linux-toradex.git/lib/dynamic_debug.c, branch v6.1-rc1

dyndbg: add drm.debug style (drm/parameters/debug) bitmap support

2022-09-07T15:04:49+00:00

Add kernel_param_ops and callbacks to use a class-map to validate and
apply input to a sysfs-node, which allows users to control classes
defined in that class-map.  This supports uses like:

  echo 0x3 > /sys/module/drm/parameters/debug

IE add these:

 - int param_set_dyndbg_classes()
 - int param_get_dyndbg_classes()
 - struct kernel_param_ops param_ops_dyndbg_classes

Following the model of kernel/params.c STANDARD_PARAM_DEFS, these are
non-static and exported.  This might be unnecessary here.

get/set use an augmented kernel_param; the arg refs a new struct
ddebug_class_param, which contains:

- A ptr to user's state-store; a union of &ulong for drm.debug, &int
  for nouveau level debug.  By ref'g the client's bit-state _var, code
  coordinates with existing code (like drm_debug_enabled) which uses
  it, so existing/remaining calls can work unchanged.  Changing
  drm.debug to a ulong allows use of BIT() etc.

- FLAGS: dyndbg.flags toggled by changes to bitmap. Usually just "p".

- MAP: a pointer to struct ddebug_classes_map, which maps those
  class-names to .class_ids 0..N that the module is using.  This
  class-map is declared & initialized by DECLARE_DYNDBG_CLASSMAP.

- map-type: 4 enums DD_CLASS_TYPE_* select 2 input forms and 2 meanings.

numeric input:
  DD_CLASS_TYPE_DISJOINT_BITS	integer input, independent bits. ie: drm.debug
  DD_CLASS_TYPE_LEVEL_NUM	integer input, 0..N levels

classnames-list (comma separated) input:
  DD_CLASS_TYPE_DISJOINT_NAMES	each name affects a bit, others preserved
  DD_CLASS_TYPE_LEVEL_NAMES	names have level meanings, like kern_levels.h

_NAMES    - comma-separated classnames (with optional +-)
_NUM      - numeric input, 0-N expected
_BITS     - numeric input, 0x1F bitmap form expected

_DISJOINT - bits are independent
_LEVEL    - (x /sys/module/drm/parameters/debug_catnames

A naive _LEVEL_NAMES use, with one class, that sets all in the
class-map according to (x /sys/module/test_dynamic_debug/parameters/p_level_names
  : problem solved
  echo -L1 > /sys/module/test_dynamic_debug/parameters/p_level_names

Note this artifact:

  : this is same as prev cmd (due to +/-)
  echo L0 > /sys/module/test_dynamic_debug/parameters/p_level_names

  : this is "even-more" off, but same wo __pr_debug_class(L0, "..").
  echo -L0 > /sys/module/test_dynamic_debug/parameters/p_level_names

A stress-test/make-work usage (kid toggling a light switch):

  echo +L7,L0,L7,L0,L7,L0,L7,L0,L7,L0,L7,L0,L7 \
       > /sys/module/test_dynamic_debug/parameters/p_level_names

ddebug_apply_class_bitmap(): inside-fn, works on bitmaps, receives
new-bits, finds diffs vs client-bitvector holding "current" state,
and issues exec_query to commit the adjustment.

param_set_dyndbg_classes(): interface fn, sends _NAMES to
param_set_dyndbg_classnames() and returns, falls thru to handle _BITS,
_NUM internally, and calls ddebug_apply_class_bitmap().  Finishes by
updating state.

param_set_dyndbg_classnames(): handles classnames-list in loop, calls
ddebug_apply_class_bitmap for each, then updates state.

NOTES:

_LEVEL_ is overlay on _DISJOINT_; inputs are converted to a bitmask,
by the callbacks.  IOW this is possible, and possibly confusing:

  echo class V3 +p > control
  echo class V1 -p > control

IMO thats ok, relative verbosity is an interface property.

_LEVEL_NUM maps still need class-names, even though the names are not
usable at the sysfs interface (unlike with _NAMES style).  The names
are the only way to >control the classes.

 - It must have a "V0" name,
   something below "V1" to turn "V1" off.
   __pr_debug_cls(V0,..) is printk, don't do that.

 - "class names" is required at the >control interface.
 - relative levels are not enforced at >control

_LEVEL_NAMES bear +/- signs, which alters the on-bit-pos by 1.  IOW,
+L2 means L0,L1,L2, and -L2 means just L0,L1.  This kinda spoils the
readback fidelity, since the L0 bit gets turned on by any use of any
L*, except "-L0".

All the interface uncertainty here pertains to the _NAMES features.
Nobody has actually asked for this, so its practical (if a little
tedious) to split it out.

Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-21-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: validate class FOO by checking with module

2022-09-07T15:04:49+00:00

Add module-to-class validation:

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

If a query has "class FOO", then ddebug_find_valid_class(), called
from ddebug_change(), requires that FOO is known to module X,
otherwize the query is skipped entirely for X.  This protects each
module's class-space, other than the default:31.

The authors' choice of FOO is highly selective, giving isolation
and/or coordinated sharing of FOOs.  For example, only DRM modules
should know and respond to DRM_UT_KMS.

So this, combined with module's opt-in declaration of known classes,
effectively privatizes the .class_id space for each module (or
coordinated set of modules).

Notes:

For all "class FOO" queries, ddebug_find_valid_class() is called, it
returns the map matching the query, and sets valid_class via an
*outvar).

If no "class FOO" is supplied, valid_class = _CLASS_DFLT.  This
insures that legacy queries do not trample on new class'd callsites,
as they get added.

Also add a new column to control-file output, displaying non-default
class-name (when found) or the "unknown _id:", if it has not been
(correctly) declared with one of the declarator macros.

Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-18-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: add ddebug_attach_module_classes

2022-09-07T15:04:49+00:00

Add ddebug_attach_module_classes(), call it from ddebug_add_module().
It scans the classes/section its given, finds records where the
module-name matches the module being added, and adds them to the
module's maps list.  No locking here, since the record
isn't yet linked into the ddebug_tables list.

It is called indirectly from 2 sources:

 - from load_module(), where it scans the module's __dyndbg_classes
   section, which contains DYNAMIC_DEBUG_CLASSES definitions from just
   the module.

 - from dynamic_debug_init(), where all DYNAMIC_DEBUG_CLASSES
   definitions of each builtin module have been packed together.
   This is why ddebug_attach_module_classes() checks module-name.

NOTES

Its (highly) likely that builtin classes will be ordered by module
name (just like prdbg descriptors are in the __dyndbg section).  So
the list can be replaced by a vector (ptr + length), which will work
for loaded modules too.  This would imitate whats currently done for
the _ddebug descriptors.

That said, converting to vector,len is close to pointless; a small
minority of modules will ever define a class-map, and almost all of
them will have only 1 or 2 class-maps, so theres only a couple dozen
pointers to save.  TODO: re-evaluate for lines removable.

Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-17-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

kernel/module: add __dyndbg_classes section

2022-09-07T15:04:49+00:00

Add __dyndbg_classes section, using __dyndbg as a model. Use it:

vmlinux.lds.h:

KEEP the new section, which also silences orphan section warning on
loadable modules.  Add (__start_/__stop_)__dyndbg_classes linker
symbols for the c externs (below).

kernel/module/main.c:
- fill new fields in find_module_sections(), using section_objs()
- extend callchain prototypes
  to pass classes, length
  load_module(): pass new info to dynamic_debug_setup()
  dynamic_debug_setup(): new params, pass through to ddebug_add_module()

dynamic_debug.c:
- add externs to the linker symbols.

ddebug_add_module():
- It currently builds a debug_table, and *will* find and attach classes.

dynamic_debug_init():
- add class fields to the _ddebug_info cursor var: di.

Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-16-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: gather __dyndbg[] state into struct _ddebug_info

2022-09-07T15:04:48+00:00

This new struct composes the linker provided (vector,len) section,
and provides a place to add other __dyndbg[] state-data later:

  descs - the vector of descriptors in __dyndbg section.
  num_descs - length of the data/section.

Use it, in several different ways, as follows:

In lib/dynamic_debug.c:

ddebug_add_module(): Alter params-list, replacing 2 args (array,index)
with a struct _ddebug_info * containing them both, with room for
expansion.  This helps future-proof the function prototype against the
looming addition of class-map info into the dyndbg-state, by providing
a place to add more member fields later.

NB: later add static struct _ddebug_info builtins_state declaration,
not needed yet.

ddebug_add_module() is called in 2 contexts:

In dynamic_debug_init(), declare, init a struct _ddebug_info di
auto-var to use as a cursor.  Then iterate over the prdbg blocks of
the builtin modules, and update the di cursor before calling
_add_module for each.

Its called from kernel/module/main.c:load_info() for each loaded
module:

In internal.h, alter struct load_info, replacing the dyndbg array,len
fields with an embedded _ddebug_info containing them both; and
populate its members in find_module_sections().

The 2 calling contexts differ in that _init deals with contiguous
subranges of __dyndbgs[] section, packed together, while loadable
modules are added one at a time.

So rename ddebug_add_module() into outer/__inner fns, call __inner
from _init, and provide the offset into the builtin __dyndbgs[] where
the module's prdbgs reside.  The cursor provides start, len of the
subrange for each.  The offset will be used later to pack the results
of builtin __dyndbg_sites[] de-duplication, and is 0 and unneeded for
loadable modules,

Note:

kernel/module/main.c includes  for struct
_ddeubg_info.  This might be prone to include loops, since its also
included by printk.h.  Nothing has broken in robot-land on this.

cc: Luis Chamberlain 
Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-12-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: cleanup auto vars in dynamic_debug_init

2022-09-07T15:04:48+00:00

rework var-names for clarity, regularity
rename variables
  - n to mod_sites - it counts sites-per-module
  - entries to i - display only
  - iter_start to iter_mod_start - marks start of each module's subrange
  - modct to mod_ct - stylistic

new iterator var:
  - site - cursor parallel to iter
    1st step towards 'demotion' of iter->site, for removal later

treat vars as iters:
  - drop init at top
    init just above for-loop, in a textual block

Acked-by: Jason Baron 
Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-11-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: drop EXPORTed dynamic_debug_exec_queries

2022-09-07T14:58:23+00:00

This exported fn is unused, and will not be needed. Lets dump it.

The export was added to let drm control pr_debugs, as part of using
them to avoid drm_debug_enabled overheads.  But its better to just
implement the drm.debug bitmap interface, then its available for
everyone.

Fixes: a2d375eda771 ("dyndbg: refine export, rename to dynamic_debug_exec_queries()")
Fixes: 4c0d77828d4f ("dyndbg: export ddebug_exec_queries")
Acked-by: Jason Baron 
Acked-by: Daniel Vetter 
Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-10-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: let query-modname override actual module name

2022-09-07T14:58:23+00:00

dyndbg's control-parser: ddebug_parse_query(), requires that search
terms: module, func, file, lineno, are used only once in a query; a
thing cannot be named both foo and bar.

The cited commit added an overriding module modname, taken from the
module loader, which is authoritative.  So it set query.module 1st,
which disallowed its use in the query-string.

But now, its useful to allow a module-load to enable classes across a
whole (or part of) a subsystem at once.

  # enable (dynamic-debug in) drm only
  modprobe drm dyndbg="class DRM_UT_CORE +p"

  # get drm_helper too
  modprobe drm dyndbg="class DRM_UT_CORE module drm* +p"

  # get everything that knows DRM_UT_CORE
  modprobe drm dyndbg="class DRM_UT_CORE module * +p"

  # also for boot-args:
  drm.dyndbg="class DRM_UT_CORE module * +p"

So convert the override into a default, by filling it only when/after
the query-string omitted the module.

NB: the query class FOO handling is forthcoming.

Fixes: 8e59b5cfb9a6 dynamic_debug: add modname arg to exec_query callchain
Acked-by: Jason Baron 
Acked-by: Daniel Vetter 
Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-8-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: use ESCAPE_SPACE for cat control

2022-09-07T14:58:23+00:00

`cat control` currently does octal escape, so '\n' becomes "\012".
Change this to display as "\n" instead, which reads much cleaner.

   :#> head -n7 /proc/dynamic_debug/control
   # filename:lineno [module]function flags format
   init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\n"
   init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\n"
   init/main.c:1424 [main]run_init_process =_ "  with arguments:\n"
   init/main.c:1426 [main]run_init_process =_ "    %s\n"
   init/main.c:1427 [main]run_init_process =_ "  with environment:\n"
   init/main.c:1429 [main]run_init_process =_ "    %s\n"

Acked-by: Jason Baron 
Acked-by: Daniel Vetter 
Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-7-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman

dyndbg: reverse module.callsite walk in cat control

2022-09-07T14:58:23+00:00

Walk the module's vector of callsites backwards; ie N..0.  This
"corrects" the backwards appearance of a module's prdbg vector when
walked 0..N.  I think this is due to linker mechanics, which I'm
inclined to treat as immutable, and the order is fixable in display.

No functional changes.

Combined with previous commit, which reversed tables-list, we get:

  :#> head -n7 /proc/dynamic_debug/control
  # filename:lineno [module]function flags format
  init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\012"
  init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\012"
  init/main.c:1424 [main]run_init_process =_ "  with arguments:\012"
  init/main.c:1426 [main]run_init_process =_ "    %s\012"
  init/main.c:1427 [main]run_init_process =_ "  with environment:\012"
  init/main.c:1429 [main]run_init_process =_ "    %s\012"

Acked-by: Jason Baron 
Acked-by: Daniel Vetter 
Signed-off-by: Jim Cromie 
Link: https://lore.kernel.org/r/20220904214134.408619-6-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman