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Subject[PATCH v5 20/33] dyndbg: add drm.debug style (drm/parameters/debug) bitmap support
Date
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 union of &ulong bits, level; which points to user module's ulong
storing the module's debug-state. By ref'g the client's bit-state
_var, code coordinates with existing code (like drm_debug_enabled)
which uses it, so existing works unchanged. Changing 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<y) on bit-pos.

_DISJOINT treats input like a bit-vector (ala drm.debug), and sets
each bit accordingly. LEVEL is layered on top of this.

_LEVEL treats input like a bit-pos:N, then sets bits(0..N)=1, and
bits(N+1..max)=0. This applies (bit<N) semantics on top of disjoint
bits.

USAGES:

A potentially typical _DISJOINT_NAMES use:

echo +DRM_UT_CORE,+DRM_UT_KMS,-DRM_UT_DRIVER,-DRM_UT_ATOMIC \
> /sys/module/drm/parameters/debug_catnames

A standard _LEVEL_NAMES use, with one class, that sets all in the
class-map according to (x<y):

: problem seen
echo +L7 > /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,
and is done by 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 <jim.cromie@gmail.com>
---
. drop kp->mod->name as unneeded (build-dependent) <lkp>
. param_set_dyndbg_classnames, not _class_strings
. DD_CLASS_TYPE_* name changes, per Jason
. callbacks:
extend comments on DD_CLASS_TYPE_* handling, flow notes
varname changes
. kdoc tweaks
. add stub macro: #define KP_NAME(kp) kp->name
later, add "$module." prefix when config doesn't do it
. s/struct ddebug_classes_bitmap_param/struct ddebug_class_param/
. fix levels state handling

v4 had trouble where level-type's state was fouled by conversion to
bitmap form given to apply-bitmap. fix by:

(simplify/clarify)
add old-bits, new-bits to sysfs-iface&support
use CLASSMAP_BITMASK more
in param_set_dyndbg_class{es,names}():
move state-saving inside switches, and tailor it to type.
this preserves lvl-state, vs -v4 which didnt.

I could "hack" in an offset, but the problem feels deeper.

The root-problem may be the ambiguity wrt 0x0 > knob; per a
input-is-assert-bitpos interpretation, it turns on bit 0.

Thus far, code has avoided this ambiguity, by recommending against
coding pr_dbg_cls(V0|L0, ""), which makes "+L0" & "-L0" equivalent,
and "0" silent.

That might be "too clever by 1/2"; accepting an int, so -1 means
all-bits-off as well as verbosity-off, might be the better way.
---
include/linux/dynamic_debug.h | 20 ++++
lib/dynamic_debug.c | 218 +++++++++++++++++++++++++++++++++-
2 files changed, 234 insertions(+), 4 deletions(-)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 46ed10682e87..956614a208a4 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -120,6 +120,14 @@ struct _ddebug_info {
unsigned int num_classes;
};

+struct ddebug_class_param {
+ union { unsigned long *bits;
+ unsigned long *lvl;
+ };
+ char flags[8];
+ const struct ddebug_class_map *map;
+};
+
#if defined(CONFIG_DYNAMIC_DEBUG_CORE)

int ddebug_add_module(struct _ddebug_info *dyndbg, const char *modname);
@@ -279,6 +287,10 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
KERN_DEBUG, prefix_str, prefix_type, \
rowsize, groupsize, buf, len, ascii)

+struct kernel_param;
+int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp);
+int param_get_dyndbg_classes(char *buffer, const struct kernel_param *kp);
+
/* for test only, generally expect drm.debug style macro wrappers */
#define __pr_debug_cls(cls, fmt, ...) do { \
BUILD_BUG_ON_MSG(!__builtin_constant_p(cls), \
@@ -325,6 +337,14 @@ static inline int ddebug_dyndbg_module_param_cb(char *param, char *val,
rowsize, groupsize, buf, len, ascii); \
} while (0)

+struct kernel_param;
+static inline int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
+{ return 0; }
+static inline int param_get_dyndbg_classes(char *buffer, const struct kernel_param *kp)
+{ return 0; }
+
#endif /* !CONFIG_DYNAMIC_DEBUG_CORE */

+extern const struct kernel_param_ops param_ops_dyndbg_classes;
+
#endif
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index eb410b412f0d..c41e22d850e0 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -596,6 +596,218 @@ static int ddebug_exec_queries(char *query, const char *modname)
return nfound;
}

+/* apply a new bitmap to the sys-knob's current bit-state */
+static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
+ unsigned long *new_bits, unsigned long *old_bits)
+{
+#define QUERY_SIZE 128
+ char query[QUERY_SIZE];
+ const struct ddebug_class_map *map = dcp->map;
+ int matches = 0;
+ int bi, ct;
+
+ v2pr_info("apply: 0x%lx to: 0x%lx\n", *new_bits, *old_bits);
+
+ for (bi = 0; bi < map->length; bi++) {
+ if (test_bit(bi, new_bits) == test_bit(bi, old_bits))
+ continue;
+
+ snprintf(query, QUERY_SIZE, "class %s %c%s", map->class_names[bi],
+ test_bit(bi, new_bits) ? '+' : '-', dcp->flags);
+
+ ct = ddebug_exec_queries(query, NULL);
+ matches += ct;
+
+ v2pr_info("bit_%d: %d matches on class: %s -> 0x%lx\n", bi,
+ ct, map->class_names[bi], *new_bits);
+ }
+ return matches;
+}
+
+/* stub to later conditionally add "$module." prefix where not already done */
+#define KP_NAME(kp) kp->name
+
+#define CLASSMAP_BITMASK(width) ((1UL << (width)) - 1)
+
+/* accept comma-separated-list of [+-] classnames */
+static int param_set_dyndbg_classnames(const char *instr, const struct kernel_param *kp)
+{
+ const struct ddebug_class_param *dcp = kp->arg;
+ const struct ddebug_class_map *map = dcp->map;
+ unsigned long curr_bits, old_bits;
+ char *cl_str, *p, *tmp;
+ int cls_id, totct = 0;
+ bool wanted;
+
+ cl_str = tmp = kstrdup(instr, GFP_KERNEL);
+ p = strchr(cl_str, '\n');
+ if (p)
+ *p = '\0';
+
+ /* start with previously set state-bits, then modify */
+ curr_bits = old_bits = *dcp->bits;
+ vpr_info("\"%s\" > %s:0x%lx\n", cl_str, KP_NAME(kp), curr_bits);
+
+ for (; cl_str; cl_str = p) {
+ p = strchr(cl_str, ',');
+ if (p)
+ *p++ = '\0';
+
+ if (*cl_str == '-') {
+ wanted = false;
+ cl_str++;
+ } else {
+ wanted = true;
+ if (*cl_str == '+')
+ cl_str++;
+ }
+ cls_id = match_string(map->class_names, map->length, cl_str);
+ if (cls_id < 0) {
+ pr_err("%s unknown to %s\n", cl_str, KP_NAME(kp));
+ continue;
+ }
+
+ /* have one or more valid class_ids of one *_NAMES type */
+ switch (map->map_type) {
+ case DD_CLASS_TYPE_DISJOINT_NAMES:
+ /* the +/- pertains to a single bit */
+ if (test_bit(cls_id, &curr_bits) == wanted) {
+ v3pr_info("no change on %s\n", cl_str);
+ continue;
+ }
+ curr_bits ^= BIT(cls_id);
+ totct += ddebug_apply_class_bitmap(dcp, &curr_bits, dcp->bits);
+ *dcp->bits = curr_bits;
+ v2pr_info("%s: changed bit %d:%s\n", KP_NAME(kp), cls_id,
+ map->class_names[cls_id]);
+ break;
+ case DD_CLASS_TYPE_LEVEL_NAMES:
+ /* cls_id = N in 0..max. wanted +/- determines N or N-1 */
+ old_bits = CLASSMAP_BITMASK(*dcp->lvl);
+ curr_bits = CLASSMAP_BITMASK(cls_id + (wanted ? 1 : 0 ));
+
+ totct += ddebug_apply_class_bitmap(dcp, &curr_bits, &old_bits);
+ *dcp->lvl = (cls_id + (wanted ? 1 : 0));
+ v2pr_info("%s: changed bit-%d: \"%s\" %lx->%lx\n", KP_NAME(kp), cls_id,
+ map->class_names[cls_id], old_bits, curr_bits);
+ break;
+ default:
+ pr_err("illegal map-type value %d\n", map->map_type);
+ }
+ }
+ kfree(tmp);
+ vpr_info("total matches: %d\n", totct);
+ return 0;
+}
+
+/**
+ * param_set_dyndbg_classes - class FOO >control
+ * @instr: string echo>d to sysfs, input depends on map_type
+ * @kp: kp->arg has state: bits/lvl, map, map_type
+ *
+ * Enable/disable prdbgs by their class, as given in the arguments to
+ * DECLARE_DYNDBG_CLASSMAP. For LEVEL map-types, enforce relative
+ * levels by bitpos.
+ *
+ * Returns: 0 or <0 if error.
+ */
+int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
+{
+ const struct ddebug_class_param *dcp = kp->arg;
+ const struct ddebug_class_map *map = dcp->map;
+ unsigned long inrep, new_bits, old_bits;
+ int rc, totct = 0;
+
+ switch (map->map_type) {
+
+ case DD_CLASS_TYPE_DISJOINT_NAMES:
+ case DD_CLASS_TYPE_LEVEL_NAMES:
+ /* handle [+-]classnames list separately, we are done here */
+ return param_set_dyndbg_classnames(instr, kp);
+
+ case DD_CLASS_TYPE_DISJOINT_BITS:
+ case DD_CLASS_TYPE_LEVEL_NUM:
+ /* numeric input, accept and fall-thru */
+ rc = kstrtoul(instr, 0, &inrep);
+ if (rc) {
+ pr_err("expecting numeric input: %s > %s\n", instr, KP_NAME(kp));
+ return -EINVAL;
+ }
+ break;
+ default:
+ pr_err("%s: bad map type: %d\n", KP_NAME(kp), map->map_type);
+ return -EINVAL;
+ }
+
+ /* only _BITS,_NUM (numeric) map-types get here */
+ switch (map->map_type) {
+ case DD_CLASS_TYPE_DISJOINT_BITS:
+ /* expect bits. mask and warn if too many */
+ if (inrep & ~CLASSMAP_BITMASK(map->length)) {
+ pr_warn("%s: input: 0x%lx exceeds mask: 0x%lx, masking\n",
+ KP_NAME(kp), inrep, CLASSMAP_BITMASK(map->length));
+ inrep &= CLASSMAP_BITMASK(map->length);
+ }
+ v2pr_info("bits:%lx > %s\n", inrep, KP_NAME(kp));
+ totct += ddebug_apply_class_bitmap(dcp, &inrep, dcp->bits);
+ *dcp->bits = inrep;
+ break;
+ case DD_CLASS_TYPE_LEVEL_NUM:
+ /* input is bitpos, of highest verbosity to be enabled */
+ if (inrep > map->length) {
+ pr_warn("%s: level:%ld exceeds max:%d, clamping\n",
+ KP_NAME(kp), inrep, map->length);
+ inrep = map->length;
+ }
+ old_bits = CLASSMAP_BITMASK(*dcp->lvl);
+ new_bits = CLASSMAP_BITMASK(inrep);
+ v2pr_info("lvl:%ld bits:0x%lx > %s\n", inrep, new_bits, KP_NAME(kp));
+ totct += ddebug_apply_class_bitmap(dcp, &new_bits, &old_bits);
+ *dcp->lvl = inrep;
+ break;
+ default:
+ pr_warn("%s: bad map type: %d\n", KP_NAME(kp), map->map_type);
+ }
+ vpr_info("%s: total matches: %d\n", KP_NAME(kp), totct);
+ return 0;
+}
+EXPORT_SYMBOL(param_set_dyndbg_classes);
+
+/**
+ * param_get_dyndbg_classes - classes reader
+ * @buffer: string description of controlled bits -> classes
+ * @kp: kp->arg has state: bits, map
+ *
+ * Reads last written state, underlying prdbg state may have been
+ * altered by direct >control. Displays 0x for DISJOINT, 0-N for
+ * LEVEL Returns: #chars written or <0 on error
+ */
+int param_get_dyndbg_classes(char *buffer, const struct kernel_param *kp)
+{
+ const struct ddebug_class_param *dcp = kp->arg;
+ const struct ddebug_class_map *map = dcp->map;
+
+ switch (map->map_type) {
+
+ case DD_CLASS_TYPE_DISJOINT_NAMES:
+ case DD_CLASS_TYPE_DISJOINT_BITS:
+ return scnprintf(buffer, PAGE_SIZE, "0x%lx\n", *dcp->bits);
+
+ case DD_CLASS_TYPE_LEVEL_NAMES:
+ case DD_CLASS_TYPE_LEVEL_NUM:
+ return scnprintf(buffer, PAGE_SIZE, "%ld\n", *dcp->lvl);
+ default:
+ return -1;
+ }
+}
+EXPORT_SYMBOL(param_get_dyndbg_classes);
+
+const struct kernel_param_ops param_ops_dyndbg_classes = {
+ .set = param_set_dyndbg_classes,
+ .get = param_get_dyndbg_classes,
+};
+EXPORT_SYMBOL(param_ops_dyndbg_classes);
+
#define PREFIX_SIZE 64

static int remaining(int wrote)
@@ -1037,13 +1249,11 @@ static int __ddebug_add_module(struct _ddebug_info *di, unsigned int base,
dt->ddebugs = di->descs;
dt->num_ddebugs = di->num_descs;

- INIT_LIST_HEAD(&dt->link);
-
INIT_LIST_HEAD(&dt->link);
INIT_LIST_HEAD(&dt->maps);

- if (classes && num_classes)
- ddebug_attach_module_classes(dt, classes, num_classes);
+ if (di->classes && di->num_classes)
+ ddebug_attach_module_classes(dt, di->classes, di->num_classes);

mutex_lock(&ddebug_lock);
list_add_tail(&dt->link, &ddebug_tables);
--
2.37.1
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