[PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management)

[Mathieu Desnoyers]

Hello,

Yet, again, a new version. I integrated a full probe management mechanism. See
below.

Comments are welcome,

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/linux/marker.h
@@ -0,0 +1,118 @@
+/*****************************************************************************
+ * 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@xxxxxxxxxx>.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#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_INLINE_PREFIX "__mark_jump_inline_"
+#define MARK_JUMP_OVER_PREFIX "__mark_jump_over_"
+
+#ifdef CONFIG_MARK_SYMBOL
+#define MARK_SYM(name) \
+	do { \
+		__label__ here; \
+		here: asm volatile \
+			(MARK_KPROBE_PREFIX#name " = %0" : : "m" (*&&here)); \
+	} while(0)
+#else 
+#define MARK_SYM(name)
+#endif
+
+#ifdef CONFIG_MARK_JUMP_CALL
+#define MARK_JUMP_CALL_PROTOTYPE(name) \
+	static void \
+		(*__mark_call_##name)(const char *fmt, ...) \
+		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
+
+#ifdef CONFIG_MARK_JUMP_INLINE
+#define MARK_JUMP_INLINE(name, format, args...) \
+		(void) (__mark_inline_##name(format, ## args))
+#else
+#define MARK_JUMP_INLINE(name, format, args...)
+#endif
+
+#define MARK_JUMP(name, format, args...) \
+	do { \
+		__label__ over_label, call_label, inline_label; \
+		volatile static void *__mark_jump_select_##name \
+				asm (MARK_JUMP_SELECT_PREFIX#name) = \
+					&&over_label; \
+		volatile static void *__mark_jump_call_##name \
+				asm (MARK_JUMP_CALL_PREFIX#name) \
+				__attribute__((unused)) =  \
+					&&call_label; \
+		volatile static void *__mark_jump_inline_##name \
+				asm (MARK_JUMP_INLINE_PREFIX#name) \
+				__attribute__((unused)) =  \
+					&&inline_label; \
+		volatile static void *__mark_jump_over_##name \
+				asm (MARK_JUMP_OVER_PREFIX#name) \
+				__attribute__((unused)) =  \
+					&&over_label; \
+		MARK_JUMP_CALL_PROTOTYPE(name); \
+		goto *__mark_jump_select_##name; \
+call_label: \
+		MARK_JUMP_CALL(name, format, ## args); \
+		goto over_label; \
+inline_label: \
+		MARK_JUMP_INLINE(name, format, ## args); \
+over_label: \
+		do {} while(0); \
+	} while(0)
+
+#define MARK(name, format, args...) \
+	do { \
+		__mark_check_format(format, ## args); \
+		MARK_SYM(name); \
+		MARK_JUMP(name, format, ## args); \
+	} while(0)
+
+enum marker_type { MARKER_CALL, MARKER_INLINE };
+
+typedef void (*marker_probe)(const char *fmt, ...);
+
+static inline __attribute__ ((format (printf, 1, 2)))
+void __mark_check_format(const char *fmt, ...)
+{ }
+
+extern void __mark_empty_function(const char *fmt, ...);
+
+int marker_set_probe(const char *name, void (*probe)(const char *fmt, ...),
+			enum marker_type type);
+
+void marker_disable_probe(const char *name, void (*probe)(const char *fmt, ...),
+			enum marker_type type);
--- /dev/null
+++ b/kernel/Kconfig.marker
@@ -0,0 +1,31 @@
+# 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_INLINE
+	bool "Replace markers with a jump over an inline function"
+	default n
+	help
+	  Put a jump over an inline function.
+
+config MARK_JUMP
+	bool "Jump marker probes set/disable infrastructure"
+	select KALLSYMS
+	default n
+	help
+	  Install or remove probes from markers.
+
+endmenu
--- 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@xxxxxxxxxxxxxxxx>, the -fno-omit-frame-pointer is
--- /dev/null
+++ b/kernel/marker.c
@@ -0,0 +1,178 @@
+/*****************************************************************************
+ * marker.c
+ *
+ * Code markup for dynamic and static tracing. Marker control module.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
+ *
+ * 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.
+ *
+ * The marker module will also deal with inline jump selection, which is
+ * the same case as presented here, but without the function pointer.
+ */
+
+
+#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 __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 jmpinline_sym[KSYM_NAME_LEN] = MARK_JUMP_INLINE_PREFIX;
+	char jmpover_sym[KSYM_NAME_LEN] = MARK_JUMP_OVER_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 jmpinline_sym_len = sizeof(MARK_JUMP_INLINE_PREFIX);
+	unsigned int jmpover_sym_len = sizeof(MARK_JUMP_OVER_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(jmpinline_sym, name, KSYM_NAME_LEN-jmpinline_sym_len);
+	strncat(jmpover_sym, name, KSYM_NAME_LEN-jmpover_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->jmpinline = (void**)kallsyms_lookup_name(jmpinline_sym);
+	ptrs->jmpover = (void**)kallsyms_lookup_name(jmpover_sym);
+
+	if(!(ptrs->call && ptrs->jmpselect && ptrs->jmpcall
+			&& ptrs->jmpinline && ptrs->jmpover)) {
+		return ENOENT;
+	}
+	return 0;
+}
+
+int marker_set_probe(const char *name, void (*probe)(const char *fmt, ...),
+			enum marker_type type)
+{
+	int result = 0;
+	struct marker_pointers ptrs;
+
+	spin_lock(&marker_lock);
+	result = marker_get_pointers(name, &ptrs);
+	if(result) {
+		printk(KERN_NOTICE
+			"Unable to find kallsyms for markers in %s\n",
+			name);
+		goto unlock;
+	}
+
+	switch(type) {
+		case MARKER_CALL:
+			if(*ptrs.call != __mark_empty_function) {
+				result = EBUSY;
+				printk(KERN_NOTICE
+					"Probe already installed on "
+					"marker in %s\n",
+					name);
+				goto unlock;
+			}
+			/* Setup the call pointer */
+			*ptrs.call = probe;
+			/* Setup the jump */
+			*ptrs.jmpselect = *ptrs.jmpcall;
+			break;
+		case MARKER_INLINE:
+			if(*ptrs.jmpover == *ptrs.jmpinline) {
+				result = ENODEV;
+				printk(KERN_NOTICE
+					"No inline probe exists "
+					"for marker in %s\n",
+					name);
+				goto unlock;
+			}
+			/* Setup the call pointer */
+			*ptrs.call = __mark_empty_function;
+			/* Setup the jump */
+			*ptrs.jmpselect = *ptrs.jmpinline;
+			break;
+		default:
+			result = ENOENT;
+			printk(KERN_ERR
+				"Unknown marker type\n");
+			break;
+	}
+unlock:
+	spin_unlock(&marker_lock);
+	return result;
+}
+EXPORT_SYMBOL_GPL(marker_set_probe);
+
+void marker_disable_probe(const char *name, void (*probe)(const char *fmt, ...),
+		enum marker_type type)
+{
+	int result = 0;
+	struct marker_pointers ptrs;
+
+	spin_lock(&marker_lock);
+	result = marker_get_pointers(name, &ptrs);
+	if(result)
+		goto unlock;
+
+	switch(type) {
+		case MARKER_CALL:
+			if(*ptrs.call == probe) {
+				*ptrs.jmpselect = *ptrs.jmpover;
+				*ptrs.call = __mark_empty_function;
+			}
+			break;
+		case MARKER_INLINE:
+			if(*ptrs.jmpselect == *ptrs.jmpinline)
+				*ptrs.jmpselect = *ptrs.jmpover;
+			break;
+		default:
+			result = ENOENT;
+			printk(KERN_ERR
+				"Unknown marker type\n");
+			break;
+	}
+unlock:
+	spin_unlock(&marker_lock);
+	if(!result && type == MARKER_CALL)
+		synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(marker_disable_probe);
---END---


-- probe module ---
---BEGIN---


/* probe.c
 *
 * Loads a function at a marker call site.
 *
 * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
 *
 * 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 */
void do_mark1(const char *format, int value)
{
	printk("value is %d\n", value);
}

int init_module(void)
{
	return marker_set_probe("subsys_mark1", (marker_probe)do_mark1,
			MARKER_CALL);
}

void cleanup_module(void)
{
	marker_disable_probe("subsys_mark1", (marker_probe)do_mark1,
		MARKER_CALL);
}

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

---END---


-- sample test marked module ---
---BEGIN---

/* test-mark.c
 *
 */

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

int x=7;

struct proc_dir_entry *pentry = NULL;

static int my_open(struct inode *inode, struct file *file)
{
	MARK(subsys_mark1, "%d", 1);
	MARK(subsys_mark2, "%d %s", 2, "blah2");
	MARK(subsys_mark3, "%d %s", x, "blah3");

	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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