[PATCH -tip -v10 7/7] tracing: add kprobe-based event tracer

[Masami Hiramatsu]

Add kprobes-based event tracer on ftrace.

This tracer is similar to the events tracer which is based on Tracepoint
infrastructure. Instead of Tracepoint, this tracer is based on kprobes(kprobe
and kretprobe). It probes anywhere where kprobes can probe(this means, all
functions body except for __kprobes functions).

Similar to the events tracer, this tracer doesn't need to be activated via
current_tracer, instead of that, just set probe points via
/sys/kernel/debug/tracing/kprobe_events. And you can set filters on each
probe events via /sys/kernel/debug/tracing/events/kprobes/<EVENT>/filter.

This tracer supports following probe arguments for each probe.

  %REG  : Fetch register REG
  sN    : Fetch Nth entry of stack (N >= 0)
  @ADDR : Fetch memory at ADDR (ADDR should be in kernel)
  @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
  aN    : Fetch function argument. (N >= 0)
  rv    : Fetch return value.
  ra    : Fetch return address.
  +|-offs(FETCHARG) : fetch memory at FETCHARG +|- offs address.

See Documentation/trace/kprobes.txt for details.

Changes from v9:
 - Select CONFIG_GENERIC_TRACER when CONFIG_KPROBE_TRACER=y.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Acked-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Tom Zanussi <tzanussi@xxxxxxxxx>
---

 Documentation/trace/kprobes.txt  |  138 ++++
 kernel/trace/Kconfig             |   12 
 kernel/trace/Makefile            |    1 
 kernel/trace/trace.h             |   22 +
 kernel/trace/trace_event_types.h |   20 +
 kernel/trace/trace_kprobe.c      | 1183 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 1376 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/trace/kprobes.txt
 create mode 100644 kernel/trace/trace_kprobe.c

diff --git a/Documentation/trace/kprobes.txt b/Documentation/trace/kprobes.txt
new file mode 100644
index 0000000..3a90ebb
--- /dev/null
+++ b/Documentation/trace/kprobes.txt
@@ -0,0 +1,138 @@
+                         Kprobe-based Event Tracer
+                         =========================
+
+                 Documentation is written by Masami Hiramatsu
+
+
+Overview
+--------
+This tracer is similar to the events tracer which is based on Tracepoint
+infrastructure. Instead of Tracepoint, this tracer is based on kprobes(kprobe
+and kretprobe). It probes anywhere where kprobes can probe(this means, all
+functions body except for __kprobes functions).
+
+Unlike the function tracer, this tracer can probe instructions inside of
+kernel functions. It allows you to check which instruction has been executed.
+
+Unlike the Tracepoint based events tracer, this tracer can add and remove
+probe points on the fly.
+
+Similar to the events tracer, this tracer doesn't need to be activated via
+current_tracer, instead of that, just set probe points via
+/sys/kernel/debug/tracing/kprobe_events. And you can set filters on each
+probe events via /sys/kernel/debug/tracing/events/kprobes/<EVENT>/filter.
+
+
+Synopsis of kprobe_events
+-------------------------
+  p[:EVENT] SYMBOL[+offs|-offs]|MEMADDR [FETCHARGS]	: set a probe
+  r[:EVENT] SYMBOL[+0] [FETCHARGS]			: set a return probe
+
+ EVENT			: Event name
+ SYMBOL[+offs|-offs]	: Symbol+offset where the probe is inserted
+ MEMADDR		: Address where the probe is inserted
+
+ FETCHARGS		: Arguments
+  %REG	: Fetch register REG
+  sN	: Fetch Nth entry of stack (N >= 0)
+  @ADDR	: Fetch memory at ADDR (ADDR should be in kernel)
+  @SYM[+|-offs]	: Fetch memory at SYM +|- offs (SYM should be a data symbol)
+  aN	: Fetch function argument. (N >= 0)(*)
+  rv	: Fetch return value.(**)
+  ra	: Fetch return address.(**)
+  +|-offs(FETCHARG) : fetch memory at FETCHARG +|- offs address.(***)
+
+  (*) aN may not correct on asmlinkaged functions and at the middle of
+      function body.
+  (**) only for return probe.
+  (***) this is useful for fetching a field of data structures.
+
+
+Per-Probe Event Filtering
+-------------------------
+ Per-probe event filtering feature allows you to set different filter on each
+probe and gives you what arguments will be shown in trace buffer. If an event
+name is specified right after 'p:' or 'r:' in kprobe_events, the tracer adds
+an event under tracing/events/kprobes/<EVENT>, at the directory you can see
+'id', 'enabled', 'format' and 'filter'.
+
+enabled:
+  You can enable/disable the probe by writing 1 or 0 on it.
+
+format:
+  It shows the format of this probe event. It also shows aliases of arguments
+ which you specified to kprobe_events.
+
+filter:
+  You can write filtering rules of this event. And you can use both of aliase
+ names and field names for describing filters.
+
+
+Usage examples
+--------------
+To add a probe as a new event, write a new definition to kprobe_events
+as below.
+
+  echo p:myprobe do_sys_open a0 a1 a2 a3 > /sys/kernel/debug/tracing/kprobe_events
+
+ This sets a kprobe on the top of do_sys_open() function with recording
+1st to 4th arguments as "myprobe" event.
+
+  echo r:myretprobe do_sys_open rv ra >> /sys/kernel/debug/tracing/kprobe_events
+
+ This sets a kretprobe on the return point of do_sys_open() function with
+recording return value and return address as "myretprobe" event.
+ You can see the format of these events via
+/sys/kernel/debug/tracing/events/kprobes/<EVENT>/format.
+
+  cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format
+name: myprobe
+ID: 23
+format:
+	field:unsigned short common_type;	offset:0;	size:2;
+	field:unsigned char common_flags;	offset:2;	size:1;
+	field:unsigned char common_preempt_count;	offset:3;	size:1;
+	field:int common_pid;	offset:4;	size:4;
+	field:int common_tgid;	offset:8;	size:4;
+
+	field: unsigned long ip;	offset:16;tsize:8;
+	field: int nargs;	offset:24;tsize:4;
+	field: unsigned long arg0;	offset:32;tsize:8;
+	field: unsigned long arg1;	offset:40;tsize:8;
+	field: unsigned long arg2;	offset:48;tsize:8;
+	field: unsigned long arg3;	offset:56;tsize:8;
+
+	alias: a0;	original: arg0;
+	alias: a1;	original: arg1;
+	alias: a2;	original: arg2;
+	alias: a3;	original: arg3;
+
+print fmt: "%lx: 0x%lx 0x%lx 0x%lx 0x%lx", ip, arg0, arg1, arg2, arg3
+
+
+ You can see that the event has 4 arguments and alias expressions
+corresponding to it.
+
+  echo > /sys/kernel/debug/tracing/kprobe_events
+
+ This clears all probe points. and you can see the traced information via
+/sys/kernel/debug/tracing/trace.
+
+  cat /sys/kernel/debug/tracing/trace
+# tracer: nop
+#
+#           TASK-PID    CPU#    TIMESTAMP  FUNCTION
+#              | |       |          |         |
+           <...>-1447  [001] 1038282.286875: do_sys_open+0x0/0xd6: 0x3 0x7fffd1ec4440 0x8000 0x0
+           <...>-1447  [001] 1038282.286878: sys_openat+0xc/0xe <- do_sys_open: 0xfffffffffffffffe 0xffffffff81367a3a
+           <...>-1447  [001] 1038282.286885: do_sys_open+0x0/0xd6: 0xffffff9c 0x40413c 0x8000 0x1b6
+           <...>-1447  [001] 1038282.286915: sys_open+0x1b/0x1d <- do_sys_open: 0x3 0xffffffff81367a3a
+           <...>-1447  [001] 1038282.286969: do_sys_open+0x0/0xd6: 0xffffff9c 0x4041c6 0x98800 0x10
+           <...>-1447  [001] 1038282.286976: sys_open+0x1b/0x1d <- do_sys_open: 0x3 0xffffffff81367a3a
+
+
+ Each line shows when the kernel hits a probe, and <- SYMBOL means kernel
+returns from SYMBOL(e.g. "sys_open+0x1b/0x1d <- do_sys_open" means kernel
+returns from do_sys_open to sys_open+0x1b).
+
+
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 860c712..60f3401 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -445,6 +445,18 @@ config BLK_DEV_IO_TRACE
 
 	  If unsure, say N.
 
+config KPROBE_TRACER
+	depends on KPROBES
+	depends on X86
+	bool "Trace kprobes"
+	select TRACING
+	select GENERIC_TRACER
+	help
+	  This tracer probes everywhere where kprobes can probe it, and
+	  records various registers and memories specified by user.
+	  This also allows you to trace kprobe probe points as a dynamic
+	  defined events. It provides per-probe event filtering interface.
+
 config DYNAMIC_FTRACE
 	bool "enable/disable ftrace tracepoints dynamically"
 	depends on FUNCTION_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index ce3b1cd..8e6884d 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -55,5 +55,6 @@ obj-$(CONFIG_FTRACE_SYSCALLS) += trace_syscalls.o
 obj-$(CONFIG_EVENT_PROFILE) += trace_event_profile.o
 obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
 obj-$(CONFIG_KSYM_TRACER) += trace_ksym.o
+obj-$(CONFIG_KPROBE_TRACER) += trace_kprobe.o
 
 libftrace-y := ftrace.o
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 206cb7d..65945eb 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -45,6 +45,8 @@ enum trace_type {
 	TRACE_POWER,
 	TRACE_BLK,
 	TRACE_KSYM,
+	TRACE_KPROBE,
+	TRACE_KRETPROBE,
 
 	__TRACE_LAST_TYPE,
 };
@@ -227,6 +229,22 @@ struct trace_ksym {
 	char			ksym_name[KSYM_NAME_LEN];
 	char			p_name[TASK_COMM_LEN];
 };
+#define TRACE_KPROBE_ARGS 6
+
+struct kprobe_trace_entry {
+	struct trace_entry	ent;
+	unsigned long		ip;
+	int			nargs;
+	unsigned long		args[TRACE_KPROBE_ARGS];
+};
+
+struct kretprobe_trace_entry {
+	struct trace_entry	ent;
+	unsigned long		func;
+	unsigned long		ret_ip;
+	int			nargs;
+	unsigned long		args[TRACE_KPROBE_ARGS];
+};
 
 /*
  * trace_flag_type is an enumeration that holds different
@@ -344,6 +362,10 @@ extern void __ftrace_bad_type(void);
 		IF_ASSIGN(var, ent, struct syscall_trace_exit,		\
 			  TRACE_SYSCALL_EXIT);				\
 		IF_ASSIGN(var, ent, struct trace_ksym, TRACE_KSYM);	\
+		IF_ASSIGN(var, ent, struct kprobe_trace_entry,		\
+			  TRACE_KPROBE);				\
+		IF_ASSIGN(var, ent, struct kretprobe_trace_entry,	\
+			  TRACE_KRETPROBE);				\
 		__ftrace_bad_type();					\
 	} while (0)
 
diff --git a/kernel/trace/trace_event_types.h b/kernel/trace/trace_event_types.h
index 6db005e..ec2e6f3 100644
--- a/kernel/trace/trace_event_types.h
+++ b/kernel/trace/trace_event_types.h
@@ -175,4 +175,24 @@ TRACE_EVENT_FORMAT(kmem_free, TRACE_KMEM_FREE, kmemtrace_free_entry, ignore,
 	TP_RAW_FMT("type:%u call_site:%lx ptr:%p")
 );
 
+TRACE_EVENT_FORMAT(kprobe, TRACE_KPROBE, kprobe_trace_entry, ignore,
+	TRACE_STRUCT(
+		TRACE_FIELD(unsigned long, ip, ip)
+		TRACE_FIELD(int, nargs, nargs)
+		TRACE_FIELD_SPECIAL(unsigned long args[TRACE_KPROBE_ARGS],
+				    args, TRACE_KPROBE_ARGS, args)
+	),
+	TP_RAW_FMT("%08lx: args:0x%lx ...")
+);
+
+TRACE_EVENT_FORMAT(kretprobe, TRACE_KRETPROBE, kretprobe_trace_entry, ignore,
+	TRACE_STRUCT(
+		TRACE_FIELD(unsigned long, func, func)
+		TRACE_FIELD(unsigned long, ret_ip, ret_ip)
+		TRACE_FIELD(int, nargs, nargs)
+		TRACE_FIELD_SPECIAL(unsigned long args[TRACE_KPROBE_ARGS],
+				    args, TRACE_KPROBE_ARGS, args)
+	),
+	TP_RAW_FMT("%08lx <- %08lx: args:0x%lx ...")
+);
 #undef TRACE_SYSTEM
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
new file mode 100644
index 0000000..0951512
--- /dev/null
+++ b/kernel/trace/trace_kprobe.c
@@ -0,0 +1,1183 @@
+/*
+ * kprobe based kernel tracer
+ *
+ * Created by Masami Hiramatsu <mhiramat@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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/uaccess.h>
+#include <linux/kprobes.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <linux/debugfs.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/ptrace.h>
+
+#include "trace.h"
+#include "trace_output.h"
+
+#define MAX_ARGSTR_LEN 63
+
+/* currently, trace_kprobe only supports X86. */
+
+struct fetch_func {
+	unsigned long (*func)(struct pt_regs *, void *);
+	void *data;
+};
+
+static __kprobes unsigned long call_fetch(struct fetch_func *f,
+					  struct pt_regs *regs)
+{
+	return f->func(regs, f->data);
+}
+
+/* fetch handlers */
+static __kprobes unsigned long fetch_register(struct pt_regs *regs,
+					      void *offset)
+{
+	return regs_get_register(regs, (unsigned)((unsigned long)offset));
+}
+
+static __kprobes unsigned long fetch_stack(struct pt_regs *regs,
+					   void *num)
+{
+	return regs_get_kernel_stack_nth(regs, (unsigned)((unsigned long)num));
+}
+
+static __kprobes unsigned long fetch_memory(struct pt_regs *regs, void *addr)
+{
+	unsigned long retval;
+	if (probe_kernel_address(addr, retval))
+		return 0;
+	return retval;
+}
+
+static __kprobes unsigned long fetch_argument(struct pt_regs *regs, void *num)
+{
+	return regs_get_argument_nth(regs, (unsigned)((unsigned long)num));
+}
+
+static __kprobes unsigned long fetch_retvalue(struct pt_regs *regs,
+					      void *dummy)
+{
+	return regs_return_value(regs);
+}
+
+static __kprobes unsigned long fetch_ip(struct pt_regs *regs, void *dummy)
+{
+	return instruction_pointer(regs);
+}
+
+/* Memory fetching by symbol */
+struct symbol_cache {
+	char *symbol;
+	long offset;
+	unsigned long addr;
+};
+
+static unsigned long update_symbol_cache(struct symbol_cache *sc)
+{
+	sc->addr = (unsigned long)kallsyms_lookup_name(sc->symbol);
+	if (sc->addr)
+		sc->addr += sc->offset;
+	return sc->addr;
+}
+
+static void free_symbol_cache(struct symbol_cache *sc)
+{
+	kfree(sc->symbol);
+	kfree(sc);
+}
+
+static struct symbol_cache *alloc_symbol_cache(const char *sym, long offset)
+{
+	struct symbol_cache *sc;
+	if (!sym || strlen(sym) == 0)
+		return NULL;
+	sc = kzalloc(sizeof(struct symbol_cache), GFP_KERNEL);
+	if (!sc)
+		return NULL;
+
+	sc->symbol = kstrdup(sym, GFP_KERNEL);
+	if (!sc->symbol) {
+		kfree(sc);
+		return NULL;
+	}
+	sc->offset = offset;
+
+	update_symbol_cache(sc);
+	return sc;
+}
+
+static __kprobes unsigned long fetch_symbol(struct pt_regs *regs, void *data)
+{
+	struct symbol_cache *sc = data;
+	if (sc->addr)
+		return fetch_memory(regs, (void *)sc->addr);
+	else
+		return 0;
+}
+
+/* Special indirect memory access interface */
+struct indirect_fetch_data {
+	struct fetch_func orig;
+	long offset;
+};
+
+static __kprobes unsigned long fetch_indirect(struct pt_regs *regs, void *data)
+{
+	struct indirect_fetch_data *ind = data;
+	unsigned long addr;
+	addr = call_fetch(&ind->orig, regs);
+	if (addr) {
+		addr += ind->offset;
+		return fetch_memory(regs, (void *)addr);
+	} else
+		return 0;
+}
+
+static __kprobes void free_indirect_fetch_data(struct indirect_fetch_data *data)
+{
+	if (data->orig.func == fetch_indirect)
+		free_indirect_fetch_data(data->orig.data);
+	else if (data->orig.func == fetch_symbol)
+		free_symbol_cache(data->orig.data);
+	kfree(data);
+}
+
+/**
+ * kprobe_trace_core
+ */
+
+struct trace_probe {
+	struct list_head	list;
+	union {
+		struct kprobe		kp;
+		struct kretprobe	rp;
+	};
+	const char		*symbol;	/* symbol name */
+	unsigned int		nr_args;
+	struct fetch_func	args[TRACE_KPROBE_ARGS];
+	struct ftrace_event_call	call;
+};
+
+static int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs);
+static int kretprobe_trace_func(struct kretprobe_instance *ri,
+				struct pt_regs *regs);
+
+static __kprobes int probe_is_return(struct trace_probe *tp)
+{
+	return (tp->rp.handler == kretprobe_trace_func);
+}
+
+static __kprobes const char *probe_symbol(struct trace_probe *tp)
+{
+	return tp->symbol ? tp->symbol : "unknown";
+}
+
+static __kprobes long probe_offset(struct trace_probe *tp)
+{
+	return (probe_is_return(tp)) ? tp->rp.kp.offset : tp->kp.offset;
+}
+
+static __kprobes void *probe_address(struct trace_probe *tp)
+{
+	return (probe_is_return(tp)) ? tp->rp.kp.addr : tp->kp.addr;
+}
+
+static int trace_arg_string(char *buf, size_t n, struct fetch_func *ff)
+{
+	int ret = -EINVAL;
+	if (ff->func == fetch_argument)
+		ret = snprintf(buf, n, "a%lu", (unsigned long)ff->data);
+	else if (ff->func == fetch_register) {
+		const char *name;
+		name = regs_query_register_name((unsigned)((long)ff->data));
+		ret = snprintf(buf, n, "%%%s", name);
+	} else if (ff->func == fetch_stack)
+		ret = snprintf(buf, n, "s%lu", (unsigned long)ff->data);
+	else if (ff->func == fetch_memory)
+		ret = snprintf(buf, n, "@0x%p", ff->data);
+	else if (ff->func == fetch_symbol) {
+		struct symbol_cache *sc = ff->data;
+		ret = snprintf(buf, n, "@%s%+ld", sc->symbol, sc->offset);
+	} else if (ff->func == fetch_retvalue)
+		ret = snprintf(buf, n, "rv");
+	else if (ff->func == fetch_ip)
+		ret = snprintf(buf, n, "ra");
+	else if (ff->func == fetch_indirect) {
+		struct indirect_fetch_data *id = ff->data;
+		ret = snprintf(buf, n, "%+ld(", id->offset);
+		if (ret > n)
+			goto end;
+		n -= ret;
+		ret = trace_arg_string(buf, n, &id->orig);
+		if (ret > n)
+			goto end;
+		n -= ret;
+		ret = snprintf(buf, n, ")");
+	}
+end:
+	if (ret > n)
+		return -ENOSPC;
+	return 0;
+}
+
+static int register_probe_event(struct trace_probe *tp);
+static void unregister_probe_event(struct trace_probe *tp);
+
+static DEFINE_MUTEX(probe_lock);
+static LIST_HEAD(probe_list);
+
+static struct trace_probe *alloc_trace_probe(const char *symbol,
+					     const char *event)
+{
+	struct trace_probe *tp;
+
+	tp = kzalloc(sizeof(struct trace_probe), GFP_KERNEL);
+	if (!tp)
+		return ERR_PTR(-ENOMEM);
+
+	if (symbol) {
+		tp->symbol = kstrdup(symbol, GFP_KERNEL);
+		if (!tp->symbol)
+			goto error;
+	}
+	if (event) {
+		tp->call.name = kstrdup(event, GFP_KERNEL);
+		if (!tp->call.name)
+			goto error;
+	}
+
+	INIT_LIST_HEAD(&tp->list);
+	return tp;
+error:
+	kfree(tp->symbol);
+	kfree(tp);
+	return ERR_PTR(-ENOMEM);
+}
+
+static void free_trace_probe(struct trace_probe *tp)
+{
+	int i;
+	for (i = 0; i < tp->nr_args; i++)
+		if (tp->args[i].func == fetch_symbol)
+			free_symbol_cache(tp->args[i].data);
+		else if (tp->args[i].func == fetch_indirect)
+			free_indirect_fetch_data(tp->args[i].data);
+
+	kfree(tp->call.name);
+	kfree(tp->symbol);
+	kfree(tp);
+}
+
+static struct trace_probe *find_probe_event(const char *event)
+{
+	struct trace_probe *tp;
+	list_for_each_entry(tp, &probe_list, list)
+		if (tp->call.name && !strcmp(tp->call.name, event))
+			return tp;
+	return NULL;
+}
+
+static void __unregister_trace_probe(struct trace_probe *tp)
+{
+	if (probe_is_return(tp))
+		unregister_kretprobe(&tp->rp);
+	else
+		unregister_kprobe(&tp->kp);
+}
+
+/* Unregister a trace_probe and probe_event: call with locking probe_lock */
+static void unregister_trace_probe(struct trace_probe *tp)
+{
+	if (tp->call.name)
+		unregister_probe_event(tp);
+	__unregister_trace_probe(tp);
+	list_del(&tp->list);
+}
+
+/* Register a trace_probe and probe_event */
+static int register_trace_probe(struct trace_probe *tp)
+{
+	struct trace_probe *old_tp;
+	int ret;
+
+	mutex_lock(&probe_lock);
+
+	if (probe_is_return(tp))
+		ret = register_kretprobe(&tp->rp);
+	else
+		ret = register_kprobe(&tp->kp);
+
+	if (ret) {
+		pr_warning("Could not insert probe(%d)\n", ret);
+		if (ret == -EILSEQ) {
+			pr_warning("Probing address(0x%p) is not an "
+				   "instruction boundary.\n",
+				   probe_address(tp));
+			ret = -EINVAL;
+		}
+		goto end;
+	}
+	/* register as an event */
+	if (tp->call.name) {
+		old_tp = find_probe_event(tp->call.name);
+		if (old_tp) {
+			/* delete old event */
+			unregister_trace_probe(old_tp);
+			free_trace_probe(old_tp);
+		}
+		ret = register_probe_event(tp);
+		if (ret) {
+			pr_warning("Faild to register probe event(%d)\n", ret);
+			__unregister_trace_probe(tp);
+		}
+	}
+	list_add_tail(&tp->list, &probe_list);
+end:
+	mutex_unlock(&probe_lock);
+	return ret;
+}
+
+/* Split symbol and offset. */
+static int split_symbol_offset(char *symbol, long *offset)
+{
+	char *tmp;
+	int ret;
+
+	if (!offset)
+		return -EINVAL;
+
+	tmp = strchr(symbol, '+');
+	if (!tmp)
+		tmp = strchr(symbol, '-');
+
+	if (tmp) {
+		/* skip sign because strict_strtol doesn't accept '+' */
+		ret = strict_strtol(tmp + 1, 0, offset);
+		if (ret)
+			return ret;
+		if (*tmp == '-')
+			*offset = -(*offset);
+		*tmp = '\0';
+	} else
+		*offset = 0;
+	return 0;
+}
+
+#define PARAM_MAX_ARGS 16
+#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
+
+static int parse_trace_arg(char *arg, struct fetch_func *ff, int is_return)
+{
+	int ret = 0;
+	unsigned long param;
+	long offset;
+	char *tmp;
+
+	switch (arg[0]) {
+	case 'a':	/* argument */
+		ret = strict_strtoul(arg + 1, 10, &param);
+		if (ret || param > PARAM_MAX_ARGS)
+			ret = -EINVAL;
+		else {
+			ff->func = fetch_argument;
+			ff->data = (void *)param;
+		}
+		break;
+	case 'r':	/* retval or retaddr */
+		if (is_return && arg[1] == 'v') {
+			ff->func = fetch_retvalue;
+			ff->data = NULL;
+		} else if (is_return && arg[1] == 'a') {
+			ff->func = fetch_ip;
+			ff->data = NULL;
+		} else
+			ret = -EINVAL;
+		break;
+	case '%':	/* named register */
+		ret = regs_query_register_offset(arg + 1);
+		if (ret >= 0) {
+			ff->func = fetch_register;
+			ff->data = (void *)(unsigned long)ret;
+			ret = 0;
+		}
+		break;
+	case 's':	/* stack */
+		ret = strict_strtoul(arg + 1, 10, &param);
+		if (ret || param > PARAM_MAX_STACK)
+			ret = -EINVAL;
+		else {
+			ff->func = fetch_stack;
+			ff->data = (void *)param;
+		}
+		break;
+	case '@':	/* memory or symbol */
+		if (isdigit(arg[1])) {
+			ret = strict_strtoul(arg + 1, 0, &param);
+			if (ret)
+				break;
+			ff->func = fetch_memory;
+			ff->data = (void *)param;
+		} else {
+			ret = split_symbol_offset(arg + 1, &offset);
+			if (ret)
+				break;
+			ff->data = alloc_symbol_cache(arg + 1,
+							      offset);
+			if (ff->data)
+				ff->func = fetch_symbol;
+			else
+				ret = -EINVAL;
+		}
+		break;
+	case '+':	/* indirect memory */
+	case '-':
+		tmp = strchr(arg, '(');
+		if (!tmp) {
+			ret = -EINVAL;
+			break;
+		}
+		*tmp = '\0';
+		ret = strict_strtol(arg + 1, 0, &offset);
+		if (ret)
+			break;
+		if (arg[0] == '-')
+			offset = -offset;
+		arg = tmp + 1;
+		tmp = strrchr(arg, ')');
+		if (tmp) {
+			struct indirect_fetch_data *id;
+			*tmp = '\0';
+			id = kzalloc(sizeof(struct indirect_fetch_data),
+				     GFP_KERNEL);
+			if (!id)
+				return -ENOMEM;
+			id->offset = offset;
+			ret = parse_trace_arg(arg, &id->orig, is_return);
+			if (ret)
+				kfree(id);
+			else {
+				ff->func = fetch_indirect;
+				ff->data = (void *)id;
+			}
+		} else
+			ret = -EINVAL;
+		break;
+	default:
+		/* TODO: support custom handler */
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+static int create_trace_probe(int argc, char **argv)
+{
+	/*
+	 * Argument syntax:
+	 *  - Add kprobe: p[:EVENT] SYMBOL[+OFFS|-OFFS]|ADDRESS [FETCHARGS]
+	 *  - Add kretprobe: r[:EVENT] SYMBOL[+0] [FETCHARGS]
+	 * Fetch args:
+	 *  aN	: fetch Nth of function argument. (N:0-)
+	 *  rv	: fetch return value
+	 *  ra	: fetch return address
+	 *  sN	: fetch Nth of stack (N:0-)
+	 *  @ADDR	: fetch memory at ADDR (ADDR should be in kernel)
+	 *  @SYM[+|-offs] : fetch memory at SYM +|- offs (SYM is a data symbol)
+	 *  %REG	: fetch register REG
+	 * Indirect memory fetch:
+	 *  +|-offs(ARG) : fetch memory at ARG +|- offs address.
+	 */
+	struct trace_probe *tp;
+	struct kprobe *kp;
+	int i, ret = 0;
+	int is_return = 0;
+	char *symbol = NULL, *event = NULL;
+	long offset = 0;
+	void *addr = NULL;
+
+	if (argc < 2)
+		return -EINVAL;
+
+	if (argv[0][0] == 'p')
+		is_return = 0;
+	else if (argv[0][0] == 'r')
+		is_return = 1;
+	else
+		return -EINVAL;
+
+	if (argv[0][1] == ':') {
+		event = &argv[0][2];
+		if (strlen(event) == 0) {
+			pr_info("Event name is not specifiled\n");
+			return -EINVAL;
+		}
+	}
+
+	if (isdigit(argv[1][0])) {
+		if (is_return)
+			return -EINVAL;
+		/* an address specified */
+		ret = strict_strtoul(&argv[0][2], 0, (unsigned long *)&addr);
+		if (ret)
+			return ret;
+	} else {
+		/* a symbol specified */
+		symbol = argv[1];
+		/* TODO: support .init module functions */
+		ret = split_symbol_offset(symbol, &offset);
+		if (ret)
+			return ret;
+		if (offset && is_return)
+			return -EINVAL;
+	}
+
+	/* setup a probe */
+	tp = alloc_trace_probe(symbol, event);
+	if (IS_ERR(tp))
+		return PTR_ERR(tp);
+
+	if (is_return) {
+		kp = &tp->rp.kp;
+		tp->rp.handler = kretprobe_trace_func;
+	} else {
+		kp = &tp->kp;
+		tp->kp.pre_handler = kprobe_trace_func;
+	}
+
+	if (tp->symbol) {
+		kp->symbol_name = tp->symbol;
+		kp->offset = offset;
+	} else
+		kp->addr = addr;
+
+	/* parse arguments */
+	argc -= 2; argv += 2; ret = 0;
+	for (i = 0; i < argc && i < TRACE_KPROBE_ARGS; i++) {
+		if (strlen(argv[i]) > MAX_ARGSTR_LEN) {
+			pr_info("Argument%d(%s) is too long.\n", i, argv[i]);
+			ret = -ENOSPC;
+			goto error;
+		}
+		ret = parse_trace_arg(argv[i], &tp->args[i], is_return);
+		if (ret)
+			goto error;
+	}
+	tp->nr_args = i;
+
+	ret = register_trace_probe(tp);
+	if (ret)
+		goto error;
+	return 0;
+
+error:
+	free_trace_probe(tp);
+	return ret;
+}
+
+static void cleanup_all_probes(void)
+{
+	struct trace_probe *tp;
+	mutex_lock(&probe_lock);
+	/* TODO: Use batch unregistration */
+	while (!list_empty(&probe_list)) {
+		tp = list_entry(probe_list.next, struct trace_probe, list);
+		unregister_trace_probe(tp);
+		free_trace_probe(tp);
+	}
+	mutex_unlock(&probe_lock);
+}
+
+
+/* Probes listing interfaces */
+static void *probes_seq_start(struct seq_file *m, loff_t *pos)
+{
+	mutex_lock(&probe_lock);
+	return seq_list_start(&probe_list, *pos);
+}
+
+static void *probes_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	return seq_list_next(v, &probe_list, pos);
+}
+
+static void probes_seq_stop(struct seq_file *m, void *v)
+{
+	mutex_unlock(&probe_lock);
+}
+
+static int probes_seq_show(struct seq_file *m, void *v)
+{
+	struct trace_probe *tp = v;
+	int i, ret;
+	char buf[MAX_ARGSTR_LEN + 1];
+
+	if (tp == NULL)
+		return 0;
+
+	seq_printf(m, "%c", probe_is_return(tp) ? 'r' : 'p');
+	if (tp->call.name)
+		seq_printf(m, ":%s", tp->call.name);
+
+	if (tp->symbol)
+		seq_printf(m, " %s%+ld", probe_symbol(tp), probe_offset(tp));
+	else
+		seq_printf(m, " 0x%p", probe_address(tp));
+
+	for (i = 0; i < tp->nr_args; i++) {
+		ret = trace_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
+		if (ret) {
+			pr_warning("Argument%d is too long.\n", i);
+			break;
+		}
+		seq_printf(m, " %s", buf);
+	}
+	seq_printf(m, "\n");
+	return 0;
+}
+
+static const struct seq_operations probes_seq_op = {
+	.start  = probes_seq_start,
+	.next   = probes_seq_next,
+	.stop   = probes_seq_stop,
+	.show   = probes_seq_show
+};
+
+static int probes_open(struct inode *inode, struct file *file)
+{
+	if ((file->f_mode & FMODE_WRITE) &&
+	    !(file->f_flags & O_APPEND))
+		cleanup_all_probes();
+
+	return seq_open(file, &probes_seq_op);
+}
+
+static int command_trace_probe(const char *buf)
+{
+	char **argv;
+	int argc = 0, ret = 0;
+
+	argv = argv_split(GFP_KERNEL, buf, &argc);
+	if (!argv)
+		return -ENOMEM;
+
+	if (argc)
+		ret = create_trace_probe(argc, argv);
+
+	argv_free(argv);
+	return ret;
+}
+
+#define WRITE_BUFSIZE 128
+
+static ssize_t probes_write(struct file *file, const char __user *buffer,
+			    size_t count, loff_t *ppos)
+{
+	char *kbuf, *tmp;
+	int ret;
+	size_t done;
+	size_t size;
+
+	if (!count || count < 0)
+		return 0;
+
+	kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	ret = done = 0;
+	do {
+		size = count - done;
+		if (size > WRITE_BUFSIZE)
+			size = WRITE_BUFSIZE;
+		if (copy_from_user(kbuf, buffer + done, size)) {
+			ret = -EFAULT;
+			goto out;
+		}
+		kbuf[size] = '\0';
+		tmp = strchr(kbuf, '\n');
+		if (!tmp) {
+			pr_warning("Line length is too long: "
+				   "Should be less than %d.", WRITE_BUFSIZE);
+			ret = -EINVAL;
+			goto out;
+		}
+		*tmp = '\0';
+		size = tmp - kbuf + 1;
+		done += size;
+		/* Remove comments */
+		tmp = strchr(kbuf, '#');
+		if (tmp)
+			*tmp = '\0';
+
+		ret = command_trace_probe(kbuf);
+		if (ret)
+			goto out;
+
+	} while (done < count);
+	ret = done;
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static const struct file_operations kprobe_events_ops = {
+	.owner          = THIS_MODULE,
+	.open           = probes_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = seq_release,
+	.write		= probes_write,
+};
+
+/* Kprobe handler */
+static __kprobes int kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
+{
+	struct trace_probe *tp = container_of(kp, struct trace_probe, kp);
+	struct kprobe_trace_entry *entry;
+	struct ring_buffer_event *event;
+	int size, i, pc;
+	unsigned long irq_flags;
+	struct ftrace_event_call *call = &event_kprobe;
+	if (&tp->call.name)
+		call = &tp->call;
+
+	local_save_flags(irq_flags);
+	pc = preempt_count();
+
+	size = sizeof(struct kprobe_trace_entry) -
+	       (sizeof(unsigned long) * (TRACE_KPROBE_ARGS - tp->nr_args));
+
+	event = trace_current_buffer_lock_reserve(TRACE_KPROBE, size,
+						  irq_flags, pc);
+	if (!event)
+		return 0;
+
+	entry = ring_buffer_event_data(event);
+	entry->nargs = tp->nr_args;
+	entry->ip = (unsigned long)kp->addr;
+	for (i = 0; i < tp->nr_args; i++)
+		entry->args[i] = call_fetch(&tp->args[i], regs);
+
+	if (!filter_current_check_discard(call, entry, event))
+		trace_nowake_buffer_unlock_commit(event, irq_flags, pc);
+	return 0;
+}
+
+/* Kretprobe handler */
+static __kprobes int kretprobe_trace_func(struct kretprobe_instance *ri,
+					  struct pt_regs *regs)
+{
+	struct trace_probe *tp = container_of(ri->rp, struct trace_probe, rp);
+	struct kretprobe_trace_entry *entry;
+	struct ring_buffer_event *event;
+	int size, i, pc;
+	unsigned long irq_flags;
+	struct ftrace_event_call *call = &event_kretprobe;
+	if (&tp->call.name)
+		call = &tp->call;
+
+	local_save_flags(irq_flags);
+	pc = preempt_count();
+
+	size = sizeof(struct kretprobe_trace_entry) -
+	       (sizeof(unsigned long) * (TRACE_KPROBE_ARGS - tp->nr_args));
+
+	event = trace_current_buffer_lock_reserve(TRACE_KRETPROBE, size,
+						  irq_flags, pc);
+	if (!event)
+		return 0;
+
+	entry = ring_buffer_event_data(event);
+	entry->nargs = tp->nr_args;
+	entry->func = (unsigned long)probe_address(tp);
+	entry->ret_ip = (unsigned long)ri->ret_addr;
+	for (i = 0; i < tp->nr_args; i++)
+		entry->args[i] = call_fetch(&tp->args[i], regs);
+
+	if (!filter_current_check_discard(call, entry, event))
+		trace_nowake_buffer_unlock_commit(event, irq_flags, pc);
+
+	return 0;
+}
+
+/* Event entry printers */
+enum print_line_t
+print_kprobe_event(struct trace_iterator *iter, int flags)
+{
+	struct kprobe_trace_entry *field;
+	struct trace_seq *s = &iter->seq;
+	int i;
+
+	trace_assign_type(field, iter->ent);
+
+	if (!seq_print_ip_sym(s, field->ip, flags | TRACE_ITER_SYM_OFFSET))
+		goto partial;
+
+	if (!trace_seq_puts(s, ":"))
+		goto partial;
+
+	for (i = 0; i < field->nargs; i++)
+		if (!trace_seq_printf(s, " 0x%lx", field->args[i]))
+			goto partial;
+
+	if (!trace_seq_puts(s, "\n"))
+		goto partial;
+
+	return TRACE_TYPE_HANDLED;
+partial:
+	return TRACE_TYPE_PARTIAL_LINE;
+}
+
+enum print_line_t
+print_kretprobe_event(struct trace_iterator *iter, int flags)
+{
+	struct kretprobe_trace_entry *field;
+	struct trace_seq *s = &iter->seq;
+	int i;
+
+	trace_assign_type(field, iter->ent);
+
+	if (!seq_print_ip_sym(s, field->ret_ip, flags | TRACE_ITER_SYM_OFFSET))
+		goto partial;
+
+	if (!trace_seq_puts(s, " <- "))
+		goto partial;
+
+	if (!seq_print_ip_sym(s, field->func, flags & ~TRACE_ITER_SYM_OFFSET))
+		goto partial;
+
+	if (!trace_seq_puts(s, ":"))
+		goto partial;
+
+	for (i = 0; i < field->nargs; i++)
+		if (!trace_seq_printf(s, " 0x%lx", field->args[i]))
+			goto partial;
+
+	if (!trace_seq_puts(s, "\n"))
+		goto partial;
+
+	return TRACE_TYPE_HANDLED;
+partial:
+	return TRACE_TYPE_PARTIAL_LINE;
+}
+
+static struct trace_event kprobe_trace_event = {
+	.type	 	= TRACE_KPROBE,
+	.trace		= print_kprobe_event,
+};
+
+static struct trace_event kretprobe_trace_event = {
+	.type	 	= TRACE_KRETPROBE,
+	.trace		= print_kretprobe_event,
+};
+
+static int probe_event_enable(struct ftrace_event_call *call)
+{
+	struct trace_probe *tp = container_of(call, struct trace_probe, call);
+	if (probe_is_return(tp))
+		return enable_kretprobe(&tp->rp);
+	else
+		return enable_kprobe(&tp->kp);
+}
+
+static void probe_event_disable(struct ftrace_event_call *call)
+{
+	struct trace_probe *tp = container_of(call, struct trace_probe, call);
+	if (probe_is_return(tp))
+		disable_kretprobe(&tp->rp);
+	else
+		disable_kprobe(&tp->kp);
+}
+
+static int probe_event_raw_init(struct ftrace_event_call *event_call)
+{
+	INIT_LIST_HEAD(&event_call->fields);
+	init_preds(event_call);
+	return 0;
+}
+
+#undef DEFINE_FIELD
+#define DEFINE_FIELD(type, item, name, is_signed)			\
+	do {								\
+		ret = trace_define_field(event_call, #type, name,	\
+					 offsetof(typeof(field), item),	\
+					 sizeof(field.item), is_signed);\
+		if (ret)						\
+			return ret;					\
+	} while (0)
+
+static int kprobe_event_define_fields(struct ftrace_event_call *event_call)
+{
+	int ret, i;
+	struct kprobe_trace_entry field;
+	char buf[MAX_ARGSTR_LEN + 1];
+	struct trace_probe *tp = container_of(event_call,
+					      struct trace_probe, call);
+
+	__common_field(int, type, 1);
+	__common_field(unsigned char, flags, 0);
+	__common_field(unsigned char, preempt_count, 0);
+	__common_field(int, pid, 1);
+	__common_field(int, tgid, 1);
+
+	DEFINE_FIELD(unsigned long, ip, "ip", 0);
+	DEFINE_FIELD(int, nargs, "nargs", 1);
+	for (i = 0; i < tp->nr_args; i++) {
+		/* Set argN as a field */
+		sprintf(buf, "arg%d", i);
+		DEFINE_FIELD(unsigned long, args[i], buf, 0);
+		/* Set argument string as an alias field */
+		ret = trace_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
+		if (ret)
+			return ret;
+		DEFINE_FIELD(unsigned long, args[i], buf, 0);
+	}
+	return 0;
+}
+
+static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
+{
+	int ret, i;
+	struct kretprobe_trace_entry field;
+	char buf[MAX_ARGSTR_LEN + 1];
+	struct trace_probe *tp = container_of(event_call,
+					      struct trace_probe, call);
+
+	__common_field(int, type, 1);
+	__common_field(unsigned char, flags, 0);
+	__common_field(unsigned char, preempt_count, 0);
+	__common_field(int, pid, 1);
+	__common_field(int, tgid, 1);
+
+	DEFINE_FIELD(unsigned long, func, "func", 0);
+	DEFINE_FIELD(unsigned long, ret_ip, "ret_ip", 0);
+	DEFINE_FIELD(int, nargs, "nargs", 1);
+	for (i = 0; i < tp->nr_args; i++) {
+		/* Set argN as a field */
+		sprintf(buf, "arg%d", i);
+		DEFINE_FIELD(unsigned long, args[i], buf, 0);
+		/* Set argument string as an alias field */
+		ret = trace_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
+		if (ret)
+			return ret;
+		DEFINE_FIELD(unsigned long, args[i], buf, 0);
+	}
+	return 0;
+}
+
+static int __probe_event_show_format(struct ftrace_event_call *call,
+				     struct trace_seq *s, const char *fmt,
+				     const char *arg)
+{
+	int i;
+	char buf[MAX_ARGSTR_LEN + 1];
+	struct trace_probe *tp = container_of(call, struct trace_probe, call);
+
+	/* Show aliases */
+	for (i = 0; i < tp->nr_args; i++) {
+		if (trace_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]))
+			return 0;
+		if (!trace_seq_printf(s, "\talias: %s;\toriginal: arg%d;\n",
+				      buf, i))
+			return 0;
+	}
+	/* Show format */
+	if (!trace_seq_printf(s, "\nprint fmt: \"%s", fmt))
+		return 0;
+
+	for (i = 0; i < tp->nr_args; i++)
+		if (!trace_seq_puts(s, " 0x%lx"))
+			return 0;
+
+	if (!trace_seq_printf(s, "\", %s", arg))
+		return 0;
+
+	for (i = 0; i < tp->nr_args; i++)
+		if (!trace_seq_printf(s, ", arg%d", i))
+			return 0;
+
+	return trace_seq_puts(s, "\n");
+}
+
+#undef SHOW_FIELD
+#define SHOW_FIELD(type, item, name)					\
+	do {								\
+		ret = trace_seq_printf(s, "\tfield: " #type " %s;\t"	\
+				"offset:%u;tsize:%u;\n", name,		\
+				(unsigned)offsetof(typeof(field), item),\
+				(unsigned)sizeof(type));		\
+		if (!ret)						\
+			return 0;					\
+	} while (0)
+
+static int kprobe_event_show_format(struct ftrace_event_call *call,
+				    struct trace_seq *s)
+{
+	struct kprobe_trace_entry field __attribute__((unused));
+	int ret, i;
+	char buf[8];
+	struct trace_probe *tp = container_of(call, struct trace_probe, call);
+
+	SHOW_FIELD(unsigned long, ip, "ip");
+	SHOW_FIELD(int, nargs, "nargs");
+
+	/* Show fields */
+	for (i = 0; i < tp->nr_args; i++) {
+		sprintf(buf, "arg%d", i);
+		SHOW_FIELD(unsigned long, args[i], buf);
+	}
+	trace_seq_puts(s, "\n");
+
+	return __probe_event_show_format(call, s, "%lx:", "ip");
+}
+
+static int kretprobe_event_show_format(struct ftrace_event_call *call,
+				       struct trace_seq *s)
+{
+	struct kretprobe_trace_entry field __attribute__((unused));
+	int ret, i;
+	char buf[8];
+	struct trace_probe *tp = container_of(call, struct trace_probe, call);
+
+	SHOW_FIELD(unsigned long, func, "func");
+	SHOW_FIELD(unsigned long, ret_ip, "ret_ip");
+	SHOW_FIELD(int, nargs, "nargs");
+
+	/* Show fields */
+	for (i = 0; i < tp->nr_args; i++) {
+		sprintf(buf, "arg%d", i);
+		SHOW_FIELD(unsigned long, args[i], buf);
+	}
+	trace_seq_puts(s, "\n");
+
+	return __probe_event_show_format(call, s, "%lx <- %lx:",
+					  "func, ret_ip");
+}
+
+static int register_probe_event(struct trace_probe *tp)
+{
+	struct ftrace_event_call *call = &tp->call;
+	int ret;
+
+	/* Initialize ftrace_event_call */
+	call->system = "kprobes";
+	if (probe_is_return(tp)) {
+		call->event = &kretprobe_trace_event;
+		call->id = TRACE_KRETPROBE;
+		call->raw_init = probe_event_raw_init;
+		call->show_format = kretprobe_event_show_format;
+		call->define_fields = kretprobe_event_define_fields;
+	} else {
+		call->event = &kprobe_trace_event;
+		call->id = TRACE_KPROBE;
+		call->raw_init = probe_event_raw_init;
+		call->show_format = kprobe_event_show_format;
+		call->define_fields = kprobe_event_define_fields;
+	}
+	call->enabled = 1;
+	call->regfunc = probe_event_enable;
+	call->unregfunc = probe_event_disable;
+	ret = trace_add_event_call(call);
+	if (ret)
+		pr_info("Failed to register kprobe event: %s\n", call->name);
+	return ret;
+}
+
+static void unregister_probe_event(struct trace_probe *tp)
+{
+	/*
+	 * Prevent to unregister event itself because the event is shared
+	 * among other probes.
+	 */
+	tp->call.event = NULL;
+	trace_remove_event_call(&tp->call);
+}
+
+/* Make a debugfs interface for controling probe points */
+static __init int init_kprobe_trace(void)
+{
+	struct dentry *d_tracer;
+	struct dentry *entry;
+	int ret;
+
+	ret = register_ftrace_event(&kprobe_trace_event);
+	if (!ret) {
+		pr_warning("Could not register kprobe_trace_event type.\n");
+		return 0;
+	}
+	ret = register_ftrace_event(&kretprobe_trace_event);
+	if (!ret) {
+		pr_warning("Could not register kretprobe_trace_event type.\n");
+		return 0;
+	}
+
+	d_tracer = tracing_init_dentry();
+	if (!d_tracer)
+		return 0;
+
+	entry = debugfs_create_file("kprobe_events", 0644, d_tracer,
+				    NULL, &kprobe_events_ops);
+
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'kprobe_events' entry\n");
+	return 0;
+}
+fs_initcall(init_kprobe_trace);
+
+
+#ifdef CONFIG_FTRACE_STARTUP_TEST
+
+static int kprobe_trace_selftest_target(int a1, int a2, int a3,
+					int a4, int a5, int a6)
+{
+	return a1 + a2 + a3 + a4 + a5 + a6;
+}
+
+static __init int kprobe_trace_self_tests_init(void)
+{
+	int ret;
+	int (*target)(int, int, int, int, int, int);
+	target = kprobe_trace_selftest_target;
+
+	pr_info("Testing kprobe tracing: ");
+
+	ret = command_trace_probe("p:testprobe kprobe_trace_selftest_target "
+				  "a1 a2 a3 a4 a5 a6");
+	if (WARN_ON_ONCE(ret))
+		pr_warning("error enabling function entry\n");
+
+	ret = command_trace_probe("r:testprobe2 kprobe_trace_selftest_target "
+				  "ra rv");
+	if (WARN_ON_ONCE(ret))
+		pr_warning("error enabling function return\n");
+
+	ret = target(1, 2, 3, 4, 5, 6);
+
+	cleanup_all_probes();
+
+	pr_cont("OK\n");
+	return 0;
+}
+
+late_initcall(kprobe_trace_self_tests_init);
+
+#endif


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx
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