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

[Frederic Weisbecker]

On Tue, Jun 30, 2009 at 09:09:23PM -0400, Masami Hiramatsu wrote:
> 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).
> +



I'm looking forward to use it for debugging :)



> 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];



I see that you actually make use of arg as a dynamic sizeable
array.
For clarity, args[TRACE_KPROBE_ARGS] could be args[0].

It's just a neat and wouldn't affect the code nor the data
but would be clearer for readers of that code.



> +};
> +
> +struct kretprobe_trace_entry {
> +	struct trace_entry	ent;
> +	unsigned long		func;
> +	unsigned long		ret_ip;
> +	int			nargs;
> +	unsigned long		args[TRACE_KPROBE_ARGS];
> +};


ditto


  
>  /*
>   * 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));


You seem to often use unsigned as an implicit type.
Would be better to explicitly use unsigned int.



Anyway, I guess we can merge it in -tip and give it a try.

Thanks,
Frederic.


> +}
> +
> +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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