linux内核原代码init/main的注释

　　#define __LIBRARY__
　　#include
　　#include
　　/*
　　* we need this inline - forking from kernel space will result
　　* in NO COPY ON WRITE (!!!), until an execve is executed. This
　　* is no problem, but for the stack. This is handled by not letting
　　* main() use the stack at all after fork(). Thus, no function
　　* calls - which means inline code for fork too, as otherwise we
　　* would use the stack upon exit from 'fork()'.
　　*
　　* Actually only pause and fork are needed inline, so that there
　　* won't be any messing with the stack from main(), but we define
　　* some others too.
　　*/
　　static inline _syscall0(int,fork) @@定义fork
　　--sys_fork在unistd.h中定义syscall0
　　static inline _syscall0(int,pause)
　　static inline _syscall0(int,setup)
　　static inline _syscall0(int,sync)

#include
　　#include
　　#include
　　#include
　　#include

#include
　　#include
　　#include
　　#include
　　#include

#include

static char printbuf[1024];

extern int vsprintf();
　　extern void init(void);
　　extern void hd_init(void);
　　extern long kernel_mktime(struct tm * tm);
　　extern long startup_time;

/*
　　* Yeah, yeah, it's ugly, but I cannot find how to do this correctly
　　* and this seems to work. I anybody has more info on the real-time
　　* clock I'd be interested. Most of this was trial and error, and some
　　* bios-listing reading. Urghh.
　　*/

#define CMOS_READ(addr) ({ \
　　outb_p(0x80|addr,0x70); \
　　inb_p(0x71); \
　　})

#define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)

static void time_init(void)
　　{
　　struct tm time;

do {
　　 time.tm_sec = CMOS_READ(0);
　　 time.tm_min = CMOS_READ(2);
　　 time.tm_hour = CMOS_READ(4);
　　 time.tm_mday = CMOS_READ(7);
　　 time.tm_mon = CMOS_READ(8)-1;
　　 time.tm_year = CMOS_READ(9);
　　} while (time.tm_sec != CMOS_READ(0));
　　BCD_TO_BIN(time.tm_sec);
　　BCD_TO_BIN(time.tm_min);
　　BCD_TO_BIN(time.tm_hour);
　　BCD_TO_BIN(time.tm_mday);
　　BCD_TO_BIN(time.tm_mon);
　　BCD_TO_BIN(time.tm_year);
　　startup_time = kernel_mktime(&time);
　　}

void main(void) /* This really IS void, no error here. */
　　{ /* The startup routine assumes (well, ...) this */
　　/*
　　* Interrupts are still disabled. Do necessary setups, then
　　* enable them
　　*/
　　time_init();
　　tty_init();