Hi everyone, In v6.1 DRM_USE_DYNAMIC_DEBUG=y has a regression enabling drm.debug in drivers at modprobe. It is due to a chicken-egg problem loading modules; on `modprobe i915`, drm is loaded 1st, and drm/parameters/debug is set. When drm_debug_enabled() tested __drm_debug at runtime, this just worked. But with DRM_USE_DYNAMIC_DEBUG=y, the runtime test is replaced with a static_key for each drm_dbg/dyndbg callsite, enabled by dyndbg's kparam callback on __drm_debug. So with drm.ko loaded and initialized before the dependent modules, their debug callsites aren't yet present to be enabled. STATUS - v3 not quite ready. rebased on -rc5, hopefully applies to patchwork head still has RFC patch -> CI_ONLY temporary, to avoid panics boots on my amdgpu box, drm.debug=0x3ff works at boot-time the "toggled" warning is repeatable with test_dynamic_debug*.ko it also occurs on amdgpu, so not just artificial. v2 is https://lore.kernel.org/lkml/20230113193016.749791-1-jim.cromie@xxxxxxxxx/ OVERVIEW As Jani Nikula noted rather more gently, DECLARE_DYNDBG_CLASSMAP is error-prone enough to call broken: sharing of a common classmap required identical classmap definitions in all modules using DRM_UT_*, which is inherently error-prone. IOW, it muddled the K&R distinction between a (single) definition, and multiple references. So patches 10-13 split it into: DYNDBG_CLASSMAP_DEFINE used once per subsystem to define each classmap. DYNDBG_CLASSMAP_USE declare dependence on a DEFINEd classmap. DYNDBG_CLASSMAP_DEFINE initializes the classmap, stores it into the (existing) __dyndbg_classes section, and exports the struct var (unlike DECLARE_DYNDBG_CLASSMAP). DYNDBG_CLASSMAP_USE initializes a class-ref struct, containing the user-module-name, and a ref to the exported classmap var. The distinction allows separate treatment of classmaps and classmap-refs, the latter getting additional behavior to propagate parent's kparam settings to USEr. (forex: drm.debug to drm-drivers) . lookup the classmap defn being referenced, and its module . find the module's kernel-params using the classmap . propagate kparam vals into the prdgs in module being added. It also makes the weird coordinated-changes-by-identical-classmaps "feature" unnecessary. Patch-10 splits the DECLARE macro into DEFINE & USE, and updates uses. Patch-11 is the core of it; the separate treatment begins in ddebug_add_module(). It calls ddebug_attach_module_classes(1) to handle class-defns; this adds ddebug_attach_client_module_classes(2) to handle class-refs, as they are found while modprobing drm drivers. (2) calls ddebug_apply_parents_params(3) on each USEr's referred classmap definition. (3) scans kernel-params owned by the module DEFINEing the classmap, either builtin or loadable, calls ddebug_match_apply_kparam(4) on each. (4) looks for kparams which are wired to dyndbg's param-ops. Those params have a struct ddebug_class_param attached, which has a classmap and a ref to a state-var (__drm_debug for DRM case). If the kparam's classmap is the same as from (2), then apply its state-var to the client module by calling ddebug_apply_class_bitmap(). Patch-12 cleans up DYNDBG_CLASSMAP_USE, dropping now unneeded args. Patch-13 improves DYNDBG_CLASSMAP_DEFINE, by accepting DRM_UT_* symbols directly, not "DRM_UT_*" (their strings). It adds new include/linux/map.h to support this. Patches 1-9 are prep, refactor, cleanup, tighten interfaces Patches 15-18 extend test_dynamic_debug to recreate DRM's multi-module regression; it builds both test_dynamic_debug.ko and _submod.ko, with an ifdef to _DEFINE in the main module, and _USE in the submod. This gives both modules identical set of prdbgs, which is helpful for comparing results. here it is, working properly: doing class DRM_UT_CORE -p [ 9904.961750] dyndbg: read 21 bytes from userspace [ 9904.962286] dyndbg: query 0: "class DRM_UT_CORE -p" mod:* [ 9904.962848] dyndbg: split into words: "class" "DRM_UT_CORE" "-p" [ 9904.963444] dyndbg: op='-' flags=0x0 maskp=0xfffffffe [ 9904.963945] dyndbg: parsed: func="" file="" module="" format="" lineno=0-0 class=DRM_UT_CORE [ 9904.964781] dyndbg: good-class: drm.DRM_UT_CORE module:drm nd:302 nc:1 nu:0 [ 9904.966411] dyndbg: class-ref: drm_kms_helper.DRM_UT_CORE module:drm_kms_helper nd:95 nc:0 nu:1 [ 9904.967265] dyndbg: class-ref: drm_display_helper.DRM_UT_CORE module:drm_display_helper nd:150 nc:0 nu:1 [ 9904.968349] dyndbg: class-ref: i915.DRM_UT_CORE module:i915 nd:1659 nc:0 nu:1 [ 9904.969801] dyndbg: class-ref: amdgpu.DRM_UT_CORE module:amdgpu nd:4425 nc:0 nu:1 [ 9904.977079] dyndbg: class-ref: nouveau.DRM_UT_CORE module:nouveau nd:103 nc:0 nu:1 [ 9904.977830] dyndbg: processed 1 queries, with 507 matches, 0 errs doing class DRM_UT_DRIVER +p [ 9906.151761] dyndbg: read 23 bytes from userspace [ 9906.152241] dyndbg: query 0: "class DRM_UT_DRIVER +p" mod:* [ 9906.152793] dyndbg: split into words: "class" "DRM_UT_DRIVER" "+p" [ 9906.153388] dyndbg: op='+' flags=0x1 maskp=0xffffffff [ 9906.153896] dyndbg: parsed: func="" file="" module="" format="" lineno=0-0 class=DRM_UT_DRIVER [ 9906.154746] dyndbg: good-class: drm.DRM_UT_DRIVER module:drm nd:302 nc:1 nu:0 [ 9906.155433] dyndbg: class-ref: drm_kms_helper.DRM_UT_DRIVER module:drm_kms_helper nd:95 nc:0 nu:1 [ 9906.156267] dyndbg: class-ref: drm_display_helper.DRM_UT_DRIVER module:drm_display_helper nd:150 nc:0 nu:1 [ 9906.157365] dyndbg: class-ref: i915.DRM_UT_DRIVER module:i915 nd:1659 nc:0 nu:1 [ 9906.163848] dyndbg: class-ref: amdgpu.DRM_UT_DRIVER module:amdgpu nd:4425 nc:0 nu:1 [ 9906.178963] dyndbg: class-ref: nouveau.DRM_UT_DRIVER module:nouveau nd:103 nc:0 nu:1 [ 9906.179934] dyndbg: processed 1 queries, with 1286 matches, 0 errs Patch-19 is a *workaround* for a panic: __jump_label_patch can "crash the box" when the jump-entry is in the wrong state. The current code makes no distinction between a well-formed "toggled" state and an "insane" state. Not for keeps. It fixes mis-initialization problems like this: [ 1594.032504] dyndbg: query 0: "class D2_DRIVER -p" mod:* [ 1594.032823] dyndbg: split into words: "class" "D2_DRIVER" "-p" [ 1594.033183] dyndbg: op='-' flags=0x0 maskp=0xfffffffe [ 1594.033507] dyndbg: parsed: func="" file="" module="" format="" lineno=0-0 class=D2_DRIVER [ 1594.034014] dyndbg: good-class: test_dynamic_debug.D2_DRIVER module:test_dynamic_debug nd:32 nc:4 nu:0 [ 1594.034695] dyndbg: changed lib/test_dynamic_debug.c:156 [test_dynamic_debug]do_cats p => _ [ 1594.035304] dyndbg: class-ref: test_dynamic_debug_submod.D2_DRIVER module:test_dynamic_debug_submod nd:32 nc:0 nu:4 [ 1594.036052] jump_label: found toggled op at do_cats+0x16/0x180 [test_dynamic_debug_submod] [00000000ff2582ac] (0f 1f 44 00 00 != e9 e1 00 00 00)) size:5 type:0 [ 1594.037036] dyndbg: changed lib/test_dynamic_debug.c:156 [test_dynamic_debug_submod]do_cats p => _ [ 1594.037604] dyndbg: processed 1 queries, with 2 matches, 0 errs [ 1594.037968] dyndbg: bit_1: 2 matches on class: D2_DRIVER -> 0x0 These errors are reliably reproduced by a shell-func which modprobes (with the right args) the test mod & submod.ko (in the commit message). So this isnt really ready for inclusion, but Id like to send the whole set to the CI-gym for a workout. The RFC/for-TESTING patch will mitigate panics, and still be detectable. Besides, Murphys law requires I publish some error before I can make progress. Jim Cromie (19): test-dyndbg: fixup CLASSMAP usage error test-dyndbg: show that DEBUG enables prdbgs at compiletime dyndbg: replace classmap list with a vector dyndbg: make ddebug_apply_class_bitmap more selective dyndbg: split param_set_dyndbg_classes to inner/outer fns dyndbg: drop NUM_TYPE_ARRAY dyndbg: reduce verbose/debug clutter dyndbg: tighten ddebug_class_name() 1st arg dyndbg: constify ddebug_apply_class_bitmap args dyndbg-API: split DECLARE_(DYNDBG_CLASSMAP) to $1(_DEFINE|_USE) dyndbg-API: specialize DYNDBG_CLASSMAP_(DEFINE|USE) dyndbg-API: DYNDBG_CLASSMAP_USE drop extra args dyndbg-API: DYNDBG_CLASSMAP_DEFINE() improvements drm_print: fix stale macro-name in comment test-dyndbg: build test_dynamic_debug_submod test-dyndbg: rename DD_SYS_WRAP to DYNDBG_CLASSMAP_PARAM test-dyndbg: disable WIP dyndbg-trace params test-dyndbg: tune sub-module behavior jump_label: RFC / temporary for CI - tolerate toggled state arch/x86/kernel/jump_label.c | 24 ++- drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 14 +- drivers/gpu/drm/display/drm_dp_helper.c | 14 +- drivers/gpu/drm/drm_crtc_helper.c | 14 +- drivers/gpu/drm/drm_print.c | 22 +- drivers/gpu/drm/i915/i915_params.c | 14 +- drivers/gpu/drm/nouveau/nouveau_drm.c | 14 +- include/asm-generic/vmlinux.lds.h | 1 + include/drm/drm_print.h | 6 +- include/linux/dynamic_debug.h | 57 ++++-- include/linux/map.h | 55 +++++ kernel/module/main.c | 3 + lib/Makefile | 3 +- lib/dynamic_debug.c | 258 ++++++++++++++++++------ lib/test_dynamic_debug.c | 118 +++++++---- lib/test_dynamic_debug_submod.c | 10 + 16 files changed, 437 insertions(+), 190 deletions(-) create mode 100644 include/linux/map.h create mode 100644 lib/test_dynamic_debug_submod.c -- 2.39.1
