1 files changed, 71 insertions, 0 deletions
diff --git a/kernel/sysfile.c b/kernel/sysfile.c
index 4b2189a..9c12d44 100644
--- a/kernel/sysfile.c
+++ b/kernel/sysfile.c
@@ -16,6 +16,15 @@
 #include "file.h"
 #include "fcntl.h"
 
+// symlink
+#define SYMLINK_MAXFOLLOW 254
+
+struct symlink {
+  uint len;
+  char target[MAXPATH];
+};
+
+
 // Fetch the nth word-sized system call argument as a file descriptor
 // and return both the descriptor and the corresponding struct file.
 static int
@@ -258,6 +267,8 @@ create(char *path, short type, short major, short minor)
     ilock(ip);
     if(type == T_FILE && (ip->type == T_FILE || ip->type == T_DEVICE))
       return ip;
+    if(type == T_SYMLINK)
+      return ip;
     iunlockput(ip);
     return 0;
   }
@@ -301,6 +312,37 @@ create(char *path, short type, short major, short minor)
   return 0;
 }
 
+// create a symbolic link to path
+uint64
+sys_symlink(void)
+{
+  char path[MAXPATH];
+  struct inode *ip;
+  struct symlink sl = {0};
+
+  if(argstr(0, sl.target, MAXPATH) < 0 || argstr(1, path, MAXPATH) < 0)
+    return -1;
+
+  sl.len = strlen(sl.target);
+
+  begin_op();
+  if((ip = create(path, T_SYMLINK, 0, 0)) == 0){
+    end_op();
+    return -1;
+  }
+
+  if(writei(ip, 0, (uint64)&sl.len, 0, sizeof(sl.len)) != sizeof(sl.len) || writei(ip, 0, (uint64)sl.target, sizeof(sl.len), sl.len+1) != sl.len+1){
+    iunlockput(ip);
+    end_op();
+    return -1;
+  }
+
+  iupdate(ip);
+  iunlockput(ip);
+  end_op();
+  return 0;
+}
+
 uint64
 sys_open(void)
 {
@@ -341,6 +383,35 @@ sys_open(void)
     return -1;
   }
 
+  if(ip->type == T_SYMLINK && !(omode & O_NOFOLLOW)){
+    int len = 0;
+    uchar i;
+    for(i = 0; i < SYMLINK_MAXFOLLOW; i++){
+      if(readi(ip, 0, (uint64)&len, 0, sizeof(len)) != sizeof(len) ||
+          readi(ip, 0, (uint64)path, sizeof(len), len+1) != len+1) {
+        iunlockput(ip);
+        end_op();
+        return -1;
+      }
+      iunlockput(ip);
+
+      if((ip = namei(path)) == 0) {
+        end_op();
+        return -1;
+      }
+
+      ilock(ip);
+      if(ip->type != T_SYMLINK)
+        break;
+    }
+
+    if (i >= SYMLINK_MAXFOLLOW) {
+      iunlockput(ip);
+      end_op();
+      return -1;
+    }
+  }
+
   if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){
     if(f)
       fileclose(f);