Add write_file () syscall, CE implement redirections, libarena arena_realloc ()

kernel/fs/vfs.c

@@ -205,6 +205,25 @@ int vfs_read_file (struct proc* proc, const char* volume_name, const char* path,
   return volume->driver_ops.read_file (volume, path, buffer, off, size);
 }
 
+int vfs_write_file (struct proc* proc, const char* volume_name, const char* path, uint8_t* buffer,
+                    size_t off, size_t size) {
+  struct vfs_volume* volume = vfs_find_volume (volume_name);
+
+  if (volume == NULL)
+    return -ST_NOT_FOUND;
+
+  spin_lock (&volume->lock);
+
+  if (volume->locked && volume->owner != proc) {
+    spin_unlock (&volume->lock);
+    return -ST_PERMISSION_ERROR;
+  }
+
+  spin_unlock (&volume->lock);
+
+  return volume->driver_ops.write_file (volume, path, buffer, off, size);
+}
+
 int vfs_create_file (struct proc* proc, const char* volume_name, const char* path) {
   struct vfs_volume* volume = vfs_find_volume (volume_name);