[Intel-gfx] [PATCH v6 00/57] DYNDBG: opt-in class'd debug for modules, use in drm.

Jim Cromie
2022-09-04T21:42:10Z

hi Greg, Jason, DRM-folk, Steven,

If Im not too late for linux-next in this cycle, heres V6. Diffs are minor:

- rebased onto e47eb90a0a9a (tag: next-20220901, linux-next/master)
gets past Kconfig conflict, same for drm-tip.
- uint debug_level, not ulong. to fit nouveau.
- -1 on param-read-back, to match prev write val.
- added back tracefs parts, missing from -V5
updated for tracing/events: Add __vstring() and __assign_vstr() helper macros
no decorations-lite in TP_printk, do it right later.
- commit-msg tweaks

Theres also new RFC stuff with the potential to reduce the size of the
__dyndbgs section by 20%. Not ready for prime time, or linux-next,
but I hope compelling.

FEATURE DESCRIPTION

dyndbg provides DECLARE_DYNAMIC_DEBUG_CLASSMAP() which allows module
authors to declare "good" class-names, of 4 types.

DYNAMIC_DEBUG_CLASSMAP(drm_debug_classes,
DD_CLASS_TYPE_DISJOINT_BITS, offset,
"DRM_UT_CORE",
"DRM_UT_DRIVER",
"DRM_UT_KMS",
"DRM_UT_PRIME",
"DRM_UT_ATOMIC",
"DRM_UT_VBL",
"DRM_UT_STATE",
"DRM_UT_LEASE",
"DRM_UT_DP",
"DRM_UT_DRMRES");

That usage authorizes dyndbg to set class'd pr_debugs accordingly:

echo class DRM_UT_CORE +p > /proc/dynamic_debug/control
echo class DRM_UT_KMS +p > /proc/dynamic_debug/control

Because the DRM modules declare the same classes, they each authorize
dyndbg with the same classnames, which allows dyndbg to effect changes
to its selected class'd prdbgs.

Opting in by using the macro effectively privatizes the limited
63-classes available per module; only modules which share classnames
must coordinate their use of the common range, and they can
independently use the remaining id-space.

Other dyndbg filtering pertains too, so single sites can be selected.

4 DD_CLASS_TYPE_*_*s determine 2 behaviors:

DISJOINT bits are independent, like drm.debug categories
LEVELs 3>2, turns on level-2, like nouveau debug-levels
NUM/BITS numeric input, bitmap if disjoint, else 0-32.
NAMES accept proper names, like DRM_UT_CORE

Dyndbg provides param-callbacks which enforce those behaviors:

# DISJOINT_BITS
echo 0x03 > /sys/module/drm/parameters/debug

# LEVEL_NUM
echo 3 > /sys/module/drm/nouveau/debug-mumble*

# DISJOINT_NAMES
echo +DRM_UT_CORE,+DRM_UT_KMS,-DRM_UT_DRIVER > /sys/module/drm/parameters/debug_categories

# LEVEL_NAMES
echo NV_TRACE > /sys/module/nouveau/parameters/debug-mumble*

That design choice is allowed cuz verbosity is always attached to a
(user visible) interface, and theres no reason not to put the
implementation there (in the callback). It also considerably
simplifies things; ddebug_change can treat class_id's as disjoint,
period.

Jim Cromie (57):
prep:
dyndbg: fix static_branch manipulation
dyndbg: fix module.dyndbg handling
dyndbg: show both old and new in change-info
dyndbg: reverse module walk in cat control
dyndbg: reverse module.callsite walk in cat control
dyndbg: use ESCAPE_SPACE for cat control
dyndbg: let query-modname override actual module name
dyndbg: add test_dynamic_debug module
dyndbg: drop EXPORTed dynamic_debug_exec_queries
dyndbg: cleanup auto vars in dynamic_debug_init
dyndbg: gather __dyndbg[] state into struct _ddebug_info

class feature:
dyndbg: add class_id to pr_debug callsites
dyndbg: add __pr_debug_cls for testing
dyndbg: add DECLARE_DYNDBG_CLASSMAP macro
kernel/module: add __dyndbg_classes section
dyndbg: add ddebug_attach_module_classes
dyndbg: validate class FOO by checking with module
doc-dyndbg: describe "class CLASS_NAME" query support
doc-dyndbg: edit dynamic-debug-howto for brevity, audience
dyndbg: add drm.debug style (drm/parameters/debug) bitmap support
dyndbg: test DECLARE_DYNDBG_CLASSMAP, sysfs nodes

drm-use-case:
drm_print: condense enum drm_debug_category
drm: POC drm on dyndbg - use in core, 2 helpers, 3 drivers.
drm_print: interpose drm_*dbg with forwarding macros
drm_print: wrap drm_*_dbg in dyndbg descriptor factory macro
drm-print.h: include dyndbg header
drm-print: add drm_dbg_driver to improve namespace symmetry
drm_print: refine drm_debug_enabled for jump-label
drm_print: prefer bare printk KERN_DEBUG on generic fn
drm_print: add _ddebug descriptor to drm_*dbg prototypes
nouveau: change nvkm_debug/trace to use dev_dbg POC
nouveau: adapt NV_DEBUG, NV_ATOMIC to use DRM.debug
nouveau: WIP add 2 LEVEL_NUM classmaps for CLI, SUBDEV

dyndbg-tracefs:
dyndbg: add _DPRINTK_FLAGS_ENABLED
dyndbg: add _DPRINTK_FLAGS_TRACE
dyndbg: add write-events-to-tracefs code
dyndbg: add 2 trace-events: drm_debug, drm_devdbg
dyndbg: add 2 more trace-events: pr_debug, dev_dbg
dyndbg/drm: POC add tracebits sysfs-knob

RFC-20%-data-reclaim:
dyndbg: abstraction macros for modname,function,filename fields
dyndbg: split repeating columns to new struct _ddebug_site
dyndbg: shrink lineno field by 2 bits
dyndbg: add _index,_map to struct _ddebug
dyndbg: extend __ddebug_add_module proto to allow packing sites
dyndbg: de-duplicate sites
dyndbg: drop site-> in add-module, more needed
dyndbg: demote iter->site in _init
dyndbg: add .gnu.linkonce slot in vmlinux.lds.h KEEPs
dyndbg: add structs _ddebug_hdr, _ddebug_site_hdr
dyndbg: count unique callsites
dyndbg: prevent build bugs via -DNO_DYNAMIC_DEBUG_TABLE
dyndbg: add DEFINE_DYNAMIC_DEBUG_TABLE, use it tacitly RFC
dyndbg: add/use is_dyndbg_header then set _uplink
dyndbg: add .gnu.linkonce. & __dyndbg* sections in module.lds.h
dyndbg: dynamic_debug_sites_reclaim() using free_reserved_page() WAG
dyndbg: work ddebug_map_site
dyndbg: fiddle with readback value on LEVEL_NAMES types

.../admin-guide/dynamic-debug-howto.rst | 249 +++---
MAINTAINERS | 2 +
arch/arm/boot/compressed/Makefile | 2 +
arch/sparc/vdso/Makefile | 2 +
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/entry/vdso/Makefile | 3 +
arch/x86/purgatory/Makefile | 1 +
drivers/firmware/efi/libstub/Makefile | 3 +-
drivers/gpu/drm/Kconfig | 12 +
drivers/gpu/drm/Makefile | 2 +
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 14 +
drivers/gpu/drm/display/drm_dp_helper.c | 13 +
drivers/gpu/drm/drm_crtc_helper.c | 13 +
drivers/gpu/drm/drm_print.c | 83 +-
drivers/gpu/drm/i915/i915_params.c | 12 +
.../gpu/drm/nouveau/include/nvkm/core/debug.h | 16 +
.../drm/nouveau/include/nvkm/core/subdev.h | 17 +-
drivers/gpu/drm/nouveau/nouveau_drm.c | 20 +
drivers/gpu/drm/nouveau/nouveau_drv.h | 16 +-
drivers/gpu/drm/nouveau/nvkm/core/subdev.c | 23 +
include/asm-generic/module.lds.h | 12 +-
include/asm-generic/vmlinux.lds.h | 10 +
include/drm/drm_print.h | 85 +-
include/linux/dynamic_debug.h | 286 ++++++-
include/trace/events/drm.h | 54 ++
include/trace/events/dyndbg.h | 73 ++
kernel/module/internal.h | 4 +-
kernel/module/main.c | 22 +-
lib/Kconfig.debug | 10 +
lib/Makefile | 1 +
lib/dynamic_debug.c | 792 +++++++++++++++---
lib/test_dynamic_debug.c | 165 ++++
32 files changed, 1680 insertions(+), 338 deletions(-)
create mode 100644 include/trace/events/drm.h
create mode 100644 include/trace/events/dyndbg.h
create mode 100644 lib/test_dynamic_debug.c

--
2.37.2