绋嬪簭12-13 linux/fs/open.c

  1 /*

  2  *  linux/fs/open.c

  3  *

  4  *  (C) 1991  Linus Torvalds

  5  */

  6

  7 #include <string.h>       // 瀛楃�︿覆澶存枃浠躲�備富瑕佸畾涔変簡涓�浜涙湁鍏冲瓧绗︿覆鎿嶄綔鐨勫祵鍏ュ嚱鏁般��

  8 #include <errno.h>        // 閿欒��鍙峰ご鏂囦欢銆傚寘鍚�绯荤粺涓�鍚勭�嶅嚭閿欏彿銆�

  9 #include <fcntl.h>        // 鏂囦欢鎺у埗澶存枃浠躲�傜敤浜庢枃浠跺強鍏舵弿杩扮�︽搷浣滄帶鍒跺父鏁扮�﹀彿瀹氫箟銆�

 10 #include <sys/types.h>    // 绫诲瀷澶存枃浠躲�傚畾涔夊熀鏈�鐨勭郴缁熷拰鏂囦欢绯荤粺缁熻�′俊鎭�缁撴瀯鍜岀被鍨嬨��

 11 #include <utime.h>        // 鐢ㄦ埛鏃堕棿澶存枃浠躲�傚畾涔夎�块棶鍜屼慨鏀规椂闂寸粨鏋勪互鍙�utime()鍘熷瀷銆�

 12 #include <sys/stat.h>     // 鏂囦欢鐘舵�佸ご鏂囦欢銆傚惈鏈夋枃浠剁姸鎬佺粨鏋�stat{}鍜岀�﹀彿甯搁噺绛夈��

 13

 14 #include <linux/sched.h>  // 璋冨害绋嬪簭澶存枃浠讹紝瀹氫箟浠诲姟缁撴瀯task_struct銆佷换鍔�0鏁版嵁绛夈��

 15 #include <linux/tty.h>    // tty澶存枃浠讹紝瀹氫箟浜嗘湁鍏�tty_io锛屼覆琛岄�氫俊鏂归潰鐨勫弬鏁般�佸父鏁般��

 16 #include <linux/kernel.h> // 鍐呮牳澶存枃浠躲�傚惈鏈変竴浜涘唴鏍稿父鐢ㄥ嚱鏁扮殑鍘熷舰瀹氫箟銆�

 17

 18 #include <asm/segment.h>  // 娈垫搷浣滃ご鏂囦欢銆傚畾涔変簡鏈夊叧娈靛瘎瀛樺櫒鎿嶄綔鐨勫祵鍏ュ紡姹囩紪鍑芥暟銆�

 19

    //// 鍙栨枃浠剁郴缁熶俊鎭�銆�

    // 鍙傛暟dev鏄�鍚�鏈夊凡瀹夎�呮枃浠剁郴缁熺殑璁惧�囧彿銆�ubuf鏄�涓�涓�ustat缁撴瀯缂撳啿鍖烘寚閽堬紝鐢ㄤ簬瀛樻斁

    // 绯荤粺杩斿洖鐨勬枃浠剁郴缁熶俊鎭�銆傝�ョ郴缁熻皟鐢ㄧ敤浜庤繑鍥炲凡瀹夎�咃紙mounted锛夋枃浠剁郴缁熺殑缁熻�′俊鎭�銆�

    // 鎴愬姛鏃惰繑鍥�0锛屽苟涓�ubuf鎸囧悜鐨�ustate缁撴瀯琚�娣诲叆鏂囦欢绯荤粺鎬荤┖闂插潡鏁板拰绌洪棽i鑺傜偣鏁般��

    // ustat缁撴瀯瀹氫箟鍦�include/sys/types.h涓�銆�

 20 int sys_ustat(int dev, struct ustat * ubuf)

 21 {

 22         return -ENOSYS;                // 鍑洪敊鐮侊細鍔熻兘杩樻湭瀹炵幇銆�

 23 }

 24

    //// 璁剧疆鏂囦欢璁块棶鍜屼慨鏀规椂闂淬��

    // 鍙傛暟filename鏄�鏂囦欢鍚嶏��times鏄�璁块棶鍜屼慨鏀规椂闂寸粨鏋勬寚閽堛��

    // 濡傛灉times鎸囬拡涓嶄负NULL锛屽垯鍙�utimbuf缁撴瀯涓�鐨勬椂闂翠俊鎭�鏉ヨ�剧疆鏂囦欢鐨勮�块棶鍜屼慨鏀规椂闂淬��

    // 濡傛灉times鎸囬拡鏄�NULL锛屽垯鍙栫郴缁熷綋鍓嶆椂闂存潵璁剧疆鎸囧畾鏂囦欢鐨勮�块棶鍜屼慨鏀规椂闂村煙銆�

 25 int sys_utime(char * filename, struct utimbuf * times)

 26 {

 27         struct m_inode * inode;

 28         long actime,modtime;

 29

    // 鏂囦欢鐨勬椂闂翠俊鎭�淇濆瓨鍦ㄥ��i鑺傜偣閽熴�傚洜姝ゆ垜浠�棣栧厛鏍规嵁鏂囦欢鍚嶅彇寰楀�瑰簲i鑺傜偣銆傚�傛灉娌℃湁鎵�

    // 鍒帮紝鍒欒繑鍥炲嚭閿欑爜銆傚�傛灉鎻愪緵鐨勮�块棶鍜屼慨鏀规椂闂寸粨鏋勬寚閽�times涓嶄负NULL锛屽垯浠庣粨鏋勪腑璇诲彇

    // 鐢ㄦ埛璁剧疆鐨勬椂闂村�笺�傚惁鍒欏氨鐢ㄧ郴缁熷綋鍓嶆椂闂存潵璁剧疆鏂囦欢鐨勮�块棶鍜屼慨鏀规椂闂淬��

 30         if (!(inode=namei(filename)))

 31                 return -ENOENT;

 32         if (times) {

 33                 actime = get_fs_long((unsigned long *) &times->actime);

 34                 modtime = get_fs_long((unsigned long *) &times->modtime);

 35         } else

 36                 actime = modtime = CURRENT_TIME;

    // 鐒跺悗淇�鏀�i鑺傜偣涓�鐨勮�块棶鏃堕棿瀛楁�靛拰淇�鏀规椂闂村瓧娈点�傚啀璁剧疆i鑺傜偣宸蹭慨鏀规爣蹇楋紝鏀惧洖璇�i鑺�

    // 鐐癸紝骞惰繑鍥�0銆�

 37         inode->i_atime = actime;

 38         inode->i_mtime = modtime;

 39         inode->i_dirt = 1;

 40         iput(inode);

 41         return 0;

 42 }

 43

 44 /*

 45  * XXX should we use the real or effective uid?  BSD uses the real uid,

 46  * so as to make this call useful to setuid programs.

 47  */

    /*

     * XXX 鎴戜滑璇ョ敤鐪熷疄鐢ㄦ埛id锛�ruid锛夎繕鏄�鏈夋晥鐢ㄦ��id锛�euid锛夛紵BSD绯荤粺浣跨敤浜�

     * 鐪熷疄鐢ㄦ埛id锛屼互浣胯�ヨ皟鐢ㄥ彲浠ヤ��setuid绋嬪簭浣跨敤銆�

     * 锛堟敞锛�POSIX鏍囧噯寤鸿��浣跨敤鐪熷疄鐢ㄦ埛ID锛夈��

     * 锛堟敞1锛氳嫳鏂囨敞閲婂紑濮嬬殑 'XXX' 琛ㄧず閲嶈�佹彁绀猴級銆�

     */

    //// 妫�鏌ユ枃浠剁殑璁块棶鏉冮檺銆�

    // 鍙傛暟filename鏄�鏂囦欢鍚嶏��mode鏄�妫�鏌ョ殑璁块棶灞炴�э紝瀹冩湁3涓�鏈夋晥姣旂壒浣嶇粍鎴愶��R_OK(鍊�4)銆�

    // W_OK(2)銆�X_OK(1) 鍜�F_OK(0) 缁勬垚锛屽垎鍒�琛ㄧず妫�娴嬫枃浠舵槸鍚﹀彲璇汇�佸彲鍐欍�佸彲鎵ц�屽拰鏂囦欢鏄�

    // 鍚﹀瓨鍦ㄣ�傚�傛灉璁块棶鍏佽�哥殑璇濓紝鍒欒繑鍥�0锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

 48 int sys_access(const char * filename,int mode)

 49 {

 50         struct m_inode * inode;

 51         int res, i_mode;

 52

    // 鏂囦欢鐨勮�块棶鏉冮檺淇℃伅涔熷悓鏍蜂繚瀛樺湪鏂囦欢鐨�i鑺傜偣缁撴瀯涓�锛屽洜姝ゆ垜浠�瑕佸厛鍙栧緱瀵瑰簲鏂囦欢鍚嶇殑i

    // 鑺傜偣銆傛��娴嬬殑璁块棶灞炴��mode鐢变綆3浣嶇粍鎴愶紝鍥犳�ら渶瑕佷笌涓婂叓杩涘埗0007鏉ユ竻闄ゆ墍鏈夐珮姣旂壒浣嶃��

    // 濡傛灉鏂囦欢鍚嶅�瑰簲鐨�i鑺傜偣涓嶅瓨鍦�锛屽垯杩斿洖娌℃湁璁稿彲鏉冮檺鍑洪敊鐮併�傝嫢i鑺傜偣瀛樺湪锛屽垯鍙�i鑺傜偣

    // 閽熸枃浠跺睘鎬х爜锛屽苟鏀惧洖璇�i鑺傜偣銆傚彟澶栵紝57琛屼笂璇�鍙モ��iput(inode);鈥濇渶鍚庢斁鍦�61琛屼箣鍚庛��

 53         mode &= 0007;

 54         if (!(inode=namei(filename)))

 55                 return -EACCES;                    // 鍑洪敊鐮侊細鏃犺�块棶鏉冮檺銆�

 56         i_mode = res = inode->i_mode & 0777;

 57         iput(inode);

    // 濡傛灉褰撳墠杩涚▼鐢ㄦ埛鏄�璇ユ枃浠剁殑瀹夸富锛屽垯鍙栨枃浠跺�夸富灞炴�с�傚惁鍒欏�傛灉褰撳墠杩涚▼鐢ㄦ埛涓庤�ユ枃浠跺��

    // 涓诲悓灞炰竴缁勶紝鍒欏彇鏂囦欢缁勫睘鎬с�傚惁鍒欙紝姝ゆ椂res鏈�浣�3姣旂壒鏄�鍏朵粬浜鸿�块棶璇ユ枃浠剁殑璁稿彲灞炴�с��

    // [[?? 杩欓噷搴�res >>3 ??]

 58         if (current->uid == inode->i_uid)

 59                 res >>= 6;

 60         else if (current->gid == inode->i_gid)

 61                 res >>= 6;

    // 姝ゆ椂res鐨勬渶浣�3姣旂壒鏄�鏍规嵁褰撳墠杩涚▼鐢ㄦ埛涓庢枃浠剁殑鍏崇郴閫夋嫨鍑烘潵鐨勮�块棶灞炴�т綅銆傜幇鍦ㄦ垜浠�

    // 鏉ュ垽鏂�杩�3姣旂壒銆傚�傛灉鏂囦欢灞炴�у叿鏈夊弬鏁版墍鏌ヨ�㈢殑灞炴�т綅mode锛屽垯璁块棶璁稿彲锛岃繑鍥�0

 62         if ((res & 0007 & mode) == mode)

 63                 return 0;

 64         /*

 65          * XXX we are doing this test last because we really should be

 66          * swapping the effective with the real user id (temporarily),

 67          * and then calling suser() routine.  If we do call the

 68          * suser() routine, it needs to be called last.

 69          */

            /*

             * XXX 鎴戜滑鏈�鍚庢墠鍋氫笅闈㈢殑娴嬭瘯锛屽洜涓烘垜浠�瀹為檯涓婇渶瑕佷氦鎹㈡湁鏁堢敤鎴�ID鍜�

             * 鐪熷疄鐢ㄦ埛ID锛堜复鏃跺湴锛夛紝鐒跺悗鎵嶈皟鐢�suser()鍑芥暟銆傚�傛灉鎴戜滑纭�瀹炶�佽皟鐢�

             * suser()鍑芥暟锛屽垯闇�瑕佹渶鍚庢墠琚�璋冪敤銆�

             */

    // 濡傛灉褰撳墠鐢ㄦ埛ID涓�0锛堣秴绾х敤鎴凤級骞朵笖灞忚斀鐮佹墽琛屼綅鏄�0鎴栬�呮枃浠跺彲浠ヨ��浠讳綍浜烘墽琛屻�佹悳

    // 绱�锛屽垯杩斿��0銆傚惁鍒欒繑鍥炲嚭閿欑爜銆�

 70         if ((!current->uid) &&

 71             (!(mode & 1) || (i_mode & 0111)))

 72                 return 0;

 73         return -EACCES;                           // 鍑洪敊鐮侊細鏃犺�块棶鏉冮檺銆�

 74 }

 75

    //// 鏀瑰彉褰撳墠宸ヤ綔鐩�褰曠郴缁熻皟鐢ㄣ��

    // 鍙傛暟filename鏄�鐩�褰曞悕銆�

    // 鎿嶄綔鎴愬姛鍒欒繑鍥�0锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

 76 int sys_chdir(const char * filename)

 77 {

 78         struct m_inode * inode;

 79

    // 鏀瑰彉褰撳墠宸ヤ綔鐩�褰曞氨鏄�瑕佹眰鎶婅繘绋嬩换鍔＄粨鏋勭殑褰撳墠宸ヤ綔鐩�褰曞瓧娈垫寚鍚戠粰瀹氱洰褰曞悕鐨�i鑺傜偣銆�

    // 鍥犳�ゆ垜浠�棣栧厛鍙栫洰褰曞悕鐨�i鑺傜偣銆傚�傛灉鐩�褰曞悕瀵瑰簲鐨�i鑺傜偣涓嶅瓨鍦�锛屽垯杩斿洖鍑洪敊鐮併�傚�傛灉璇�

    // i鑺傜偣涓嶆槸涓�涓�鐩�褰�i鑺傜偣锛屽垯鏀惧洖璇�i鑺傜偣锛屽苟杩斿洖鍑洪敊鐮併��

 80         if (!(inode = namei(filename)))

 81                 return -ENOENT;                    // 鍑洪敊鐮侊細鏂囦欢鎴栫洰褰曚笉瀛樺湪銆�

 82         if (!S_ISDIR(inode->i_mode)) {

 83                 iput(inode);

 84                 return -ENOTDIR;                   // 鍑洪敊鐮侊細涓嶆槸鐩�褰曞悕銆�

 85         }

    // 鐒跺悗閲婃斁杩涚▼鍘熷伐浣滅洰褰�i鑺傜偣锛屽苟浣垮叾鎸囧悜鏂拌�剧疆鐨勫伐浣滅洰褰�i鑺傜偣銆傝繑鍥�0銆�

 86         iput(current->pwd);

 87         current->pwd = inode;

 88         return (0);

 89 }

 90

    //// 鏀瑰彉鏍圭洰褰曠郴缁熻皟鐢ㄣ��

    // 鎶婃寚瀹氱殑鐩�褰曞悕璁剧疆鎴愪负褰撳墠杩涚▼鐨勬牴鐩�褰�'/'銆�

    // 濡傛灉鎿嶄綔鎴愬姛鍒欒繑鍥�0锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

 91 int sys_chroot(const char * filename)

 92 {

 93         struct m_inode * inode;

 94

    // 璇ヨ皟鐢ㄧ敤浜庢敼鍙樺綋鍓嶈繘绋嬩换鍔＄粨鏋勪腑鐨勬牴鐩�褰曞瓧娈�root锛岃�╁叾鎸囧悜鍙傛暟缁欏畾鐩�褰曞悕鐨�i鑺傜偣銆�

    // 濡傛灉鐩�褰曞悕瀵瑰簲鐨�i鑺傜偣涓嶅瓨鍦�锛屽垯杩斿洖鍑洪敊鐮併�傚�傛灉璇�i鑺傜偣涓嶆槸鐩�褰�i鑺傜偣锛屽垯鏀惧洖璇�

    // i鑺傜偣锛屼篃杩斿洖鍑洪敊鐮併��

 95         if (!(inode=namei(filename)))

 96                 return -ENOENT;

 97         if (!S_ISDIR(inode->i_mode)) {

 98                 iput(inode);

 99                 return -ENOTDIR;

100         }

    // 鐒跺悗閲婃斁褰撳墠杩涚▼鐨勬牴鐩�褰�i鑺傜偣锛屽苟閲嶆柊璁剧疆涓烘寚瀹氱洰褰曞悕鐨�i鑺傜偣锛岃繑鍥�0銆�

101         iput(current->root);

102         current->root = inode;

103         return (0);

104 }

105

    //// 淇�鏀规枃浠跺睘鎬х郴缁熻皟鐢ㄣ��

    // 鍙傛暟filename鏄�鏂囦欢鍚嶏��mode鏄�鏂扮殑鏂囦欢灞炴�с��

    // 鑻ユ搷浣滄垚鍔熷垯杩斿洖0锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

106 int sys_chmod(const char * filename,int mode)

107 {

108         struct m_inode * inode;

109

    // 璇ヨ皟鐢ㄤ负鎸囧畾鏂囦欢璁剧疆鏂扮殑璁块棶灞炴��mode銆傛枃浠剁殑璁块棶灞炴�у湪鏂囦欢鍚嶅�瑰簲鐨�i鑺傜偣涓�锛屽洜姝�

    // 鎴戜滑棣栧厛鍙栨枃浠跺悕瀵瑰簲鐨�i鑺傜偣銆傚�傛��i鑺傜偣涓嶅瓨鍦�锛屽垯杩斿洖鍑洪敊鐮侊紙鏂囦欢鎴栫洰褰曚笉瀛樺湪锛夈��

    // 濡傛灉褰撳墠杩涚▼鐨勬湁鏁堢敤鎴�id涓庢枃浠�i鑺傜偣鐨勭敤鎴�id涓嶅悓锛屽苟涓斾篃涓嶆槸瓒呯骇鐢ㄦ埛锛屽垯鏀惧洖璇�

    // 鏂囦欢i鑺傜偣锛岃繑鍥炲嚭閿欑爜锛堟病鏈夎�块棶鏉冮檺锛夈��

110         if (!(inode=namei(filename)))

111                 return -ENOENT;

112         if ((current->euid != inode->i_uid) && !suser()) {

113                 iput(inode);

114                 return -EACCES;

115         }

    // 鍚﹀垯灏遍噸鏂拌�剧疆璇�i鑺傜偣鐨勬枃浠跺睘鎬э紝骞剁疆璇�i鑺傜偣宸蹭慨鏀规爣蹇椼�傛斁鍥炶��i鑺傜偣锛岃繑鍥�0銆�

116         inode->i_mode = (mode & 07777) | (inode->i_mode & ~07777);

117         inode->i_dirt = 1;

118         iput(inode);

119         return 0;

120 }

121

    //// 淇�鏀规枃浠跺�夸富绯荤粺璋冪敤銆�

    // 鍙傛暟filename鏄�鏂囦欢鍚嶏��uid鏄�鐢ㄦ埛鏍囪瘑绗�(鐢ㄦ埛ID)锛�gid鏄�缁�ID銆�

    // 鑻ユ搷浣滄垚鍔熷垯杩斿洖0锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

122 int sys_chown(const char * filename,int uid,int gid)

123 {

124         struct m_inode * inode;

125

    // 璇ヨ皟鐢ㄧ敤浜庤�剧疆鏂囦��i鑺傜偣涓�鐨勭敤鎴峰拰缁�ID锛屽洜姝ら�栧厛瑕佸彇寰楃粰瀹氭枃浠跺悕鐨�i鑺傜偣銆傚�傛灉鏂�

    // 浠跺悕鐨�i鑺傜偣涓嶅瓨鍦�锛屽垯杩斿洖鍑洪敊鐮侊紙鏂囦欢鎴栫洰褰曚笉瀛樺湪锛夈�傚�傛灉褰撳墠杩涚▼涓嶆槸瓒呯骇鐢ㄦ埛锛�

    // 鍒欐斁鍥炶��i鑺傜偣锛屽苟杩斿洖鍑洪敊鐮侊紙娌℃湁璁块棶鏉冮檺锛夈��

126         if (!(inode=namei(filename)))

127                 return -ENOENT;

128         if (!suser()) {

129                 iput(inode);

130                 return -EACCES;

131         }

    // 鍚﹀垯鎴戜滑灏辩敤鍙傛暟鎻愪緵鐨勫�兼潵璁剧疆鏂囦欢i鑺傜偣鐨勭敤鎴�ID鍜岀粍ID锛屽苟缃�i鑺傜偣宸茬粡淇�鏀规爣蹇楋��

    // 鏀惧洖璇�i鑺傜偣锛岃繑鍥�0銆�

132         inode->i_uid=uid;

133         inode->i_gid=gid;

134         inode->i_dirt=1;

135         iput(inode);

136         return 0;

137 }

138

    //// 妫�鏌ュ瓧绗﹁�惧�囩被鍨嬨��

    // 璇ュ嚱鏁颁粎鐢ㄤ簬涓嬮潰鏂囦欢鎵撳紑绯荤粺璋冪敤sys_open()锛岀敤浜庢��鏌ヨ嫢鎵撳紑鐨勬枃浠舵槸tty缁堢��瀛楃�﹁��

    // 澶囨椂锛岄渶瑕佸�瑰綋鍓嶈繘绋嬬殑璁剧疆鍜屽��tty琛ㄧ殑璁剧疆銆�

    // 杩斿洖0妫�娴嬪�勭悊鎴愬姛锛岃繑鍥�-1琛ㄧず澶辫触锛屽�瑰簲瀛楃�﹁�惧�囦笉鑳芥墦寮�銆�

139 static int check_char_dev(struct m_inode * inode, int dev, int flag)

140 {

141         struct tty_struct *tty;

142         int min;                                     // 瀛愯�惧�囧彿銆�

143

    // 鍙�澶勭悊涓昏�惧�囧彿鏄�4锛�/dev/ttyxx鏂囦欢锛夋垨5锛�/dev/tty鏂囦欢锛夌殑鎯呭喌銆�/dev/tty鐨勫瓙璁惧��

    // 鍙锋槸0銆傚�傛灉涓�涓�杩涚▼鏈夋帶鍒剁粓绔�锛屽垯瀹冩槸杩涚▼鎺у埗缁堢��璁惧�囩殑鍚屼箟鍚嶃�傚嵆/dev/tty璁惧�囨��

    // 涓�涓�铏氭嫙璁惧�囷紝瀹冨�瑰簲鍒拌繘绋嬪疄闄呬娇鐢ㄧ��/dev/ttyxx璁惧�囦箣涓�銆傚�逛簬涓�涓�杩涚▼鏉ヨ�达紝鑻ュ叾鏈�

    // 鎺у埗缁堢��锛岄偅涔堝畠鐨勪换鍔＄粨鏋勪腑鐨�tty瀛楁�靛皢鏄�4鍙疯�惧�囩殑鏌愪竴涓�瀛愯�惧�囧彿銆�

    // 濡傛灉鎵撳紑鎿嶄綔鐨勬枃浠舵槸 /dev/tty锛堝嵆MAJOR(dev) = 5锛夛紝閭ｄ箞鎴戜滑浠�min = 杩涚▼浠诲姟缁撴瀯

    // 涓�鐨�tty瀛楁�碉紝鍗冲��4鍙疯�惧�囩殑瀛愯�惧�囧彿銆傚惁鍒欏�傛灉鎵撳紑鐨勬槸鏌愪釜4鍙疯�惧�囷紝鍒欑洿鎺ュ彇鍏跺瓙

    // 璁惧�囧彿銆傚�傛灉寰楀埌鐨� 4鍙疯�惧�囧瓙璁惧�囧彿灏忎��0锛岄偅涔堣�存槑杩涚▼娌℃湁鎺у埗缁堢��锛屾垨鑰呰�惧�囧彿閿�

    // 璇�锛屽垯杩斿�� -1锛岃〃绀虹敱浜庤繘绋嬫病鏈夋帶鍒剁粓绔�锛屾垨鑰呬笉鑳芥墦寮�杩欎釜璁惧�囥��

144         if (MAJOR(dev) == 4 || MAJOR(dev) == 5) {

145                 if (MAJOR(dev) == 5)

146                         min = current->tty;

147                 else

148                         min = MINOR(dev);

149                 if (min < 0)

150                         return -1;

    // 涓讳吉缁堢��璁惧�囨枃浠跺彧鑳借��杩涚▼鐙�鍗犱娇鐢ㄣ�傚�傛灉瀛愯�惧�囧彿琛ㄦ槑鏄�涓�涓�涓讳吉缁堢��锛屽苟涓旇�ユ墦寮�鏂囦欢

    // i 鑺傜偣寮曠敤璁℃暟澶т簬 1锛屽垯璇存槑璇ヨ�惧�囧凡琚�鍏朵粬杩涚▼浣跨敤銆傚洜姝や笉鑳藉啀鎵撳紑璇ュ瓧绗﹁�惧�囨枃浠讹紝

    // 浜庢槸杩斿洖 -1銆傚惁鍒欙紝鎴戜滑璁�tty缁撴瀯鎸囬拡tty鎸囧悜tty琛ㄤ腑瀵瑰簲缁撴瀯椤广�傝嫢鎵撳紑鏂囦欢鎿嶄綔鏍�

    // 蹇�flag涓�涓嶅惈鏃犻渶鎺у埗缁堢��鏍囧織O_NOCTTY锛屽苟涓旇繘绋嬫槸杩涚▼缁勯�栭�嗭紝骞朵笖褰撳墠杩涚▼娌℃湁鎺у埗

    // 缁堢��锛屽苟涓�tty缁撴瀯涓�session瀛楃��涓�0锛堣〃绀鸿�ョ粓绔�杩樹笉鏄�浠讳綍杩涚▼缁勭殑鎺у埗缁堢��锛夛紝閭ｄ��

    // 灏卞厑璁镐负杩涚▼璁剧疆杩欎釜缁堢��璁惧�� min 涓哄叾鎺у埗缁堢��銆備簬鏄�璁剧疆杩涚▼浠诲姟缁撴瀯缁堢��璁惧�囧彿瀛楁��

    // tty鍊肩瓑浜�min锛屽苟涓旇�剧疆瀵瑰��tty缁撴瀯鐨勪細璇濆彿session鍜岃繘绋嬬粍鍙�pgrp鍒嗗埆绛変簬杩涚▼鐨勪細

    // 璇濆彿鍜岃繘绋嬬粍鍙枫��

151                 if ((IS_A_PTY_MASTER(min)) && (inode->i_count>1))

152                         return -1;

153                 tty = TTY_TABLE(min);

154                 if (!(flag & O_NOCTTY) &&

155                     current->leader &&

156                     current->tty<0 &&

157                     tty->session==0) {

158                         current->tty = min;

159                         tty->session= current->session;

160                         tty->pgrp = current->pgrp;

161                 }

    // 濡傛灉鎵撳紑鏂囦欢鎿嶄綔鏍囧織flag涓�鍚�鏈�O_NONBLOCK锛堥潪闃诲�烇級鏍囧織锛屽垯鎴戜滑闇�瑕佸�硅�ュ瓧绗︾粓绔�

    // 璁惧�囪繘琛岀浉鍏宠�剧疆锛岃�剧疆涓烘弧瓒宠�绘搷浣滈渶瑕佽�诲彇鐨勬渶灏戝瓧绗︽暟涓�0锛岃�剧疆瓒呮椂瀹氭椂鍊间负0锛�

    // 骞舵妸缁堢��璁惧�囪�剧疆鎴愰潪瑙勮寖妯″紡銆傞潪闃诲�炴柟寮忓彧鑳藉伐浣滀簬闈炶�勮寖妯″紡銆傚湪姝ゆā寮忎笅褰�VMIN

    // 鍜�VTIME鍧囪�剧疆涓�0鏃讹紝杈呭姪闃熷垪涓�鏈夊�氬皯鏀�浠樿繘绋嬪氨璇诲彇澶氬皯瀛楃�︼紝骞剁珛鍒昏繑鍥炪�傚弬瑙�

    // include/termios.h鏂囦欢鍚庣殑璇存槑銆�

162                 if (flag & O_NONBLOCK) {

163                         TTY_TABLE(min)->termios.c_cc[VMIN] =0;

164                         TTY_TABLE(min)->termios.c_cc[VTIME] =0;

165                         TTY_TABLE(min)->termios.c_lflag &= ~ICANON;

166                 }

167         }

168         return 0;

169 }

170

    //// 鎵撳紑锛堟垨鍒涘缓锛夋枃浠剁郴缁熻皟鐢ㄣ��

    // 鍙傛暟filename鏄�鏂囦欢鍚嶏��flag鏄�鎵撳紑鏂囦欢鏍囧織锛屽畠鍙�鍙栧�硷細O_RDONLY锛堝彧璇伙級銆�O_WRONLY

    // 锛堝彧鍐欙級鎴�O_RDWR锛堣�诲啓锛夛紝浠ュ��O_CREAT锛堝垱寤猴級銆�O_EXCL锛堣��鍒涘缓鏂囦欢蹇呴』涓嶅瓨鍦�锛夈��

    // O_APPEND锛堝湪鏂囦欢灏炬坊鍔犳暟鎹�锛夌瓑鍏朵粬涓�浜涙爣蹇楃殑缁勫悎锛屽�傛灉鏈�璋冪敤鍒涘缓浜嗕竴涓�鏂版枃浠讹紝鍒�

    // mode灏辩敤浜庢寚瀹氭枃浠剁殑璁稿彲灞炴�с�傝繖浜涘睘鎬ф湁S_IRWXU锛堟枃浠跺�夸富鍏锋湁璇汇�佸啓鍜屾墽琛屾潈闄愶級銆�

    // S_IRUSR锛堢敤鎴峰叿鏈夎�绘枃浠舵潈闄愶級銆�S_IRWXG锛堢粍鎴愬憳鍏锋湁璇汇�佸啓鍜屾墽琛屾潈闄愶級绛夌瓑銆傚�逛簬鏂�

    // 鍒涘缓鐨勬枃浠讹紝杩欎簺灞炴�у彧搴旂敤浜庡皢鏉ュ�规枃浠剁殑璁块棶锛屽垱寤轰簡鍙�璇绘枃浠剁殑鎵撳紑璋冪敤涔熷皢杩斿洖涓�

    // 涓�鍙�璇诲啓鐨勬枃浠跺彞鏌勩�傚�傛灉璋冪敤鎿嶄綔鎴愬姛锛屽垯杩斿洖鏂囦欢鍙ユ��(鏂囦欢鎻忚堪绗�)锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

    // 鍙傝��sys/stat.h銆�fcntl.h銆�

171 int sys_open(const char * filename,int flag,int mode)

172 {

173         struct m_inode * inode;

174         struct file * f;

175         int i,fd;

176

    // 棣栧厛瀵瑰弬鏁拌繘琛屽�勭悊銆傚皢鐢ㄦ埛璁剧疆鐨勬枃浠舵ā寮忓拰杩涚▼妯″紡灞忚斀鐮佺浉涓庯紝浜х敓璁稿彲鐨勬枃浠舵ā寮忋��

    // 涓轰簡涓烘墦寮�鏂囦欢寤虹珛涓�涓�鏂囦欢鍙ユ焺锛岄渶瑕佹悳绱㈣繘绋嬬粨鏋勪腑鏂囦欢缁撴瀯鎸囬拡鏁扮粍锛屼互鏌ユ壘涓�涓�绌�

    // 闂查」銆傜┖闂查」鐨勭储寮曞彿fd鍗虫槸鍙ユ焺鍊笺�傝嫢宸茬粡娌℃湁绌洪棽椤癸紝鍒欒繑鍥炲嚭閿欑爜锛堝弬鏁版棤鏁堬級銆�

177         mode &= 0777 & ~current->umask;

178         for(fd=0 ; fd<NR_OPEN ; fd++)

179                 if (!current->filp[fd])                       // 鎵惧埌绌洪棽椤广��

180                         break;

181         if (fd>=NR_OPEN)

182                 return -EINVAL;

    // 鐒跺悗鎴戜滑璁剧疆褰撳墠杩涚▼鐨勬墽琛屾椂鍏抽棴鏂囦欢鍙ユ焺锛�close_on_exec锛変綅鍥撅紝澶嶄綅瀵瑰簲鐨勬瘮鐗逛綅銆�

    // close_on_exec 鏄�涓�涓�杩涚▼鎵�鏈夋枃浠跺彞鏌勭殑浣嶅浘鏍囧織銆傛瘡涓�姣旂壒浣嶄唬琛ㄤ竴涓�鎵撳紑鐫�鐨勬枃浠舵弿

    // 杩扮�︼紝鐢ㄤ簬纭�瀹氬湪璋冪敤绯荤粺璋冪敤 execve()鏃堕渶瑕佸叧闂�鐨勬枃浠跺彞鏌勩�傚綋绋嬪簭浣跨敤 fork()鍑芥暟

    // 鍒涘缓浜嗕竴涓�瀛愯繘绋嬫椂锛岄�氬父浼氬湪璇ュ瓙杩涚▼涓�璋冪��execve()鍑芥暟鍔犺浇鎵ц�屽彟涓�涓�鏂扮▼搴忋�傛�ゆ��

    // 瀛愯繘绋嬩腑寮�濮嬫墽琛屾柊绋嬪簭銆傝嫢涓�涓�鏂囦欢鍙ユ焺鍦�close_on_exec涓�鐨勫�瑰簲姣旂壒浣嶈��缃�浣嶏紝閭ｄ��

    // 鍦ㄦ墽琛�execve()鏃惰�ュ�瑰簲鏂囦欢鍙ユ焺灏嗚��鍏抽棴锛屽惁鍒欒�ユ枃浠跺彞鏌勫皢濮嬬粓澶勪簬鎵撳紑鐘舵�併�傚綋鎵撳紑

    // 涓�涓�鏂囦欢鏃讹紝榛樿�ゆ儏鍐典笅鏂囦欢鍙ユ焺鍦ㄥ瓙杩涚▼涓�涔熷�勪簬鎵撳紑鐘舵�併�傚洜姝よ繖閲岃�佸�嶄綅瀵瑰簲姣旂壒浣嶃��

    // 鐒跺悗涓烘墦寮�鏂囦欢鍦ㄦ枃浠惰〃涓�瀵绘壘涓�涓�绌洪棽缁撴瀯椤广�傛垜浠�浠�f鎸囧悜鏂囦欢琛ㄦ暟缁勫紑濮嬪�勩�傛悳绱㈢┖

    // 闂叉枃浠剁粨鏋勯」锛堝紩鐢ㄨ�℃暟涓�0鐨勯」锛夛紝鑻ュ凡缁忔病鏈夌┖闂叉枃浠惰〃缁撴瀯椤癸紝鍒欒繑鍥炲嚭閿欑爜銆傚彟澶栵紝

    // 绗�184琛屼笂鐨勬寚閽堣祴鍊� "0+file_table " 绛夊悓浜� "file_table" 鍜� "&file_table[0]"銆�

    // 涓嶈繃杩欐牱鍐欏彲鑳芥洿鑳芥槑浜嗕竴浜涖��

183         current->close_on_exec &= ~(1<<fd);

184         f=0+file_table;

185         for (i=0 ; i<NR_FILE ; i++,f++)

186                 if (!f->f_count) break;

187         if (i>=NR_FILE)

188                 return -EINVAL;

    // 姝ゆ椂鎴戜滑璁╄繘绋嬪�瑰簲鏂囦欢鍙ユ��fd鐨勬枃浠剁粨鏋勬寚閽堟寚鍚戞悳绱㈠埌鐨勬枃浠剁粨鏋勶紝骞朵护鏂囦欢寮曠敤璁℃暟

    // 閫掑��1銆傜劧鍚庤皟鐢ㄥ嚱鏁�open_namei()鎵ц�屾墦寮�鎿嶄綔锛岃嫢杩斿洖鍊煎皬浜�0锛屽垯璇存槑鍑洪敊锛屼簬鏄�閲婃��

    // 鍒氱敵璇峰埌鐨勬枃浠剁粨鏋勶紝杩斿洖鍑洪敊鐮�i銆傝嫢鏂囦欢鎵撳紑鎿嶄綔鎴愬姛锛屽垯inode鏄�宸叉墦寮�鏂囦欢鐨�i鑺傜偣

    // 鎸囬拡銆�

189         (current->filp[fd]=f)->f_count++;

190         if ((i=open_namei(filename,flag,mode,&inode))<0) {

191                 current->filp[fd]=NULL;

192                 f->f_count=0;

193                 return i;

194         }

    // 鏍规嵁宸叉墦寮�鏂囦欢i鑺傜偣鐨勫睘鎬у瓧娈碉紝鎴戜滑鍙�浠ョ煡閬撴枃浠剁殑绫诲瀷銆傚�逛簬涓嶅悓绫诲瀷鐨勬枃浠讹紝鎴戜��

    // 闇�瑕佷綔涓�浜涚壒鍒�澶勭悊銆� 濡傛灉鎵撳紑鐨勬槸瀛楃�﹁�惧�囨枃浠讹紝閭ｄ箞鎴戜滑灏辫�佽皟鐢�check_char_dev()

    // 鍑芥暟鏉ユ��鏌ュ綋鍓嶈繘绋嬫槸鍚﹁兘鎵撳紑杩欎釜瀛楃�﹁�惧�囨枃浠躲�傚�傛灉鍏佽�革紙鍑芥暟杩斿洖0锛夛紝閭ｄ箞鍦�

    // check_char_dev()涓�浼氭牴鎹�鍏蜂綋鏂囦欢鎵撳紑鏍囧織涓鸿繘绋嬭�剧疆鎺у埗缁堢��銆� 濡傛灉涓嶅厑璁告墦寮�

    // 浣跨敤璇ュ瓧绗﹁�惧�囨枃浠讹紝閭ｄ箞鎴戜滑鍙�鑳介噴鏀句笂闈㈢敵璇风殑鏂囦欢椤瑰拰鍙ユ焺璧勬簮锛岃繑鍥炲嚭閿欑爜銆�

195 /* ttys are somewhat special (ttyxx major==4, tty major==5) */

    /* ttys鏈変簺鐗规畩锛�ttyxx鐨勪富璁惧�囧��==4锛�tty鐨勪富璁惧�囧��==5锛�*/

196         if (S_ISCHR(inode->i_mode))

197                 if (check_char_dev(inode,inode->i_zone[0],flag)) {

198                         iput(inode);

199                         current->filp[fd]=NULL;

200                         f->f_count=0;

201                         return -EAGAIN;          // 鍑洪敊鍙凤細璧勬簮鏆傛椂涓嶅彲鐢ㄣ��

202                 }

    // 濡傛灉鎵撳紑鐨勬槸鍧楄�惧�囨枃浠讹紝鍒欐��鏌ョ洏鐗囨槸鍚︽洿鎹㈣繃銆傝嫢鏇存崲杩囧垯闇�瑕佽�╅珮閫熺紦鍐插尯涓�璇ヨ�惧��

    // 鐨勬墍鏈夌紦鍐插潡澶辨晥銆�

203 /* Likewise with block-devices: check for floppy_change */

    /* 鍚屾牱瀵逛簬鍧楄�惧�囨枃浠讹細闇�瑕佹��鏌ョ洏鐗囨槸鍚﹁��鏇存崲 */

204         if (S_ISBLK(inode->i_mode))

205                 check_disk_change(inode->i_zone[0]);

    // 鐜板湪鎴戜滑鍒濆�嬪寲鎵撳紑鏂囦欢鐨勬枃浠剁粨鏋勩�傝�剧疆鏂囦欢缁撴瀯灞炴�у拰鏍囧織锛岀疆鍙ユ焺寮曠敤璁℃暟涓�1锛屽苟

    // 璁剧疆i鑺傜偣瀛楁�典负鎵撳紑鏂囦欢鐨�i鑺傜偣锛屽垵濮嬪寲鏂囦欢璇诲啓鎸囬拡涓�0銆傛渶鍚庤繑鍥炴枃浠跺彞鏌勫彿銆�

206         f->f_mode = inode->i_mode;

207         f->f_flags = flag;

208         f->f_count = 1;

209         f->f_inode = inode;

210         f->f_pos = 0;

211         return (fd);

212 }

213

    //// 鍒涘缓鏂囦欢绯荤粺璋冪敤銆�

    // 鍙傛暟pathname鏄�璺�寰勫悕锛�mode涓庝笂闈㈢殑sys_open()鍑芥暟鐩稿悓銆�

    // 鎴愬姛鍒欒繑鍥炴枃浠跺彞鏌勶紝鍚﹀垯杩斿洖鍑洪敊鐮併��

214 int sys_creat(const char * pathname, int mode)

215 {

216         return sys_open(pathname, O_CREAT | O_TRUNC, mode);

217 }

218

    // 鍏抽棴鏂囦欢绯荤粺璋冪敤銆�

    // 鍙傛暟fd鏄�鏂囦欢鍙ユ焺銆�

    // 鎴愬姛鍒欒繑鍥�0锛屽惁鍒欒繑鍥炲嚭閿欑爜銆�

219 int sys_close(unsigned int fd)

220 {      

221         struct file * filp;

222

    // 棣栧厛妫�鏌ュ弬鏁版湁鏁堟�с�傝嫢缁欏嚭鐨勬枃浠跺彞鏌勫�煎ぇ浜庣▼搴忓悓鏃惰兘鎵撳紑鐨勬枃浠舵暟NR_OPEN锛屽垯杩斿洖

    // 鍑洪敊鐮侊紙鍙傛暟鏃犳晥锛夈�傜劧鍚庡�嶄綅杩涚▼鐨勬墽琛屾椂鍏抽棴鏂囦欢鍙ユ焺浣嶅浘瀵瑰簲浣嶃�傝嫢璇ユ枃浠跺彞鏌勫�瑰��

    // 鐨勬枃浠剁粨鏋勬寚閽堟槸NULL锛屽垯杩斿洖鍑洪敊鐮併��

223         if (fd >= NR_OPEN)

224                 return -EINVAL;

225         current->close_on_exec &= ~(1<<fd);

226         if (!(filp = current->filp[fd]))

227                 return -EINVAL;

    // 鐜板湪缃�璇ユ枃浠跺彞鏌勭殑鏂囦欢缁撴瀯鎸囬拡涓�NULL銆傝嫢鍦ㄥ叧闂�鏂囦欢涔嬪墠锛屽�瑰簲鏂囦欢缁撴瀯涓�鐨勫彞鏌勫紩鐢�

    // 璁℃暟宸茬粡涓�0锛屽垯璇存槑鍐呮牳鍑洪敊锛屽仠鏈恒�傚惁鍒欏皢瀵瑰簲鏂囦欢缁撴瀯鐨勫紩鐢ㄨ�℃暟鍑�1銆傛�ゆ椂濡傛灉瀹冭��

    // 涓嶄负0锛屽垯璇存槑鏈夊叾浠栬繘绋嬫�ｅ湪浣跨敤璇ユ枃浠讹紝浜庢槸杩斿��0锛堟垚鍔燂級銆傚�傛灉寮曠敤璁℃暟宸茬瓑浜�0锛�

    // 璇存槑璇ユ枃浠跺凡缁忔病鏈夎繘绋嬪紩鐢�锛岃�ユ枃浠剁粨鏋勫凡鍙樹负绌洪棽銆傚垯閲婃斁璇ユ枃浠�i鑺傜偣锛岃繑鍥�0銆�

228         current->filp[fd] = NULL;

229         if (filp->f_count == 0)

230                 panic("Close: file count is 0");

231         if (--filp->f_count)

232                 return (0);

233         iput(filp->f_inode);

234         return (0);

235 }

236