root/init/main.c

/* */

DEFINITIONS

1. time_init
2. main
3. printf
4. init

   1 #define __LIBRARY__
   2 #include <unistd.h>
   3 #include <time.h>
   4 
   5 /*
   6  * we need this inline - forking from kernel space will result
   7  * in NO COPY ON WRITE (!!!), until an execve is executed. This
   8  * is no problem, but for the stack. This is handled by not letting
   9  * main() use the stack at all after fork(). Thus, no function
  10  * calls - which means inline code for fork too, as otherwise we
  11  * would use the stack upon exit from 'fork()'.
  12  *
  13  * Actually only pause and fork are needed inline, so that there
  14  * won't be any messing with the stack from main(), but we define
  15  * some others too.
  16  */
  17 static inline _syscall0(int,fork)
  18 static inline _syscall0(int,pause)
  19 static inline _syscall0(int,setup)
  20 static inline _syscall0(int,sync)
  21 
  22 #include <linux/tty.h>
  23 #include <linux/sched.h>
  24 #include <linux/head.h>
  25 #include <asm/system.h>
  26 #include <asm/io.h>
  27 
  28 #include <stddef.h>
  29 #include <stdarg.h>
  30 #include <unistd.h>
  31 #include <fcntl.h>
  32 #include <sys/types.h>
  33 
  34 #include <linux/fs.h>
  35 
  36 static char printbuf[1024];
  37 
  38 extern int vsprintf();
  39 extern void init(void);
  40 extern void hd_init(void);
  41 extern long kernel_mktime(struct tm * tm);
  42 extern long startup_time;
  43 
  44 /*
  45  * Yeah, yeah, it's ugly, but I cannot find how to do this correctly
  46  * and this seems to work. I anybody has more info on the real-time
  47  * clock I'd be interested. Most of this was trial and error, and some
  48  * bios-listing reading. Urghh.
  49  */
  50 
  51 #define CMOS_READ(addr) ({ \
  52 outb_p(0x80|addr,0x70); \
  53 inb_p(0x71); \
  54 })
  55 
  56 #define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
  57 
  58 static void time_init(void)
     /*  */
  59 {
  60         struct tm time;
  61 
  62         do {
  63                 time.tm_sec = CMOS_READ(0);
  64                 time.tm_min = CMOS_READ(2);
  65                 time.tm_hour = CMOS_READ(4);
  66                 time.tm_mday = CMOS_READ(7);
  67                 time.tm_mon = CMOS_READ(8)-1;
  68                 time.tm_year = CMOS_READ(9);
  69         } while (time.tm_sec != CMOS_READ(0));
  70         BCD_TO_BIN(time.tm_sec);
  71         BCD_TO_BIN(time.tm_min);
  72         BCD_TO_BIN(time.tm_hour);
  73         BCD_TO_BIN(time.tm_mday);
  74         BCD_TO_BIN(time.tm_mon);
  75         BCD_TO_BIN(time.tm_year);
  76         startup_time = kernel_mktime(&time);
  77 }
  78 
  79 void main(void)         /* This really IS void, no error here. */
     /*  */
  80 {                       /* The startup routine assumes (well, ...) this */
  81 /*
  82  * Interrupts are still disabled. Do necessary setups, then
  83  * enable them
  84  */
  85         time_init();
  86         tty_init();
  87         trap_init();
  88         sched_init();
  89         buffer_init();
  90         hd_init();
  91         sti();
  92         move_to_user_mode();
  93         if (!fork()) {          /* we count on this going ok */
  94                 init();
  95         }
  96 /*
  97  *   NOTE!!   For any other task 'pause()' would mean we have to get a
  98  * signal to awaken, but task0 is the sole exception (see 'schedule()')
  99  * as task 0 gets activated at every idle moment (when no other tasks
 100  * can run). For task0 'pause()' just means we go check if some other
 101  * task can run, and if not we return here.
 102  */
 103         for(;;) pause();
 104 }
 105 
 106 static int printf(const char *fmt, ...)
     /*  */
 107 {
 108         va_list args;
 109         int i;
 110 
 111         va_start(args, fmt);
 112         write(1,printbuf,i=vsprintf(printbuf, fmt, args));
 113         va_end(args);
 114         return i;
 115 }
 116 
 117 static char * argv[] = { "-",NULL };
 118 static char * envp[] = { "HOME=/usr/root", NULL };
 119 
 120 void init(void)
     /*  */
 121 {
 122         int i,j;
 123 
 124         setup();
 125         if (!fork())
 126                 _exit(execve("/bin/update",NULL,NULL));
 127         (void) open("/dev/tty0",O_RDWR,0);
 128         (void) dup(0);
 129         (void) dup(0);
 130         printf("%d buffers = %d bytes buffer space\n\r",NR_BUFFERS,
 131                 NR_BUFFERS*BLOCK_SIZE);
 132         printf(" Ok.\n\r");
 133         if ((i=fork())<0)
 134                 printf("Fork failed in init\r\n");
 135         else if (!i) {
 136                 close(0);close(1);close(2);
 137                 setsid();
 138                 (void) open("/dev/tty0",O_RDWR,0);
 139                 (void) dup(0);
 140                 (void) dup(0);
 141                 _exit(execve("/bin/sh",argv,envp));
 142         }
 143         j=wait(&i);
 144         printf("child %d died with code %04x\n",j,i);
 145         sync();
 146         _exit(0);       /* NOTE! _exit, not exit() */
 147 }

/* */