Make cast() a function instead of a method

drgn/__init__.py

@@ -47,6 +47,16 @@ from drgn.type import Type, PointerType
 from drgn.typename import TypeName
 
 
+def cast(type: Union[str, Type, TypeName], obj: Object) -> Object:
+        """
+        Return a copy of the given object casted to another type. The given
+        type is usually a string, but it can also be a Type or TypeName object.
+        """
+        if not isinstance(type, Type):
+            type = obj.prog_.type(type)
+        return Object(obj.prog_, type, value=obj._value, address=obj.address_)
+
+
 def container_of(ptr: Object, type: Union[str, Type, TypeName],
                  member: str) -> Object:
     """

drgn/helpers/kernel/device.py

@@ -8,7 +8,7 @@ This module provides helpers for working with Linux devices, including the
 kernel encoding of dev_t.
 """
 
-from drgn import Object
+from drgn import cast, Object
 
 __all__ = [
     'MAJOR',
@@ -30,7 +30,7 @@ def MAJOR(dev):
     """
     major = dev >> _MINORBITS
     if isinstance(major, Object):
-        return major.cast_('unsigned int')
+        return cast('unsigned int', major)
     return major
 
 
@@ -42,7 +42,7 @@ def MINOR(dev):
     """
     minor = dev & _MINORMASK
     if isinstance(minor, Object):
-        return minor.cast_('unsigned int')
+        return cast('unsigned int', minor)
     return minor
 
 
@@ -54,5 +54,5 @@ def MKDEV(major, minor):
     """
     dev = (major << _MINORBITS) | minor
     if isinstance(dev, Object):
-        return dev.cast_('dev_t')
+        return cast('dev_t', dev)
     return dev

drgn/helpers/kernel/mm.py

@@ -8,7 +8,7 @@ This module provides helpers for working with the Linux memory management (mm)
 subsystem. Only x86-64 support is currently implemented.
 """
 
-from drgn import Object
+from drgn import cast, Object
 
 
 __all__ = [
@@ -25,7 +25,7 @@ __all__ = [
 def _vmemmap(prog):
     try:
         # KASAN
-        return prog['vmemmap_base'].cast_('struct page *')
+        return cast('struct page *', prog['vmemmap_base'])
     except KeyError:
         # x86-64
         return Object(prog, 'struct page *', value=0xffffea0000000000)
@@ -57,7 +57,7 @@ def page_to_pfn(page):
 
     Get the page frame number (PFN) of a page.
     """
-    return (page - _vmemmap(page.prog_)).cast_('unsigned long')
+    return cast('unsigned long', page - _vmemmap(page.prog_))
 
 
 def pfn_to_page(prog_or_pfn, pfn=None):

drgn/helpers/kernel/pid.py

@@ -7,7 +7,7 @@ Linux kernel process ID helpers
 This module provides helpers for looking up process IDs.
 """
 
-from drgn import container_of, NULL, Program
+from drgn import cast, container_of, NULL, Program
 from drgn.helpers.kernel.idr import idr_find, idr_for_each
 from drgn.helpers.kernel.list import hlist_for_each_entry
 
@@ -34,7 +34,7 @@ def find_pid(prog_or_ns, nr):
         prog = prog_or_ns.prog_
         ns = prog_or_ns
     if hasattr(ns, 'idr'):
-        return idr_find(ns.idr, nr).cast_('struct pid *')
+        return cast('struct pid *', idr_find(ns.idr, nr))
     else:
         # We could implement pid_hashfn() and only search that bucket, but it's
         # different for 32-bit and 64-bit systems, and it has changed at least
@@ -67,7 +67,7 @@ def for_each_pid(prog_or_ns):
         ns = prog_or_ns
     if hasattr(ns, 'idr'):
         for nr, entry in idr_for_each(ns.idr):
-            yield entry.cast_('struct pid *')
+            yield cast('struct pid *', entry)
     else:
         pid_hash = prog['pid_hash']
         for i in range(1 << prog['pidhash_shift'].value_()):

drgn/helpers/kernel/radixtree.py

@@ -8,7 +8,7 @@ This module provides helpers for working with radix trees from
 "linux/radix-tree.h".
 """
 
-from drgn import Object
+from drgn import cast, Object
 
 
 __all__ = [
@@ -33,7 +33,7 @@ def _radix_tree_root_node(root):
     except AttributeError:
         return root.rnode.read_once_(), 1
     else:
-        return node.cast_('struct xa_node *').read_once_(), 2
+        return cast('struct xa_node *', node).read_once_(), 2
 
 
 def radix_tree_lookup(root, index):
@@ -50,8 +50,8 @@ def radix_tree_lookup(root, index):
             break
         parent = _entry_to_node(node, RADIX_TREE_INTERNAL_NODE)
         offset = (index >> parent.shift) & RADIX_TREE_MAP_MASK
-        node = parent.slots[offset].cast_(parent.type_).read_once_()
-    return node.cast_('void *')
+        node = cast(parent.type_, parent.slots[offset]).read_once_()
+    return cast('void *', node)
 
 
 def radix_tree_for_each(root):
@@ -66,8 +66,8 @@ def radix_tree_for_each(root):
         if _is_internal_node(node, RADIX_TREE_INTERNAL_NODE):
             parent = _entry_to_node(node, RADIX_TREE_INTERNAL_NODE)
             for i, slot in enumerate(parent.slots):
-                yield from aux(slot.cast_(parent.type_).read_once_(),
+                yield from aux(cast(parent.type_, slot).read_once_(),
                                index + (i << parent.shift.value_()))
         elif node:
-            yield index, node.cast_('void *')
+            yield index, cast('void *', node)
     yield from aux(node, 0)

drgn/internal/cli.py

@@ -80,7 +80,8 @@ def main() -> None:
             from drgn.internal.rlcompleter import Completer
 
             init_globals['drgn'] = drgn
-            for attr in ['container_of', 'Object', 'NULL']:
+            drgn_globals = ['cast', 'container_of', 'NULL', 'Object']
+            for attr in drgn_globals:
                 init_globals[attr] = getattr(drgn, attr)
             init_globals['__name__'] = '__main__'
             init_globals['__doc__'] = None
@@ -102,7 +103,7 @@ def main() -> None:
             banner = version + """
 For help, type help(drgn).
 >>> import drgn
->>> from drgn import container_of, Object, NULL"""
+>>> from drgn import """ + ', '.join(drgn_globals)
             if prog._is_kernel():
                 banner += '\n>>> from drgn.helpers.kernel import *'
                 module = importlib.import_module('drgn.helpers.kernel')

drgn/internal/program.py

@@ -246,16 +246,6 @@ class Object:
             raise ValueError(f'member access must be on a struct or union, not {self.type_.name!r}') from None
         return Object(self.prog_, member_type, address=address + offset)
 
-    def cast_(self, type: Union[str, Type, TypeName]) -> 'Object':
-        """
-        Return a copy of this object casted to another type. The given type is
-        usually a string, but it can also be a Type or TypeName object.
-        """
-        if not isinstance(type, Type):
-            type = self.prog_.type(type)
-        return Object(self.prog_, type, value=self._value,
-                      address=self.address_)
-
     def address_of_(self) -> 'Object':
         """
         Return an object pointing to this object. Corresponds to the address-of

tests/test_program.py

@@ -2,7 +2,7 @@ import math
 import operator
 import tempfile
 
-from drgn import container_of, NULL, Object, Program
+from drgn import cast, container_of, NULL, Object, Program
 from drgn.internal.corereader import CoreReader
 from drgn.type import IntType, StructType, TypedefType
 from tests.test_type import color_type, point_type
@@ -52,12 +52,12 @@ class TestObject(TypeIndexTestCase):
 
     def test_cast(self):
         obj = Object(self.prog, TYPES['int'], value=-1)
-        cast_obj = obj.cast_('unsigned int')
+        cast_obj = cast('unsigned int', obj)
         self.assertEqual(cast_obj,
                          Object(self.prog, TYPES['unsigned int'], value=2**32 - 1))
 
         obj = Object(self.prog, TYPES['double'], value=1.0)
-        self.assertRaises(TypeError, obj.cast_, self.type_index.pointer(TYPES['int']))
+        self.assertRaises(TypeError, cast, self.type_index.pointer(TYPES['int']), obj)
 
     def test_str(self):
         obj = Object(self.prog, TYPES['int'], value=1)
@@ -170,7 +170,7 @@ class TestObject(TypeIndexTestCase):
         with self.assertRaises(ValueError):
             obj.member_('foo')
 
-        cast_obj = obj.cast_('unsigned long')
+        cast_obj = cast('unsigned long', obj)
         self.assertEqual(cast_obj,
                          Object(self.prog, TYPES['unsigned long'], value=0))
         self.assertRaises(TypeError, obj.__index__)