[PATCH v4 08/41] dyndbg: add test_dynamic_debug module

[Jim Cromie <jim.cromie@xxxxxxxxx>]

Provide a simple module to allow testing DYNAMIC_DEBUG behavior.  It
calls do_prints() from module-init, and with a sysfs-node.

  dmesg -C
  dmesg -w &
  modprobe test_dynamic_debug dyndbg=+p
  echo 1 > /sys/module/dynamic_debug/parameters/verbose

  cat /sys/module/test_dynamic_debug/parameters/do_prints
  echo module test_dynamic_debug +mftl > /proc/dynamic_debug/control
  echo junk > /sys/module/test_dynamic_debug/parameters/do_prints

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 MAINTAINERS              |  2 ++
 lib/Kconfig.debug        | 10 ++++++
 lib/Makefile             |  1 +
 lib/test_dynamic_debug.c | 70 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+)
 create mode 100644 lib/test_dynamic_debug.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f679152bdbad..663307268285 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7094,6 +7094,8 @@ M:	Jason Baron <jbaron@xxxxxxxxxx>
 S:	Maintained
 F:	include/linux/dynamic_debug.h
 F:	lib/dynamic_debug.c
+M:	Jim Cromie <jim.cromie@xxxxxxxxx>
+F:	lib/test_dynamic_debug.c
 
 DYNAMIC INTERRUPT MODERATION
 M:	Tal Gilboa <talgi@xxxxxxxxxx>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2e24db4bff19..ca5978e1d18a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2529,6 +2529,16 @@ config TEST_STATIC_KEYS
 
 	  If unsure, say N.
 
+config TEST_DYNAMIC_DEBUG
+	tristate "Test DYNAMIC_DEBUG"
+	depends on DYNAMIC_DEBUG
+	help
+	  This module registers a tracer callback to count enabled
+	  pr_debugs in a 'do_debugging' function, then alters their
+	  enablements, calls the function, and compares counts.
+
+	  If unsure, say N.
+
 config TEST_KMOD
 	tristate "kmod stress tester"
 	depends on m
diff --git a/lib/Makefile b/lib/Makefile
index f99bf61f8bbc..9c316df868de 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_TEST_SORT) += test_sort.o
 obj-$(CONFIG_TEST_USER_COPY) += test_user_copy.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
+obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
 obj-$(CONFIG_TEST_PRINTF) += test_printf.o
 obj-$(CONFIG_TEST_SCANF) += test_scanf.o
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
new file mode 100644
index 000000000000..ba3882ca3e48
--- /dev/null
+++ b/lib/test_dynamic_debug.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kernel module for testing dynamic_debug
+ *
+ * Authors:
+ *      Jim Cromie	<jim.cromie@xxxxxxxxx>
+ */
+
+#define pr_fmt(fmt) "test_dd: " fmt
+
+#include <linux/module.h>
+
+static void do_prints(void); /* device under test */
+
+/* run tests by reading or writing sysfs node */
+
+static int param_set_do_prints(const char *instr, const struct kernel_param *kp)
+{
+	do_prints();
+	return 0;
+}
+
+static int param_get_do_prints(char *buffer, const struct kernel_param *kp)
+{
+	do_prints();
+	return scnprintf(buffer, PAGE_SIZE, "did do_prints\n");
+}
+
+static const struct kernel_param_ops param_ops_do_prints = {
+	.set = param_set_do_prints,
+	.get = param_get_do_prints,
+};
+
+module_param_cb(do_prints, &param_ops_do_prints, NULL, 0600);
+
+static void do_alpha(void)
+{
+	pr_debug("do alpha\n");
+}
+static void do_beta(void)
+{
+	pr_debug("do beta\n");
+}
+
+static void do_prints(void)
+{
+	do_alpha();
+	do_beta();
+}
+
+static int __init test_dynamic_debug_init(void)
+{
+	pr_debug("init start\n");
+
+	do_prints();
+
+	pr_debug("init done\n");
+	return 0;
+}
+
+static void __exit test_dynamic_debug_exit(void)
+{
+	pr_debug("exiting\n");
+}
+
+module_init(test_dynamic_debug_init);
+module_exit(test_dynamic_debug_exit);
+
+MODULE_AUTHOR("Jim Cromie <jim.cromie@xxxxxxxxx>");
+MODULE_LICENSE("GPL");
-- 
2.36.1