[PATCH v9 16/39] dyndbg: refactor param_set_dyndbg_classes and below

[Jim Cromie via B4 Relay <devnull+jim.cromie.gmail.com@kernel.org>]

From: Jim Cromie <jim.cromie@gmail.com>

Refactor the callchain below param_set_dyndbg_classes(1) to allow
mod-name specific settings.  Split (1) into upper/lower fns, adding
modname param to lower, and passing NULL in from upper.  Below that,
add the same param to ddebug_apply_class_bitmap(), and pass it thru to
_ddebug_queries(), replacing NULL with the param.

This allows the callchain to update the classmap in just one module,
vs just all as currently done.  While the sysfs param is unlikely to
ever update just one module, the callchain will be used for modprobe
handling, which should update only that just-probed module.

In ddebug_apply_class_bitmap(), also check for actual changes to the
bits before announcing them, to declutter logs.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
v2: move RvB after SoB
v8: drop kdoc on static fn,
---
 lib/dynamic_debug.c | 73 ++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 47 insertions(+), 26 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index d4dbbd1a91ef..b0e9f4768eb8 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -618,9 +618,10 @@ static int ddebug_exec_queries(char *query, const char *modname)
 	return nfound;
 }
 
-/* apply a new bitmap to the sys-knob's current bit-state */
+/* apply a new class-param setting */
 static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
-				     unsigned long *new_bits, unsigned long *old_bits)
+				     unsigned long *new_bits, unsigned long *old_bits,
+				     const char *query_modname)
 {
 #define QUERY_SIZE 128
 	char query[QUERY_SIZE];
@@ -628,7 +629,9 @@ static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
 	int matches = 0;
 	int bi, ct;
 
-	v2pr_info("apply: 0x%lx to: 0x%lx\n", *new_bits, *old_bits);
+	if (*new_bits != *old_bits)
+		v2pr_info("apply bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits,
+			  *old_bits, query_modname ?: "'*'");
 
 	for (bi = 0; bi < map->length; bi++) {
 		if (test_bit(bi, new_bits) == test_bit(bi, old_bits))
@@ -637,12 +640,16 @@ static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
 		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);
+		ct = ddebug_exec_queries(query, query_modname);
 		matches += ct;
 
 		v2pr_info("bit_%d: %d matches on class: %s -> 0x%lx\n", bi,
 			  ct, map->class_names[bi], *new_bits);
 	}
+	if (*new_bits != *old_bits)
+		v2pr_info("applied bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits,
+			  *old_bits, query_modname ?: "'*'");
+
 	return matches;
 }
 
@@ -651,22 +658,17 @@ static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
 
 #define CLASSMAP_BITMASK(width) ((1UL << (width)) - 1)
 
-/**
- * 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.
+/*
+ * param-setter helper to validate numeric input, clamp its value by
+ * the classmap type and size, and apply the bits.
  */
-int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
+static int param_set_dyndbg_module_classes(const char *instr,
+					   const struct kernel_param *kp,
+					   const char *mod_name)
 {
 	const struct ddebug_class_param *dcp = kp->arg;
 	const struct ddebug_class_map *map = dcp->map;
-	unsigned long inrep, new_bits, old_bits;
+	unsigned long inrep, new_bits, old_bits, old_val;
 	int rc, totct = 0;
 
 	rc = kstrtoul(instr, 0, &inrep);
@@ -686,9 +688,10 @@ int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
 				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;
+		old_val = READ_ONCE(*dcp->bits);
+		v2pr_info("bits:0x%lx > %s.%s\n", inrep, mod_name ?: "*", KP_NAME(kp));
+		totct += ddebug_apply_class_bitmap(dcp, &inrep, &old_val, mod_name);
+		WRITE_ONCE(*dcp->bits, inrep);
 		break;
 	case DD_CLASS_TYPE_LEVEL_NUM:
 		/* input is bitpos, of highest verbosity to be enabled */
@@ -697,11 +700,12 @@ int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
 				KP_NAME(kp), inrep, map->length);
 			inrep = map->length;
 		}
-		old_bits = CLASSMAP_BITMASK(*dcp->lvl);
+		old_val = READ_ONCE(*dcp->lvl);
+		old_bits = CLASSMAP_BITMASK(old_val);
 		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;
+		totct += ddebug_apply_class_bitmap(dcp, &new_bits, &old_bits, mod_name);
+		WRITE_ONCE(*dcp->lvl, inrep);
 		break;
 	default:
 		pr_warn("%s: bad map type: %d\n", KP_NAME(kp), map->map_type);
@@ -710,16 +714,33 @@ int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
 	vpr_info("%s: total matches: %d\n", KP_NAME(kp), totct);
 	return 0;
 }
+
+/**
+ * param_set_dyndbg_classes - classmap-based kernel parameter setter
+ * @instr: string value to set (numeric bitmask or level)
+ * @kp:    kernel parameter info referencing classmap state
+ *
+ * Enable or disable all class'd pr_debug callsites in the classmap,
+ * independent of the module they're in.
+ *
+ * Returns: 0 on success, or a negative error code.
+ */
+int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
+{
+	return param_set_dyndbg_module_classes(instr, kp, NULL);
+}
 EXPORT_SYMBOL(param_set_dyndbg_classes);
 
 /**
- * param_get_dyndbg_classes - classes reader
+ * param_get_dyndbg_classes - classmap kparam getter
  * @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
+ * Reads last written state, underlying pr_debug states may have been
+ * altered by direct >control.  Displays 0x for DISJOINT classmap
+ * types, 0-N for LEVEL types.
+ *
+ * Returns: ct of chars written or <0 on error
  */
 int param_get_dyndbg_classes(char *buffer, const struct kernel_param *kp)
 {

-- 
2.55.0