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();
trap_init();
sched_init();
buffer_init();
hd_init();
sti();
move_to_user_mode(); @@切至用户模式???到哪去了,回来了!!!
if (!fork()) { /* we count on this going ok */
init(); @@fork在unistd.h有其宏扩展int 0x80
如何返回两次?应该说子进程如何激活?
}
/*
* NOTE!! For any other task 'pause()' would mean we have to get a
* signal to awaken, but task0 is the sole exception (see 'schedule()')
* as task 0 gets activated at every idle moment (when no other tasks
* can run). For task0 'pause()' just means we go check if some other
* task can run, and if not we return here.
*/
for(;;) pause();
@@pause 同fork在unistd.h有其宏扩展int 0x80 然后调schedule()
}
static int printf(const char *fmt, ...)
{
va_list args;
int i;
va_start(args, fmt);
write(1,printbuf,i=vsprintf(printbuf, fmt, args));
va_end(args);
return i;
}
static char * argv[] = { "-",NULL };
static char * envp[] = { "HOME=/usr/root", NULL };
void init(void)
{
int i,j;
setup(); @@系统0号调用
if (!fork())
_exit(execve("/bin/update",NULL,NULL));
(void) open("/dev/tty0",O_RDWR,0); @@打开控制台
(void) dup(0); @@复制
(void) dup(0);
printf("%d buffers = %d bytes buffer spacenr",NR_BUFFERS,
NR_BUFFERS*BLOCK_SIZE);
printf(" Ok.nr");
if ((i=fork())<0)
printf("Fork failed in initrn");
else if (!i) { @@启动一root shell进程?
close(0);close(1);close(2);
setsid();
(void) open("/dev/tty0",O_RDWR,0);
(void) dup(0);
(void) dup(0);
_exit(execve("/bin/sh",argv,envp));
}
j=wait(&i);
printf("child %d died with code %04xn",j,i);
sync();
_exit(0); /* NOTE! _exit, not exit() */
}
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