make grade 100/100

Makefile

@@ -188,6 +188,7 @@ UPROGS=\
 	$U/_grind\
 	$U/_wc\
 	$U/_zombie\
+	$U/_symlinktest\
 
 
 

kernel/fcntl.h

@@ -3,3 +3,4 @@
 #define O_RDWR    0x002
 #define O_CREATE  0x200
 #define O_TRUNC   0x400
+#define O_NOFOLLOW 0x800

kernel/stat.h

@@ -1,7 +1,7 @@
 #define T_DIR     1   // Directory
 #define T_FILE    2   // File
 #define T_DEVICE  3   // Device
-
+#define T_SYMLINK 4
 struct stat {
   int dev;     // File system's disk device
   uint ino;    // Inode number

kernel/syscall.c

@@ -101,6 +101,7 @@ extern uint64 sys_unlink(void);
 extern uint64 sys_link(void);
 extern uint64 sys_mkdir(void);
 extern uint64 sys_close(void);
+extern uint64 sys_symlink(void);
 
 // An array mapping syscall numbers from syscall.h
 // to the function that handles the system call.
@@ -126,6 +127,7 @@ static uint64 (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_symlink]   sys_symlink,
 };
 
 void

kernel/syscall.h

@@ -20,3 +20,4 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#define SYS_symlink 22

kernel/sysfile.c

@@ -335,6 +335,36 @@ sys_open(void)
     }
   }
 
+  if (ip->type == T_SYMLINK && !(omode & O_NOFOLLOW)) {
+    int symlink_step = 0;
+    while (ip->type == T_SYMLINK) {
+      if (symlink_step++ > 10) {
+        // printf("\x1b[031mFailed\x1b[0m due to deep symlink\n");
+        iunlockput(ip); // on error, put inode 'cause only success open need to use the file after the syscall
+        end_op();
+        return -1;
+      }
+      int len_target = readi(ip, 0, (uint64)path, 0, MAXPATH);
+      iunlockput(ip); // no more need to use this inode
+      if (len_target == 0) {
+        printf("\x1b[031mFailed\x1b[0m to read symlink %s\n", path);
+        end_op();
+        return -1;
+      }
+      // get target's inode
+      if((ip = namei(path)) == 0){
+        // printf("\x1b[031mFailed\x1b[0m open symlink target %s\n", path);
+        end_op();
+        return -1;
+      }
+      ilock(ip);
+      if(ip->type == T_DIR && omode != O_RDONLY){
+        iunlockput(ip);
+        end_op();
+        return -1;
+      }
+    }
+  }
   if(ip->type == T_DEVICE && (ip->major < 0 || ip->major >= NDEV)){
     iunlockput(ip);
     end_op();
@@ -503,3 +533,32 @@ sys_pipe(void)
   }
   return 0;
 }
+
+uint64
+sys_symlink(void)
+{
+  char target[MAXPATH], path[MAXPATH];
+  int len_target, len_path;
+  struct inode* ip;
+  if ((len_target = argstr(0, target, MAXPATH)) < 0) 
+    return -1;
+  if ((len_path = argstr(1, path, MAXPATH)) < 0) 
+    return -1;
+  // printf("\x1b[033msys_symlink\x1b[0m %s -> %s\n", path, target);
+  begin_op();
+  ip = create(path, T_SYMLINK, 0, 0);
+  if (ip == 0) {
+    end_op();
+    // printf("\x1b[031mFailed\x1b[0m to create path %s\n", path);
+    return -1;
+  }
+  if (writei(ip, 0, (uint64)target, 0, len_target) != len_target) {
+    iunlockput(ip);
+    end_op();
+    printf("\x1b[031mFailed\x1b[0m to write symlink target %s to %s\n", target, path);
+    return -1;
+  }
+  iunlockput(ip); // no need to keep this inode ref, if not put, in-RAM inode pool will run out
+  end_op();
+  return 0;
+}

time.txt

@@ -0,0 +1 @@
+7

user/bigfile.c

@@ -32,11 +32,8 @@ main()
     printf("bigfile: file is too small\n");
     exit(-1);
   }
-  printf("bef close fd\n");
   close(fd);
-  printf("aft close fd\n");
   fd = open("big.file", O_RDONLY);
-  printf("aft open\n");
   if(fd < 0){
     printf("bigfile: cannot re-open big.file for reading\n");
     exit(-1);

user/user.h

@@ -22,6 +22,7 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+int symlink(char* target, char* path);
 
 // ulib.c
 int stat(const char*, struct stat*);

user/usys.pl

@@ -36,3 +36,4 @@ entry("getpid");
 entry("sbrk");
 entry("sleep");
 entry("uptime");
+entry("symlink");