我以前分析的linux内核1.0,我会逐渐的贴出来的,希望大家给予赐教

main.c /* * linux/init/main.c * * Copyright (C) 1991, 1992 Linus Torvalds */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include extern unsigned long * prof_buffer; extern unsigned long prof_len; extern char edata, end; extern char *linux_banner; asmlinkage void lcall7(void); struct desc_struct default_ldt; /* * 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. */ #define __NR__exit __NR_exit static inline _syscall0(int,idle) static inline _syscall0(int,fork) static inline _syscall0(int,pause) static inline _syscall1(int,setup,void *,BIOS) static inline _syscall0(int,sync) static inline _syscall0(pid_t,setsid) static inline _syscall3(int,write,int,fd,const char *,buf,off_t,count) static inline _syscall1(int,dup,int,fd) static inline _syscall3(int,execve,const char *,file,char **,argv,char **,envp) static inline _syscall3(int,open,const char *,file,int,flag,int,mode) static inline _syscall1(int,close,int,fd) static inline _syscall1(int,_exit,int,exitcode) static inline _syscall3(pid_t,waitpid,pid_t,pid,int *,wait_stat,int,options) static inline pid_t wait(int * wait_stat) { return waitpid(-1,wait_stat,0); } static char printbuf[1024]; extern int console_loglevel; extern char empty_zero_page[PAGE_SIZE]; extern int vsprintf(char *,const char *,va_list); extern void init(void); extern void init_IRQ(void); extern long kmalloc_init (long,long); extern long blk_dev_init(long,long); extern long chr_dev_init(long,long); extern void floppy_init(void); extern void sock_init(void); extern long rd_init(long mem_start, int length); unsigned long net_dev_init(unsigned long, unsigned long); extern unsigned long simple_strtoul(const char *,char **,unsigned int); extern void hd_setup(char *str, int *ints); extern void bmouse_setup(char *str, int *ints); extern void eth_setup(char *str, int *ints); extern void xd_setup(char *str, int *ints); extern void mcd_setup(char *str, int *ints); extern void st0x_setup(char *str, int *ints); extern void tmc8xx_setup(char *str, int *ints); extern void t128_setup(char *str, int *ints); extern void generic_NCR5380_setup(char *str, int *intr); extern void aha152x_setup(char *str, int *ints); extern void sound_setup(char *str, int *ints); #ifdef CONFIG_SBPCD extern void sbpcd_setup(char *str, int *ints); #endif CONFIG_SBPCD #ifdef CONFIG_SYSVIPC extern void ipc_init(void); #endif #ifdef CONFIG_SCSI extern unsigned long scsi_dev_init(unsigned long, unsigned long); #endif /* * This is set up by the setup-routine at boot-time */ #define PARAMempty_zero_page #define EXT_MEM_K (*(unsigned short *) (PARAM+2)) #define DRIVE_INFO (*(struct drive_info_struct *) (PARAM+0x80)) #define SCREEN_INFO (*(struct screen_info *) (PARAM+0)) #define MOUNT_ROOT_RDONLY (*(unsigned short *) (PARAM+0x1F2)) #define RAMDISK_SIZE (*(unsigned short *) (PARAM+0x1F8)) #define ORIG_ROOT_DEV (*(unsigned short *) (PARAM+0x1FC)) #define AUX_DEVICE_INFO (*(unsigned char *) (PARAM+0x1FF)) /* * Boot command-line arguments */ #define MAX_INIT_ARGS 8 #define MAX_INIT_ENVS 8 #define COMMAND_LINE ((char *) (PARAM+2048)) extern void time_init(void); static unsigned long memory_start = 0;/* After mem_init, stores the */ /* amount of free user memory */ static unsigned long memory_end = 0; static unsigned long low_memory_start = 0; static char term[21]; int rows, cols; static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, }; static char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", term, NULL, }; static char * argv_rc[] = { "/bin/sh", NULL }; static char * envp_rc[] = { "HOME=/", term, NULL }; static char * argv[] = { "-/bin/sh",NULL }; static char * envp[] = { "HOME=/usr/root", term, NULL }; struct drive_info_struct { char dummy[32]; } drive_info; struct screen_info screen_info; unsigned char aux_device_present; int ramdisk_size; int root_mountflags = 0; static char fpu_error = 0; static char command_line[80] = { 0, }; char *get_options(char *str, int *ints)//从一段字符串中分离出参数来 { char *cur = str; int i=1; while (cur && isdigit(*cur) && i <= 10) { ints[i++] = simple_strtoul(cur,NULL,0); if ((cur = strchr(cur,',')) != NULL) cur++; } ints[0] = i-1; return(cur); } struct { char *str; void (*setup_func)(char *, int *); } bootsetups[] = { { "reserve=", reserve_setup }, #ifdef CONFIG_INET { "ether=", eth_setup }, #endif #ifdef CONFIG_BLK_DEV_HD { "hd=", hd_setup }, #endif #ifdef CONFIG_BUSMOUSE { "bmouse=", bmouse_setup }, #endif #ifdef CONFIG_SCSI_SEAGATE { "st0x=", st0x_setup }, { "tmc8xx=", tmc8xx_setup }, #endif #ifdef CONFIG_SCSI_T128 { "t128=", t128_setup }, #endif #ifdef CONFIG_SCSI_GENERIC_NCR5380 { "ncr5380=", generic_NCR5380_setup }, #endif #ifdef CONFIG_SCSI_AHA152X { "aha152x=", aha152x_setup}, #endif #ifdef CONFIG_BLK_DEV_XD { "xd=", xd_setup }, #endif #ifdef CONFIG_MCD { "mcd=", mcd_setup }, #endif #ifdef CONFIG_SOUND { "sound=", sound_setup }, #endif #ifdef CONFIG_SBPCD { "sbpcd=", sbpcd_setup }, #endif CONFIG_SBPCD { 0, 0 } }; int checksetup(char *line)//调用line所对应的bootsetups数组中的setup程序 { int i = 0; int ints[11]; while (bootsetups.str) { int n = strlen(bootsetups.str); if (!strncmp(line,bootsetups.str,n)) {//判断是否有与line对应的setup程序 bootsetups.setup_func(get_options(line+n,ints), ints);//调用 return(0); } i++; } return(1); } unsigned long loops_per_sec = 1;//每秒钟循环一次 static void calibrate_delay(void) { int ticks; printk("Calibrating delay loop.. "); while (loops_per_sec <<= 1) { ticks = jiffies; __delay(loops_per_sec);//延迟1秒 ticks = jiffies - ticks;//计算嘀嗒数 if (ticks >= HZ) { __asm__("mull %1 ; divl %2" :"=a" (loops_per_sec) :"d" (HZ), "r" (ticks), "0" (loops_per_sec) :"dx"); printk("ok - %lu.%02lu BogoMips\n", loops_per_sec/500000, (loops_per_sec/5000) % 100); return; } } printk("failed\n"); } /* * This is a simple kernel command line parsing function: it parses * the command line, and fills in the arguments/environment to init * as appropriate. Any cmd-line option is taken to be an environment * variable if it contains the character '='. * * * This routine also checks for options meant for the kernel - currently * only the "root=XXXX" option is recognized. These options are not given * to init - they are for internal kernel use only. //parse是用来分析命令行参数的，而以root=xxx的选项一概传递给内核，他们不是初始化的选项 */ static void parse_options(char *line) { char *next; char *devnames[] = { "hda", "hdb", "sda", "sdb", "sdc", "sdd", "sde", "fd", "xda", "xdb", NULL }; int devnums[] = { 0x300, 0x340, 0x800, 0x810, 0x820, 0x830, 0x840, 0x200, 0xC00, 0xC40, 0}; int args, envs; if (!*line)//line为空时返回 return; args = 0; envs = 1;/* TERM is set to 'console' by default */ next = line; while ((line = next) != NULL) { if ((next = strchr(line,' ')) != NULL) *next++ = 0; /* * check for kernel options first.. */ if (!strncmp(line,"root=",5)) { int n; line += 5; if (strncmp(line,"/dev/",5)) { ROOT_DEV = simple_strtoul(line,NULL,16); continue; } line += 5; for (n = 0 ; devnames[n] ; n++) { int len = strlen(devnames[n]); if (!strncmp(line,devnames[n],len)) { ROOT_DEV = devnums[n]+simple_strtoul(line+len,NULL,16); break; } } } else if (!strcmp(line,"ro")) root_mountflags |= MS_RDONLY;//只读的挂接根文件系统 else if (!strcmp(line,"rw")) root_mountflags &= ~MS_RDONLY;//可写 else if (!strcmp(line,"debug")) console_loglevel = 10;//若为调试则将终端消息输出的优先权置为10 else if (!strcmp(line,"no387")) {//没有协处理器 hard_math = 0; __asm__("movl %%cr0,%%eax\n\t" "orl $0xE,%%eax\n\t" "movl %%eax,%%cr0\n\t" : : : "ax");//？ } else checksetup(line); /* * Then check if it's an environment variable or * an option. */ if (strchr(line,'=')) { if (envs >= MAX_INIT_ENVS) break; envp_init[++envs] = line; } else { if (args >= MAX_INIT_ARGS) break; argv_init[++args] = line; } } argv_init[args+1] = NULL; envp_init[envs+1] = NULL;//环境变量的初始化 } static void copy_options(char * to, char * from) { char c = ' '; do { if (c == ' ' && !memcmp("mem=", from, 4))//设置内存结束 memory_end = simple_strtoul(from+4, &from, 0); c = *(to++) = *(from++); } while (c); } static void copro_timeout(void)//////////? { fpu_error = 1; timer_table[COPRO_TIMER].expires = jiffies+100; timer_active |= 1< 16*1024*1024) memory_end = 16*1024*1024; #endif if (MOUNT_ROOT_RDONLY) root_mountflags |= MS_RDONLY;//只读挂接根文件系统 if ((unsigned long)&end >= (1024*1024)) {//看可用内存是不是大于1兆,若是,则可用内存从end开始,否则从1兆开始 memory_start = (unsigned long) &end; low_memory_start = PAGE_SIZE;//低端内存从第二页开始 } else { memory_start = 1024*1024; low_memory_start = (unsigned long) &end; } low_memory_start = PAGE_ALIGN(low_memory_start); memory_start = paging_init(memory_start,memory_end);//初始化页表 if (strncmp((char*)0x0FFFD9, "EISA", 4) == 0)//是否有eisa总线 EISA_bus = 1; trap_init();// init_IRQ(); sched_init(); parse_options(command_line); #ifdef CONFIG_PROFILE prof_buffer = (unsigned long *) memory_start; prof_len = (unsigned long) &end; prof_len >>= 2; memory_start += prof_len * sizeof(unsigned long); #endif memory_start = kmalloc_init(memory_start,memory_end); memory_start = chr_dev_init(memory_start,memory_end); memory_start = blk_dev_init(memory_start,memory_end); sti(); calibrate_delay(); #ifdef CONFIG_INET memory_start = net_dev_init(memory_start,memory_end); #endif #ifdef CONFIG_SCSI memory_start = scsi_dev_init(memory_start,memory_end); #endif memory_start = inode_init(memory_start,memory_end); memory_start = file_table_init(memory_start,memory_end); mem_init(low_memory_start,memory_start,memory_end); buffer_init(); time_init(); floppy_init(); sock_init(); #ifdef CONFIG_SYSVIPC ipc_init(); #endif sti(); /* * check if exception 16 works correctly.. This is truly evil * code: it disables the high 8 interrupts to make sure that * the irq13 doesn't happen. But as this will lead to a lockup * if no exception16 arrives, it depends on the fact that the * high 8 interrupts will be re-enabled by the next timer tick. * So the irq13 will happen eventually, but the exception 16 * should get there first.. */ if (hard_math) { unsigned short control_word; printk("Checking 386/387 coupling... "); timer_table[COPRO_TIMER].expires = jiffies+50; timer_table[COPRO_TIMER].fn = copro_timeout; timer_active |= 1<0) while (pid != wait(&i))//等待子进程的结束 /* nothing */; while (1) { if ((pid = fork()) < 0) { printf("Fork failed in init\n\r"); continue; } if (!pid) { close(0);close(1);close(2); setsid();//? (void) open("/dev/tty1",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); }