1 files changed, 57 insertions, 18 deletions
diff --git a/src/sys/os/os_filedes.c b/src/sys/os/os_filedes.c
index ca56fc3..3eaee0d 100644
--- a/src/sys/os/os_filedes.c
+++ b/src/sys/os/os_filedes.c
@@ -44,16 +44,9 @@
 #define STDOUT_FILENO 1
 
 /*
- * Allocate a file descriptor from a specific process's
- * file descriptor table
- *
- * @procp: Process to allocate fd from
- * @fd_res: Result pointer is written here
- *
- * Returns zero on success, otherwise a less than
- * zero value upon failure
+ * Allocate a file descriptor
  */
-static int
+int
 fd_alloc(struct proc *procp, struct filedesc **fd_res)
 {
     struct filedesc *fd;
@@ -91,16 +84,9 @@ fd_alloc(struct proc *procp, struct filedesc **fd_res)
 }
 
 /*
- * Look up a file descriptor that belongs to a specific
- * process by using its fd number
- *
- * @procp: Process to look up
- * @fd: File descriptor number
- *
- * Returns the file descriptor pointer on success,
- * otherwise a less than zero value on failure
+ * Get a file descriptor
  */
-static struct filedesc *
+struct filedesc *
 fd_get(struct proc *procp, int fd)
 {
     struct filedesc *fdp;
@@ -359,6 +345,44 @@ read(int fd, void *buf, size_t count)
     return retval;
 }
 
+off_t
+lseek(int fd, off_t offset, int whence)
+{
+    struct filedesc *fdp;
+    struct proc *self = proc_self();
+    struct vattr attr;
+    int error;
+
+    if (fd < 0) {
+        return -EBADF;
+    }
+
+    fdp = fd_get(self, fd);
+    if (fdp == NULL) {
+        return -EBADF;
+    }
+
+    /* Could not get vnode attributes */
+    error = vop_getattr(fdp->vp, &attr);
+    if (error < 0) {
+        return 0;
+    }
+
+    switch (whence) {
+    case SEEK_SET:
+        fdp->off = offset;
+        break;
+    case SEEK_CUR:
+        fdp->off += offset;
+        break;
+    case SEEK_END:
+        fdp->off = attr.size;
+        break;
+    }
+
+    return fdp->off;
+}
+
 /*
  * ARG0: Path
  * ARG1: Mode
@@ -378,3 +402,18 @@ sys_open(struct syscall_args *scargs)
 
     return fd_open(pathbuf, mode);
 }
+
+/*
+ * ARG0: Fd
+ * ARG1: Offset
+ * ARG2: Whence
+ */
+scret_t
+sys_lseek(struct syscall_args *scargs)
+{
+    int fd = SCARG(scargs, int, 0);
+    off_t off = SCARG(scargs, off_t, 1);
+    int whence = SCARG(scargs, int, 2);
+
+    return lseek(fd, off, whence);
+}