[PATCH 0/3] module: Allow parameters without arguments

[Steven Rostedt <rostedt@goodmis.org>]

Rusty,

I'm looking at porting my "enable tracepoints in module load" patches
and one of the comments you gave me (long ago) was to not have:

 trace_foo=1

but to just have:

 trace_foo

as a parameter name. I went and implemented this but discovered that the
functions that allow no arguments are hard coded in the params.c file.

I changed this to allow other "set" functions to be given no arguments,
and even noticed that a few already exist in the kernel. So I'm sending
you this patch set that implements a modification to the parameter
parsing to allow other kernel_param_ops to not bother with arguments
passed in.

What do you think?

-- Steve

Steven Rostedt (1):
      tracing: Enable tracepoints via module parameters

Steven Rostedt (Red Hat) (3):
      module: Add flag to allow mod params to have no arguments
      module: Add NOARG flag for ops with param_set_bool_enable_only() set function
      module/lsm: Have apparmor module parameters work with no args

----
 include/linux/ftrace_event.h |    4 +++
 include/linux/moduleparam.h  |   13 +++++++-
 include/trace/ftrace.h       |   23 ++++++++++++--
 kernel/module.c              |    1 +
 kernel/params.c              |    6 ++--
 kernel/trace/trace_events.c  |   71 ++++++++++++++++++++++++++++++++++++++++++
 security/apparmor/lsm.c      |    2 ++
 7 files changed, 115 insertions(+), 5 deletions(-)
---------------------------
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 120d57a..0395182 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -164,6 +164,8 @@ void tracing_record_cmdline(struct task_struct *tsk);
 
 struct event_filter;
 
+extern struct kernel_param_ops ftrace_mod_ops;
+
 enum trace_reg {
 	TRACE_REG_REGISTER,
 	TRACE_REG_UNREGISTER,
@@ -202,6 +204,7 @@ enum {
 	TRACE_EVENT_FL_NO_SET_FILTER_BIT,
 	TRACE_EVENT_FL_IGNORE_ENABLE_BIT,
 	TRACE_EVENT_FL_WAS_ENABLED_BIT,
+	TRACE_EVENT_FL_MOD_ENABLE_BIT,
 };
 
 /*
@@ -220,6 +223,7 @@ enum {
 	TRACE_EVENT_FL_NO_SET_FILTER	= (1 << TRACE_EVENT_FL_NO_SET_FILTER_BIT),
 	TRACE_EVENT_FL_IGNORE_ENABLE	= (1 << TRACE_EVENT_FL_IGNORE_ENABLE_BIT),
 	TRACE_EVENT_FL_WAS_ENABLED	= (1 << TRACE_EVENT_FL_WAS_ENABLED_BIT),
+	TRACE_EVENT_FL_MOD_ENABLE	= (1 << TRACE_EVENT_FL_MOD_ENABLE_BIT),
 };
 
 struct ftrace_event_call {
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 27d9da3..c3eb102 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -36,7 +36,18 @@ static const char __UNIQUE_ID(name)[]					  \
 
 struct kernel_param;
 
+/*
+ * Flags available for kernel_param_ops
+ *
+ * NOARG - the parameter allows for no argument (foo instead of foo=1)
+ */
+enum {
+	KERNEL_PARAM_FL_NOARG = (1 << 0)
+};
+
 struct kernel_param_ops {
+	/* How the ops should behave */
+	unsigned int flags;
 	/* Returns 0, or -errno.  arg is in kp->arg. */
 	int (*set)(const char *val, const struct kernel_param *kp);
 	/* Returns length written or -errno.  Buffer is 4k (ie. be short!) */
@@ -187,7 +198,7 @@ struct kparam_array
 /* Obsolete - use module_param_cb() */
 #define module_param_call(name, set, get, arg, perm)			\
 	static struct kernel_param_ops __param_ops_##name =		\
-		 { (void *)set, (void *)get };				\
+		{ 0, (void *)set, (void *)get };			\
 	__module_param_call(MODULE_PARAM_PREFIX,			\
 			    name, &__param_ops_##name, arg,		\
 			    (perm) + sizeof(__check_old_set_param(set))*0, -1)
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 41a6643..d6029ed 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -17,6 +17,7 @@
  */
 
 #include <linux/ftrace_event.h>
+#include <linux/module.h>
 
 /*
  * DECLARE_EVENT_CLASS can be used to add a generic function
@@ -577,6 +578,22 @@ static inline void ftrace_test_probe_##call(void)			\
 #undef __get_dynamic_array
 #undef __get_str
 
+/*
+ * Add ftrace trace points in modules to be set by module
+ * parameters. This adds "trace_##call" as a module parameter.
+ * The user could enable trace points on module load with:
+ *  trace_##call=1 as a module parameter.
+ */
+#undef ftrace_mod_params
+#ifdef MODULE
+#define ftrace_mod_params(call)				\
+	module_param_cb(trace_##call, &ftrace_mod_ops,	\
+			&event_##call, 0644);		\
+	MODULE_INFO(tracepoint, #call)
+#else
+#define ftrace_mod_params(call)
+#endif
+
 #undef TP_printk
 #define TP_printk(fmt, args...) "\"" fmt "\", "  __stringify(args)
 
@@ -604,7 +621,8 @@ static struct ftrace_event_call __used event_##call = {			\
 	.print_fmt		= print_fmt_##template,			\
 };									\
 static struct ftrace_event_call __used					\
-__attribute__((section("_ftrace_events"))) *__event_##call = &event_##call
+__attribute__((section("_ftrace_events"))) *__event_##call = &event_##call;\
+ftrace_mod_params(call)
 
 #undef DEFINE_EVENT_PRINT
 #define DEFINE_EVENT_PRINT(template, call, proto, args, print)		\
@@ -618,7 +636,8 @@ static struct ftrace_event_call __used event_##call = {			\
 	.print_fmt		= print_fmt_##call,			\
 };									\
 static struct ftrace_event_call __used					\
-__attribute__((section("_ftrace_events"))) *__event_##call = &event_##call
+__attribute__((section("_ftrace_events"))) *__event_##call = &event_##call; \
+ftrace_mod_params(call)
 
 #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
 
diff --git a/kernel/module.c b/kernel/module.c
index 2069158..4eb26b6 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -136,6 +136,7 @@ static int param_set_bool_enable_only(const char *val,
 }
 
 static const struct kernel_param_ops param_ops_bool_enable_only = {
+	.flags = KERNEL_PARAM_FL_NOARG,
 	.set = param_set_bool_enable_only,
 	.get = param_get_bool,
 };
diff --git a/kernel/params.c b/kernel/params.c
index 440e65d..27a0af9 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -103,8 +103,8 @@ static int parse_one(char *param,
 			    || params[i].level > max_level)
 				return 0;
 			/* No one handled NULL, so do it here. */
-			if (!val && params[i].ops->set != param_set_bool
-			    && params[i].ops->set != param_set_bint)
+			if (!val &&
+			    !(params[i].ops->flags & KERNEL_PARAM_FL_NOARG))
 				return -EINVAL;
 			pr_debug("handling %s with %p\n", param,
 				params[i].ops->set);
@@ -320,6 +320,7 @@ int param_get_bool(char *buffer, const struct kernel_param *kp)
 EXPORT_SYMBOL(param_get_bool);
 
 struct kernel_param_ops param_ops_bool = {
+	.flags = KERNEL_PARAM_FL_NOARG,
 	.set = param_set_bool,
 	.get = param_get_bool,
 };
@@ -370,6 +371,7 @@ int param_set_bint(const char *val, const struct kernel_param *kp)
 EXPORT_SYMBOL(param_set_bint);
 
 struct kernel_param_ops param_ops_bint = {
+	.flags = KERNEL_PARAM_FL_NOARG,
 	.set = param_set_bint,
 	.get = param_get_int,
 };
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 29a7ebc..5bd3f51 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1839,10 +1839,32 @@ trace_create_file_ops(struct module *mod)
 	return file_ops;
 }
 
+static void
+enable_event_on_trace_array(struct trace_array *tr,
+			    struct ftrace_event_call *call)
+{
+	struct ftrace_event_file *file;
+	int ret;
+
+	call->flags &= ~TRACE_EVENT_FL_MOD_ENABLE;
+
+	/* find event on top trace array */
+	list_for_each_entry(file, &tr->events, list) {
+		if (file->event_call == call) {
+			ret = ftrace_event_enable_disable(file, 1);
+			if (ret < 0)
+				pr_warning("unable to enable tracepoint %s",
+					   call->name);
+			return;
+		}
+	}
+}
+
 static void trace_module_add_events(struct module *mod)
 {
 	struct ftrace_module_file_ops *file_ops = NULL;
 	struct ftrace_event_call **call, **start, **end;
+	struct trace_array *tr = NULL;
 
 	start = mod->trace_events;
 	end = mod->trace_events + mod->num_trace_events;
@@ -1857,6 +1879,12 @@ static void trace_module_add_events(struct module *mod)
 	for_each_event(call, start, end) {
 		__register_event(*call, mod);
 		__add_event_to_tracers(*call, file_ops);
+		/* If the module tracepoint parameter was set */
+		if ((*call)->flags & TRACE_EVENT_FL_MOD_ENABLE) {
+			if (!tr)
+				tr = top_trace_array();
+			enable_event_on_trace_array(tr, *call);
+		}
 	}
 }
 
@@ -2569,6 +2597,49 @@ early_initcall(event_trace_memsetup);
 core_initcall(event_trace_enable);
 fs_initcall(event_trace_init);
 
+/* Allow modules to load with enabled trace points */
+int ftrace_mod_param_set(const char *val, const struct kernel_param *kp)
+{
+	struct ftrace_event_call *call = kp->arg;
+
+	/* This is set like param_set_bool() */
+
+	/* No equals means "set"... */
+	if (!val)
+		val = "1";
+
+	/* One of =[yYnN01] */
+	switch (val[0]) {
+	case 'y': case 'Y': case '1':
+		break;
+	case 'n': case 'N': case '0':
+		/* Do nothing */
+		return 0;
+	default:
+		return -EINVAL;
+	}
+
+	/* Set flag to tell ftrace to enable this event on init */
+	call->flags = TRACE_EVENT_FL_MOD_ENABLE;
+
+	return 0;
+}
+
+int ftrace_mod_param_get(char *buffer, const struct kernel_param *kp)
+{
+	struct ftrace_event_call *call = kp->arg;
+
+	return sprintf(buffer, "%d",
+		       !!(call->flags & TRACE_EVENT_FL_MOD_ENABLE));
+}
+
+struct kernel_param_ops ftrace_mod_ops = {
+	.flags = KERNEL_PARAM_FL_NOARG,
+	.set = ftrace_mod_param_set,
+	.get = ftrace_mod_param_get,
+};
+EXPORT_SYMBOL(ftrace_mod_ops);
+
 #ifdef CONFIG_FTRACE_STARTUP_TEST
 
 static DEFINE_SPINLOCK(test_spinlock);
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 2e2a0dd..e3a704c 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -666,6 +666,7 @@ static int param_set_aabool(const char *val, const struct kernel_param *kp);
 static int param_get_aabool(char *buffer, const struct kernel_param *kp);
 #define param_check_aabool param_check_bool
 static struct kernel_param_ops param_ops_aabool = {
+	.flags = KERNEL_PARAM_FL_NOARG,
 	.set = param_set_aabool,
 	.get = param_get_aabool
 };
@@ -682,6 +683,7 @@ static int param_set_aalockpolicy(const char *val, const struct kernel_param *kp
 static int param_get_aalockpolicy(char *buffer, const struct kernel_param *kp);
 #define param_check_aalockpolicy param_check_bool
 static struct kernel_param_ops param_ops_aalockpolicy = {
+	.flags = KERNEL_PARAM_FL_NOARG,
 	.set = param_set_aalockpolicy,
 	.get = param_get_aalockpolicy
 };