Implement Thread API for the live kernel

This commit implements the API outlined in #92 for the case
where the current target is the live Linux kernel. In order to
facilitate this, several of the already existing linux kernel helpers
which were written in Python have been rewritten in C in order to make
them accessible from libdrgn.

Signed-off-by: Kevin Svetlitski <[email protected]>

Author: Svetlitski

_drgn.pyi

@@ -765,7 +765,10 @@ class Thread:
     prstatus: bytes
     """ The contents of the PRSTATUS note associated with this thread in the core dump. """
     object: Object
-    """ Presently undefined. """
+    """
+    If debugging the kernel, the ``struct task_struct *`` object for this thread.
+    Otherwise, not defined.
+    """
     def stack_trace(self) -> StackTrace:
         """
         A convenience function for retrieving the stack trace associated with a given thread.

drgn/helpers/linux/idr.py

@@ -13,13 +13,17 @@
 
 from typing import Iterator, Tuple
 
-from _drgn import _linux_helper_idr_find as idr_find
+from _drgn import (
+    _linux_helper_idr_find as idr_find,
+    _linux_helper_my_idr_for_each as my_idr_for_each,
+)
 from drgn import Object
 from drgn.helpers.linux.radixtree import radix_tree_for_each
 
 __all__ = (
     "idr_find",
     "idr_for_each",
+    "my_idr_for_each",
 )
 
 

drgn/helpers/linux/pid.py

@@ -15,6 +15,8 @@
     _linux_helper_find_pid as find_pid,
     _linux_helper_find_task as find_task,
     _linux_helper_pid_task as pid_task,
+    _linux_helper_my_for_each_task as my_for_each_task,
+    _linux_helper_my_for_each_pid as my_for_each_pid,
 )
 from drgn import Object, Program, cast, container_of
 from drgn.helpers.linux.idr import idr_for_each
@@ -26,6 +28,8 @@
     "for_each_pid",
     "for_each_task",
     "pid_task",
+    "my_for_each_task",
+    "my_for_each_pid",
 )
 
 

drgn/helpers/linux/radixtree.py

@@ -11,13 +11,13 @@
 
 from typing import Iterator, Tuple
 
-from _drgn import _linux_helper_radix_tree_lookup as radix_tree_lookup
+from _drgn import (
+    _linux_helper_radix_tree_lookup as radix_tree_lookup,
+    _linux_helper_my_radix_tree_for_each as my_radix_tree_for_each,
+)
 from drgn import Object, cast
 
-__all__ = (
-    "radix_tree_for_each",
-    "radix_tree_lookup",
-)
+__all__ = ("radix_tree_for_each", "radix_tree_lookup", "my_radix_tree_for_each")
 
 _RADIX_TREE_ENTRY_MASK = 3
 

libdrgn/Makefile.am

@@ -42,6 +42,8 @@ libdrgnimpl_la_SOURCES = $(ARCH_DEFS:.defs=.c) \
 			 hash_table.c \
 			 hash_table.h \
 			 helpers.h \
+			 iterators.h \
+			 iterators.c \
 			 language.c \
 			 language.h \
 			 language_c.c \