linux-0.11 [内核源代码带英文注解]

/* * 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 (*(unsigned short *)0x90002) #define DRIVE_INFO (*(struct drive_info *)0x90080) #define ORIG_ROOT_DEV (*(unsigned short *)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() */ }