main.c

~/linux-0.11/init/main.c.html

/*
 *  linux/init/main.c
 *
 *  (C) 1991  Linus Torvalds
*/

#define __LIBRARY__
#include <unistd.h>
#include <time.h>

/*
 * 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)
static inline _syscall0(int,pause)
static inline _syscall1(int,setup,void *,BIOS)
static inline _syscall0(int,sync)

#include <linux/tty.h>
#include <linux/sched.h>
#include <linux/head.h>
#include <asm/system.h>
#include <asm/io.h>

#include <stddef.h>
#include <stdarg.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>

#include <linux/fs.h>

static char printbuf[1024];

extern int vsprintf();
extern void init(void);
extern void blk_dev_init(void);
extern void chr_dev_init(void);
extern void hd_init(void);
extern void floppy_init(void);
extern void mem_init(long start, long end);
extern long rd_init(long mem_start, int length);
extern long kernel_mktime(struct tm * tm);
extern long startup_time;

/*
 * This is set up by the setup-routine at boot-time
*/
#define EXT_MEM_K (*(unsignedshort *)0x90002)
#define DRIVE_INFO (*(struct drive_info *)0x90080)
#define ORIG_ROOT_DEV (*(unsignedshort *)0x901FC)

/*
 * 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);
                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);
        time.tm_mon--;
        startup_time = kernel_mktime(&time);
}

static long memory_end = 0;
static long buffer_memory_end = 0;
static long main_memory_start = 0;

struct drive_info { char dummy[32]; } drive_info;

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
*/
        ROOT_DEV = ORIG_ROOT_DEV;
        drive_info = DRIVE_INFO;
        memory_end = (1<<20) + (EXT_MEM_K<<10);
        memory_end &= 0xfffff000;
        if (memory_end > 16*1024*1024)
                memory_end = 16*1024*1024;
        if (memory_end > 12*1024*1024)
                buffer_memory_end = 4*1024*1024;
        else if (memory_end > 6*1024*1024)
                buffer_memory_end = 2*1024*1024;
        else
                buffer_memory_end = 1*1024*1024;
        main_memory_start = buffer_memory_end;
#ifdef RAMDISK
        main_memory_start += rd_init(main_memory_start, RAMDISK*1024);
#endif
        mem_init(main_memory_start,memory_end);
        trap_init();
        blk_dev_init();
        chr_dev_init();
        tty_init();
        time_init();
        sched_init();
        buffer_init(buffer_memory_end);
        hd_init();
        floppy_init();
        sti();
        move_to_user_mode();
        if (!fork()) {          /* we count on this going ok */
                init();
        }
/*
 *   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();
}

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_rc[] = { "/bin/sh", NULL };
static char * envp_rc[] = { "HOME=/", NULL };

static char * argv[] = { "-/bin/sh",NULL };
static char * envp[] = { "HOME=/usr/root", NULL };

void init(void)
{
        int pid,i;

        setup((void *) &drive_info);
        (void) open("/dev/tty0",O_RDWR,0);
        (void) dup(0);
        (void) dup(0);
        printf("%d buffers = %d bytes buffer space\n\r",NR_BUFFERS,
                NR_BUFFERS*BLOCK_SIZE);
        printf("Free mem: %d bytes\n\r",memory_end-main_memory_start);
        if (!(pid=fork())) {
                close(0);
                if (open("/etc/rc",O_RDONLY,0))
                        _exit(1);
                execve("/bin/sh",argv_rc,envp_rc);
                _exit(2);
        }
        if (pid>0)
                while (pid != wait(&i))
                        /* nothing */;
        while (1) {
                if ((pid=fork())<0) {
                        printf("Fork failed in init\r\n");
                        continue;
                }
                if (!pid) {
                        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));
                }
                while (1)
                        if (pid == wait(&i))
                                break;
                printf("\n\rchild %d died with code %04x\n\r",pid,i);
                sync();
        }
        _exit(0);       /* NOTE! _exit, not exit() */
}