[PATCH v4 3/7] dyndbg: add dyndbg-bitmap definer and callbacks

[Jim Cromie <jim.cromie@gmail.com>]

Add DEFINE_DYNDBG_BITMAP(name, var, bitmap_desc, @bit_descs) to allow
users to define a /sys/module/*/parameter/name, and a mapping from
bits[0-N] to the debug-class-prefixes that the author wishes to
control.

DEFINE_DYNDBG_BITMAP(debug_gvt, __gvt_debug,
	"dyndbg bitmap desc",
	{ "gvt:cmd: ",	"command processing" },
	{ "gvt:core: ",	"core help" },
	{ "gvt:dpy: ",	"display help" },
	{ "gvt:el: ",	"help" },
	{ "gvt:irq: ",	"help" },
	{ "gvt:mm: ",	"help" },
	{ "gvt:mmio: ", "help" },
	{ "gvt:render: ", "help" },
	{ "gvt:sched: ", "help" });

dynamic_debug.c: add 3 new elements:

- int param_set_dyndbg() - not working yet, // __gvt_debug
- int param_get_dyndbg()
- struct param_ops_dyndbg

Following the model of kernel/params.c STANDARD_PARAM_DEFS, All 3 are
non-static and exported.

dynamic_debug.h:

extern the struct param_ops_dyndbg prototype.  This appears to be
needed to reference the var, forex in i915_params.c

TBD: set_dyndbg() works to enable categories, but fails to disable
them.  This is because the code relied on having an old copy of the
param (__gvt_debug) to detect +/- changes.  Rewriting the loop is
probably easier than stashing the old state for change detection.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 include/linux/dynamic_debug.h | 36 +++++++++++++++++++++++
 lib/dynamic_debug.c           | 55 +++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index dce631e678dd..677ad176b167 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -2,6 +2,8 @@
 #ifndef _DYNAMIC_DEBUG_H
 #define _DYNAMIC_DEBUG_H
 
+#include <linux/moduleparam.h>
+
 #if defined(CONFIG_JUMP_LABEL)
 #include <linux/jump_label.h>
 #endif
@@ -227,6 +229,40 @@ static inline int dynamic_debug_exec_queries(const char *query, const char *modn
 	return 0;
 }
 
+static int param_set_dyndbg(const char *instr, struct kernel_param *kp)
+{ return 0; }
+static int param_get_dyndbg(char *buffer, struct kernel_param *kp)
+{ return 0; }
+
 #endif /* !CONFIG_DYNAMIC_DEBUG_CORE */
 
+struct dyndbg_bitdesc {
+	/* bitpos is inferred from index in containing array */
+	char *prefix;
+	char *help;
+};
+
+/**
+ * DYNDBG_BITMAP_DESC(name, var, bitmap_desc, @bit_descs)
+ * @name: basename under /sys
+ * @var: C identifier to map
+ * @bitmap_desc: string summarizing dyndbg categories
+ * @bit_descs: list of struct dydbg_bitdesc initializations
+ *
+ * Defines the mapping of bits 0-N to categories/prefixes of
+ * debug-callsites to be controlled.
+ *
+ * Users should also call MODULE_PARM_DESC(name, bitmap_desc).
+ * Maybe we can invoke it on their behalf, but we want MOD-NAME to be
+ * correct, test soon.  may also need modname in name - "debug" will
+ * not be unique.
+ */
+#define DEFINE_DYNDBG_BITMAP(name, value, bitmap_desc, ...)	\
+	struct dyndbg_bitdesc dyndbg_classes_##name[] =		\
+	{ __VA_ARGS__, { NULL, NULL } };			\
+	module_param_cbd(name, &param_ops_dyndbg, value, 0644,	\
+			 &dyndbg_classes_##name);
+
+extern const struct kernel_param_ops param_ops_dyndbg;
+
 #endif
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index cb5abb42c16a..045e1cf92c44 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1154,3 +1154,58 @@ early_initcall(dynamic_debug_init);
 
 /* Debugfs setup must be done later */
 fs_initcall(dynamic_debug_init_control);
+
+#include <linux/moduleparam.h>
+
+#define OUR_QUERY_SIZE 128 /* typically need <40 */
+
+int param_set_dyndbg(const char *instr, const struct kernel_param *kp)
+{
+	unsigned int val;
+	unsigned long changes, result;
+	int rc, chgct = 0, totct = 0, bitpos, bitsmax;
+	char query[OUR_QUERY_SIZE];
+	struct dyndbg_bitdesc *bitmap = (struct dyndbg_bitdesc *) kp->data;
+
+	// pr_info("set_dyndbg: instr: %s curr: %d\n", instr, *kp->arg);
+
+	rc = kstrtouint(instr, 0, &val);
+	if (rc) {
+		pr_err("set_dyndbg: failed\n");
+		return -EINVAL;
+	}
+	result = val;
+	pr_info("set_dyndbg: result:0x%lx from %s\n", result, instr);
+
+	changes = result; // ^ __gvt_debug;
+
+	for (bitsmax = 0; bitmap[bitsmax].prefix; bitsmax++);
+
+	for_each_set_bit(bitpos, &changes, min(--bitsmax, 64)) {
+
+		sprintf(query, "format '^%s' %cp", bitmap[bitpos].prefix,
+			test_bit(bitpos, &result) ? '+' : '-');
+
+		chgct = dynamic_debug_exec_queries(query, "i915");
+
+		pr_info("bit-%d: %d changes on: %s\n", bitpos, chgct, query);
+		totct += chgct;
+	}
+	pr_info("total changes: %d\n", totct);
+	// __gvt_debug = result;
+	return 0;
+}
+EXPORT_SYMBOL(param_set_dyndbg);
+
+int param_get_dyndbg(char *buffer, const struct kernel_param *kp)
+{
+	return scnprintf(buffer, PAGE_SIZE, "%u\n",
+			 *((unsigned int *)kp->arg));
+}
+EXPORT_SYMBOL(param_get_dyndbg);
+
+const struct kernel_param_ops param_ops_dyndbg = {
+	.set = param_set_dyndbg,
+	.get = param_get_dyndbg,
+};
+EXPORT_SYMBOL(param_ops_dyndbg);
-- 
2.31.1