0.0.24 (Released September 8th, 2023)

These are some of the highlights of drgn 0.0.24. See the GitHub release for the full release notes, including more improvements and bug fixes.

Linked List Length Helper

This release added list_count_nodes(), which returns the length of a Linux kernel linked list:

>>> list_count_nodes(prog["workqueues"].address_of_())

Networking Helpers

This release added a couple of Linux kernel networking helpers requested by Jakub Kicinski.

netdev_priv() returns the private data of a network device:

>>> dev = netdev_get_by_name(prog, "wlp0s20f3")
>>> netdev_priv(dev)
(void *)0xffff9419c9dec9c0
>>> netdev_priv(dev, "struct ieee80211_sub_if_data")
*(struct ieee80211_sub_if_data *)0xffff9419c9dec9c0 = {

skb_shinfo() returns the shared info for a socket buffer.

C++ Lookups

This release added support for a few C++ features.

Simple Type Specifiers

Unlike C, C++ allows referring to class, struct, union, and enum types without their respective keywords. For example:

class Foo { ... };
Foo foo; // Equivalent to class Foo foo;

Previously, drgn always required the keyword, so prog.type("class Foo") would succeed but prog.type("Foo") would fail with a LookupError. This requirement was surprising to C++ developers, so it was removed. For C++ programs, prog.type("Foo") will now find a class, struct, union, or enum type named Foo (for C programs, the keyword is still required).

Nested Classes

Again unlike C, C++ allows class, struct, and union types to be defined inside of other class, struct, and union types. For example:

class Foo {
  class Bar { ... };
Foo::Bar bar;

drgn can now find such types with prog.type("Foo::Bar").

Member Functions

C++ supports member functions (a.k.a. methods). For example:

class Foo {
  int method() { ... }

drgn can now find member functions with drgn.Program.function(), drgn.Program.object(), or drgn.Program[] (e.g., prog.function("Foo::method") or prog["Foo::method"]).


drgn now supports split DWARF object (.dwo) files. This is enabled by the -gsplit-dwarf option in GCC and Clang or for the Linux kernel with CONFIG_DEBUG_INFO_SPLIT=y.

Split DWARF package (.dwp) file support is still in progress.

Performance Improvements

Thierry Treyer found a bug that made us search through much more debugging information than necessary when getting a stack trace. Fixing this made stack traces almost twice as fast.

The C++ lookup and split DWARF support mentioned above require processing more information in drgn’s debugging information indexing step, which it does on startup and whenever debugging information is manually loaded. This could’ve been a performance regression, but instead, indexing was reworked from the ground up in a way that’s usually faster despite the added features.