movl $0x10,%eax mov %ax,%ds # mov %ax,%es lss init_stack,%esp;将init_stack+4送入ss，并将init_stack地址送入esp # setup base fields of descriptors.;设置基本描述符域 call setup_idt call setup_gdt;在完成两个设置程序的调用之后就重置所有段寄存器 movl $0x10,%eax # reload all the segment registers mov %ax,%ds # after changing gdt. mov %ax,%es mov %ax,%fs mov %ax,%gs lss init_stack,%esp # setup up timer 8253 chip.;设置计时器芯片8523 movb $0x36, %al movl $0x43, %edx outb %al, %dx #向43端口写入36 movl $11930, %eax # timer frequency 100 HZ movl $0x40, %edx outb %al, %dx #向40端口写入11930 movb %ah, %al outb %al, %dx # setup timer system call interrupt descriptors.; movl $0 %eax movw $timer_interrupt, %ax;中断 movw $0x8E00, %dx movl $0x08, %ecx # The PC default timer int. lea idt(,%ecx,8), %esi movl %eax,(%esi) movl %edx,4(%esi) movw $system_interrupt, %ax movw $0xef00, %dx movl $0x80, %ecx lea idt(,%ecx,8), %esi movl %eax,(%esi) movl %edx,4(%esi) # unmask the timer interrupt. # movl $0x21, %edx # inb %dx, %al # andb $0xfe, %al # outb %al, %dx # Move to user mode (task 0) pushfl andl $0xffffbfff, (%esp) popfl movl $TSS0_SEL, %eax ltr %ax movl $LDT0_SEL, %eax lldt %ax movl $0, current sti pushl $0x17 pushl $init_stack pushfl pushl $0x0f pushl $task0 iret /****************************************/ setup_gdt: /****************************将lgdt_opcode的入口地址装入GDTR寄存器 lgdt lgdt_opcode ret 将中断描述符表 idt 设置成具有 256 个项，并都