{

char * command_line;

unsigned long mempages;

extern char saved_command_line[];

/*

* Interrupts are still disabled. Do necessary setups, then

* enable them

*/

lock_kernel();

printk(linux_banner);

setup_arch(&command_line);

printk("Kernel command line: %s\n", saved_command_line);

parse_options(command_line);

trap_init();

init_IRQ();

sched_init();

softirq_init();

time_init();

/*

* HACK ALERT! This is early. We're enabling the console before

* we've done PCI setups etc, and console_init() must be aware of

* this. But we do want output early, in case something goes wrong.

*/

console_init();

#ifdef CONFIG_MODULES

init_modules();

#endif

if (prof_shift) {

unsigned int size;

/* only text is profiled */

prof_len = (unsigned long) &_etext - (unsigned long) &_stext;

prof_len >>= prof_shift;

size = prof_len * sizeof(unsigned int) + PAGE_SIZE-1;

prof_buffer = (unsigned int *) alloc_bootmem(size);

}

kmem_cache_init();

sti();

calibrate_delay();

#ifdef CONFIG_BLK_DEV_INITRD

if (initrd_start && !initrd_below_start_ok &&

initrd_start < min_low_pfn << PAGE_SHIFT) {

printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "

"disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);

initrd_start = 0;

}

#endif

mem_init();

kmem_cache_sizes_init();

pgtable_cache_init();

mempages = num_physpages;

fork_init(mempages);

proc_caches_init();

vfs_caches_init(mempages);

buffer_init(mempages);

page_cache_init(mempages);

#if defined(CONFIG_ARCH_S390)

ccwcache_init();

#endif

signals_init();

#ifdef CONFIG_PROC_FS

proc_root_init();

#endif

#if defined(CONFIG_SYSVIPC)

ipc_init();

#endif

check_bugs();

printk("POSIX conformance testing by UNIFIX\n");

/*

* We count on the initial thread going ok

* Like idlers init is an unlocked kernel thread, which will

* make syscalls (and thus be locked).

*/

smp_init();

rest_init();

}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

5. 系统源码的修改

移植一个操作系统到新的硬件平台，比较好的办法是寻找一个架构相近并且已经做好操作系统移植的硬件平台。然后，对原先的操作系统做