root/init/main.c

/* */

DEFINITIONS

1. _syscall0
2. sprintf
3. time_init
4. start_kernel
5. printf
6. init

   1 /*
   2  *  linux/init/main.c
   3  *
   4  *  (C) 1991  Linus Torvalds
   5  */
   6 
   7 #include <stddef.h>
   8 #include <stdarg.h>
   9 #include <time.h>
  10 
  11 #include <sys/types.h>
  12 
  13 #include <asm/system.h>
  14 #include <asm/io.h>
  15 
  16 #include <linux/fcntl.h>
  17 #include <linux/config.h>
  18 #include <linux/sched.h>
  19 #include <linux/tty.h>
  20 #include <linux/head.h>
  21 #include <linux/unistd.h>
  22 
  23 /*
  24  * we need this inline - forking from kernel space will result
  25  * in NO COPY ON WRITE (!!!), until an execve is executed. This
  26  * is no problem, but for the stack. This is handled by not letting
  27  * main() use the stack at all after fork(). Thus, no function
  28  * calls - which means inline code for fork too, as otherwise we
  29  * would use the stack upon exit from 'fork()'.
  30  *
  31  * Actually only pause and fork are needed inline, so that there
  32  * won't be any messing with the stack from main(), but we define
  33  * some others too.
  34  */
  35 static inline _syscall0(int,fork)
     /*  */
  36 static inline _syscall0(int,pause)
  37 static inline _syscall1(int,setup,void *,BIOS)
  38 static inline _syscall0(int,sync)
  39 static inline _syscall0(pid_t,setsid)
  40 static inline _syscall3(int,write,int,fd,const char *,buf,off_t,count)
  41 static inline _syscall1(int,dup,int,fd)
  42 static inline _syscall3(int,execve,const char *,file,char **,argv,char **,envp)
  43 static inline _syscall3(int,open,const char *,file,int,flag,int,mode)
  44 static inline _syscall1(int,close,int,fd)
  45 static inline _syscall3(pid_t,waitpid,pid_t,pid,int *,wait_stat,int,options)
  46 
  47 static inline pid_t wait(int * wait_stat)
  48 {
  49         return waitpid(-1,wait_stat,0);
  50 }
  51 
  52 static char printbuf[1024];
  53 
  54 extern int vsprintf();
  55 extern void init(void);
  56 extern long blk_dev_init(long,long);
  57 extern long chr_dev_init(long,long);
  58 extern void hd_init(void);
  59 extern void floppy_init(void);
  60 extern void sock_init(void);
  61 extern void mem_init(long start, long end);
  62 extern long rd_init(long mem_start, int length);
  63 extern long kernel_mktime(struct tm * tm);
  64 
  65 #ifdef CONFIG_SCSI
  66 extern void scsi_dev_init(void);
  67 #endif
  68 
  69 static int sprintf(char * str, const char *fmt, ...)
     /*  */
  70 {
  71         va_list args;
  72         int i;
  73 
  74         va_start(args, fmt);
  75         i = vsprintf(str, fmt, args);
  76         va_end(args);
  77         return i;
  78 }
  79 
  80 /*
  81  * This is set up by the setup-routine at boot-time
  82  */
  83 #define EXT_MEM_K (*(unsigned short *)0x90002)
  84 #define CON_ROWS ((*(unsigned short *)0x9000e) & 0xff)
  85 #define CON_COLS (((*(unsigned short *)0x9000e) & 0xff00) >> 8)
  86 #define DRIVE_INFO (*(struct drive_info *)0x90080)
  87 #define ORIG_ROOT_DEV (*(unsigned short *)0x901FC)
  88 
  89 /*
  90  * Yeah, yeah, it's ugly, but I cannot find how to do this correctly
  91  * and this seems to work. I anybody has more info on the real-time
  92  * clock I'd be interested. Most of this was trial and error, and some
  93  * bios-listing reading. Urghh.
  94  */
  95 
  96 #define CMOS_READ(addr) ({ \
  97 outb_p(0x80|addr,0x70); \
  98 inb_p(0x71); \
  99 })
 100 
 101 #define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)
 102 
 103 static void time_init(void)
     /*  */
 104 {
 105         struct tm time;
 106 
 107         do {
 108                 time.tm_sec = CMOS_READ(0);
 109                 time.tm_min = CMOS_READ(2);
 110                 time.tm_hour = CMOS_READ(4);
 111                 time.tm_mday = CMOS_READ(7);
 112                 time.tm_mon = CMOS_READ(8);
 113                 time.tm_year = CMOS_READ(9);
 114         } while (time.tm_sec != CMOS_READ(0));
 115         BCD_TO_BIN(time.tm_sec);
 116         BCD_TO_BIN(time.tm_min);
 117         BCD_TO_BIN(time.tm_hour);
 118         BCD_TO_BIN(time.tm_mday);
 119         BCD_TO_BIN(time.tm_mon);
 120         BCD_TO_BIN(time.tm_year);
 121         time.tm_mon--;
 122         startup_time = kernel_mktime(&time);
 123 }
 124 
 125 static long memory_end = 0;
 126 static long buffer_memory_end = 0;
 127 static long main_memory_start = 0;
 128 static char term[32];
 129 
 130 static char * argv_init[] = { "/bin/init", NULL };
 131 static char * envp_init[] = { "HOME=/", NULL, NULL };
 132 
 133 static char * argv_rc[] = { "/bin/sh", NULL };
 134 static char * envp_rc[] = { "HOME=/", NULL ,NULL };
 135 
 136 static char * argv[] = { "-/bin/sh",NULL };
 137 static char * envp[] = { "HOME=/usr/root", NULL, NULL };
 138 
 139 struct drive_info { char dummy[32]; } drive_info;
 140 
 141 void start_kernel(void)
     /*  */
 142 {
 143 /*
 144  * Interrupts are still disabled. Do necessary setups, then
 145  * enable them
 146  */
 147         ROOT_DEV = ORIG_ROOT_DEV;
 148         sprintf(term, "TERM=con%dx%d", CON_COLS, CON_ROWS);
 149         envp[1] = term; 
 150         envp_rc[1] = term;
 151         envp_init[1] = term;
 152         drive_info = DRIVE_INFO;
 153         memory_end = (1<<20) + (EXT_MEM_K<<10);
 154         memory_end &= 0xfffff000;
 155         if (memory_end > 16*1024*1024)
 156                 memory_end = 16*1024*1024;
 157         if (memory_end >= 12*1024*1024) 
 158                 buffer_memory_end = 4*1024*1024;
 159         else if (memory_end >= 6*1024*1024)
 160                 buffer_memory_end = 2*1024*1024;
 161         else if (memory_end >= 4*1024*1024)
 162                 buffer_memory_end = 3*512*1024;
 163         else
 164                 buffer_memory_end = 1*1024*1024;
 165         main_memory_start = buffer_memory_end;
 166         trap_init();
 167         sched_init();
 168         main_memory_start = chr_dev_init(main_memory_start,memory_end);
 169         main_memory_start = blk_dev_init(main_memory_start,memory_end);
 170         mem_init(main_memory_start,memory_end);
 171         time_init();
 172         printk("Linux version " UTS_RELEASE " " __DATE__ " " __TIME__ "\n");
 173         buffer_init(buffer_memory_end);
 174         hd_init();
 175         floppy_init();
 176         sock_init();
 177         sti();
 178 #ifdef CONFIG_SCSI
 179         scsi_dev_init();
 180 #endif
 181         move_to_user_mode();
 182         if (!fork()) {          /* we count on this going ok */
 183                 init();
 184         }
 185 /*
 186  *   NOTE!!   For any other task 'pause()' would mean we have to get a
 187  * signal to awaken, but task0 is the sole exception (see 'schedule()')
 188  * as task 0 gets activated at every idle moment (when no other tasks
 189  * can run). For task0 'pause()' just means we go check if some other
 190  * task can run, and if not we return here.
 191  */
 192         for(;;)
 193                 __asm__("int $0x80"::"a" (__NR_pause):"ax");
 194 }
 195 
 196 static int printf(const char *fmt, ...)
     /*  */
 197 {
 198         va_list args;
 199         int i;
 200 
 201         va_start(args, fmt);
 202         write(1,printbuf,i=vsprintf(printbuf, fmt, args));
 203         va_end(args);
 204         return i;
 205 }
 206 
 207 void init(void)
     /*  */
 208 {
 209         int pid,i;
 210 
 211         setup((void *) &drive_info);
 212         (void) open("/dev/tty1",O_RDWR,0);
 213         (void) dup(0);
 214         (void) dup(0);
 215         printf("%d buffers = %d bytes buffer space\n\r",NR_BUFFERS,
 216                 NR_BUFFERS*BLOCK_SIZE);
 217         printf("Free mem: %d bytes\n\r",memory_end-main_memory_start);
 218 
 219         execve("/etc/init",argv_init,envp_init);
 220         execve("/bin/init",argv_init,envp_init);
 221         /* if this fails, fall through to original stuff */
 222 
 223         if (!(pid=fork())) {
 224                 close(0);
 225                 if (open("/etc/rc",O_RDONLY,0))
 226                         _exit(1);
 227                 execve("/bin/sh",argv_rc,envp_rc);
 228                 _exit(2);
 229         }
 230         if (pid>0)
 231                 while (pid != wait(&i))
 232                         /* nothing */;
 233         while (1) {
 234                 if ((pid=fork())<0) {
 235                         printf("Fork failed in init\r\n");
 236                         continue;
 237                 }
 238                 if (!pid) {
 239                         close(0);close(1);close(2);
 240                         setsid();
 241                         (void) open("/dev/tty1",O_RDWR,0);
 242                         (void) dup(0);
 243                         (void) dup(0);
 244                         _exit(execve("/bin/sh",argv,envp));
 245                 }
 246                 while (1)
 247                         if (pid == wait(&i))
 248                                 break;
 249                 printf("\n\rchild %d died with code %04x\n\r",pid,i);
 250                 sync();
 251         }
 252         _exit(0);       /* NOTE! _exit, not exit() */
 253 }

/* */