From: jbaron@redhat.com <jbaron@redhat.com>
Date: Fri, 22 Aug 2008 14:04:49 -0400
Subject: [misc] markers and tracepoints: markers
Message-id: 1219428298-7519-6-git-send-email-jbaron@redhat.com
O-Subject: [rhel5.3 patch 05/14] markers and tracepoints - markers
Bugzilla: 329821

bz# 329821

diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S
index 0e155cc..e254231 100644
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/arch/i386/kernel/vmlinux.lds.S
@@ -68,6 +68,7 @@ SECTIONS
   .data : AT(ADDR(.data) - LOAD_OFFSET) {	/* Data */
 	*(.data)
 	TRACEPOINTS_DATA
+	MARKERS_DATA
 	CONSTRUCTORS
   } :data
 
diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
index 4349de0..f62c8d2 100644
--- a/arch/ia64/kernel/vmlinux.lds.S
+++ b/arch/ia64/kernel/vmlinux.lds.S
@@ -207,7 +207,7 @@ SECTIONS
 
   data : { } :data
   .data : AT(ADDR(.data) - LOAD_OFFSET)
-	{ *(.data) TRACEPOINTS_DATA *(.data1) *(.gnu.linkonce.d*) CONSTRUCTORS }
+	{ *(.data) MARKERS_DATA TRACEPOINTS_DATA *(.data1) *(.gnu.linkonce.d*) CONSTRUCTORS }
 
   . = ALIGN(16);	/* gp must be 16-byte aligned for exc. table */
   .got : AT(ADDR(.got) - LOAD_OFFSET)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 6024347..9032b85 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -174,6 +174,7 @@ SECTIONS
 	.data    :
 	{
 		*(.data)
+		MARKERS_DATA
 		TRACEPOINTS_DATA
 		*(.sdata)
 		*(.got.plt) *(.got)
@@ -181,6 +182,7 @@ SECTIONS
 #else
 	.data : {
 		*(.data)
+		MARKERS_DATA
 		TRACEPOINTS_DATA
 		*(.data.rel* .toc1)
 		*(.branch_lt)
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 0971eed..5630caf 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -46,6 +46,7 @@ SECTIONS
 
   .data : {			/* Data */
 	*(.data)
+	MARKERS_DATA
 	TRACEPOINTS_DATA
 	CONSTRUCTORS
 	}
diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S
index 56cab2a..cf41f55 100644
--- a/arch/x86_64/kernel/vmlinux.lds.S
+++ b/arch/x86_64/kernel/vmlinux.lds.S
@@ -68,6 +68,7 @@ SECTIONS
 				/* Data */
   .data : AT(ADDR(.data) - LOAD_OFFSET) {
 	*(.data)
+	MARKERS_DATA
 	TRACEPOINTS_DATA
 	CONSTRUCTORS
 	} :data
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 94ee54f..7a56cb2 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -16,6 +16,7 @@
 		*(.rodata) *(.rodata.*)					\
 		*(__vermagic)		/* Kernel version magic */	\
 		*(__tracepoints_strings)/* Tracepoints: strings */      \
+		*(__markers_strings)    /* Markers: strings */          \
 	}								\
 									\
 	.rodata1          : AT(ADDR(.rodata1) - LOAD_OFFSET) {		\
@@ -158,6 +159,12 @@
 		*(.kprobes.text)					\
 		VMLINUX_SYMBOL(__kprobes_text_end) = .;
 
+#define MARKERS_DATA							\
+		ALIGN_FUNCTION();                                       \
+		VMLINUX_SYMBOL(__start___markers) = .;                  \
+		*(__markers)                                            \
+		VMLINUX_SYMBOL(__stop___markers) = .;
+
 #define TRACEPOINTS_DATA						\
 		ALIGN_FUNCTION();					\
 		VMLINUX_SYMBOL(__start___tracepoints) = .;		\
diff --git a/include/linux/marker.h b/include/linux/marker.h
new file mode 100644
index 0000000..a7ac360
--- /dev/null
+++ b/include/linux/marker.h
@@ -0,0 +1,142 @@
+#ifndef _LINUX_MARKER_H
+#define _LINUX_MARKER_H
+
+/*
+ * Code markup for dynamic and static tracing.
+ *
+ * See Documentation/marker.txt.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/types.h>
+
+struct module;
+struct marker;
+
+/**
+ * marker_probe_func - Type of a marker probe function
+ * @probe_private: probe private data
+ * @call_private: call site private data
+ * @fmt: format string
+ * @args: variable argument list pointer. Use a pointer to overcome C's
+ *        inability to pass this around as a pointer in a portable manner in
+ *        the callee otherwise.
+ *
+ * Type of marker probe functions. They receive the mdata and need to parse the
+ * format string to recover the variable argument list.
+ */
+typedef void marker_probe_func(void *probe_private, void *call_private,
+		const char *fmt, va_list *args);
+
+struct marker_probe_closure {
+	marker_probe_func *func;	/* Callback */
+	void *probe_private;		/* Private probe data */
+};
+
+struct marker {
+	const char *name;	/* Marker name */
+	const char *format;	/* Marker format string, describing the
+				 * variable argument list.
+				 */
+	char state;		/* Marker state. */
+	char ptype;		/* probe type : 0 : single, 1 : multi */
+				/* Probe wrapper */
+	void (*call)(const struct marker *mdata, void *call_private, ...);
+	struct marker_probe_closure single;
+	struct marker_probe_closure *multi;
+} __attribute__((aligned(8)));
+
+#ifdef CONFIG_MARKERS
+
+/*
+ * Note : the empty asm volatile with read constraint is used here instead of a
+ * "used" attribute to fix a gcc 4.1.x bug.
+ * Make sure the alignment of the structure in the __markers section will
+ * not add unwanted padding between the beginning of the section and the
+ * structure. Force alignment to the same alignment as the section start.
+ */
+#define __trace_mark(name, call_private, format, args...)		\
+	do {								\
+		static const char __mstrtab_name_##name[]		\
+		__attribute__((section("__markers_strings")))		\
+		= #name;						\
+		static const char __mstrtab_format_##name[]		\
+		__attribute__((section("__markers_strings")))		\
+		= format;						\
+		static struct marker __mark_##name			\
+		__attribute__((section("__markers"), aligned(8))) =	\
+		{ __mstrtab_name_##name, __mstrtab_format_##name,	\
+		0, 0, marker_probe_cb,                                  \
+		{ __mark_empty_function, NULL}, NULL };                 \
+		asm volatile("" : : "i" (&__mark_##name));		\
+		__mark_check_format(format, ## args);			\
+		if (unlikely(__mark_##name.state)) {			\
+			(*__mark_##name.call)				\
+				(&__mark_##name, call_private, ## args);\
+		}							\
+	} while (0)
+
+extern void marker_update_probe_range(struct marker *begin,
+	struct marker *end);
+#else /* !CONFIG_MARKERS */
+#define __trace_mark(name, call_data, format, args...) \
+		__mark_check_format(format, ## args)
+static inline void marker_update_probe_range(struct marker *begin,
+	struct marker *end)
+{ }
+#endif /* CONFIG_MARKERS */
+
+/**
+ * trace_mark - Marker
+ * @name: marker name, not quoted.
+ * @format: format string
+ * @args...: variable argument list
+ *
+ * Places a marker.
+ */
+#define trace_mark(name, format, args...) \
+	__trace_mark(name, NULL, format, ## args)
+
+/**
+ * MARK_NOARGS - Format string for a marker with no argument.
+ */
+#define MARK_NOARGS " "
+
+/* To be used for string format validity checking with gcc */
+static inline void __attribute__((format(printf,1,2))) __mark_check_format(const char *fmt, ...)
+{
+}
+
+extern marker_probe_func __mark_empty_function;
+
+extern void marker_probe_cb(const struct marker *mdata,
+	void *call_private, ...);
+extern void marker_probe_cb_noarg(const struct marker *mdata,
+	void *call_private, ...);
+
+/*
+ * Connect a probe to a marker.
+ * private data pointer must be a valid allocated memory address, or NULL.
+ */
+extern int marker_probe_register(const char *name, const char *format,
+				marker_probe_func *probe, void *probe_private);
+
+/*
+ * Returns the private data given to marker_probe_register.
+ */
+extern int marker_probe_unregister(const char *name,
+	marker_probe_func *probe, void *probe_private);
+/*
+ * Unregister a marker by providing the registered private data.
+ */
+extern int marker_probe_unregister_private_data(marker_probe_func *probe,
+	void *probe_private);
+
+extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
+	int num);
+
+#endif
diff --git a/include/linux/module.h b/include/linux/module.h
index 78e649f..14f1add 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -18,6 +18,7 @@
 #include <linux/kobject.h>
 #include <linux/moduleparam.h>
 #include <linux/tracepoint.h>
+#include <linux/marker.h>
 #include <asm/local.h>
 
 #include <asm/module.h>
@@ -358,6 +359,10 @@ struct module
 	struct tracepoint *tracepoints;
 	unsigned int num_tracepoints;
 #endif
+#ifdef CONFIG_MARKERS
+	struct marker *markers;
+	unsigned int num_markers;
+#endif
 };
 
 /* FIXME: It'd be nice to isolate modules during init, too, so they
@@ -485,6 +490,8 @@ void module_remove_driver(struct device_driver *);
 extern void module_update_tracepoints(void);
 extern int module_get_iter_tracepoints(struct tracepoint_iter *iter);
 
+extern void module_update_markers(void);
+
 #else /* !CONFIG_MODULES... */
 #define EXPORT_SYMBOL(sym)
 #define EXPORT_SYMBOL_GPL(sym)
@@ -602,6 +609,10 @@ static inline int module_get_iter_tracepoints(struct tracepoint_iter *iter)
 	return 0;
 }
 
+static inline void module_update_markers(void)
+{
+}
+
 #endif /* CONFIG_MODULES */
 
 #define symbol_request(x) try_then_request_module(symbol_get(x), "symbol:" #x)
diff --git a/init/Kconfig b/init/Kconfig
index da1e0c1..f039fb3 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -416,6 +416,12 @@ config TRACEPOINTS
 	  Place an empty function call at each tracepoint site. Can be
 	  dynamically changed for a probe function.
 
+config MARKERS
+	bool "Activate markers"
+	help
+	  Place an empty function call at each marker site. Can be
+	  dynamically changed for a probe function.
+
 endmenu		# General setup
 
 config RT_MUTEXES
diff --git a/kernel/Makefile b/kernel/Makefile
index 5a70634..f1c92c2 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_TASKSTATS) += taskstats.o
 obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
 obj-$(CONFIG_UTRACE) += utrace.o
 obj-$(CONFIG_PTRACE) += ptrace.o
+obj-$(CONFIG_MARKERS) += marker.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/marker.c b/kernel/marker.c
new file mode 100644
index 0000000..7154e5f
--- /dev/null
+++ b/kernel/marker.c
@@ -0,0 +1,858 @@
+/*
+ * Copyright (C) 2007 Mathieu Desnoyers
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/jhash.h>
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+#include <linux/marker.h>
+#include <linux/err.h>
+
+extern struct marker __start___markers[];
+extern struct marker __stop___markers[];
+
+/* Set to 1 to enable marker debug output */
+static const int marker_debug;
+
+/*
+ * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
+ * and module markers and the hash table.
+ */
+static DEFINE_MUTEX(markers_mutex);
+
+/*
+ * Marker hash table, containing the active markers.
+ * Protected by module_mutex.
+ */
+#define MARKER_HASH_BITS 6
+#define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
+
+/*
+ * Note about RCU :
+ * It is used to make sure every handler has finished using its private data
+ * between two consecutive operation (add or remove) on a given marker.  It is
+ * also used to delay the free of multiple probes array until a quiescent state
+ * is reached.
+ * marker entries modifications are protected by the markers_mutex.
+ */
+struct marker_entry {
+	struct hlist_node hlist;
+	char *format;
+			/* Probe wrapper */
+	void (*call)(const struct marker *mdata, void *call_private, ...);
+	struct marker_probe_closure single;
+	struct marker_probe_closure *multi;
+	int refcount;	/* Number of times armed. 0 if disarmed. */
+	struct rcu_head rcu;
+	void *oldptr;
+	unsigned char rcu_pending:1;
+	unsigned char ptype:1;
+	char name[0];	/* Contains name'\0'format'\0' */
+};
+
+static struct hlist_head marker_table[MARKER_TABLE_SIZE];
+
+/**
+ * __mark_empty_function - Empty probe callback
+ * @probe_private: probe private data
+ * @call_private: call site private data
+ * @fmt: format string
+ * @...: variable argument list
+ *
+ * Empty callback provided as a probe to the markers. By providing this to a
+ * disabled marker, we make sure the  execution flow is always valid even
+ * though the function pointer change and the marker enabling are two distinct
+ * operations that modifies the execution flow of preemptible code.
+ */
+void __mark_empty_function(void *probe_private, void *call_private,
+	const char *fmt, va_list *args)
+{
+}
+EXPORT_SYMBOL_GPL(__mark_empty_function);
+
+/*
+ * marker_probe_cb Callback that prepares the variable argument list for probes.
+ * @mdata: pointer of type struct marker
+ * @call_private: caller site private data
+ * @...:  Variable argument list.
+ *
+ * Since we do not use "typical" pointer based RCU in the 1 argument case, we
+ * need to put a full smp_rmb() in this branch. This is why we do not use
+ * rcu_dereference() for the pointer read.
+ */
+void marker_probe_cb(const struct marker *mdata, void *call_private, ...)
+{
+	va_list args;
+	char ptype;
+
+	/*
+	 * rcu_read_lock does two things : disabling preemption to make sure the
+	 * teardown of the callbacks can be done correctly when they are in
+	 * modules and they insure RCU read coherency.
+	 */
+	rcu_read_lock();
+	ptype = mdata->ptype;
+	if (likely(!ptype)) {
+		marker_probe_func *func;
+		/* Must read the ptype before ptr. They are not data dependant,
+		 * so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		func = mdata->single.func;
+		/* Must read the ptr before private data. They are not data
+		 * dependant, so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		va_start(args, call_private);
+		func(mdata->single.probe_private, call_private, mdata->format,
+			&args);
+		va_end(args);
+	} else {
+		struct marker_probe_closure *multi;
+		int i;
+		/*
+		 * Read mdata->ptype before mdata->multi.
+		 */
+		smp_rmb();
+		multi = mdata->multi;
+		/*
+		 * multi points to an array, therefore accessing the array
+		 * depends on reading multi. However, even in this case,
+		 * we must insure that the pointer is read _before_ the array
+		 * data. Same as rcu_dereference, but we need a full smp_rmb()
+		 * in the fast path, so put the explicit barrier here.
+		 */
+		smp_read_barrier_depends();
+		for (i = 0; multi[i].func; i++) {
+			va_start(args, call_private);
+			multi[i].func(multi[i].probe_private, call_private,
+				mdata->format, &args);
+			va_end(args);
+		}
+	}
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(marker_probe_cb);
+
+/*
+ * marker_probe_cb Callback that does not prepare the variable argument list.
+ * @mdata: pointer of type struct marker
+ * @call_private: caller site private data
+ * @...:  Variable argument list.
+ *
+ * Should be connected to markers "MARK_NOARGS".
+ */
+void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)
+{
+	va_list args;	/* not initialized */
+	char ptype;
+
+	preempt_disable();
+	ptype = mdata->ptype;
+	if (likely(!ptype)) {
+		marker_probe_func *func;
+		/* Must read the ptype before ptr. They are not data dependant,
+		 * so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		func = mdata->single.func;
+		/* Must read the ptr before private data. They are not data
+		 * dependant, so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		func(mdata->single.probe_private, call_private, mdata->format,
+			&args);
+	} else {
+		struct marker_probe_closure *multi;
+		int i;
+		/*
+		 * Read mdata->ptype before mdata->multi.
+		 */
+		smp_rmb();
+		multi = mdata->multi;
+		/*
+		 * multi points to an array, therefore accessing the array
+		 * depends on reading multi. However, even in this case,
+		 * we must insure that the pointer is read _before_ the array
+		 * data. Same as rcu_dereference, but we need a full smp_rmb()
+		 * in the fast path, so put the explicit barrier here.
+		 */
+		smp_read_barrier_depends();
+		for (i = 0; multi[i].func; i++)
+			multi[i].func(multi[i].probe_private, call_private,
+				mdata->format, &args);
+	}
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
+
+static void free_old_closure(struct rcu_head *head)
+{
+	struct marker_entry *entry = container_of(head,
+		struct marker_entry, rcu);
+	kfree(entry->oldptr);
+	/* Make sure we free the data before setting the pending flag to 0 */
+	smp_wmb();
+	entry->rcu_pending = 0;
+}
+
+static void debug_print_probes(struct marker_entry *entry)
+{
+	int i;
+
+	if (!marker_debug)
+		return;
+
+	if (!entry->ptype) {
+		printk(KERN_DEBUG "Single probe : %p %p\n",
+			entry->single.func,
+			entry->single.probe_private);
+	} else {
+		for (i = 0; entry->multi[i].func; i++)
+			printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
+				entry->multi[i].func,
+				entry->multi[i].probe_private);
+	}
+}
+
+static struct marker_probe_closure *
+marker_entry_add_probe(struct marker_entry *entry,
+		marker_probe_func *probe, void *probe_private)
+{
+	int nr_probes = 0;
+	struct marker_probe_closure *old, *new;
+
+	WARN_ON(!probe);
+
+	debug_print_probes(entry);
+	old = entry->multi;
+	if (!entry->ptype) {
+		if (entry->single.func == probe &&
+				entry->single.probe_private == probe_private)
+			return ERR_PTR(-EBUSY);
+		if (entry->single.func == __mark_empty_function) {
+			/* 0 -> 1 probes */
+			entry->single.func = probe;
+			entry->single.probe_private = probe_private;
+			entry->refcount = 1;
+			entry->ptype = 0;
+			debug_print_probes(entry);
+			return NULL;
+		} else {
+			/* 1 -> 2 probes */
+			nr_probes = 1;
+			old = NULL;
+		}
+	} else {
+		/* (N -> N+1), (N != 0, 1) probes */
+		for (nr_probes = 0; old[nr_probes].func; nr_probes++)
+			if (old[nr_probes].func == probe
+					&& old[nr_probes].probe_private
+						== probe_private)
+				return ERR_PTR(-EBUSY);
+	}
+	/* + 2 : one for new probe, one for NULL func */
+	new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
+			GFP_KERNEL);
+	if (new == NULL)
+		return ERR_PTR(-ENOMEM);
+	if (!old)
+		new[0] = entry->single;
+	else
+		memcpy(new, old,
+			nr_probes * sizeof(struct marker_probe_closure));
+	new[nr_probes].func = probe;
+	new[nr_probes].probe_private = probe_private;
+	entry->refcount = nr_probes + 1;
+	entry->multi = new;
+	entry->ptype = 1;
+	debug_print_probes(entry);
+	return old;
+}
+
+static struct marker_probe_closure *
+marker_entry_remove_probe(struct marker_entry *entry,
+		marker_probe_func *probe, void *probe_private)
+{
+	int nr_probes = 0, nr_del = 0, i;
+	struct marker_probe_closure *old, *new;
+
+	old = entry->multi;
+
+	debug_print_probes(entry);
+	if (!entry->ptype) {
+		/* 0 -> N is an error */
+		WARN_ON(entry->single.func == __mark_empty_function);
+		/* 1 -> 0 probes */
+		WARN_ON(probe && entry->single.func != probe);
+		WARN_ON(entry->single.probe_private != probe_private);
+		entry->single.func = __mark_empty_function;
+		entry->refcount = 0;
+		entry->ptype = 0;
+		debug_print_probes(entry);
+		return NULL;
+	} else {
+		/* (N -> M), (N > 1, M >= 0) probes */
+		for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+			if ((!probe || old[nr_probes].func == probe)
+					&& old[nr_probes].probe_private
+						== probe_private)
+				nr_del++;
+		}
+	}
+
+	if (nr_probes - nr_del == 0) {
+		/* N -> 0, (N > 1) */
+		entry->single.func = __mark_empty_function;
+		entry->refcount = 0;
+		entry->ptype = 0;
+	} else if (nr_probes - nr_del == 1) {
+		/* N -> 1, (N > 1) */
+		for (i = 0; old[i].func; i++)
+			if ((probe && old[i].func != probe) ||
+					old[i].probe_private != probe_private)
+				entry->single = old[i];
+		entry->refcount = 1;
+		entry->ptype = 0;
+	} else {
+		int j = 0;
+		/* N -> M, (N > 1, M > 1) */
+		/* + 1 for NULL */
+		new = kzalloc((nr_probes - nr_del + 1)
+			* sizeof(struct marker_probe_closure), GFP_KERNEL);
+		if (new == NULL)
+			return ERR_PTR(-ENOMEM);
+		for (i = 0; old[i].func; i++)
+			if ((probe && old[i].func != probe) ||
+					old[i].probe_private != probe_private)
+				new[j++] = old[i];
+		entry->refcount = nr_probes - nr_del;
+		entry->ptype = 1;
+		entry->multi = new;
+	}
+	debug_print_probes(entry);
+	return old;
+}
+
+/*
+ * Get marker if the marker is present in the marker hash table.
+ * Must be called with markers_mutex held.
+ * Returns NULL if not present.
+ */
+static struct marker_entry *get_marker(const char *name)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	u32 hash = jhash(name, strlen(name), 0);
+
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name))
+			return e;
+	}
+	return NULL;
+}
+
+/*
+ * Add the marker to the marker hash table. Must be called with markers_mutex
+ * held.
+ */
+static struct marker_entry *add_marker(const char *name, const char *format)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	size_t name_len = strlen(name) + 1;
+	size_t format_len = 0;
+	u32 hash = jhash(name, name_len-1, 0);
+
+	if (format)
+		format_len = strlen(format) + 1;
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name)) {
+			printk(KERN_NOTICE
+				"Marker %s busy\n", name);
+			return ERR_PTR(-EBUSY);	/* Already there */
+		}
+	}
+	/*
+	 * Using kmalloc here to allocate a variable length element. Could
+	 * cause some memory fragmentation if overused.
+	 */
+	e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
+			GFP_KERNEL);
+	if (!e)
+		return ERR_PTR(-ENOMEM);
+	memcpy(&e->name[0], name, name_len);
+	if (format) {
+		e->format = &e->name[name_len];
+		memcpy(e->format, format, format_len);
+		if (strcmp(e->format, MARK_NOARGS) == 0)
+			e->call = marker_probe_cb_noarg;
+		else
+			e->call = marker_probe_cb;
+		trace_mark(core_marker_format, "name %s format %s",
+				e->name, e->format);
+	} else {
+		e->format = NULL;
+		e->call = marker_probe_cb;
+	}
+	e->single.func = __mark_empty_function;
+	e->single.probe_private = NULL;
+	e->multi = NULL;
+	e->ptype = 0;
+	e->refcount = 0;
+	e->rcu_pending = 0;
+	hlist_add_head(&e->hlist, head);
+	return e;
+}
+
+/*
+ * Remove the marker from the marker hash table. Must be called with mutex_lock
+ * held.
+ */
+static int remove_marker(const char *name)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	int found = 0;
+	size_t len = strlen(name) + 1;
+	u32 hash = jhash(name, len-1, 0);
+
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name)) {
+			found = 1;
+			break;
+		}
+	}
+	if (!found)
+		return -ENOENT;
+	if (e->single.func != __mark_empty_function)
+		return -EBUSY;
+	hlist_del(&e->hlist);
+	/* Make sure the call_rcu has been executed */
+	if (e->rcu_pending)
+		rcu_barrier();
+	kfree(e);
+	return 0;
+}
+
+/*
+ * Set the mark_entry format to the format found in the element.
+ */
+static int marker_set_format(struct marker_entry **entry, const char *format)
+{
+	struct marker_entry *e;
+	size_t name_len = strlen((*entry)->name) + 1;
+	size_t format_len = strlen(format) + 1;
+
+
+	e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
+			GFP_KERNEL);
+	if (!e)
+		return -ENOMEM;
+	memcpy(&e->name[0], (*entry)->name, name_len);
+	e->format = &e->name[name_len];
+	memcpy(e->format, format, format_len);
+	if (strcmp(e->format, MARK_NOARGS) == 0)
+		e->call = marker_probe_cb_noarg;
+	else
+		e->call = marker_probe_cb;
+	e->single = (*entry)->single;
+	e->multi = (*entry)->multi;
+	e->ptype = (*entry)->ptype;
+	e->refcount = (*entry)->refcount;
+	e->rcu_pending = 0;
+	hlist_add_before(&e->hlist, &(*entry)->hlist);
+	hlist_del(&(*entry)->hlist);
+	/* Make sure the call_rcu has been executed */
+	if ((*entry)->rcu_pending)
+		rcu_barrier();
+	kfree(*entry);
+	*entry = e;
+	trace_mark(core_marker_format, "name %s format %s",
+			e->name, e->format);
+	return 0;
+}
+
+/*
+ * Sets the probe callback corresponding to one marker.
+ */
+static int set_marker(struct marker_entry **entry, struct marker *elem,
+		int active)
+{
+	int ret;
+	WARN_ON(strcmp((*entry)->name, elem->name) != 0);
+
+	if ((*entry)->format) {
+		if (strcmp((*entry)->format, elem->format) != 0) {
+			printk(KERN_NOTICE
+				"Format mismatch for probe %s "
+				"(%s), marker (%s)\n",
+				(*entry)->name,
+				(*entry)->format,
+				elem->format);
+			return -EPERM;
+		}
+	} else {
+		ret = marker_set_format(entry, elem->format);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * probe_cb setup (statically known) is done here. It is
+	 * asynchronous with the rest of execution, therefore we only
+	 * pass from a "safe" callback (with argument) to an "unsafe"
+	 * callback (does not set arguments).
+	 */
+	elem->call = (*entry)->call;
+	/*
+	 * Sanity check :
+	 * We only update the single probe private data when the ptr is
+	 * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
+	 */
+	WARN_ON(elem->single.func != __mark_empty_function
+		&& elem->single.probe_private
+		!= (*entry)->single.probe_private &&
+		!elem->ptype);
+	elem->single.probe_private = (*entry)->single.probe_private;
+	/*
+	 * Make sure the private data is valid when we update the
+	 * single probe ptr.
+	 */
+	smp_wmb();
+	elem->single.func = (*entry)->single.func;
+	/*
+	 * We also make sure that the new probe callbacks array is consistent
+	 * before setting a pointer to it.
+	 */
+	rcu_assign_pointer(elem->multi, (*entry)->multi);
+	/*
+	 * Update the function or multi probe array pointer before setting the
+	 * ptype.
+	 */
+	smp_wmb();
+	elem->ptype = (*entry)->ptype;
+	elem->state = active;
+
+	return 0;
+}
+
+/*
+ * Disable a marker and its probe callback.
+ * Note: only after a synchronize_sched() issued after setting elem->call to the
+ * empty function insures that the original callback is not used anymore. This
+ * insured by preemption disabling around the call site.
+ */
+static void disable_marker(struct marker *elem)
+{
+	/* leave "call" as is. It is known statically. */
+	elem->state = 0;
+	elem->single.func = __mark_empty_function;
+	/* Update the function before setting the ptype */
+	smp_wmb();
+	elem->ptype = 0;	/* single probe */
+	/*
+	 * Leave the private data and id there, because removal is racy and
+	 * should be done only after a synchronize_sched(). These are never used
+	 * until the next initialization anyway.
+	 */
+}
+
+/**
+ * marker_update_probe_range - Update a probe range
+ * @begin: beginning of the range
+ * @end: end of the range
+ *
+ * Updates the probe callback corresponding to a range of markers.
+ */
+void marker_update_probe_range(struct marker *begin,
+	struct marker *end)
+{
+	struct marker *iter;
+	struct marker_entry *mark_entry;
+
+	mutex_lock(&markers_mutex);
+	for (iter = begin; iter < end; iter++) {
+		mark_entry = get_marker(iter->name);
+		if (mark_entry) {
+			set_marker(&mark_entry, iter,
+					!!mark_entry->refcount);
+			/*
+			 * ignore error, continue
+			 */
+		} else {
+			disable_marker(iter);
+		}
+	}
+	mutex_unlock(&markers_mutex);
+}
+
+/*
+ * Update probes, removing the faulty probes.
+ * Issues a synchronize_sched() when no reference to the module passed
+ * as parameter is found in the probes so the probe module can be
+ * safely unloaded from now on.
+ *
+ * Internal callback only changed before the first probe is connected to it.
+ * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
+ * transitions.  All other transitions will leave the old private data valid.
+ * This makes the non-atomicity of the callback/private data updates valid.
+ *
+ * "special case" updates :
+ * 0 -> 1 callback
+ * 1 -> 0 callback
+ * 1 -> 2 callbacks
+ * 2 -> 1 callbacks
+ * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
+ * Site effect : marker_set_format may delete the marker entry (creating a
+ * replacement).
+ */
+static void marker_update_probes(void)
+{
+	/* Core kernel markers */
+	marker_update_probe_range(__start___markers, __stop___markers);
+	/* Markers in modules. */
+	module_update_markers();
+}
+
+/**
+ * marker_probe_register -  Connect a probe to a marker
+ * @name: marker name
+ * @format: format string
+ * @probe: probe handler
+ * @probe_private: probe private data
+ *
+ * private data must be a valid allocated memory address, or NULL.
+ * Returns 0 if ok, error value on error.
+ * The probe address must at least be aligned on the architecture pointer size.
+ */
+int marker_probe_register(const char *name, const char *format,
+			marker_probe_func *probe, void *probe_private)
+{
+	struct marker_entry *entry;
+	int ret = 0;
+	struct marker_probe_closure *old;
+
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry) {
+		entry = add_marker(name, format);
+		if (IS_ERR(entry)) {
+			ret = PTR_ERR(entry);
+			goto end;
+		}
+	}
+	/*
+	 * If we detect that a call_rcu is pending for this marker,
+	 * make sure it's executed now.
+	 */
+	if (entry->rcu_pending)
+		rcu_barrier();
+	old = marker_entry_add_probe(entry, probe, probe_private);
+	if (IS_ERR(old)) {
+		ret = PTR_ERR(old);
+		goto end;
+	}
+	mutex_unlock(&markers_mutex);
+	marker_update_probes();		/* may update entry */
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	WARN_ON(!entry);
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu(&entry->rcu, free_old_closure);
+end:
+	mutex_unlock(&markers_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(marker_probe_register);
+
+/**
+ * marker_probe_unregister -  Disconnect a probe from a marker
+ * @name: marker name
+ * @probe: probe function pointer
+ * @probe_private: probe private data
+ *
+ * Returns the private data given to marker_probe_register, or an ERR_PTR().
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
+ */
+int marker_probe_unregister(const char *name,
+	marker_probe_func *probe, void *probe_private)
+{
+	struct marker_entry *entry;
+	struct marker_probe_closure *old;
+	int ret = -ENOENT;
+
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry)
+		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier();
+	old = marker_entry_remove_probe(entry, probe, probe_private);
+	mutex_unlock(&markers_mutex);
+	marker_update_probes();		/* may update entry */
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry)
+		goto end;
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu(&entry->rcu, free_old_closure);
+	remove_marker(name);	/* Ignore busy error message */
+	ret = 0;
+end:
+	mutex_unlock(&markers_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(marker_probe_unregister);
+
+static struct marker_entry *
+get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
+{
+	struct marker_entry *entry;
+	unsigned int i;
+	struct hlist_head *head;
+	struct hlist_node *node;
+
+	for (i = 0; i < MARKER_TABLE_SIZE; i++) {
+		head = &marker_table[i];
+		hlist_for_each_entry(entry, node, head, hlist) {
+			if (!entry->ptype) {
+				if (entry->single.func == probe
+						&& entry->single.probe_private
+						== probe_private)
+					return entry;
+			} else {
+				struct marker_probe_closure *closure;
+				closure = entry->multi;
+				for (i = 0; closure[i].func; i++) {
+					if (closure[i].func == probe &&
+							closure[i].probe_private
+							== probe_private)
+						return entry;
+				}
+			}
+		}
+	}
+	return NULL;
+}
+
+/**
+ * marker_probe_unregister_private_data -  Disconnect a probe from a marker
+ * @probe: probe function
+ * @probe_private: probe private data
+ *
+ * Unregister a probe by providing the registered private data.
+ * Only removes the first marker found in hash table.
+ * Return 0 on success or error value.
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
+ */
+int marker_probe_unregister_private_data(marker_probe_func *probe,
+		void *probe_private)
+{
+	struct marker_entry *entry;
+	int ret = 0;
+	struct marker_probe_closure *old;
+
+	mutex_lock(&markers_mutex);
+	entry = get_marker_from_private_data(probe, probe_private);
+	if (!entry) {
+		ret = -ENOENT;
+		goto end;
+	}
+	if (entry->rcu_pending)
+		rcu_barrier();
+	old = marker_entry_remove_probe(entry, NULL, probe_private);
+	mutex_unlock(&markers_mutex);
+	marker_update_probes();		/* may update entry */
+	mutex_lock(&markers_mutex);
+	entry = get_marker_from_private_data(probe, probe_private);
+	WARN_ON(!entry);
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu(&entry->rcu, free_old_closure);
+	remove_marker(entry->name);	/* Ignore busy error message */
+end:
+	mutex_unlock(&markers_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
+
+/**
+ * marker_get_private_data - Get a marker's probe private data
+ * @name: marker name
+ * @probe: probe to match
+ * @num: get the nth matching probe's private data
+ *
+ * Returns the nth private data pointer (starting from 0) matching, or an
+ * ERR_PTR.
+ * Returns the private data pointer, or an ERR_PTR.
+ * The private data pointer should _only_ be dereferenced if the caller is the
+ * owner of the data, or its content could vanish. This is mostly used to
+ * confirm that a caller is the owner of a registered probe.
+ */
+void *marker_get_private_data(const char *name, marker_probe_func *probe,
+		int num)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	size_t name_len = strlen(name) + 1;
+	u32 hash = jhash(name, name_len-1, 0);
+	int i;
+
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name)) {
+			if (!e->ptype) {
+				if (num == 0 && e->single.func == probe)
+					return e->single.probe_private;
+				else
+					break;
+			} else {
+				struct marker_probe_closure *closure;
+				int match = 0;
+				closure = e->multi;
+				for (i = 0; closure[i].func; i++) {
+					if (closure[i].func != probe)
+						continue;
+					if (match++ == num)
+						return closure[i].probe_private;
+				}
+			}
+		}
+	}
+	return ERR_PTR(-ENOENT);
+}
+EXPORT_SYMBOL_GPL(marker_get_private_data);
diff --git a/kernel/module.c b/kernel/module.c
index 3fd5d43..6cf428e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1529,6 +1529,8 @@ static struct module *load_module(void __user *umod,
 	unsigned int unusedgplcrcindex;
 	unsigned int tracepointsindex;
 	unsigned int tracepointsstringsindex;
+	unsigned int markersindex;
+	unsigned int markersstringsindex;
 	struct module *mod;
 	long err = 0;
 	void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -1636,6 +1638,10 @@ static struct module *load_module(void __user *umod,
 	tracepointsindex = find_sec(hdr, sechdrs, secstrings, "__tracepoints");
 	tracepointsstringsindex = find_sec(hdr, sechdrs, secstrings,
 					"__tracepoints_strings");
+	markersindex = find_sec(hdr, sechdrs, secstrings, "__markers");
+	markersstringsindex = find_sec(hdr, sechdrs, secstrings,
+					"__markers_strings");
+
 #ifdef ARCH_UNWIND_SECTION_NAME
 	unwindex = find_sec(hdr, sechdrs, secstrings, ARCH_UNWIND_SECTION_NAME);
 #endif
@@ -1809,7 +1815,11 @@ static struct module *load_module(void __user *umod,
 	mod->num_tracepoints =
 		sechdrs[tracepointsindex].sh_size / sizeof(*mod->tracepoints);
 #endif
-
+#ifdef CONFIG_MARKERS
+	mod->markers = (void *)sechdrs[markersindex].sh_addr;
+	mod->num_markers =
+		sechdrs[markersindex].sh_size / sizeof(*mod->markers);
+#endif
 
 	/* Now do relocations. */
 	for (i = 1; i < hdr->e_shnum; i++) {
@@ -1854,7 +1864,10 @@ static struct module *load_module(void __user *umod,
 		tracepoint_update_probe_range(mod->tracepoints,
 			mod->tracepoints + mod->num_tracepoints);
 #endif
-
+#ifdef CONFIG_MARKERS
+	marker_update_probe_range(mod->markers,
+		mod->markers + mod->num_markers);
+#endif
 	err = module_finalize(hdr, sechdrs, mod);
 	if (err < 0)
 		goto cleanup;
@@ -1968,7 +1981,6 @@ sys_init_module(void __user *umod,
 		mutex_unlock(&module_mutex);
 		return PTR_ERR(mod);
 	}
-
 	/* Now sew it into the lists.  They won't access us, since
            strong_try_module_get() will fail. */
 	stop_machine_run(__link_module, mod, NR_CPUS);
@@ -2393,3 +2405,16 @@ int module_get_iter_tracepoints(struct tracepoint_iter *iter)
 	return found;
 }
 #endif
+
+#ifdef CONFIG_MARKERS
+void module_update_markers(void)
+{
+	struct module *mod;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry(mod, &modules, list)
+		marker_update_probe_range(mod->markers,
+			mod->markers + mod->num_markers);
+	mutex_unlock(&module_mutex);
+}
+#endif