linux-kernel - [PATCH 00/30] dyndbg: Rework classmap API to fix module dependency issues

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Message-ID: <20250911213823.374806-1-jim.cromie@gmail.com>
Date: Thu, 11 Sep 2025 15:37:53 -0600
From: Jim Cromie <jim.cromie@...il.com>
To: jbaron@...mai.com
Cc: gregkh@...uxfoundation.org,
	ukaszb@...omium.org,
	louis.chauvet@...tlin.com,
	linux-kernel@...r.kernel.org,
	Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH 00/30] dyndbg: Rework classmap API to fix module dependency issues

This series reworks the dynamic_debug (dyndbg) classmap API to fix a
fundamental design flaw that caused issues in subsystems sharing
classmaps across several modules, in the 1st use case: DRM

This broke it:
commit aad0214f3026 ("dyndbg: add DECLARE_DYNDBG_CLASSMAP macro")
This recognized it:
commit bb2ff6c27bc9 ("drm: Disable dynamic debug as broken").

Key changes in this series:

* Core API Rework:
  - Replaced DECLARE_DYNDBG_CLASSMAP with a new DEFINE/USE pattern
    (DYNAMIC_DEBUG_CLASSMAP_DEFINE and DYNAMIC_DEBUG_CLASSMAP_USE) to
    allow for shared classmap definitions between modules. This is the
    core fix for the module dependency issue.
  - compile-time and run-time checks to detect and prevent misuses of
    the classmap API, such as overlapping class_id ranges.
  - Refined the logic for "protecting" classmaps that implement a
    stable ABI (like drm.debug).
  - undo dumb namespace noise: DYNDBG_, ddebug (w/o the leading _)
  
* New Test:
  - `cd tools/testing/selftests; make TARGETS=dynamic_debug run_tests`
  - supplants DRM as the necessary test
  - good for `Tested-by:` ?

* cleanup, maintenance, refactoring:
  - drop unneeded linked list, keep classmaps as "vector"
  - tighten/declutter internal callchains, etc
  - several macros to de-duplicate code.

* excluded DRM parts
  - previous revisions included them for testing, validating
  - but this complicated things: audience & purpose

* Documentation:
  - The documentation has been updated to reflect all the new API
    changes and explain the design rationale.

This series has been tested on 3 x86 boxen (w amdgpu, nouveau) and in
virtme-ng with 8 permuted variations of the CONFIG_*DYNAMIC_DEBUG*
options and others.

The testing included DRM-specific adaptation patches which are
excluded here for clarity, but which are the actual user of this
feature, and needed for "proof-on-HW-devices".


Jim Cromie (30):
  docs/dyndbg: update examples \012 to \n
  docs/dyndbg: explain flags parse 1st
  test-dyndbg: fixup CLASSMAP usage error
  dyndbg: reword "class unknown," to "class:_UNKNOWN_"
  dyndbg: make ddebug_class_param union members same size
  dyndbg: drop NUM_TYPE_ARRAY
  dyndbg: tweak pr_fmt to avoid expansion conflicts
  dyndbg: reduce verbose/debug clutter
  dyndbg: refactor param_set_dyndbg_classes and below
  dyndbg: tighten fn-sig of ddebug_apply_class_bitmap
  dyndbg: replace classmap list with a vector
  dyndbg: macrofy a 2-index for-loop pattern
  dyndbg: DECLARE_DYNDBG_CLASSMAP needs stub defn
  dyndbg,module: make proper substructs in _ddebug_info
  dyndbg: hoist classmap-filter-by-modname up to ddebug_add_module
  dyndbg: move mod_name from ddebug_table down to _ddebug_info
  dyndbg-API: remove DD_CLASS_TYPE_(DISJOINT|LEVEL)_NAMES and code
  selftests-dyndbg: add a dynamic_debug run_tests target
  dyndbg: change __dynamic_func_call_cls* macros into expressions
  dyndbg-API: replace DECLARE_DYNDBG_CLASSMAP
  dyndbg: detect class_id reservation conflicts
  dyndbg: check DYNAMIC_DEBUG_CLASSMAP_DEFINE args at compile-time
  dyndbg-test: change do_prints testpoint to accept a loopct
  dyndbg-API: promote DYNAMIC_DEBUG_CLASSMAP_PARAM to API
  dyndbg: treat comma as a token separator
  dyndbg: split multi-query strings with %
  selftests-dyndbg: add test_mod_submod
  dyndbg: resolve "protection" of class'd pr_debugs
  dyndbg: add DYNAMIC_DEBUG_CLASSMAP_USE_(clname,_base)
  docs/dyndbg: add classmap info to howto

 .../admin-guide/dynamic-debug-howto.rst       | 179 ++++-
 MAINTAINERS                                   |   3 +-
 include/asm-generic/vmlinux.lds.h             |   5 +-
 include/linux/dynamic_debug.h                 | 304 ++++++--
 kernel/module/main.c                          |  15 +-
 lib/Kconfig.debug                             |  24 +-
 lib/Makefile                                  |   5 +
 lib/dynamic_debug.c                           | 675 +++++++++++-------
 lib/test_dynamic_debug.c                      | 198 +++--
 lib/test_dynamic_debug_submod.c               |  21 +
 tools/testing/selftests/Makefile              |   1 +
 .../testing/selftests/dynamic_debug/Makefile  |   9 +
 tools/testing/selftests/dynamic_debug/config  |   7 +
 .../dynamic_debug/dyndbg_selftest.sh          | 373 ++++++++++
 14 files changed, 1392 insertions(+), 427 deletions(-)
 create mode 100644 lib/test_dynamic_debug_submod.c
 create mode 100644 tools/testing/selftests/dynamic_debug/Makefile
 create mode 100644 tools/testing/selftests/dynamic_debug/config
 create mode 100755 tools/testing/selftests/dynamic_debug/dyndbg_selftest.sh

-- 
2.51.0