\u30c6\u30ad\u30b9\u30c8\u306e74\u30da\u30fc\u30b8<\/p>\n
\u4f4e\u30ec\u30a4\u30e4\u304c\u63d0\u4f9b\u3059\u308b\u95a2\u6570\u3092\u4f7f\u3063\u3066\u5b9f\u88c5\u3055\u308c\u308b\u591a\u304f\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u4e9b\u7d30\u306a\u3082\u306e\u3067\u3042\u308b\u3002\uff08sysfile.c\u3092\u898b\u3088\uff09
\n\u305d\u306e\u4e2d\u3067\u6ce8\u76ee\u306b\u5024\u3059\u308b\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u304c\u3044\u304f\u3064\u304b\u3042\u308b\u3002<\/p>\n
sys_link\u3068sys_unlink\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u3001\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3092\u5909\u66f4\u3057\u3001inode\u3078\u306e\u53c2\u7167\u3092\u751f\u6210\u3057\u305f\u308a\u6d88\u53bb\u3057\u305f\u308a\u3059\u308b\u3002
\n\u305d\u308c\u3089\u306f\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u306e\u4fbf\u5229\u3055\u3092\u793a\u3059\u3044\u3044\u4f8b\u3067\u3042\u308b\u3002
\nsys_link\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u3001\u305d\u306e\u5f15\u6570\u3001old\u3068new\u3068\u3044\u3046\u6587\u5b57\u5217\u5909\u6570\u3092\u53d6\u308a\u51fa\u3059\u3068\u3053\u308d\u304b\u3089\u306f\u3058\u3081\u308b\u3002
\nold\u306f\u5b58\u5728\u3057\u3001\u304b\u3064\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3067\u306f\u306a\u3044\u3068\u4eee\u5b9a\u3057\u3001sys_link\u306f\u305d\u306eip->nlink\u3092\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u3059\u308b\u3002
\n\u305d\u308c\u304b\u3089sys_link\u306f\u3001new\u306e\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3068\u6700\u5f8c\u306e\u30d1\u30b9\u8981\u7d20\u3092\u63a2\u3059\u305f\u3081\u306bnameiparent\u95a2\u6570\u3092\u547c\u3073\u3001\u305d\u3057\u3066old\u306einode\u3092\u53c2\u7167\u3059\u308b\u65b0\u3057\u3044\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u4f5c\u6210\u3059\u308b\u3002
\nnew\u306e\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306f\u5b58\u5728\u3057\u3066\u3044\u308b\u5fc5\u8981\u304c\u3042\u308a\u3001old\u306einode\u3068\u540c\u3058\u30c7\u30d0\u30a4\u30b9\u4e0a\u306b\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002
\ninode\u756a\u53f7\u306f\u3001\u4e00\u3064\u306e\u30c7\u30a3\u30b9\u30af\u4e0a\u3067\u306e\u307f\u4e00\u610f\u3060\u304b\u3089\u3067\u3042\u308b\u3002
\n\u4ee5\u4e0a\u306e\u30eb\u30fc\u30eb\u306b\u6cbf\u308f\u306a\u3044\u3088\u3046\u306a\u30a8\u30e9\u30fc\u304c\u8d77\u304d\u305f\u5834\u5408\u3001sys_link\u306f\u9014\u4e2d\u307e\u3067\u884c\u3063\u305f\u64cd\u4f5c\u3092\u5143\u306b\u623b\u3057\u3066\u3001ip->nlink\u3092\u30c7\u30af\u30ea\u30e1\u30f3\u30c8\u3057\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002<\/p>\n
sys_link\u306f\u8907\u6570\u306e\u30c7\u30a3\u30b9\u30af\u30d6\u30ed\u30c3\u30af\u3092\u66f4\u65b0\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b\u306e\u3067\u3001\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u306f\u305d\u306e\u5b9f\u88c5\u3092\u5358\u7d14\u5316\u3059\u308b\u304c\u3001\u3069\u306e\u3088\u3046\u306a\u9806\u756a\u3067\u30d6\u30ed\u30c3\u30af\u304c\u66f4\u65b0\u3055\u308c\u308b\u304b\u306b\u3064\u3044\u3066\u306f\u6211\u3005\u304c\u5fc3\u914d\u3059\u308b\u5fc5\u8981\u306f\u306a\u3044\u3002
\n\u6700\u7d42\u7684\u306b\u306f\u6210\u529f\u3059\u308b\u304b\u5931\u6557\u3059\u308b\u304b\u306e\u3069\u3061\u3089\u304b\u3067\u3042\u308b\u3002
\n\u4f8b\u3048\u3070\u3001\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u7121\u3057\u3060\u3068\u3001\u30ea\u30f3\u30af\u3092\u4f5c\u6210\u3059\u308b\u307e\u3048\u306bip->nlink\u3092\u66f4\u65b0\u3059\u308b\u3068\u304d\u306b\u3001\u4e00\u6642\u7684\u306b\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u304c\u5371\u967a\u306a\u72b6\u614b\u306b\u306a\u308a\u3001\u305d\u306e\u9593\u306b\u30af\u30e9\u30c3\u30b7\u30e5\u304c\u8d77\u304d\u308b\u3068\u3001\u5927\u7834\u58ca\u304c\u3082\u305f\u3089\u3055\u308c\u308b\u3060\u308d\u3046\u3002
\n\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u3092\u4f7f\u3048\u3070\u3001\u3053\u306e\u3088\u3046\u306a\u4e8b\u306b\u3064\u3044\u3066\u5fc3\u914d\u3059\u308b\u5fc5\u8981\u306f\u306a\u304f\u306a\u308b\u3002<\/p>\n
sys_link\u306f\u3001\u65e2\u5b58\u306einode\u306e\u305f\u3081\u306e\u65b0\u3057\u3044\u540d\u524d\u3092\u4f5c\u6210\u3059\u308b\u3002
\ncreate\u95a2\u6570\u306f\u3001\u65b0\u3057\u3044inode\u306e\u305f\u3081\u306e\u65b0\u3057\u3044\u540d\u524d\u3092\u4f5c\u6210\u3059\u308b\u3002
\ncreate\u95a2\u6570\u306f\u3001\u30d5\u30a1\u30a4\u30eb\u751f\u6210\u306b\u95a2\u308f\u308b3\u3064\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306e\u51e6\u7406\u3092\u4e00\u822c\u5316\u3057\u305f\u3082\u306e\u3067\u3042\u308b\u3002
\nopen\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u304cO_CREATE\u30d5\u30e9\u30b0\u3068\u3068\u3082\u306b\u547c\u3070\u308c\u308b\u3068\u3001\u901a\u5e38\u306e\u65b0\u3057\u3044\u30d5\u30a1\u30a4\u30eb\u3092\u751f\u6210\u3057\u3001mkdir\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u65b0\u3057\u3044\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3092\u4f5c\u6210\u3057\u3001mkdev\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u65b0\u3057\u3044\u30c7\u30d0\u30a4\u30b9\u30d5\u30a1\u30a4\u30eb\u3092\u4f5c\u6210\u3059\u308b\u3002
\nsys_link\u306e\u3088\u3046\u306b\u3001create\u95a2\u6570\u306f\u3001\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306einode\u3092\u5f97\u308b\u305f\u3081\u306bnameiparent\u95a2\u6570\u3092\u547c\u3076\u3053\u3068\u304b\u3089\u521d\u3081\u308b\u3002
\n\u305d\u308c\u304b\u3089dirlookup\u95a2\u6570\u3092\u4f7f\u3063\u3066\u3001\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3066\u3044\u306a\u3044\u304b\u30c1\u30a7\u30c3\u30af\u3059\u308b\u3002
\n\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3066\u3044\u305f\u5834\u5408\u3001create\u95a2\u6570\u306e\u632f\u308b\u821e\u3044\u306f\u3069\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306b\u547c\u3070\u308c\u305f\u304b\u306b\u4f9d\u5b58\u3059\u308b\u3002
\n\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3066\u3044\u308b\u3068\u3044\u3046\u4e8b\u5b9f\u306f\u3001open\u3067\u306f\u3001mkdir\u3084mkdev\u3068\u306f\u9055\u3063\u305f\u610f\u5473\u3092\u6301\u3064\u3002
\ncreate\u304copen\u306e\u305f\u3081\u306b\u547c\u3070\u308c\uff08type == T_FILE\uff09\u3001\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3001\u305d\u308c\u304c\u901a\u5e38\u306e\u30d5\u30a1\u30a4\u30eb\u3060\u3063\u305f\u5834\u5408\u3001open\u306f\u6210\u529f\u3068\u3057\u3066\u6271\u3044\u3001create\u3082\u305d\u308c\u306b\u5f93\u3046\u3002
\n\u305d\u3046\u3067\u306a\u3051\u308c\u3070\u30a8\u30e9\u30fc\u3068\u306a\u308b\u3002
\n\u540d\u524d\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u3001create\u306fialloc\u3092\u4f7f\u3063\u3066\u65b0\u3057\u3044inode\u3092\u5272\u308a\u5f53\u3066\u308b\u3002
\n\u65b0\u3057\u3044inode\u304c\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3067\u3042\u308b\u5834\u5408\u3001create\u306f”.”\u3068”..”\u3067\u305d\u306e\u30a8\u30f3\u30c8\u30ea\u3092\u521d\u671f\u5316\u3059\u308b\u3002
\n\u6700\u5f8c\u306b\u3001\u305d\u306e\u30c7\u30fc\u30bf\u304c\u6b63\u5e38\u306b\u521d\u671f\u5316\u3055\u308c\u305f\u3089\u3001create\u306f\u305d\u306e\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b\u305d\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3078\u306e\u30ea\u30f3\u30af\u3092\u4f5c\u6210\u3059\u308b\u3002
\ncreate\u306f\u3001sys_link\u306e\u3088\u3046\u306b\u3001\u540c\u6642\u306b2\u3064\u306einode\uff08ip\u3068dp\uff09\u306e\u30ed\u30c3\u30af\u3092\u4fdd\u6301\u3059\u308b\u3002
\ninode ip\u306f\u65b0\u305f\u306b\u5272\u308a\u5f53\u3066\u3089\u308c\u305f\u3082\u306e\u306a\u306e\u3067\u3001\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u306f\u8d77\u3053\u308a\u3048\u306a\u3044\u3002
\n\u307e\u305aip\u3092\u30ed\u30c3\u30af\u3057\u3001\u305d\u308c\u304b\u3089dp\u3092\u30ed\u30c3\u30af\u3057\u3088\u3046\u3068\u3059\u308b\u3088\u3046\u306a\u4ed6\u306e\u30d7\u30ed\u30bb\u30b9\u306f\u5b58\u5728\u3057\u306a\u3044\u3002<\/p>\n
create\u3092\u4f7f\u3046\u3068\u3001sys_open, sys_mkdir, sys_mknod\u306e\u5b9f\u88c5\u304c\u7c21\u5358\u306b\u306a\u308b\u3002
\nsys_open\u304c\u305d\u306e\u4e2d\u3067\u306f\u4e00\u756a\u8907\u96d1\u3067\u3042\u308b\u3002
\n\u306a\u305c\u306a\u3089\u65b0\u3057\u3044\u30d5\u30a1\u30a4\u30eb\u3092\u751f\u6210\u3059\u308b\u3053\u3068\u306f\u3001\u305d\u308c\u304c\u51fa\u6765\u308b\u3053\u3068\u306e\u4e00\u90e8\u306b\u904e\u304e\u306a\u3044\u304b\u3089\u3067\u3042\u308b\u3002
\nopen\u306bO_CREATE\u30d5\u30e9\u30b0\u304c\u6e21\u3055\u308c\u305f\u5834\u5408\u3001create\u3092\u547c\u3076\u3002
\n\u305d\u308c\u4ee5\u5916\u306e\u5834\u5408\u306f\u3001namei\u3092\u547c\u3076\u3002
\ncreate\u306f\u30ed\u30c3\u30af\u6e08\u307f\u306einode\u3092\u8fd4\u3059\u304c\u3001namei\u306f\u305d\u3046\u3058\u3083\u306a\u3044\u306e\u3067\u3001sys_open\u306f\u305d\u306einode\u3092\u81ea\u5206\u81ea\u8eab\u3067\u30ed\u30c3\u30af\u3059\u308b\u3002
\n\u3053\u308c\u306f\u3001\u5bfe\u8c61\u306einode\u304c\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u304b\u3064\u8aad\u307f\u8fbc\u307f\u5c02\u7528\u3067\u958b\u304b\u308c\u3066\u308b\u3060\u3051\u304b\u3069\u3046\u304b\u3092\u30c1\u30a7\u30c3\u30af\u3059\u308b\u306b\u306f\u3088\u3044\u7b87\u6240\u3067\u3042\u308b\u3002
\n\u3044\u305a\u308c\u306b\u3057\u3066\u3082\u3001inode\u304c\u5f97\u3089\u308c\u305f\u3068\u4eee\u5b9a\u3057\u3001sys_open\u306f\u30d5\u30a1\u30a4\u30eb\u3068\u30d5\u30a1\u30a4\u30eb\u30c7\u30a3\u30b9\u30af\u30ea\u30d7\u30bf\u3092\u5272\u308a\u5f53\u3066\u3001\u305d\u308c\u304b\u3089\u30d5\u30a1\u30a4\u30eb\u306e\u30e1\u30bf\u30c7\u30fc\u30bf\u3092\u8a2d\u5b9a\u3059\u308b\u3002
\n\u3053\u306e\u30d5\u30a1\u30a4\u30eb\u306f\u3001\u73fe\u5728\u306e\u30d7\u30ed\u30bb\u30b9\u306e\u30c6\u30fc\u30d6\u30eb\u306b\u3057\u304b\u5b58\u5728\u3057\u306a\u3044\u306e\u3067\u3001\u521d\u671f\u5316\u9014\u4e2d\u306e\u30d5\u30a1\u30a4\u30eb\u306b\u4ed6\u306e\u30d7\u30ed\u30bb\u30b9\u304c\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u306f\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u306b\u6ce8\u610f\u305b\u3088\u3002<\/p>\n
\u7b2c4\u7ae0\u3067\u306f\u3001\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u306e\u8aac\u660e\u306e\u524d\u306b\u3001\u30d1\u30a4\u30d7\u306e\u5b9f\u88c5\u306b\u3064\u3044\u3066\u8aac\u660e\u3057\u305f\u3002
\nsys_pipe\u95a2\u6570\u306f\u3001\u30d1\u30a4\u30d7\u306e\u7d44\u3092\u751f\u6210\u3059\u308b\u65b9\u6cd5\u3092\u63d0\u4f9b\u3059\u308b\u4e8b\u306b\u3088\u3063\u3066\u3001\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u306e\u5b9f\u88c5\u3078\u306e\u6a4b\u6e21\u3057\u3092\u3057\u3066\u3044\u308b\u3002
\nsys_pipe\u306e\u5f15\u6570\u306f\u30012\u3064\u306e\u6574\u6570\u306e\u9818\u57df\u3092\u6307\u3059\u30dd\u30a4\u30f3\u30bf\u3067\u3042\u308a\u3001\u65b0\u3057\u30442\u3064\u306e\u30d5\u30a1\u30a4\u30eb\u30c7\u30a3\u30b9\u30af\u30ea\u30d7\u30bf\u3092\u8a18\u9332\u3059\u308b\u5834\u6240\u306b\u306a\u308b\u3002
\nsys_pipe\u306f\u30d1\u30a4\u30d7\u3092\u5272\u308a\u5f53\u3066\u3001\u30d5\u30a1\u30a4\u30eb\u30c7\u30a3\u30b9\u30af\u30ea\u30d7\u30bf\u306b\u305d\u306e\u30d1\u30a4\u30d7\u3092\u8a2d\u5b9a\u3059\u308b\u3002<\/p>\n
sysfile.c<\/p>\n
#include "types.h"\r\n#include "defs.h"\r\n#include "param.h"\r\n#include "stat.h"\r\n#include "mmu.h"\r\n#include "proc.h"\r\n#include "fs.h"\r\n#include "file.h"\r\n#include "fcntl.h"\r\n\r\n\/\/ Fetch the nth word-sized system call argument as a file descriptor\r\n\/\/ and return both the descriptor and the corresponding struct file.\r\nstatic int\r\nargfd(int n, int *pfd, struct file **pf)\r\n{\r\n int fd;\r\n struct file *f;\r\n\r\n if(argint(n, &fd) < 0)\r\n return -1;\r\n if(fd < 0 || fd >= NOFILE || (f=proc->ofile[fd]) == 0)\r\n return -1;\r\n if(pfd)\r\n *pfd = fd;\r\n if(pf)\r\n *pf = f;\r\n return 0;\r\n}\r\n\r\n\/\/ Allocate a file descriptor for the given file.\r\n\/\/ Takes over file reference from caller on success.\r\nstatic int\r\nfdalloc(struct file *f)\r\n{\r\n int fd;\r\n\r\n for(fd = 0; fd < NOFILE; fd++){\r\n if(proc->ofile[fd] == 0){\r\n proc->ofile[fd] = f;\r\n return fd;\r\n }\r\n }\r\n return -1;\r\n}\r\n\r\nint\r\nsys_dup(void)\r\n{\r\n struct file *f;\r\n int fd;\r\n \r\n if(argfd(0, 0, &f) < 0)\r\n return -1;\r\n if((fd=fdalloc(f)) < 0)\r\n return -1;\r\n filedup(f);\r\n return fd;\r\n}\r\n\r\nint\r\nsys_read(void)\r\n{\r\n struct file *f;\r\n int n;\r\n char *p;\r\n\r\n if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0)\r\n return -1;\r\n return fileread(f, p, n);\r\n}\r\n\r\nint\r\nsys_write(void)\r\n{\r\n struct file *f;\r\n int n;\r\n char *p;\r\n\r\n if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0)\r\n return -1;\r\n return filewrite(f, p, n);\r\n}\r\n\r\nint\r\nsys_close(void)\r\n{\r\n int fd;\r\n struct file *f;\r\n \r\n if(argfd(0, &fd, &f) < 0)\r\n return -1;\r\n proc->ofile[fd] = 0;\r\n fileclose(f);\r\n return 0;\r\n}\r\n\r\nint\r\nsys_fstat(void)\r\n{\r\n struct file *f;\r\n struct stat *st;\r\n \r\n if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof(*st)) < 0)\r\n return -1;\r\n return filestat(f, st);\r\n}\r\n\r\n\/\/ Create the path new as a link to the same inode as old.\r\nint\r\nsys_link(void)\r\n{\r\n char name[DIRSIZ], *new, *old;\r\n struct inode *dp, *ip;\r\n\r\n if(argstr(0, &old) < 0 || argstr(1, &new) < 0)\r\n return -1;\r\n if((ip = namei(old)) == 0)\r\n return -1;\r\n\r\n begin_trans();\r\n\r\n ilock(ip);\r\n if(ip->type == T_DIR){\r\n iunlockput(ip);\r\n commit_trans();\r\n return -1;\r\n }\r\n\r\n ip->nlink++;\r\n iupdate(ip);\r\n iunlock(ip);\r\n\r\n if((dp = nameiparent(new, name)) == 0)\r\n goto bad;\r\n ilock(dp);\r\n if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0){\r\n iunlockput(dp);\r\n goto bad;\r\n }\r\n iunlockput(dp);\r\n iput(ip);\r\n\r\n commit_trans();\r\n\r\n return 0;\r\n\r\nbad:\r\n ilock(ip);\r\n ip->nlink--;\r\n iupdate(ip);\r\n iunlockput(ip);\r\n commit_trans();\r\n return -1;\r\n}\r\n\r\n\/\/ Is the directory dp empty except for "." and ".." ?\r\nstatic int\r\nisdirempty(struct inode *dp)\r\n{\r\n int off;\r\n struct dirent de;\r\n\r\n for(off=2*sizeof(de); off<dp->size; off+=sizeof(de)){\r\n if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n panic("isdirempty: readi");\r\n if(de.inum != 0)\r\n return 0;\r\n }\r\n return 1;\r\n}\r\n\r\n\/\/PAGEBREAK!\r\nint\r\nsys_unlink(void)\r\n{\r\n struct inode *ip, *dp;\r\n struct dirent de;\r\n char name[DIRSIZ], *path;\r\n uint off;\r\n\r\n if(argstr(0, &path) < 0)\r\n return -1;\r\n if((dp = nameiparent(path, name)) == 0)\r\n return -1;\r\n\r\n begin_trans();\r\n\r\n ilock(dp);\r\n\r\n \/\/ Cannot unlink "." or "..".\r\n if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0)\r\n goto bad;\r\n\r\n if((ip = dirlookup(dp, name, &off)) == 0)\r\n goto bad;\r\n ilock(ip);\r\n\r\n if(ip->nlink < 1)\r\n panic("unlink: nlink < 1");\r\n if(ip->type == T_DIR && !isdirempty(ip)){\r\n iunlockput(ip);\r\n goto bad;\r\n }\r\n\r\n memset(&de, 0, sizeof(de));\r\n if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n panic("unlink: writei");\r\n if(ip->type == T_DIR){\r\n dp->nlink--;\r\n iupdate(dp);\r\n }\r\n iunlockput(dp);\r\n\r\n ip->nlink--;\r\n iupdate(ip);\r\n iunlockput(ip);\r\n\r\n commit_trans();\r\n\r\n return 0;\r\n\r\nbad:\r\n iunlockput(dp);\r\n commit_trans();\r\n return -1;\r\n}\r\n\r\nstatic struct inode*\r\ncreate(char *path, short type, short major, short minor)\r\n{\r\n uint off;\r\n struct inode *ip, *dp;\r\n char name[DIRSIZ];\r\n\r\n if((dp = nameiparent(path, name)) == 0)\r\n return 0;\r\n ilock(dp);\r\n\r\n if((ip = dirlookup(dp, name, &off)) != 0){\r\n iunlockput(dp);\r\n ilock(ip);\r\n if(type == T_FILE && ip->type == T_FILE)\r\n return ip;\r\n iunlockput(ip);\r\n return 0;\r\n }\r\n\r\n if((ip = ialloc(dp->dev, type)) == 0)\r\n panic("create: ialloc");\r\n\r\n ilock(ip);\r\n ip->major = major;\r\n ip->minor = minor;\r\n ip->nlink = 1;\r\n iupdate(ip);\r\n\r\n if(type == T_DIR){ \/\/ Create . and .. entries.\r\n dp->nlink++; \/\/ for ".."\r\n iupdate(dp);\r\n \/\/ No ip->nlink++ for ".": avoid cyclic ref count.\r\n if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0)\r\n panic("create dots");\r\n }\r\n\r\n if(dirlink(dp, name, ip->inum) < 0)\r\n panic("create: dirlink");\r\n\r\n iunlockput(dp);\r\n\r\n return ip;\r\n}\r\n\r\nint\r\nsys_open(void)\r\n{\r\n char *path;\r\n int fd, omode;\r\n struct file *f;\r\n struct inode *ip;\r\n\r\n if(argstr(0, &path) < 0 || argint(1, &omode) < 0)\r\n return -1;\r\n if(omode & O_CREATE){\r\n begin_trans();\r\n ip = create(path, T_FILE, 0, 0);\r\n commit_trans();\r\n if(ip == 0)\r\n return -1;\r\n } else {\r\n if((ip = namei(path)) == 0)\r\n return -1;\r\n ilock(ip);\r\n if(ip->type == T_DIR && omode != O_RDONLY){\r\n iunlockput(ip);\r\n return -1;\r\n }\r\n }\r\n\r\n if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){\r\n if(f)\r\n fileclose(f);\r\n iunlockput(ip);\r\n return -1;\r\n }\r\n iunlock(ip);\r\n\r\n f->type = FD_INODE;\r\n f->ip = ip;\r\n f->off = 0;\r\n f->readable = !(omode & O_WRONLY);\r\n f->writable = (omode & O_WRONLY) || (omode & O_RDWR);\r\n return fd;\r\n}\r\n\r\nint\r\nsys_mkdir(void)\r\n{\r\n char *path;\r\n struct inode *ip;\r\n\r\n begin_trans();\r\n if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){\r\n commit_trans();\r\n return -1;\r\n }\r\n iunlockput(ip);\r\n commit_trans();\r\n return 0;\r\n}\r\n\r\nint\r\nsys_mknod(void)\r\n{\r\n struct inode *ip;\r\n char *path;\r\n int len;\r\n int major, minor;\r\n \r\n begin_trans();\r\n if((len=argstr(0, &path)) < 0 ||\r\n argint(1, &major) < 0 ||\r\n argint(2, &minor) < 0 ||\r\n (ip = create(path, T_DEV, major, minor)) == 0){\r\n commit_trans();\r\n return -1;\r\n }\r\n iunlockput(ip);\r\n commit_trans();\r\n return 0;\r\n}\r\n\r\nint\r\nsys_chdir(void)\r\n{\r\n char *path;\r\n struct inode *ip;\r\n\r\n if(argstr(0, &path) < 0 || (ip = namei(path)) == 0)\r\n return -1;\r\n ilock(ip);\r\n if(ip->type != T_DIR){\r\n iunlockput(ip);\r\n return -1;\r\n }\r\n iunlock(ip);\r\n iput(proc->cwd);\r\n proc->cwd = ip;\r\n return 0;\r\n}\r\n\r\nint\r\nsys_exec(void)\r\n{\r\n char *path, *argv[MAXARG];\r\n int i;\r\n uint uargv, uarg;\r\n\r\n if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0){\r\n return -1;\r\n }\r\n memset(argv, 0, sizeof(argv));\r\n for(i=0;; i++){\r\n if(i >= NELEM(argv))\r\n return -1;\r\n if(fetchint(proc, uargv+4*i, (int*)&uarg) < 0)\r\n return -1;\r\n if(uarg == 0){\r\n argv[i] = 0;\r\n break;\r\n }\r\n if(fetchstr(proc, uarg, &argv[i]) < 0)\r\n return -1;\r\n }\r\n return exec(path, argv);\r\n}\r\n\r\nint\r\nsys_pipe(void)\r\n{\r\n int *fd;\r\n struct file *rf, *wf;\r\n int fd0, fd1;\r\n\r\n if(argptr(0, (void*)&fd, 2*sizeof(fd[0])) < 0)\r\n return -1;\r\n if(pipealloc(&rf, &wf) < 0)\r\n return -1;\r\n fd0 = -1;\r\n if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){\r\n if(fd0 >= 0)\r\n proc->ofile[fd0] = 0;\r\n fileclose(rf);\r\n fileclose(wf);\r\n return -1;\r\n }\r\n fd[0] = fd0;\r\n fd[1] = fd1;\r\n return 0;\r\n}<\/pre>\n\u611f\u60f3<\/h3>\n
\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u95a2\u9023\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306e\u5b9f\u88c5\u306b\u3064\u3044\u3066\u3067\u3059\u3002<\/p>\n
\u539f\u6587\u3067\u3082\u660e\u8a18\u3055\u308c\u3066\u306a\u304b\u3063\u305f\u308a\u3059\u308b\u306e\u3067\u3001\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u3068\u3044\u3046\u540d\u79f0\u3068\u95a2\u6570\u3068\u3044\u3046\u540d\u79f0\u306e\u4f7f\u3044\u5206\u3051\u304c\u66d6\u6627\u306a\u90e8\u5206\u304c\u3042\u308a\u307e\u3059\u3002
\n\u307e\u3041\u95a2\u6570\u306e\u307b\u3046\u304c\u3088\u308a\u4e00\u822c\u7684\u306a\u6982\u5ff5\u306a\u306e\u3067\u3069\u3061\u3089\u3082\u95a2\u6570\u3068\u8a00\u3063\u3066\u304a\u3051\u3070\u9593\u9055\u3044\u306a\u3044\u3068\u601d\u3044\u307e\u3059\u304c\u3001\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306b\u95a2\u3057\u3066\u306f\u3001SYSCALL\u30de\u30af\u30ed\u3067\u751f\u6210\u3055\u308c\u305f\uff08\u4f8b\u3048\u3070\uff09open\u306e\u3088\u3046\u306a\u3082\u306e\u3060\u3051\u3092\u305d\u3046\u547c\u3076\u306e\u304b\u3001\u305d\u306e\u5b9f\u4f53\u3067\u3042\u308b\uff08\u4f8b\u3048\u3070\uff09sys_open\u307e\u3067\u542b\u3081\u308b\u306e\u304b\u3069\u3046\u304b\u304c\u5fae\u5999\u306a\u3068\u3053\u308d\u3067\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u30c6\u30ad\u30b9\u30c8\u306e74\u30da\u30fc\u30b8<\/p>\n
\u672c\u6587<\/h3>\n
\u4f4e\u30ec\u30a4\u30e4\u304c\u63d0\u4f9b\u3059\u308b\u95a2\u6570\u3092\u4f7f\u3063\u3066\u5b9f\u88c5\u3055\u308c\u308b\u591a\u304f\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u4e9b\u7d30\u306a\u3082\u306e\u3067\u3042\u308b\u3002\uff08sysfile.c\u3092\u898b\u3088\uff09
\n\u305d\u306e\u4e2d\u3067\u6ce8\u76ee\u306b\u5024\u3059\u308b\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u304c\u3044\u304f\u3064\u304b\u3042\u308b\u3002<\/p>\n
sys_link\u3068sys_unlink\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u3001\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3092\u5909\u66f4\u3057\u3001inode\u3078\u306e\u53c2\u7167\u3092\u751f\u6210\u3057\u305f\u308a\u6d88\u53bb\u3057\u305f\u308a\u3059\u308b\u3002
\n\u305d\u308c\u3089\u306f\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u306e\u4fbf\u5229\u3055\u3092\u793a\u3059\u3044\u3044\u4f8b\u3067\u3042\u308b\u3002
\nsys_link\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u3001\u305d\u306e\u5f15\u6570\u3001old\u3068new\u3068\u3044\u3046\u6587\u5b57\u5217\u5909\u6570\u3092\u53d6\u308a\u51fa\u3059\u3068\u3053\u308d\u304b\u3089\u306f\u3058\u3081\u308b\u3002
\nold\u306f\u5b58\u5728\u3057\u3001\u304b\u3064\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3067\u306f\u306a\u3044\u3068\u4eee\u5b9a\u3057\u3001sys_link\u306f\u305d\u306eip->nlink\u3092\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u3059\u308b\u3002
\n\u305d\u308c\u304b\u3089sys_link\u306f\u3001new\u306e\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3068\u6700\u5f8c\u306e\u30d1\u30b9\u8981\u7d20\u3092\u63a2\u3059\u305f\u3081\u306bnameiparent\u95a2\u6570\u3092\u547c\u3073\u3001\u305d\u3057\u3066old\u306einode\u3092\u53c2\u7167\u3059\u308b\u65b0\u3057\u3044\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u4f5c\u6210\u3059\u308b\u3002
\nnew\u306e\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306f\u5b58\u5728\u3057\u3066\u3044\u308b\u5fc5\u8981\u304c\u3042\u308a\u3001old\u306einode\u3068\u540c\u3058\u30c7\u30d0\u30a4\u30b9\u4e0a\u306b\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002
\ninode\u756a\u53f7\u306f\u3001\u4e00\u3064\u306e\u30c7\u30a3\u30b9\u30af\u4e0a\u3067\u306e\u307f\u4e00\u610f\u3060\u304b\u3089\u3067\u3042\u308b\u3002
\n\u4ee5\u4e0a\u306e\u30eb\u30fc\u30eb\u306b\u6cbf\u308f\u306a\u3044\u3088\u3046\u306a\u30a8\u30e9\u30fc\u304c\u8d77\u304d\u305f\u5834\u5408\u3001sys_link\u306f\u9014\u4e2d\u307e\u3067\u884c\u3063\u305f\u64cd\u4f5c\u3092\u5143\u306b\u623b\u3057\u3066\u3001ip->nlink\u3092\u30c7\u30af\u30ea\u30e1\u30f3\u30c8\u3057\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u3002<\/p>\n
sys_link\u306f\u8907\u6570\u306e\u30c7\u30a3\u30b9\u30af\u30d6\u30ed\u30c3\u30af\u3092\u66f4\u65b0\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b\u306e\u3067\u3001\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u306f\u305d\u306e\u5b9f\u88c5\u3092\u5358\u7d14\u5316\u3059\u308b\u304c\u3001\u3069\u306e\u3088\u3046\u306a\u9806\u756a\u3067\u30d6\u30ed\u30c3\u30af\u304c\u66f4\u65b0\u3055\u308c\u308b\u304b\u306b\u3064\u3044\u3066\u306f\u6211\u3005\u304c\u5fc3\u914d\u3059\u308b\u5fc5\u8981\u306f\u306a\u3044\u3002
\n\u6700\u7d42\u7684\u306b\u306f\u6210\u529f\u3059\u308b\u304b\u5931\u6557\u3059\u308b\u304b\u306e\u3069\u3061\u3089\u304b\u3067\u3042\u308b\u3002
\n\u4f8b\u3048\u3070\u3001\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u7121\u3057\u3060\u3068\u3001\u30ea\u30f3\u30af\u3092\u4f5c\u6210\u3059\u308b\u307e\u3048\u306bip->nlink\u3092\u66f4\u65b0\u3059\u308b\u3068\u304d\u306b\u3001\u4e00\u6642\u7684\u306b\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u304c\u5371\u967a\u306a\u72b6\u614b\u306b\u306a\u308a\u3001\u305d\u306e\u9593\u306b\u30af\u30e9\u30c3\u30b7\u30e5\u304c\u8d77\u304d\u308b\u3068\u3001\u5927\u7834\u58ca\u304c\u3082\u305f\u3089\u3055\u308c\u308b\u3060\u308d\u3046\u3002
\n\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u3092\u4f7f\u3048\u3070\u3001\u3053\u306e\u3088\u3046\u306a\u4e8b\u306b\u3064\u3044\u3066\u5fc3\u914d\u3059\u308b\u5fc5\u8981\u306f\u306a\u304f\u306a\u308b\u3002<\/p>\n
sys_link\u306f\u3001\u65e2\u5b58\u306einode\u306e\u305f\u3081\u306e\u65b0\u3057\u3044\u540d\u524d\u3092\u4f5c\u6210\u3059\u308b\u3002
\ncreate\u95a2\u6570\u306f\u3001\u65b0\u3057\u3044inode\u306e\u305f\u3081\u306e\u65b0\u3057\u3044\u540d\u524d\u3092\u4f5c\u6210\u3059\u308b\u3002
\ncreate\u95a2\u6570\u306f\u3001\u30d5\u30a1\u30a4\u30eb\u751f\u6210\u306b\u95a2\u308f\u308b3\u3064\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306e\u51e6\u7406\u3092\u4e00\u822c\u5316\u3057\u305f\u3082\u306e\u3067\u3042\u308b\u3002
\nopen\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u304cO_CREATE\u30d5\u30e9\u30b0\u3068\u3068\u3082\u306b\u547c\u3070\u308c\u308b\u3068\u3001\u901a\u5e38\u306e\u65b0\u3057\u3044\u30d5\u30a1\u30a4\u30eb\u3092\u751f\u6210\u3057\u3001mkdir\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u65b0\u3057\u3044\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3092\u4f5c\u6210\u3057\u3001mkdev\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306f\u65b0\u3057\u3044\u30c7\u30d0\u30a4\u30b9\u30d5\u30a1\u30a4\u30eb\u3092\u4f5c\u6210\u3059\u308b\u3002
\nsys_link\u306e\u3088\u3046\u306b\u3001create\u95a2\u6570\u306f\u3001\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306einode\u3092\u5f97\u308b\u305f\u3081\u306bnameiparent\u95a2\u6570\u3092\u547c\u3076\u3053\u3068\u304b\u3089\u521d\u3081\u308b\u3002
\n\u305d\u308c\u304b\u3089dirlookup\u95a2\u6570\u3092\u4f7f\u3063\u3066\u3001\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3066\u3044\u306a\u3044\u304b\u30c1\u30a7\u30c3\u30af\u3059\u308b\u3002
\n\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3066\u3044\u305f\u5834\u5408\u3001create\u95a2\u6570\u306e\u632f\u308b\u821e\u3044\u306f\u3069\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306b\u547c\u3070\u308c\u305f\u304b\u306b\u4f9d\u5b58\u3059\u308b\u3002
\n\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3066\u3044\u308b\u3068\u3044\u3046\u4e8b\u5b9f\u306f\u3001open\u3067\u306f\u3001mkdir\u3084mkdev\u3068\u306f\u9055\u3063\u305f\u610f\u5473\u3092\u6301\u3064\u3002
\ncreate\u304copen\u306e\u305f\u3081\u306b\u547c\u3070\u308c\uff08type == T_FILE\uff09\u3001\u540d\u524d\u304c\u3059\u3067\u306b\u5b58\u5728\u3057\u3001\u305d\u308c\u304c\u901a\u5e38\u306e\u30d5\u30a1\u30a4\u30eb\u3060\u3063\u305f\u5834\u5408\u3001open\u306f\u6210\u529f\u3068\u3057\u3066\u6271\u3044\u3001create\u3082\u305d\u308c\u306b\u5f93\u3046\u3002
\n\u305d\u3046\u3067\u306a\u3051\u308c\u3070\u30a8\u30e9\u30fc\u3068\u306a\u308b\u3002
\n\u540d\u524d\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u3001create\u306fialloc\u3092\u4f7f\u3063\u3066\u65b0\u3057\u3044inode\u3092\u5272\u308a\u5f53\u3066\u308b\u3002
\n\u65b0\u3057\u3044inode\u304c\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3067\u3042\u308b\u5834\u5408\u3001create\u306f”.”\u3068”..”\u3067\u305d\u306e\u30a8\u30f3\u30c8\u30ea\u3092\u521d\u671f\u5316\u3059\u308b\u3002
\n\u6700\u5f8c\u306b\u3001\u305d\u306e\u30c7\u30fc\u30bf\u304c\u6b63\u5e38\u306b\u521d\u671f\u5316\u3055\u308c\u305f\u3089\u3001create\u306f\u305d\u306e\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b\u305d\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u3078\u306e\u30ea\u30f3\u30af\u3092\u4f5c\u6210\u3059\u308b\u3002
\ncreate\u306f\u3001sys_link\u306e\u3088\u3046\u306b\u3001\u540c\u6642\u306b2\u3064\u306einode\uff08ip\u3068dp\uff09\u306e\u30ed\u30c3\u30af\u3092\u4fdd\u6301\u3059\u308b\u3002
\ninode ip\u306f\u65b0\u305f\u306b\u5272\u308a\u5f53\u3066\u3089\u308c\u305f\u3082\u306e\u306a\u306e\u3067\u3001\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u306f\u8d77\u3053\u308a\u3048\u306a\u3044\u3002
\n\u307e\u305aip\u3092\u30ed\u30c3\u30af\u3057\u3001\u305d\u308c\u304b\u3089dp\u3092\u30ed\u30c3\u30af\u3057\u3088\u3046\u3068\u3059\u308b\u3088\u3046\u306a\u4ed6\u306e\u30d7\u30ed\u30bb\u30b9\u306f\u5b58\u5728\u3057\u306a\u3044\u3002<\/p>\n
create\u3092\u4f7f\u3046\u3068\u3001sys_open, sys_mkdir, sys_mknod\u306e\u5b9f\u88c5\u304c\u7c21\u5358\u306b\u306a\u308b\u3002
\nsys_open\u304c\u305d\u306e\u4e2d\u3067\u306f\u4e00\u756a\u8907\u96d1\u3067\u3042\u308b\u3002
\n\u306a\u305c\u306a\u3089\u65b0\u3057\u3044\u30d5\u30a1\u30a4\u30eb\u3092\u751f\u6210\u3059\u308b\u3053\u3068\u306f\u3001\u305d\u308c\u304c\u51fa\u6765\u308b\u3053\u3068\u306e\u4e00\u90e8\u306b\u904e\u304e\u306a\u3044\u304b\u3089\u3067\u3042\u308b\u3002
\nopen\u306bO_CREATE\u30d5\u30e9\u30b0\u304c\u6e21\u3055\u308c\u305f\u5834\u5408\u3001create\u3092\u547c\u3076\u3002
\n\u305d\u308c\u4ee5\u5916\u306e\u5834\u5408\u306f\u3001namei\u3092\u547c\u3076\u3002
\ncreate\u306f\u30ed\u30c3\u30af\u6e08\u307f\u306einode\u3092\u8fd4\u3059\u304c\u3001namei\u306f\u305d\u3046\u3058\u3083\u306a\u3044\u306e\u3067\u3001sys_open\u306f\u305d\u306einode\u3092\u81ea\u5206\u81ea\u8eab\u3067\u30ed\u30c3\u30af\u3059\u308b\u3002
\n\u3053\u308c\u306f\u3001\u5bfe\u8c61\u306einode\u304c\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u304b\u3064\u8aad\u307f\u8fbc\u307f\u5c02\u7528\u3067\u958b\u304b\u308c\u3066\u308b\u3060\u3051\u304b\u3069\u3046\u304b\u3092\u30c1\u30a7\u30c3\u30af\u3059\u308b\u306b\u306f\u3088\u3044\u7b87\u6240\u3067\u3042\u308b\u3002
\n\u3044\u305a\u308c\u306b\u3057\u3066\u3082\u3001inode\u304c\u5f97\u3089\u308c\u305f\u3068\u4eee\u5b9a\u3057\u3001sys_open\u306f\u30d5\u30a1\u30a4\u30eb\u3068\u30d5\u30a1\u30a4\u30eb\u30c7\u30a3\u30b9\u30af\u30ea\u30d7\u30bf\u3092\u5272\u308a\u5f53\u3066\u3001\u305d\u308c\u304b\u3089\u30d5\u30a1\u30a4\u30eb\u306e\u30e1\u30bf\u30c7\u30fc\u30bf\u3092\u8a2d\u5b9a\u3059\u308b\u3002
\n\u3053\u306e\u30d5\u30a1\u30a4\u30eb\u306f\u3001\u73fe\u5728\u306e\u30d7\u30ed\u30bb\u30b9\u306e\u30c6\u30fc\u30d6\u30eb\u306b\u3057\u304b\u5b58\u5728\u3057\u306a\u3044\u306e\u3067\u3001\u521d\u671f\u5316\u9014\u4e2d\u306e\u30d5\u30a1\u30a4\u30eb\u306b\u4ed6\u306e\u30d7\u30ed\u30bb\u30b9\u304c\u30a2\u30af\u30bb\u30b9\u3059\u308b\u3053\u3068\u306f\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u306b\u6ce8\u610f\u305b\u3088\u3002<\/p>\n
\u7b2c4\u7ae0\u3067\u306f\u3001\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u306e\u8aac\u660e\u306e\u524d\u306b\u3001\u30d1\u30a4\u30d7\u306e\u5b9f\u88c5\u306b\u3064\u3044\u3066\u8aac\u660e\u3057\u305f\u3002
\nsys_pipe\u95a2\u6570\u306f\u3001\u30d1\u30a4\u30d7\u306e\u7d44\u3092\u751f\u6210\u3059\u308b\u65b9\u6cd5\u3092\u63d0\u4f9b\u3059\u308b\u4e8b\u306b\u3088\u3063\u3066\u3001\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u306e\u5b9f\u88c5\u3078\u306e\u6a4b\u6e21\u3057\u3092\u3057\u3066\u3044\u308b\u3002
\nsys_pipe\u306e\u5f15\u6570\u306f\u30012\u3064\u306e\u6574\u6570\u306e\u9818\u57df\u3092\u6307\u3059\u30dd\u30a4\u30f3\u30bf\u3067\u3042\u308a\u3001\u65b0\u3057\u30442\u3064\u306e\u30d5\u30a1\u30a4\u30eb\u30c7\u30a3\u30b9\u30af\u30ea\u30d7\u30bf\u3092\u8a18\u9332\u3059\u308b\u5834\u6240\u306b\u306a\u308b\u3002
\nsys_pipe\u306f\u30d1\u30a4\u30d7\u3092\u5272\u308a\u5f53\u3066\u3001\u30d5\u30a1\u30a4\u30eb\u30c7\u30a3\u30b9\u30af\u30ea\u30d7\u30bf\u306b\u305d\u306e\u30d1\u30a4\u30d7\u3092\u8a2d\u5b9a\u3059\u308b\u3002<\/p>\n
sysfile.c<\/p>\n
#include "types.h"\r\n#include "defs.h"\r\n#include "param.h"\r\n#include "stat.h"\r\n#include "mmu.h"\r\n#include "proc.h"\r\n#include "fs.h"\r\n#include "file.h"\r\n#include "fcntl.h"\r\n\r\n\/\/ Fetch the nth word-sized system call argument as a file descriptor\r\n\/\/ and return both the descriptor and the corresponding struct file.\r\nstatic int\r\nargfd(int n, int *pfd, struct file **pf)\r\n{\r\n int fd;\r\n struct file *f;\r\n\r\n if(argint(n, &fd) < 0)\r\n return -1;\r\n if(fd < 0 || fd >= NOFILE || (f=proc->ofile[fd]) == 0)\r\n return -1;\r\n if(pfd)\r\n *pfd = fd;\r\n if(pf)\r\n *pf = f;\r\n return 0;\r\n}\r\n\r\n\/\/ Allocate a file descriptor for the given file.\r\n\/\/ Takes over file reference from caller on success.\r\nstatic int\r\nfdalloc(struct file *f)\r\n{\r\n int fd;\r\n\r\n for(fd = 0; fd < NOFILE; fd++){\r\n if(proc->ofile[fd] == 0){\r\n proc->ofile[fd] = f;\r\n return fd;\r\n }\r\n }\r\n return -1;\r\n}\r\n\r\nint\r\nsys_dup(void)\r\n{\r\n struct file *f;\r\n int fd;\r\n \r\n if(argfd(0, 0, &f) < 0)\r\n return -1;\r\n if((fd=fdalloc(f)) < 0)\r\n return -1;\r\n filedup(f);\r\n return fd;\r\n}\r\n\r\nint\r\nsys_read(void)\r\n{\r\n struct file *f;\r\n int n;\r\n char *p;\r\n\r\n if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0)\r\n return -1;\r\n return fileread(f, p, n);\r\n}\r\n\r\nint\r\nsys_write(void)\r\n{\r\n struct file *f;\r\n int n;\r\n char *p;\r\n\r\n if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0)\r\n return -1;\r\n return filewrite(f, p, n);\r\n}\r\n\r\nint\r\nsys_close(void)\r\n{\r\n int fd;\r\n struct file *f;\r\n \r\n if(argfd(0, &fd, &f) < 0)\r\n return -1;\r\n proc->ofile[fd] = 0;\r\n fileclose(f);\r\n return 0;\r\n}\r\n\r\nint\r\nsys_fstat(void)\r\n{\r\n struct file *f;\r\n struct stat *st;\r\n \r\n if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof(*st)) < 0)\r\n return -1;\r\n return filestat(f, st);\r\n}\r\n\r\n\/\/ Create the path new as a link to the same inode as old.\r\nint\r\nsys_link(void)\r\n{\r\n char name[DIRSIZ], *new, *old;\r\n struct inode *dp, *ip;\r\n\r\n if(argstr(0, &old) < 0 || argstr(1, &new) < 0)\r\n return -1;\r\n if((ip = namei(old)) == 0)\r\n return -1;\r\n\r\n begin_trans();\r\n\r\n ilock(ip);\r\n if(ip->type == T_DIR){\r\n iunlockput(ip);\r\n commit_trans();\r\n return -1;\r\n }\r\n\r\n ip->nlink++;\r\n iupdate(ip);\r\n iunlock(ip);\r\n\r\n if((dp = nameiparent(new, name)) == 0)\r\n goto bad;\r\n ilock(dp);\r\n if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0){\r\n iunlockput(dp);\r\n goto bad;\r\n }\r\n iunlockput(dp);\r\n iput(ip);\r\n\r\n commit_trans();\r\n\r\n return 0;\r\n\r\nbad:\r\n ilock(ip);\r\n ip->nlink--;\r\n iupdate(ip);\r\n iunlockput(ip);\r\n commit_trans();\r\n return -1;\r\n}\r\n\r\n\/\/ Is the directory dp empty except for "." and ".." ?\r\nstatic int\r\nisdirempty(struct inode *dp)\r\n{\r\n int off;\r\n struct dirent de;\r\n\r\n for(off=2*sizeof(de); off<dp->size; off+=sizeof(de)){\r\n if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n panic("isdirempty: readi");\r\n if(de.inum != 0)\r\n return 0;\r\n }\r\n return 1;\r\n}\r\n\r\n\/\/PAGEBREAK!\r\nint\r\nsys_unlink(void)\r\n{\r\n struct inode *ip, *dp;\r\n struct dirent de;\r\n char name[DIRSIZ], *path;\r\n uint off;\r\n\r\n if(argstr(0, &path) < 0)\r\n return -1;\r\n if((dp = nameiparent(path, name)) == 0)\r\n return -1;\r\n\r\n begin_trans();\r\n\r\n ilock(dp);\r\n\r\n \/\/ Cannot unlink "." or "..".\r\n if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0)\r\n goto bad;\r\n\r\n if((ip = dirlookup(dp, name, &off)) == 0)\r\n goto bad;\r\n ilock(ip);\r\n\r\n if(ip->nlink < 1)\r\n panic("unlink: nlink < 1");\r\n if(ip->type == T_DIR && !isdirempty(ip)){\r\n iunlockput(ip);\r\n goto bad;\r\n }\r\n\r\n memset(&de, 0, sizeof(de));\r\n if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n panic("unlink: writei");\r\n if(ip->type == T_DIR){\r\n dp->nlink--;\r\n iupdate(dp);\r\n }\r\n iunlockput(dp);\r\n\r\n ip->nlink--;\r\n iupdate(ip);\r\n iunlockput(ip);\r\n\r\n commit_trans();\r\n\r\n return 0;\r\n\r\nbad:\r\n iunlockput(dp);\r\n commit_trans();\r\n return -1;\r\n}\r\n\r\nstatic struct inode*\r\ncreate(char *path, short type, short major, short minor)\r\n{\r\n uint off;\r\n struct inode *ip, *dp;\r\n char name[DIRSIZ];\r\n\r\n if((dp = nameiparent(path, name)) == 0)\r\n return 0;\r\n ilock(dp);\r\n\r\n if((ip = dirlookup(dp, name, &off)) != 0){\r\n iunlockput(dp);\r\n ilock(ip);\r\n if(type == T_FILE && ip->type == T_FILE)\r\n return ip;\r\n iunlockput(ip);\r\n return 0;\r\n }\r\n\r\n if((ip = ialloc(dp->dev, type)) == 0)\r\n panic("create: ialloc");\r\n\r\n ilock(ip);\r\n ip->major = major;\r\n ip->minor = minor;\r\n ip->nlink = 1;\r\n iupdate(ip);\r\n\r\n if(type == T_DIR){ \/\/ Create . and .. entries.\r\n dp->nlink++; \/\/ for ".."\r\n iupdate(dp);\r\n \/\/ No ip->nlink++ for ".": avoid cyclic ref count.\r\n if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0)\r\n panic("create dots");\r\n }\r\n\r\n if(dirlink(dp, name, ip->inum) < 0)\r\n panic("create: dirlink");\r\n\r\n iunlockput(dp);\r\n\r\n return ip;\r\n}\r\n\r\nint\r\nsys_open(void)\r\n{\r\n char *path;\r\n int fd, omode;\r\n struct file *f;\r\n struct inode *ip;\r\n\r\n if(argstr(0, &path) < 0 || argint(1, &omode) < 0)\r\n return -1;\r\n if(omode & O_CREATE){\r\n begin_trans();\r\n ip = create(path, T_FILE, 0, 0);\r\n commit_trans();\r\n if(ip == 0)\r\n return -1;\r\n } else {\r\n if((ip = namei(path)) == 0)\r\n return -1;\r\n ilock(ip);\r\n if(ip->type == T_DIR && omode != O_RDONLY){\r\n iunlockput(ip);\r\n return -1;\r\n }\r\n }\r\n\r\n if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){\r\n if(f)\r\n fileclose(f);\r\n iunlockput(ip);\r\n return -1;\r\n }\r\n iunlock(ip);\r\n\r\n f->type = FD_INODE;\r\n f->ip = ip;\r\n f->off = 0;\r\n f->readable = !(omode & O_WRONLY);\r\n f->writable = (omode & O_WRONLY) || (omode & O_RDWR);\r\n return fd;\r\n}\r\n\r\nint\r\nsys_mkdir(void)\r\n{\r\n char *path;\r\n struct inode *ip;\r\n\r\n begin_trans();\r\n if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){\r\n commit_trans();\r\n return -1;\r\n }\r\n iunlockput(ip);\r\n commit_trans();\r\n return 0;\r\n}\r\n\r\nint\r\nsys_mknod(void)\r\n{\r\n struct inode *ip;\r\n char *path;\r\n int len;\r\n int major, minor;\r\n \r\n begin_trans();\r\n if((len=argstr(0, &path)) < 0 ||\r\n argint(1, &major) < 0 ||\r\n argint(2, &minor) < 0 ||\r\n (ip = create(path, T_DEV, major, minor)) == 0){\r\n commit_trans();\r\n return -1;\r\n }\r\n iunlockput(ip);\r\n commit_trans();\r\n return 0;\r\n}\r\n\r\nint\r\nsys_chdir(void)\r\n{\r\n char *path;\r\n struct inode *ip;\r\n\r\n if(argstr(0, &path) < 0 || (ip = namei(path)) == 0)\r\n return -1;\r\n ilock(ip);\r\n if(ip->type != T_DIR){\r\n iunlockput(ip);\r\n return -1;\r\n }\r\n iunlock(ip);\r\n iput(proc->cwd);\r\n proc->cwd = ip;\r\n return 0;\r\n}\r\n\r\nint\r\nsys_exec(void)\r\n{\r\n char *path, *argv[MAXARG];\r\n int i;\r\n uint uargv, uarg;\r\n\r\n if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0){\r\n return -1;\r\n }\r\n memset(argv, 0, sizeof(argv));\r\n for(i=0;; i++){\r\n if(i >= NELEM(argv))\r\n return -1;\r\n if(fetchint(proc, uargv+4*i, (int*)&uarg) < 0)\r\n return -1;\r\n if(uarg == 0){\r\n argv[i] = 0;\r\n break;\r\n }\r\n if(fetchstr(proc, uarg, &argv[i]) < 0)\r\n return -1;\r\n }\r\n return exec(path, argv);\r\n}\r\n\r\nint\r\nsys_pipe(void)\r\n{\r\n int *fd;\r\n struct file *rf, *wf;\r\n int fd0, fd1;\r\n\r\n if(argptr(0, (void*)&fd, 2*sizeof(fd[0])) < 0)\r\n return -1;\r\n if(pipealloc(&rf, &wf) < 0)\r\n return -1;\r\n fd0 = -1;\r\n if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){\r\n if(fd0 >= 0)\r\n proc->ofile[fd0] = 0;\r\n fileclose(rf);\r\n fileclose(wf);\r\n return -1;\r\n }\r\n fd[0] = fd0;\r\n fd[1] = fd1;\r\n return 0;\r\n}<\/pre>\n\u611f\u60f3<\/h3>\n
\u30d5\u30a1\u30a4\u30eb\u30b7\u30b9\u30c6\u30e0\u95a2\u9023\u306e\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306e\u5b9f\u88c5\u306b\u3064\u3044\u3066\u3067\u3059\u3002<\/p>\n
\u539f\u6587\u3067\u3082\u660e\u8a18\u3055\u308c\u3066\u306a\u304b\u3063\u305f\u308a\u3059\u308b\u306e\u3067\u3001\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u3068\u3044\u3046\u540d\u79f0\u3068\u95a2\u6570\u3068\u3044\u3046\u540d\u79f0\u306e\u4f7f\u3044\u5206\u3051\u304c\u66d6\u6627\u306a\u90e8\u5206\u304c\u3042\u308a\u307e\u3059\u3002
\n\u307e\u3041\u95a2\u6570\u306e\u307b\u3046\u304c\u3088\u308a\u4e00\u822c\u7684\u306a\u6982\u5ff5\u306a\u306e\u3067\u3069\u3061\u3089\u3082\u95a2\u6570\u3068\u8a00\u3063\u3066\u304a\u3051\u3070\u9593\u9055\u3044\u306a\u3044\u3068\u601d\u3044\u307e\u3059\u304c\u3001\u30b7\u30b9\u30c6\u30e0\u30b3\u30fc\u30eb\u306b\u95a2\u3057\u3066\u306f\u3001SYSCALL\u30de\u30af\u30ed\u3067\u751f\u6210\u3055\u308c\u305f\uff08\u4f8b\u3048\u3070\uff09open\u306e\u3088\u3046\u306a\u3082\u306e\u3060\u3051\u3092\u305d\u3046\u547c\u3076\u306e\u304b\u3001\u305d\u306e\u5b9f\u4f53\u3067\u3042\u308b\uff08\u4f8b\u3048\u3070\uff09sys_open\u307e\u3067\u542b\u3081\u308b\u306e\u304b\u3069\u3046\u304b\u304c\u5fae\u5999\u306a\u3068\u3053\u308d\u3067\u3059\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[405],"class_list":["post-1673","post","type-post","status-publish","format-standard","hentry","category-tech","tag-xv6"],"_links":{"self":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1673","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/comments?post=1673"}],"version-history":[{"count":0,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1673\/revisions"}],"wp:attachment":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/media?parent=1673"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/categories?post=1673"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/tags?post=1673"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}