Message-ID: <20060922214239.GA28625@Krystal>
Date:	Fri, 22 Sep 2006 17:42:40 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Martin Bligh <mbligh@...gle.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	prasanna@...ibm.com, Andrew Morton <akpm@...l.org>,
	Ingo Molnar <mingo@...e.hu>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Paul Mundt <lethal@...ux-sh.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jes Sorensen <jes@....com>, Tom Zanussi <zanussi@...ibm.com>,
	Richard J Moore <richardj_moore@...ibm.com>,
	Michel Dagenais <michel.dagenais@...ymtl.ca>,
	Christoph Hellwig <hch@...radead.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	William Cohen <wcohen@...hat.com>, ltt-dev@...fik.org,
	systemtap@...rces.redhat.com, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: [PATCH] Linux Kernel Markers 0.8 for 2.6.17 (with near jump for i386)

Hi,

Here is a new version of the LKM. I added support for a near jump as an
optimisation for i386. I guess that changing the one byte offset of the near
jump instruction won't have any effect on the i386 erratas, anyone can confirm
this ?

With this optimisation, the cost of this inactive marker shrinks from a memory
load+far jump to a near jump.

Feel free to implement similar optimisations for other architectures.

Mathieu


---BEGIN---

--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -1082,6 +1082,8 @@ config KPROBES
 	  for kernel debugging, non-intrusive instrumentation and testing.
 	  If in doubt, say "N".
 
+source "kernel/Kconfig.marker"
+
 source "ltt/Kconfig"
 
 endmenu
--- /dev/null
+++ b/include/asm-alpha/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-arm/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-arm26/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-cris/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-frv/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-generic/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-h8300/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-i386/marker.h
@@ -0,0 +1,29 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. i386 architecture optimisations.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#define ARCH_HAS_MARK_NEAR_JUMP
+
+/* Note : max 256 bytes between over_label and near_jump */
+#define MARK_DO_JUMP(name) \
+	do { \
+		__label__ near_jump_select; \
+		volatile static void *__mark_jump_select_##name \
+			asm (MARK_JUMP_SELECT_PREFIX#name) \
+			__attribute__((unused)) = &&near_jump_select; \
+		asm volatile (	".align 16;\n\t" : : ); \
+		asm volatile (	".byte 0xeb;\n\t" : : ); \
+near_jump_select: \
+		asm volatile (	".byte %0-%1;\n\t" : : \
+				"m" (*&&over_label), \
+				"m" (*&&call_label)); \
+call_label: \
+		asm volatile (	"" : : ); \
+	} while(0)
--- /dev/null
+++ b/include/asm-ia64/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-m32r/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-m68k/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-m68knommu/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-mips/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-parisc/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-powerpc/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-ppc/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-ppc64/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-s390/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-sh/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-sh64/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-sparc/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-sparc64/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-um/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-v850/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-x86_64/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/asm-xtensa/marker.h
@@ -0,0 +1,12 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing. Architecture specific
+ * optimisations.
+ * 
+ * No optimisation implemented.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
--- /dev/null
+++ b/include/linux/marker.h
@@ -0,0 +1,132 @@
+/*****************************************************************************
+ * marker.h
+ *
+ * Code markup for dynamic and static tracing.
+ *
+ * Example :
+ *
+ * MARK(subsystem_event, "%d %s", someint, somestring);
+ * Where :
+ * - Subsystem is the name of your subsystem.
+ * - event is the name of the event to mark.
+ * - "%d %s" is the formatted string for printk.
+ * - someint is an integer.
+ * - somestring is a char *.
+ * - subsystem_event must be unique thorough the kernel!
+ *
+ * Dynamically overridable function call based on marker mechanism
+ *          from Frank Ch. Eigler <fche@...hat.com>.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/linkage.h>
+
+#define MARK_KPROBE_PREFIX "__mark_kprobe_"
+#define MARK_CALL_PREFIX "__mark_call_"
+#define MARK_JUMP_SELECT_PREFIX "__mark_jump_select_"
+#define MARK_JUMP_CALL_PREFIX "__mark_jump_call_"
+#define MARK_JUMP_OVER_PREFIX "__mark_jump_over_"
+#define MARK_FORMAT_PREFIX "__mark_format_"
+
+#include <asm/marker.h>
+
+#define MARK_MAX_FORMAT_LEN	1024
+
+
+struct __mark_kprobe_marker {
+	const char *name;
+	const void *location;
+};
+
+#ifdef CONFIG_MARK_SYMBOL
+#define MARK_SYM(name, format, args...) \
+	do { \
+		__label__ here; \
+here:   	asm volatile(".section \".markers\"; .long %0, %1;\n\t" \
+			".previous\n\t" : : "m" (*(MARK_KPROBE_PREFIX#name)), \
+			"m" (*&&here)); \
+	} while(0)
+#else 
+#define MARK_SYM(name, format, args...)
+#endif
+
+#ifdef CONFIG_MARK_JUMP_CALL
+#define MARK_JUMP_CALL_PROTOTYPE(name) \
+	static marker_probe_func *__mark_call_##name \
+			asm (MARK_CALL_PREFIX#name) = \
+			__mark_empty_function
+#define MARK_JUMP_CALL(name, format, args...) \
+	do { \
+		preempt_disable(); \
+		(*__mark_call_##name)(format, ## args); \
+		preempt_enable_no_resched(); \
+	} while(0)
+#else
+#define MARK_JUMP_CALL_PROTOTYPE(name)
+#define MARK_JUMP_CALL(name, format, args...)
+#endif
+
+#ifndef ARCH_HAS_MARK_NEAR_JUMP
+#define MARK_DO_JUMP(name) \
+	goto *__mark_jump_select_##name; \
+call_label:
+#define MARK_JUMP_SELECT_DECLARE(name) \
+	volatile static void *__mark_jump_select_##name \
+			asm (MARK_JUMP_SELECT_PREFIX#name) \
+			__attribute__((unused)) = \
+				&&over_label
+#else
+#define MARK_JUMP_SELECT_DECLARE(name)
+#endif
+
+#ifndef FORCE_MARK_JUMP_INLINE
+#define MARK_JUMP(name, format, args...) \
+	do { \
+		__label__ over_label, call_label; \
+		volatile static void *__mark_jump_call_##name \
+				asm (MARK_JUMP_CALL_PREFIX#name) \
+				__attribute__((unused)) = \
+					&&call_label; \
+		volatile static void *__mark_jump_over_##name \
+				asm (MARK_JUMP_OVER_PREFIX#name) \
+				__attribute__((unused)) = \
+					&&over_label; \
+		static const char *__mark_format_##name \
+				asm (MARK_FORMAT_PREFIX#name) \
+				__attribute__((unused)) = \
+					format; \
+		MARK_JUMP_CALL_PROTOTYPE(name); \
+		MARK_JUMP_SELECT_DECLARE(name); \
+		MARK_DO_JUMP(name); \
+		MARK_JUMP_CALL(name, format, ## args); \
+over_label: \
+		do {} while(0); \
+	} while(0)
+#else
+#define MARK_JUMP(name, format, args...) \
+	(void) (__mark_inline_##name(format, ## args))
+#endif
+
+#define MARK(name, format, args...) \
+	do { \
+		__mark_check_format(format, ## args); \
+		MARK_SYM(name, format, ## args); \
+		MARK_JUMP(name, format, ## args); \
+	} while(0)
+
+typedef asmlinkage void marker_probe_func(const char *fmt, ...);
+
+static inline __attribute__ ((format (printf, 1, 2)))
+void __mark_check_format(const char *fmt, ...)
+{ }
+
+extern marker_probe_func __mark_empty_function;
+
+int marker_set_probe(const char *name, const char *format,
+			marker_probe_func *probe);
+
+void marker_disable_probe(const char *name, marker_probe_func *probe);
--- /dev/null
+++ b/kernel/Kconfig.marker
@@ -0,0 +1,25 @@
+# Code markers configuration
+
+menu "Marker configuration"
+
+
+config MARK_SYMBOL
+	bool "Replace markers with symbols"
+	default n
+	help
+	  Put symbols in place of markers, useful for kprobe.
+
+config MARK_JUMP_CALL
+	bool "Replace markers with a jump over an inactive function call"
+	default n
+	help
+	  Put a jump over a call in place of markers.
+
+config MARK_JUMP
+	bool "Jump marker probes set/disable infrastructure"
+	select KALLSYMS
+	default n
+	help
+	  Install or remove probes from markers.
+
+endmenu
index 6844e18..1a01e5d 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_RELAY) += relay.o
+obj-$(CONFIG_MARK_JUMP) += marker.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@...uxcare.com.au>, the -fno-omit-frame-pointer is
--- /dev/null
+++ b/kernel/marker.c
@@ -0,0 +1,161 @@
+/*****************************************************************************
+ * marker.c
+ *
+ * Code markup for dynamic and static tracing. Marker control module.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ *
+ * Design :
+ * kernel/marker.c deals with all marker activation from a centralized,
+ * coherent mechanism. The functions that will be called will simply sit in
+ * modules.
+ *
+ * Before activating a probe, the marker module :
+ * 1 - takes proper locking
+ * 2 - verifies that the function pointer and jmp target are at their default
+ *     values, otherwise the "set" operation fails.
+ * 4 - does function pointer and jump setup.
+ *
+ * Setting them back to disabled is :
+ * 1 - setting back the default jmp and call values
+ * 2 - call synchronize_sched()
+ * 
+ * A probe module must call marker disable on all its markers before module
+ * unload.
+ */
+
+
+#include <linux/marker.h>
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/string.h>
+
+static DEFINE_SPINLOCK(marker_lock);
+
+struct marker_pointers {
+	void **call;
+	void **jmpselect;
+	void **jmpcall;
+	void **jmpinline;
+	void **jmpover;
+	void **format;
+};
+
+asmlinkage void __mark_empty_function(const char *fmt, ...)
+{
+}
+EXPORT_SYMBOL(__mark_empty_function);
+
+/* Pointers can be used around preemption disabled */
+static int marker_get_pointers(const char *name,
+	struct marker_pointers *ptrs)
+{
+	char call_sym[KSYM_NAME_LEN] = MARK_CALL_PREFIX;
+	char jmpselect_sym[KSYM_NAME_LEN] = MARK_JUMP_SELECT_PREFIX;
+	char jmpcall_sym[KSYM_NAME_LEN] = MARK_JUMP_CALL_PREFIX;
+	char jmpover_sym[KSYM_NAME_LEN] = MARK_JUMP_OVER_PREFIX;
+	char format_sym[KSYM_NAME_LEN] = MARK_FORMAT_PREFIX;
+	unsigned int call_sym_len = sizeof(MARK_CALL_PREFIX);
+	unsigned int jmpselect_sym_len = sizeof(MARK_JUMP_SELECT_PREFIX);
+	unsigned int jmpcall_sym_len = sizeof(MARK_JUMP_CALL_PREFIX);
+	unsigned int jmpover_sym_len = sizeof(MARK_JUMP_OVER_PREFIX);
+	unsigned int format_sym_len = sizeof(MARK_FORMAT_PREFIX);
+
+	strncat(call_sym, name, KSYM_NAME_LEN-call_sym_len);
+	strncat(jmpselect_sym, name, KSYM_NAME_LEN-jmpselect_sym_len);
+	strncat(jmpcall_sym, name, KSYM_NAME_LEN-jmpcall_sym_len);
+	strncat(jmpover_sym, name, KSYM_NAME_LEN-jmpover_sym_len);
+	strncat(format_sym, name, KSYM_NAME_LEN-format_sym_len);
+
+	ptrs->call = (void**)kallsyms_lookup_name(call_sym);
+	ptrs->jmpselect = (void**)kallsyms_lookup_name(jmpselect_sym);
+	ptrs->jmpcall = (void**)kallsyms_lookup_name(jmpcall_sym);
+	ptrs->jmpover = (void**)kallsyms_lookup_name(jmpover_sym);
+	ptrs->format = (void**)kallsyms_lookup_name(format_sym);
+
+	if (!(ptrs->call && ptrs->jmpselect && ptrs->jmpcall
+		&& ptrs->jmpover && ptrs->format)) {
+		return ENOENT;
+	}
+	return 0;
+}
+
+int marker_set_probe(const char *name, const char *format,
+		marker_probe_func *probe)
+{
+	int result = 0;
+	struct marker_pointers ptrs;
+
+	spin_lock(&marker_lock);
+	result = marker_get_pointers(name, &ptrs);
+	if (result) {
+		result = ENODEV;
+		printk(KERN_NOTICE
+			"Unable to find kallsyms for markers in %s\n",
+			name);
+		goto unlock;
+	}
+
+	if (*ptrs.call != __mark_empty_function) {
+		result = EBUSY;
+		printk(KERN_NOTICE
+			"Probe already installed on "
+			"marker in %s\n",
+			name);
+		goto unlock;
+	}
+	/* Check the types if format provided by probe */
+	if (format && strncmp(format, *ptrs.format,
+			MARK_MAX_FORMAT_LEN)) {
+		result = EPERM;
+		printk(KERN_NOTICE
+			"Format mismatch for probe %s "
+			"(%s), marker (%s)\n",
+			name,
+			format,
+			(const char*)*ptrs.format);
+		goto unlock;
+	}
+	/* Setup the call pointer */
+	*ptrs.call = probe;
+	/* Setup the jump */
+#ifndef ARCH_HAS_MARK_NEAR_JUMP
+	*ptrs.jmpselect = *ptrs.jmpcall;
+#else
+	**(char**)ptrs.jmpselect = 0;
+#endif
+unlock:
+	spin_unlock(&marker_lock);
+	return result;
+}
+EXPORT_SYMBOL_GPL(marker_set_probe);
+
+void marker_disable_probe(const char *name, marker_probe_func *probe)
+{
+	int result = 0;
+	struct marker_pointers ptrs;
+
+	spin_lock(&marker_lock);
+	result = marker_get_pointers(name, &ptrs);
+	if (result)
+		goto unlock;
+
+	if (*ptrs.call == probe) {
+#ifndef ARCH_HAS_MARK_NEAR_JUMP
+		*ptrs.jmpselect = *ptrs.jmpover;
+#else
+		**(char**)ptrs.jmpselect =
+			*ptrs.jmpover - *ptrs.jmpcall;
+#endif
+		*ptrs.call = __mark_empty_function;
+	}
+unlock:
+	spin_unlock(&marker_lock);
+	if (!result)
+		synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(marker_disable_probe);

---END---

---BEGIN---

/* probe.c
 *
 * Loads a function at a marker call site.
 *
 * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
 *
 * This file is released under the GPLv2.
 * See the file COPYING for more details.
 */

#include <linux/marker.h>
#include <linux/module.h>
#include <linux/kallsyms.h>

/* function to install */
#define DO_MARK1_FORMAT "%d"
asmlinkage void do_mark1(const char *format, int value)
{
	__mark_check_format(DO_MARK1_FORMAT, value);
	printk("value is %d\n", value);
}

#define DO_MARK2_FORMAT "%d %s"
asmlinkage void do_mark2(const char *format, int value, const char *string)
{
	__mark_check_format(DO_MARK2_FORMAT, value, string);
	printk("value is %d %s\n", value, string);
}

#define DO_MARK3_FORMAT "%d %s %s"
asmlinkage void do_mark3(const char *format, int value, const char *s1,
				const char *s2)
{
	__mark_check_format(DO_MARK3_FORMAT, value, s1, s2);
	printk("value is %d %s %s\n", value, s1, s2);
}

int init_module(void)
{
	int result;
	result = marker_set_probe("subsys_mark1", DO_MARK1_FORMAT,
			(marker_probe_func*)do_mark1);
	if(result) goto end;
	result = marker_set_probe("subsys_mark2", DO_MARK2_FORMAT,
			(marker_probe_func*)do_mark2);
	if(result) goto cleanup1;
	result = marker_set_probe("subsys_mark3", DO_MARK3_FORMAT,
			(marker_probe_func*)do_mark3);
	if(result) goto cleanup2;

	return -result;

cleanup2:
	marker_disable_probe("subsys_mark2", (marker_probe_func*)do_mark2);
cleanup1:
	marker_disable_probe("subsys_mark1", (marker_probe_func*)do_mark1);
end:
	return -result;
}

void cleanup_module(void)
{
	marker_disable_probe("subsys_mark1", (marker_probe_func*)do_mark1);
	marker_disable_probe("subsys_mark2", (marker_probe_func*)do_mark2);
	marker_disable_probe("subsys_mark3", (marker_probe_func*)do_mark3);
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mathieu Desnoyers");
MODULE_DESCRIPTION("Probe");
---END---


---BEGIN---

/* test-mark.c
 *
 */

#include <linux/marker.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>

volatile int x=7;

struct proc_dir_entry *pentry = NULL;

static int my_open(struct inode *inode, struct file *file)
{
	unsigned int i;

	for(i=0; i<2; i++) {
		MARK(subsys_mark1, "%d", 1);
		x=i;
		barrier();
	}
	MARK(subsys_mark2, "%d %s", 2, "blah2");
	MARK(subsys_mark3, "%d %s %s", x, "blah3", "blah5");

	return -EPERM;
}


static struct file_operations my_operations = {
	.open = my_open,
};

int init_module(void)
{
	pentry = create_proc_entry("testmark", 0444, NULL);
	if (pentry)
		pentry->proc_fops = &my_operations;
	return 0;
}

void cleanup_module(void)
{
	remove_proc_entry("testmark", NULL);
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mathieu Desnoyers");
MODULE_DESCRIPTION("Marker Test");
---END---

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