StarPilot

system/loggerd/xattr_cache.py

@@ -1,17 +1,57 @@
 import errno
 
-import xattr
+import os
+
+try:
+  import xattr  # type: ignore[import-not-found]
+except ImportError:
+  xattr = None
 
 _cached_attributes: dict[tuple, bytes | None] = {}
+_backend_disabled = False
+
+
+def _backend_getxattr(path: str, attr_name: str) -> bytes:
+  if xattr is not None:
+    return xattr.getxattr(path, attr_name)
+  if hasattr(os, "getxattr"):
+    return os.getxattr(path, attr_name)
+  raise OSError(errno.ENOTSUP, "xattr backend unavailable")
+
+
+def _backend_setxattr(path: str, attr_name: str, attr_value: bytes) -> None:
+  if xattr is not None:
+    xattr.setxattr(path, attr_name, attr_value)
+    return
+  if hasattr(os, "setxattr"):
+    os.setxattr(path, attr_name, attr_value)
+    return
+  raise OSError(errno.ENOTSUP, "xattr backend unavailable")
+
+
+def _is_missing_attr_error(e: OSError) -> bool:
+  return e.errno == errno.ENODATA or (hasattr(errno, "ENOATTR") and e.errno == errno.ENOATTR)
+
+
+def _is_unsupported_error(e: OSError) -> bool:
+  unsupported_errnos = {errno.ENOTSUP, errno.EOPNOTSUPP, errno.ENOSYS}
+  return e.errno in unsupported_errnos
 
 def getxattr(path: str, attr_name: str) -> bytes | None:
+  global _backend_disabled
+
   key = (path, attr_name)
   if key not in _cached_attributes:
+    response: bytes | None = None
     try:
-      response = xattr.getxattr(path, attr_name)
+      if not _backend_disabled:
+        response = _backend_getxattr(path, attr_name)
     except OSError as e:
       # ENODATA (Linux) or ENOATTR (macOS) means attribute hasn't been set
-      if e.errno == errno.ENODATA or (hasattr(errno, 'ENOATTR') and e.errno == errno.ENOATTR):
+      if _is_missing_attr_error(e):
+        response = None
+      elif _is_unsupported_error(e):
+        _backend_disabled = True
         response = None
       else:
         raise
@@ -19,5 +59,22 @@ def getxattr(path: str, attr_name: str) -> bytes | None:
   return _cached_attributes[key]
 
 def setxattr(path: str, attr_name: str, attr_value: bytes) -> None:
-  _cached_attributes.pop((path, attr_name), None)
-  xattr.setxattr(path, attr_name, attr_value)
+  global _backend_disabled
+
+  key = (path, attr_name)
+  if _backend_disabled:
+    # In environments without xattr support, keep behavior stable for this process.
+    _cached_attributes[key] = attr_value
+    return
+
+  try:
+    _backend_setxattr(path, attr_name, attr_value)
+  except OSError as e:
+    if _is_unsupported_error(e):
+      _backend_disabled = True
+      _cached_attributes[key] = attr_value
+      return
+    _cached_attributes.pop(key, None)
+    raise
+
+  _cached_attributes[key] = attr_value