1、1,第六章 Linux內(nèi)核引導(dǎo),內(nèi)核引導(dǎo)過程 (bootchain) 注：以從硬盤上引導(dǎo)Linux為例,start_kernel() Process 0,init() Process 1,MBR grub,2,BIOS,Power-on Upon power-on the processor first accesses an address that usually resides in read-only memory (ROM, Flash). BIOS (Basic Input Output System) BIOS stores hardware-specific system re

2、source initialization code self-test and hardware identification The interface to BIOS is a uniform set of functions known as interrupts. At load time, Linux uses these interrupts to query available system resources. E.g., hard disk At the end of self-test and hardware identification, the system ini

3、tialization code (BIOS) accesses the hard drive controller to read the MBR. After BIOS completes its initialization, it copies the first 512 bytes from the boot device to address 0 x7c00 and jumps to it.,3,MBR (hard drive),Master Boot Record (MBR) Disk Formatting (head 0, cylinder 0, sector 0),4-ent

4、ry,4,MBR (hard drive),5,Boot Loader,MBR copies the code from the active boot partition to address 0 x7c00 and begins executing it. the active boot partition can have a bootloader that, in turn, loads the operating system. (自舉) Bootloader GRUB (Grand Unified Bootloader) LILO (LInux LOader),6,Boot Loa

5、der - grub,GRUB is an x86-based bootloader thats used to load Linux. (/software/grub) GRUB recognizes filesystems on the boot drives, and the kernel can be loaded by specifying the filename, drive, and partition where the kernel resides. /boot/grub/menu.lst,7,Boot Loader - grub,GRUB is a

6、two-stage bootloader Stage 1 is installed in the MBR and is called by BIOS. Stage 2 is partially loaded by Stage 1 and then finishes loading itself from the filesystem.,8,initrd - initial RAM disk,initrd acts as a root filesystem before the final root filesystem is loaded and initialized. This initi

7、al step allows Linux to initially come up with certain modules precompiled and then dynamically load other modules and drivers from initrd. The major difference to the bootloader is that it loads a minimal kernel and the RAM disk during Stage 2. The kernel initializes using initrd, mounts the final

8、root filesystem, and then removes the initrd. initrd allows for Configuring a kernel at boot time Keeping a small general-purpose kernel Having one kernel for several hardware configurations,9,Kernel initiation - start_kernel(),start_kernel() (init/main.c) start_kernel(), Process 0.,10,Kernel initia

9、tion - start_kernel(),11,Kernel initiation - start_kernel(),12,Kernel initiation - start_kernel(),Starting and locking the kernel Initializing the page cache and page addresses for memory management in Linux Preparing multiple CPUs Displaying the Linux banner Initializing the Linux scheduler Parsing the arguments passed to the Linux kernel Initializing the interrupts, timers, and signal handlers Mounting the initial filesystems (initrd) Finishing system initialization and passing control out of init and ba