linux-stable/kernel/trace/trace_kprobe.c

/*
 * Kprobes-based tracing events
 *
 * Created by Masami Hiramatsu <mhiramat@redhat.com>
 *
 * 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 <linux/perf_event.h>

#include "trace.h"
#include "trace_output.h"

#define MAX_TRACE_ARGS 128
#define MAX_ARGSTR_LEN 63
#define MAX_EVENT_NAME_LEN 64
#define KPROBE_EVENT_SYSTEM "kprobes"

/* Reserved field names */
#define FIELD_STRING_IP "__probe_ip"
#define FIELD_STRING_NARGS "__probe_nargs"
#define FIELD_STRING_RETIP "__probe_ret_ip"
#define FIELD_STRING_FUNC "__probe_func"

const char *reserved_field_names[] = {
	"common_type",
	"common_flags",
	"common_preempt_count",
	"common_pid",
	"common_tgid",
	"common_lock_depth",
	FIELD_STRING_IP,
	FIELD_STRING_NARGS,
	FIELD_STRING_RETIP,
	FIELD_STRING_FUNC,
};

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 int)((unsigned long)offset));
}

static __kprobes unsigned long fetch_stack(struct pt_regs *regs,
					   void *num)
{
	return regs_get_kernel_stack_nth(regs,
					 (unsigned int)((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 int)((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_stack_address(struct pt_regs *regs,
						   void *dummy)
{
	return kernel_stack_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 event core functions
 */

struct probe_arg {
	struct fetch_func	fetch;
	const char		*name;
};

/* Flags for trace_probe */
#define TP_FLAG_TRACE	1
#define TP_FLAG_PROFILE	2

struct trace_probe {
	struct list_head	list;
	struct kretprobe	rp;	/* Use rp.kp for kprobe use */
	unsigned long 		nhit;
	unsigned int		flags;	/* For TP_FLAG_* */
	const char		*symbol;	/* symbol name */
	struct ftrace_event_call	call;
	struct trace_event		event;
	unsigned int		nr_args;
	struct probe_arg	args[];
};

#define SIZEOF_TRACE_PROBE(n)			\
	(offsetof(struct trace_probe, args) +	\
	(sizeof(struct probe_arg) * (n)))

static __kprobes int probe_is_return(struct trace_probe *tp)
{
	return tp->rp.handler != NULL;
}

static __kprobes const char *probe_symbol(struct trace_probe *tp)
{
	return tp->symbol ? tp->symbol : "unknown";
}

static int probe_arg_string(char *buf, size_t n, struct fetch_func *ff)
{
	int ret = -EINVAL;

	if (ff->func == fetch_argument)
		ret = snprintf(buf, n, "$arg%lu", (unsigned long)ff->data);
	else if (ff->func == fetch_register) {
		const char *name;
		name = regs_query_register_name((unsigned int)((long)ff->data));
		ret = snprintf(buf, n, "%%%s", name);
	} else if (ff->func == fetch_stack)
		ret = snprintf(buf, n, "$stack%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;
		if (sc->offset)
			ret = snprintf(buf, n, "@%s%+ld", sc->symbol,
					sc->offset);
		else
			ret = snprintf(buf, n, "@%s", sc->symbol);
	} else if (ff->func == fetch_retvalue)
		ret = snprintf(buf, n, "$retval");
	else if (ff->func == fetch_stack_address)
		ret = snprintf(buf, n, "$stack");
	else if (ff->func == fetch_indirect) {
		struct indirect_fetch_data *id = ff->data;
		size_t l = 0;
		ret = snprintf(buf, n, "%+ld(", id->offset);
		if (ret >= n)
			goto end;
		l += ret;
		ret = probe_arg_string(buf + l, n - l, &id->orig);
		if (ret < 0)
			goto end;
		l += ret;
		ret = snprintf(buf + l, n - l, ")");
		ret += l;
	}
end:
	if (ret >= n)
		return -ENOSPC;
	return ret;
}

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 int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
static int kretprobe_dispatcher(struct kretprobe_instance *ri,
				struct pt_regs *regs);

/* Check the name is good for event/group */
static int check_event_name(const char *name)
{
	if (!isalpha(*name) && *name != '_')
		return 0;
	while (*++name != '\0') {
		if (!isalpha(*name) && !isdigit(*name) && *name != '_')
			return 0;
	}
	return 1;
}

/*
 * Allocate new trace_probe and initialize it (including kprobes).
 */
static struct trace_probe *alloc_trace_probe(const char *group,
					     const char *event,
					     void *addr,
					     const char *symbol,
					     unsigned long offs,
					     int nargs, int is_return)
{
	struct trace_probe *tp;
	int ret = -ENOMEM;

	tp = kzalloc(SIZEOF_TRACE_PROBE(nargs), GFP_KERNEL);
	if (!tp)
		return ERR_PTR(ret);

	if (symbol) {
		tp->symbol = kstrdup(symbol, GFP_KERNEL);
		if (!tp->symbol)
			goto error;
		tp->rp.kp.symbol_name = tp->symbol;
		tp->rp.kp.offset = offs;
	} else
		tp->rp.kp.addr = addr;

	if (is_return)
		tp->rp.handler = kretprobe_dispatcher;
	else
		tp->rp.kp.pre_handler = kprobe_dispatcher;

	if (!event || !check_event_name(event)) {
		ret = -EINVAL;
		goto error;
	}

	tp->call.name = kstrdup(event, GFP_KERNEL);
	if (!tp->call.name)
		goto error;

	if (!group || !check_event_name(group)) {
		ret = -EINVAL;
		goto error;
	}

	tp->call.system = kstrdup(group, GFP_KERNEL);
	if (!tp->call.system)
		goto error;

	INIT_LIST_HEAD(&tp->list);
	return tp;
error:
	kfree(tp->call.name);
	kfree(tp->symbol);
	kfree(tp);
	return ERR_PTR(ret);
}

static void free_probe_arg(struct probe_arg *arg)
{
	if (arg->fetch.func == fetch_symbol)
		free_symbol_cache(arg->fetch.data);
	else if (arg->fetch.func == fetch_indirect)
		free_indirect_fetch_data(arg->fetch.data);
	kfree(arg->name);
}

static void free_trace_probe(struct trace_probe *tp)
{
	int i;

	for (i = 0; i < tp->nr_args; i++)
		free_probe_arg(&tp->args[i]);

	kfree(tp->call.system);
	kfree(tp->call.name);
	kfree(tp->symbol);
	kfree(tp);
}

static struct trace_probe *find_probe_event(const char *event,
					    const char *group)
{
	struct trace_probe *tp;

	list_for_each_entry(tp, &probe_list, list)
		if (strcmp(tp->call.name, event) == 0 &&
		    strcmp(tp->call.system, group) == 0)
			return tp;
	return NULL;
}

/* Unregister a trace_probe and probe_event: call with locking probe_lock */
static void unregister_trace_probe(struct trace_probe *tp)
{
	if (probe_is_return(tp))
		unregister_kretprobe(&tp->rp);
	else
		unregister_kprobe(&tp->rp.kp);
	list_del(&tp->list);
	unregister_probe_event(tp);
}

/* 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);

	/* register as an event */
	old_tp = find_probe_event(tp->call.name, tp->call.system);
	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);
		goto end;
	}

	tp->rp.kp.flags |= KPROBE_FLAG_DISABLED;
	if (probe_is_return(tp))
		ret = register_kretprobe(&tp->rp);
	else
		ret = register_kprobe(&tp->rp.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",
				   tp->rp.kp.addr);
			ret = -EINVAL;
		}
		unregister_probe_event(tp);
	} else
		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, unsigned long *offset)
{
	char *tmp;
	int ret;

	if (!offset)
		return -EINVAL;

	tmp = strchr(symbol, '+');
	if (tmp) {
		/* skip sign because strict_strtol doesn't accept '+' */
		ret = strict_strtoul(tmp + 1, 0, offset);
		if (ret)
			return ret;
		*tmp = '\0';
	} else
		*offset = 0;
	return 0;
}

#define PARAM_MAX_ARGS 16
#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))

static int parse_probe_vars(char *arg, struct fetch_func *ff, int is_return)
{
	int ret = 0;
	unsigned long param;

	if (strcmp(arg, "retval") == 0) {
		if (is_return) {
			ff->func = fetch_retvalue;
			ff->data = NULL;
		} else
			ret = -EINVAL;
	} else if (strncmp(arg, "stack", 5) == 0) {
		if (arg[5] == '\0') {
			ff->func = fetch_stack_address;
			ff->data = NULL;
		} else if (isdigit(arg[5])) {
			ret = strict_strtoul(arg + 5, 10, &param);
			if (ret || param > PARAM_MAX_STACK)
				ret = -EINVAL;
			else {
				ff->func = fetch_stack;
				ff->data = (void *)param;
			}
		} else
			ret = -EINVAL;
	} else if (strncmp(arg, "arg", 3) == 0 && isdigit(arg[3])) {
		ret = strict_strtoul(arg + 3, 10, &param);
		if (ret || param > PARAM_MAX_ARGS)
			ret = -EINVAL;
		else {
			ff->func = fetch_argument;
			ff->data = (void *)param;
		}
	} else
		ret = -EINVAL;
	return ret;
}

/* Recursive argument parser */
static int __parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
{
	int ret = 0;
	unsigned long param;
	long offset;
	char *tmp;

	switch (arg[0]) {
	case '$':
		ret = parse_probe_vars(arg + 1, ff, is_return);
		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 '@':	/* 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_probe_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;
}

/* String length checking wrapper */
static int parse_probe_arg(char *arg, struct fetch_func *ff, int is_return)
{
	if (strlen(arg) > MAX_ARGSTR_LEN) {
		pr_info("Argument is too long.: %s\n",  arg);
		return -ENOSPC;
	}
	return __parse_probe_arg(arg, ff, is_return);
}

/* Return 1 if name is reserved or already used by another argument */
static int conflict_field_name(const char *name,
			       struct probe_arg *args, int narg)
{
	int i;
	for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
		if (strcmp(reserved_field_names[i], name) == 0)
			return 1;
	for (i = 0; i < narg; i++)
		if (strcmp(args[i].name, name) == 0)
			return 1;
	return 0;
}

static int create_trace_probe(int argc, char **argv)
{
	/*
	 * Argument syntax:
	 *  - Add kprobe: p[:[GRP/]EVENT] KSYM[+OFFS]|KADDR [FETCHARGS]
	 *  - Add kretprobe: r[:[GRP/]EVENT] KSYM[+0] [FETCHARGS]
	 * Fetch args:
	 *  $argN	: fetch Nth of function argument. (N:0-)
	 *  $retval	: fetch return value
	 *  $stack	: fetch stack address
	 *  $stackN	: 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.
	 * Alias name of args:
	 *  NAME=FETCHARG : set NAME as alias of FETCHARG.
	 */
	struct trace_probe *tp;
	int i, ret = 0;
	int is_return = 0, is_delete = 0;
	char *symbol = NULL, *event = NULL, *arg = NULL, *group = NULL;
	unsigned long offset = 0;
	void *addr = NULL;
	char buf[MAX_EVENT_NAME_LEN];

	/* argc must be >= 1 */
	if (argv[0][0] == 'p')
		is_return = 0;
	else if (argv[0][0] == 'r')
		is_return = 1;
	else if (argv[0][0] == '-')
		is_delete = 1;
	else {
		pr_info("Probe definition must be started with 'p', 'r' or"
			" '-'.\n");
		return -EINVAL;
	}

	if (argv[0][1] == ':') {
		event = &argv[0][2];
		if (strchr(event, '/')) {
			group = event;
			event = strchr(group, '/') + 1;
			event[-1] = '\0';
			if (strlen(group) == 0) {
				pr_info("Group name is not specifiled\n");
				return -EINVAL;
			}
		}
		if (strlen(event) == 0) {
			pr_info("Event name is not specifiled\n");
			return -EINVAL;
		}
	}
	if (!group)
		group = KPROBE_EVENT_SYSTEM;

	if (is_delete) {
		if (!event) {
			pr_info("Delete command needs an event name.\n");
			return -EINVAL;
		}
		tp = find_probe_event(event, group);
		if (!tp) {
			pr_info("Event %s/%s doesn't exist.\n", group, event);
			return -ENOENT;
		}
		/* delete an event */
		unregister_trace_probe(tp);
		free_trace_probe(tp);
		return 0;
	}

	if (argc < 2) {
		pr_info("Probe point is not specified.\n");
		return -EINVAL;
	}
	if (isdigit(argv[1][0])) {
		if (is_return) {
			pr_info("Return probe point must be a symbol.\n");
			return -EINVAL;
		}
		/* an address specified */
		ret = strict_strtoul(&argv[0][2], 0, (unsigned long *)&addr);
		if (ret) {
			pr_info("Failed to parse address.\n");
			return ret;
		}
	} else {
		/* a symbol specified */
		symbol = argv[1];
		/* TODO: support .init module functions */
		ret = split_symbol_offset(symbol, &offset);
		if (ret) {
			pr_info("Failed to parse symbol.\n");
			return ret;
		}
		if (offset && is_return) {
			pr_info("Return probe must be used without offset.\n");
			return -EINVAL;
		}
	}
	argc -= 2; argv += 2;

	/* setup a probe */
	if (!event) {
		/* Make a new event name */
		if (symbol)
			snprintf(buf, MAX_EVENT_NAME_LEN, "%c_%s_%ld",
				 is_return ? 'r' : 'p', symbol, offset);
		else
			snprintf(buf, MAX_EVENT_NAME_LEN, "%c_0x%p",
				 is_return ? 'r' : 'p', addr);
		event = buf;
	}
	tp = alloc_trace_probe(group, event, addr, symbol, offset, argc,
			       is_return);
	if (IS_ERR(tp)) {
		pr_info("Failed to allocate trace_probe.(%d)\n",
			(int)PTR_ERR(tp));
		return PTR_ERR(tp);
	}

	/* parse arguments */
	ret = 0;
	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
		/* Parse argument name */
		arg = strchr(argv[i], '=');
		if (arg)
			*arg++ = '\0';
		else
			arg = argv[i];

		if (conflict_field_name(argv[i], tp->args, i)) {
			pr_info("Argument%d name '%s' conflicts with "
				"another field.\n", i, argv[i]);
			ret = -EINVAL;
			goto error;
		}

		tp->args[i].name = kstrdup(argv[i], GFP_KERNEL);
		if (!tp->args[i].name) {
			pr_info("Failed to allocate argument%d name '%s'.\n",
				i, argv[i]);
			ret = -ENOMEM;
			goto error;
		}

		/* Parse fetch argument */
		ret = parse_probe_arg(arg, &tp->args[i].fetch, is_return);
		if (ret) {
			pr_info("Parse error at argument%d. (%d)\n", i, ret);
			kfree(tp->args[i].name);
			goto error;
		}

		tp->nr_args++;
	}

	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];

	seq_printf(m, "%c", probe_is_return(tp) ? 'r' : 'p');
	seq_printf(m, ":%s/%s", tp->call.system, tp->call.name);

	if (!tp->symbol)
		seq_printf(m, " 0x%p", tp->rp.kp.addr);
	else if (tp->rp.kp.offset)
		seq_printf(m, " %s+%u", probe_symbol(tp), tp->rp.kp.offset);
	else
		seq_printf(m, " %s", probe_symbol(tp));

	for (i = 0; i < tp->nr_args; i++) {
		ret = probe_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i].fetch);
		if (ret < 0) {
			pr_warning("Argument%d decoding error(%d).\n", i, ret);
			return ret;
		}
		seq_printf(m, " %s=%s", tp->args[i].name, 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_TRUNC))
		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;

	kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
	if (!kbuf)
		return -ENOMEM;

	ret = done = 0;
	while (done < count) {
		size = count - done;
		if (size >= WRITE_BUFSIZE)
			size = WRITE_BUFSIZE - 1;
		if (copy_from_user(kbuf, buffer + done, size)) {
			ret = -EFAULT;
			goto out;
		}
		kbuf[size] = '\0';
		tmp = strchr(kbuf, '\n');
		if (tmp) {
			*tmp = '\0';
			size = tmp - kbuf + 1;
		} else if (done + size < count) {
			pr_warning("Line length is too long: "
				   "Should be less than %d.", WRITE_BUFSIZE);
			ret = -EINVAL;
			goto out;
		}
		done += size;
		/* Remove comments */
		tmp = strchr(kbuf, '#');
		if (tmp)
			*tmp = '\0';

		ret = command_trace_probe(kbuf);
		if (ret)
			goto out;
	}
	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,
};

/* Probes profiling interfaces */
static int probes_profile_seq_show(struct seq_file *m, void *v)
{
	struct trace_probe *tp = v;

	seq_printf(m, "  %-44s %15lu %15lu\n", tp->call.name, tp->nhit,
		   tp->rp.kp.nmissed);

	return 0;
}

static const struct seq_operations profile_seq_op = {
	.start  = probes_seq_start,
	.next   = probes_seq_next,
	.stop   = probes_seq_stop,
	.show   = probes_profile_seq_show
};

static int profile_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &profile_seq_op);
}

static const struct file_operations kprobe_profile_ops = {
	.owner          = THIS_MODULE,
	.open           = profile_open,
	.read           = seq_read,
	.llseek         = seq_lseek,
	.release        = seq_release,
};

/* 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, rp.kp);
	struct kprobe_trace_entry *entry;
	struct ring_buffer_event *event;
	struct ring_buffer *buffer;
	int size, i, pc;
	unsigned long irq_flags;
	struct ftrace_event_call *call = &tp->call;

	tp->nhit++;

	local_save_flags(irq_flags);
	pc = preempt_count();

	size = SIZEOF_KPROBE_TRACE_ENTRY(tp->nr_args);

	event = trace_current_buffer_lock_reserve(&buffer, call->id, 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].fetch, regs);

	if (!filter_current_check_discard(buffer, call, entry, event))
		trace_nowake_buffer_unlock_commit(buffer, 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;
	struct ring_buffer *buffer;
	int size, i, pc;
	unsigned long irq_flags;
	struct ftrace_event_call *call = &tp->call;

	local_save_flags(irq_flags);
	pc = preempt_count();

	size = SIZEOF_KRETPROBE_TRACE_ENTRY(tp->nr_args);

	event = trace_current_buffer_lock_reserve(&buffer, call->id, size,
						  irq_flags, pc);
	if (!event)
		return 0;

	entry = ring_buffer_event_data(event);
	entry->nargs = tp->nr_args;
	entry->func = (unsigned long)tp->rp.kp.addr;
	entry->ret_ip = (unsigned long)ri->ret_addr;
	for (i = 0; i < tp->nr_args; i++)
		entry->args[i] = call_fetch(&tp->args[i].fetch, regs);

	if (!filter_current_check_discard(buffer, call, entry, event))
		trace_nowake_buffer_unlock_commit(buffer, 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;
	struct trace_event *event;
	struct trace_probe *tp;
	int i;

	field = (struct kprobe_trace_entry *)iter->ent;
	event = ftrace_find_event(field->ent.type);
	tp = container_of(event, struct trace_probe, event);

	if (!trace_seq_printf(s, "%s: (", tp->call.name))
		goto partial;

	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, " %s=%lx",
				      tp->args[i].name, 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;
	struct trace_event *event;
	struct trace_probe *tp;
	int i;

	field = (struct kretprobe_trace_entry *)iter->ent;
	event = ftrace_find_event(field->ent.type);
	tp = container_of(event, struct trace_probe, event);

	if (!trace_seq_printf(s, "%s: (", tp->call.name))
		goto partial;

	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, " %s=%lx",
				      tp->args[i].name, field->args[i]))
			goto partial;

	if (!trace_seq_puts(s, "\n"))
		goto partial;

	return TRACE_TYPE_HANDLED;
partial:
	return TRACE_TYPE_PARTIAL_LINE;
}

static int probe_event_enable(struct ftrace_event_call *call)
{
	struct trace_probe *tp = (struct trace_probe *)call->data;

	tp->flags |= TP_FLAG_TRACE;
	if (probe_is_return(tp))
		return enable_kretprobe(&tp->rp);
	else
		return enable_kprobe(&tp->rp.kp);
}

static void probe_event_disable(struct ftrace_event_call *call)
{
	struct trace_probe *tp = (struct trace_probe *)call->data;

	tp->flags &= ~TP_FLAG_TRACE;
	if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
		if (probe_is_return(tp))
			disable_kretprobe(&tp->rp);
		else
			disable_kprobe(&tp->rp.kp);
	}
}

static int probe_event_raw_init(struct ftrace_event_call *event_call)
{
	INIT_LIST_HEAD(&event_call->fields);

	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, \
					 FILTER_OTHER);			\
		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;
	struct trace_probe *tp = (struct trace_probe *)event_call->data;

	DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
	DEFINE_FIELD(int, nargs, FIELD_STRING_NARGS, 1);
	/* Set argument names as fields */
	for (i = 0; i < tp->nr_args; i++)
		DEFINE_FIELD(unsigned long, args[i], tp->args[i].name, 0);
	return 0;
}

static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
{
	int ret, i;
	struct kretprobe_trace_entry field;
	struct trace_probe *tp = (struct trace_probe *)event_call->data;

	DEFINE_FIELD(unsigned long, func, FIELD_STRING_FUNC, 0);
	DEFINE_FIELD(unsigned long, ret_ip, FIELD_STRING_RETIP, 0);
	DEFINE_FIELD(int, nargs, FIELD_STRING_NARGS, 1);
	/* Set argument names as fields */
	for (i = 0; i < tp->nr_args; i++)
		DEFINE_FIELD(unsigned long, args[i], tp->args[i].name, 0);
	return 0;
}

static int __set_print_fmt(struct trace_probe *tp, char *buf, int len)
{
	int i;
	int pos = 0;

	const char *fmt, *arg;

	if (!probe_is_return(tp)) {
		fmt = "(%lx)";
		arg = "REC->" FIELD_STRING_IP;
	} else {
		fmt = "(%lx <- %lx)";
		arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
	}

	/* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)

	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);

	for (i = 0; i < tp->nr_args; i++) {
		pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%%lx",
				tp->args[i].name);
	}

	pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);

	for (i = 0; i < tp->nr_args; i++) {
		pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
				tp->args[i].name);
	}

#undef LEN_OR_ZERO

	/* return the length of print_fmt */
	return pos;
}

static int set_print_fmt(struct trace_probe *tp)
{
	int len;
	char *print_fmt;

	/* First: called with 0 length to calculate the needed length */
	len = __set_print_fmt(tp, NULL, 0);
	print_fmt = kmalloc(len + 1, GFP_KERNEL);
	if (!print_fmt)
		return -ENOMEM;

	/* Second: actually write the @print_fmt */
	__set_print_fmt(tp, print_fmt, len + 1);
	tp->call.print_fmt = print_fmt;

	return 0;
}

#ifdef CONFIG_EVENT_PROFILE

/* Kprobe profile handler */
static __kprobes int kprobe_profile_func(struct kprobe *kp,
					 struct pt_regs *regs)
{
	struct trace_probe *tp = container_of(kp, struct trace_probe, rp.kp);
	struct ftrace_event_call *call = &tp->call;
	struct kprobe_trace_entry *entry;
	struct trace_entry *ent;
	int size, __size, i, pc, __cpu;
	unsigned long irq_flags;
	char *trace_buf;
	char *raw_data;
	int rctx;

	pc = preempt_count();
	__size = SIZEOF_KPROBE_TRACE_ENTRY(tp->nr_args);
	size = ALIGN(__size + sizeof(u32), sizeof(u64));
	size -= sizeof(u32);
	if (WARN_ONCE(size > FTRACE_MAX_PROFILE_SIZE,
		     "profile buffer not large enough"))
		return 0;

	/*
	 * Protect the non nmi buffer
	 * This also protects the rcu read side
	 */
	local_irq_save(irq_flags);

	rctx = perf_swevent_get_recursion_context();
	if (rctx < 0)
		goto end_recursion;

	__cpu = smp_processor_id();

	if (in_nmi())
		trace_buf = rcu_dereference(perf_trace_buf_nmi);
	else
		trace_buf = rcu_dereference(perf_trace_buf);

	if (!trace_buf)
		goto end;

	raw_data = per_cpu_ptr(trace_buf, __cpu);

	/* Zero dead bytes from alignment to avoid buffer leak to userspace */
	*(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
	entry = (struct kprobe_trace_entry *)raw_data;
	ent = &entry->ent;

	tracing_generic_entry_update(ent, irq_flags, pc);
	ent->type = call->id;
	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].fetch, regs);
	perf_tp_event(call->id, entry->ip, 1, entry, size);

end:
	perf_swevent_put_recursion_context(rctx);
end_recursion:
	local_irq_restore(irq_flags);

	return 0;
}

/* Kretprobe profile handler */
static __kprobes int kretprobe_profile_func(struct kretprobe_instance *ri,
					    struct pt_regs *regs)
{
	struct trace_probe *tp = container_of(ri->rp, struct trace_probe, rp);
	struct ftrace_event_call *call = &tp->call;
	struct kretprobe_trace_entry *entry;
	struct trace_entry *ent;
	int size, __size, i, pc, __cpu;
	unsigned long irq_flags;
	char *trace_buf;
	char *raw_data;
	int rctx;

	pc = preempt_count();
	__size = SIZEOF_KRETPROBE_TRACE_ENTRY(tp->nr_args);
	size = ALIGN(__size + sizeof(u32), sizeof(u64));
	size -= sizeof(u32);
	if (WARN_ONCE(size > FTRACE_MAX_PROFILE_SIZE,
		     "profile buffer not large enough"))
		return 0;

	/*
	 * Protect the non nmi buffer
	 * This also protects the rcu read side
	 */
	local_irq_save(irq_flags);

	rctx = perf_swevent_get_recursion_context();
	if (rctx < 0)
		goto end_recursion;

	__cpu = smp_processor_id();

	if (in_nmi())
		trace_buf = rcu_dereference(perf_trace_buf_nmi);
	else
		trace_buf = rcu_dereference(perf_trace_buf);

	if (!trace_buf)
		goto end;

	raw_data = per_cpu_ptr(trace_buf, __cpu);

	/* Zero dead bytes from alignment to avoid buffer leak to userspace */
	*(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
	entry = (struct kretprobe_trace_entry *)raw_data;
	ent = &entry->ent;

	tracing_generic_entry_update(ent, irq_flags, pc);
	ent->type = call->id;
	entry->nargs = tp->nr_args;
	entry->func = (unsigned long)tp->rp.kp.addr;
	entry->ret_ip = (unsigned long)ri->ret_addr;
	for (i = 0; i < tp->nr_args; i++)
		entry->args[i] = call_fetch(&tp->args[i].fetch, regs);
	perf_tp_event(call->id, entry->ret_ip, 1, entry, size);

end:
	perf_swevent_put_recursion_context(rctx);
end_recursion:
	local_irq_restore(irq_flags);

	return 0;
}

static int probe_profile_enable(struct ftrace_event_call *call)
{
	struct trace_probe *tp = (struct trace_probe *)call->data;

	tp->flags |= TP_FLAG_PROFILE;

	if (probe_is_return(tp))
		return enable_kretprobe(&tp->rp);
	else
		return enable_kprobe(&tp->rp.kp);
}

static void probe_profile_disable(struct ftrace_event_call *call)
{
	struct trace_probe *tp = (struct trace_probe *)call->data;

	tp->flags &= ~TP_FLAG_PROFILE;

	if (!(tp->flags & TP_FLAG_TRACE)) {
		if (probe_is_return(tp))
			disable_kretprobe(&tp->rp);
		else
			disable_kprobe(&tp->rp.kp);
	}
}
#endif	/* CONFIG_EVENT_PROFILE */


static __kprobes
int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
{
	struct trace_probe *tp = container_of(kp, struct trace_probe, rp.kp);

	if (tp->flags & TP_FLAG_TRACE)
		kprobe_trace_func(kp, regs);
#ifdef CONFIG_EVENT_PROFILE
	if (tp->flags & TP_FLAG_PROFILE)
		kprobe_profile_func(kp, regs);
#endif	/* CONFIG_EVENT_PROFILE */
	return 0;	/* We don't tweek kernel, so just return 0 */
}

static __kprobes
int kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs)
{
	struct trace_probe *tp = container_of(ri->rp, struct trace_probe, rp);

	if (tp->flags & TP_FLAG_TRACE)
		kretprobe_trace_func(ri, regs);
#ifdef CONFIG_EVENT_PROFILE
	if (tp->flags & TP_FLAG_PROFILE)
		kretprobe_profile_func(ri, regs);
#endif	/* CONFIG_EVENT_PROFILE */
	return 0;	/* We don't tweek kernel, so just return 0 */
}

static int register_probe_event(struct trace_probe *tp)
{
	struct ftrace_event_call *call = &tp->call;
	int ret;

	/* Initialize ftrace_event_call */
	if (probe_is_return(tp)) {
		tp->event.trace = print_kretprobe_event;
		call->raw_init = probe_event_raw_init;
		call->define_fields = kretprobe_event_define_fields;
	} else {
		tp->event.trace = print_kprobe_event;
		call->raw_init = probe_event_raw_init;
		call->define_fields = kprobe_event_define_fields;
	}
	if (set_print_fmt(tp) < 0)
		return -ENOMEM;
	call->event = &tp->event;
	call->id = register_ftrace_event(&tp->event);
	if (!call->id) {
		kfree(call->print_fmt);
		return -ENODEV;
	}
	call->enabled = 0;
	call->regfunc = probe_event_enable;
	call->unregfunc = probe_event_disable;

#ifdef CONFIG_EVENT_PROFILE
	call->profile_enable = probe_profile_enable;
	call->profile_disable = probe_profile_disable;
#endif
	call->data = tp;
	ret = trace_add_event_call(call);
	if (ret) {
		pr_info("Failed to register kprobe event: %s\n", call->name);
		kfree(call->print_fmt);
		unregister_ftrace_event(&tp->event);
	}
	return ret;
}

static void unregister_probe_event(struct trace_probe *tp)
{
	/* tp->event is unregistered in trace_remove_event_call() */
	trace_remove_event_call(&tp->call);
	kfree(tp->call.print_fmt);
}

/* Make a debugfs interface for controling probe points */
static __init int init_kprobe_trace(void)
{
	struct dentry *d_tracer;
	struct dentry *entry;

	d_tracer = tracing_init_dentry();
	if (!d_tracer)
		return 0;

	entry = debugfs_create_file("kprobe_events", 0644, d_tracer,
				    NULL, &kprobe_events_ops);

	/* Event list interface */
	if (!entry)
		pr_warning("Could not create debugfs "
			   "'kprobe_events' entry\n");

	/* Profile interface */
	entry = debugfs_create_file("kprobe_profile", 0444, d_tracer,
				    NULL, &kprobe_profile_ops);

	if (!entry)
		pr_warning("Could not create debugfs "
			   "'kprobe_profile' 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 "
				  "$arg1 $arg2 $arg3 $arg4 $stack $stack0");
	if (WARN_ON_ONCE(ret))
		pr_warning("error enabling function entry\n");

	ret = command_trace_probe("r:testprobe2 kprobe_trace_selftest_target "
				  "$retval");
	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