Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1772 insertions, 0 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
new file mode 100644
index 000000000..36dfea29d
--- /dev/null
+++ b/kernel/trace/trace_kprobe.c
@@ -0,0 +1,1772 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kprobes-based tracing events
+ *
+ * Created by Masami Hiramatsu <mhiramat@redhat.com>
+ *
+ */
+#define pr_fmt(fmt)	"trace_kprobe: " fmt
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/rculist.h>
+#include <linux/error-injection.h>
+
+#include "trace_kprobe_selftest.h"
+#include "trace_probe.h"
+
+#define KPROBE_EVENT_SYSTEM "kprobes"
+#define KRETPROBE_MAXACTIVE_MAX 4096
+
+/**
+ * Kprobe event core functions
+ */
+struct trace_kprobe {
+	struct list_head	list;
+	struct kretprobe	rp;	/* Use rp.kp for kprobe use */
+	unsigned long __percpu *nhit;
+	const char		*symbol;	/* symbol name */
+	struct trace_probe	tp;
+};
+
+#define SIZEOF_TRACE_KPROBE(n)				\
+	(offsetof(struct trace_kprobe, tp.args) +	\
+	(sizeof(struct probe_arg) * (n)))
+
+static nokprobe_inline bool trace_kprobe_is_return(struct trace_kprobe *tk)
+{
+	return tk->rp.handler != NULL;
+}
+
+static nokprobe_inline const char *trace_kprobe_symbol(struct trace_kprobe *tk)
+{
+	return tk->symbol ? tk->symbol : "unknown";
+}
+
+static nokprobe_inline unsigned long trace_kprobe_offset(struct trace_kprobe *tk)
+{
+	return tk->rp.kp.offset;
+}
+
+static nokprobe_inline bool trace_kprobe_has_gone(struct trace_kprobe *tk)
+{
+	return !!(kprobe_gone(&tk->rp.kp));
+}
+
+static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
+						 struct module *mod)
+{
+	int len = strlen(mod->name);
+	const char *name = trace_kprobe_symbol(tk);
+	return strncmp(mod->name, name, len) == 0 && name[len] == ':';
+}
+
+static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
+{
+	char *p;
+	bool ret;
+
+	if (!tk->symbol)
+		return false;
+	p = strchr(tk->symbol, ':');
+	if (!p)
+		return true;
+	*p = '\0';
+	mutex_lock(&module_mutex);
+	ret = !!find_module(tk->symbol);
+	mutex_unlock(&module_mutex);
+	*p = ':';
+
+	return ret;
+}
+
+static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
+{
+	unsigned long nhit = 0;
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		nhit += *per_cpu_ptr(tk->nhit, cpu);
+
+	return nhit;
+}
+
+/* Return 0 if it fails to find the symbol address */
+static nokprobe_inline
+unsigned long trace_kprobe_address(struct trace_kprobe *tk)
+{
+	unsigned long addr;
+
+	if (tk->symbol) {
+		addr = (unsigned long)
+			kallsyms_lookup_name(trace_kprobe_symbol(tk));
+		if (addr)
+			addr += tk->rp.kp.offset;
+	} else {
+		addr = (unsigned long)tk->rp.kp.addr;
+	}
+	return addr;
+}
+
+bool trace_kprobe_on_func_entry(struct trace_event_call *call)
+{
+	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
+
+	return (kprobe_on_func_entry(tk->rp.kp.addr,
+			tk->rp.kp.addr ? NULL : tk->rp.kp.symbol_name,
+			tk->rp.kp.addr ? 0 : tk->rp.kp.offset) == 0);
+}
+
+bool trace_kprobe_error_injectable(struct trace_event_call *call)
+{
+	struct trace_kprobe *tk = (struct trace_kprobe *)call->data;
+
+	return within_error_injection_list(trace_kprobe_address(tk));
+}
+
+static int register_kprobe_event(struct trace_kprobe *tk);
+static int unregister_kprobe_event(struct trace_kprobe *tk);
+
+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);
+
+/* Memory fetching by symbol */
+struct symbol_cache {
+	char		*symbol;
+	long		offset;
+	unsigned long	addr;
+};
+
+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;
+}
+
+void free_symbol_cache(struct symbol_cache *sc)
+{
+	kfree(sc->symbol);
+	kfree(sc);
+}
+
+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;
+}
+
+/*
+ * Kprobes-specific fetch functions
+ */
+#define DEFINE_FETCH_stack(type)					\
+static void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,		\
+					  void *offset, void *dest)	\
+{									\
+	*(type *)dest = (type)regs_get_kernel_stack_nth(regs,		\
+				(unsigned int)((unsigned long)offset));	\
+}									\
+NOKPROBE_SYMBOL(FETCH_FUNC_NAME(stack, type));
+
+DEFINE_BASIC_FETCH_FUNCS(stack)
+/* No string on the stack entry */
+#define fetch_stack_string	NULL
+#define fetch_stack_string_size	NULL
+
+#define DEFINE_FETCH_memory(type)					\
+static void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,		\
+					  void *addr, void *dest)	\
+{									\
+	type retval;							\
+	if (probe_kernel_address(addr, retval))				\
+		*(type *)dest = 0;					\
+	else								\
+		*(type *)dest = retval;					\
+}									\
+NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, type));
+
+DEFINE_BASIC_FETCH_FUNCS(memory)
+/*
+ * Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
+ * length and relative data location.
+ */
+static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
+					    void *addr, void *dest)
+{
+	int maxlen = get_rloc_len(*(u32 *)dest);
+	u8 *dst = get_rloc_data(dest);
+	long ret;
+
+	if (!maxlen)
+		return;
+
+	/*
+	 * Try to get string again, since the string can be changed while
+	 * probing.
+	 */
+	ret = strncpy_from_unsafe(dst, addr, maxlen);
+
+	if (ret < 0) {	/* Failed to fetch string */
+		dst[0] = '\0';
+		*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
+	} else {
+		*(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
+	}
+}
+NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string));
+
+/* Return the length of string -- including null terminal byte */
+static void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
+						 void *addr, void *dest)
+{
+	mm_segment_t old_fs;
+	int ret, len = 0;
+	u8 c;
+
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+
+	do {
+		ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1);
+		len++;
+	} while (c && ret == 0 && len < MAX_STRING_SIZE);
+
+	pagefault_enable();
+	set_fs(old_fs);
+
+	if (ret < 0)	/* Failed to check the length */
+		*(u32 *)dest = 0;
+	else
+		*(u32 *)dest = len;
+}
+NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string_size));
+
+#define DEFINE_FETCH_symbol(type)					\
+void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs, void *data, void *dest)\
+{									\
+	struct symbol_cache *sc = data;					\
+	if (sc->addr)							\
+		fetch_memory_##type(regs, (void *)sc->addr, dest);	\
+	else								\
+		*(type *)dest = 0;					\
+}									\
+NOKPROBE_SYMBOL(FETCH_FUNC_NAME(symbol, type));
+
+DEFINE_BASIC_FETCH_FUNCS(symbol)
+DEFINE_FETCH_symbol(string)
+DEFINE_FETCH_symbol(string_size)
+
+/* kprobes don't support file_offset fetch methods */
+#define fetch_file_offset_u8		NULL
+#define fetch_file_offset_u16		NULL
+#define fetch_file_offset_u32		NULL
+#define fetch_file_offset_u64		NULL
+#define fetch_file_offset_string	NULL
+#define fetch_file_offset_string_size	NULL
+
+/* Fetch type information table */
+static const struct fetch_type kprobes_fetch_type_table[] = {
+	/* Special types */
+	[FETCH_TYPE_STRING] = __ASSIGN_FETCH_TYPE("string", string, string,
+					sizeof(u32), 1, "__data_loc char[]"),
+	[FETCH_TYPE_STRSIZE] = __ASSIGN_FETCH_TYPE("string_size", u32,
+					string_size, sizeof(u32), 0, "u32"),
+	/* Basic types */
+	ASSIGN_FETCH_TYPE(u8,  u8,  0),
+	ASSIGN_FETCH_TYPE(u16, u16, 0),
+	ASSIGN_FETCH_TYPE(u32, u32, 0),
+	ASSIGN_FETCH_TYPE(u64, u64, 0),
+	ASSIGN_FETCH_TYPE(s8,  u8,  1),
+	ASSIGN_FETCH_TYPE(s16, u16, 1),
+	ASSIGN_FETCH_TYPE(s32, u32, 1),
+	ASSIGN_FETCH_TYPE(s64, u64, 1),
+	ASSIGN_FETCH_TYPE_ALIAS(x8,  u8,  u8,  0),
+	ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
+	ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
+	ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
+
+	ASSIGN_FETCH_TYPE_END
+};
+
+/*
+ * Allocate new trace_probe and initialize it (including kprobes).
+ */
+static struct trace_kprobe *alloc_trace_kprobe(const char *group,
+					     const char *event,
+					     void *addr,
+					     const char *symbol,
+					     unsigned long offs,
+					     int maxactive,
+					     int nargs, bool is_return)
+{
+	struct trace_kprobe *tk;
+	int ret = -ENOMEM;
+
+	tk = kzalloc(SIZEOF_TRACE_KPROBE(nargs), GFP_KERNEL);
+	if (!tk)
+		return ERR_PTR(ret);
+
+	tk->nhit = alloc_percpu(unsigned long);
+	if (!tk->nhit)
+		goto error;
+
+	if (symbol) {
+		tk->symbol = kstrdup(symbol, GFP_KERNEL);
+		if (!tk->symbol)
+			goto error;
+		tk->rp.kp.symbol_name = tk->symbol;
+		tk->rp.kp.offset = offs;
+	} else
+		tk->rp.kp.addr = addr;
+
+	if (is_return)
+		tk->rp.handler = kretprobe_dispatcher;
+	else
+		tk->rp.kp.pre_handler = kprobe_dispatcher;
+
+	tk->rp.maxactive = maxactive;
+
+	if (!event || !is_good_name(event)) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	tk->tp.call.class = &tk->tp.class;
+	tk->tp.call.name = kstrdup(event, GFP_KERNEL);
+	if (!tk->tp.call.name)
+		goto error;
+
+	if (!group || !is_good_name(group)) {
+		ret = -EINVAL;
+		goto error;
+	}
+
+	tk->tp.class.system = kstrdup(group, GFP_KERNEL);
+	if (!tk->tp.class.system)
+		goto error;
+
+	INIT_LIST_HEAD(&tk->list);
+	INIT_LIST_HEAD(&tk->tp.files);
+	return tk;
+error:
+	kfree(tk->tp.call.name);
+	kfree(tk->symbol);
+	free_percpu(tk->nhit);
+	kfree(tk);
+	return ERR_PTR(ret);
+}
+
+static void free_trace_kprobe(struct trace_kprobe *tk)
+{
+	int i;
+
+	for (i = 0; i < tk->tp.nr_args; i++)
+		traceprobe_free_probe_arg(&tk->tp.args[i]);
+
+	kfree(tk->tp.call.class->system);
+	kfree(tk->tp.call.name);
+	kfree(tk->symbol);
+	free_percpu(tk->nhit);
+	kfree(tk);
+}
+
+static struct trace_kprobe *find_trace_kprobe(const char *event,
+					      const char *group)
+{
+	struct trace_kprobe *tk;
+
+	list_for_each_entry(tk, &probe_list, list)
+		if (strcmp(trace_event_name(&tk->tp.call), event) == 0 &&
+		    strcmp(tk->tp.call.class->system, group) == 0)
+			return tk;
+	return NULL;
+}
+
+static inline int __enable_trace_kprobe(struct trace_kprobe *tk)
+{
+	int ret = 0;
+
+	if (trace_probe_is_registered(&tk->tp) && !trace_kprobe_has_gone(tk)) {
+		if (trace_kprobe_is_return(tk))
+			ret = enable_kretprobe(&tk->rp);
+		else
+			ret = enable_kprobe(&tk->rp.kp);
+	}
+
+	return ret;
+}
+
+/*
+ * Enable trace_probe
+ * if the file is NULL, enable "perf" handler, or enable "trace" handler.
+ */
+static int
+enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
+{
+	struct event_file_link *link;
+	int ret = 0;
+
+	if (file) {
+		link = kmalloc(sizeof(*link), GFP_KERNEL);
+		if (!link) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		link->file = file;
+		list_add_tail_rcu(&link->list, &tk->tp.files);
+
+		tk->tp.flags |= TP_FLAG_TRACE;
+		ret = __enable_trace_kprobe(tk);
+		if (ret) {
+			list_del_rcu(&link->list);
+			kfree(link);
+			tk->tp.flags &= ~TP_FLAG_TRACE;
+		}
+
+	} else {
+		tk->tp.flags |= TP_FLAG_PROFILE;
+		ret = __enable_trace_kprobe(tk);
+		if (ret)
+			tk->tp.flags &= ~TP_FLAG_PROFILE;
+	}
+ out:
+	return ret;
+}
+
+/*
+ * Disable trace_probe
+ * if the file is NULL, disable "perf" handler, or disable "trace" handler.
+ */
+static int
+disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
+{
+	struct event_file_link *link = NULL;
+	int wait = 0;
+	int ret = 0;
+
+	if (file) {
+		link = find_event_file_link(&tk->tp, file);
+		if (!link) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		list_del_rcu(&link->list);
+		wait = 1;
+		if (!list_empty(&tk->tp.files))
+			goto out;
+
+		tk->tp.flags &= ~TP_FLAG_TRACE;
+	} else
+		tk->tp.flags &= ~TP_FLAG_PROFILE;
+
+	if (!trace_probe_is_enabled(&tk->tp) && trace_probe_is_registered(&tk->tp)) {
+		if (trace_kprobe_is_return(tk))
+			disable_kretprobe(&tk->rp);
+		else
+			disable_kprobe(&tk->rp.kp);
+		wait = 1;
+	}
+
+	/*
+	 * if tk is not added to any list, it must be a local trace_kprobe
+	 * created with perf_event_open. We don't need to wait for these
+	 * trace_kprobes
+	 */
+	if (list_empty(&tk->list))
+		wait = 0;
+ out:
+	if (wait) {
+		/*
+		 * Synchronize with kprobe_trace_func/kretprobe_trace_func
+		 * to ensure disabled (all running handlers are finished).
+		 * This is not only for kfree(), but also the caller,
+		 * trace_remove_event_call() supposes it for releasing
+		 * event_call related objects, which will be accessed in
+		 * the kprobe_trace_func/kretprobe_trace_func.
+		 */
+		synchronize_sched();
+		kfree(link);	/* Ignored if link == NULL */
+	}
+
+	return ret;
+}
+
+#if defined(CONFIG_DYNAMIC_FTRACE) && \
+	!defined(CONFIG_KPROBE_EVENTS_ON_NOTRACE)
+static bool __within_notrace_func(unsigned long addr)
+{
+	unsigned long offset, size;
+
+	if (!addr || !kallsyms_lookup_size_offset(addr, &size, &offset))
+		return false;
+
+	/* Get the entry address of the target function */
+	addr -= offset;
+
+	/*
+	 * Since ftrace_location_range() does inclusive range check, we need
+	 * to subtract 1 byte from the end address.
+	 */
+	return !ftrace_location_range(addr, addr + size - 1);
+}
+
+static bool within_notrace_func(struct trace_kprobe *tk)
+{
+	unsigned long addr = trace_kprobe_address(tk);
+	char symname[KSYM_NAME_LEN], *p;
+
+	if (!__within_notrace_func(addr))
+		return false;
+
+	/* Check if the address is on a suffixed-symbol */
+	if (!lookup_symbol_name(addr, symname)) {
+		p = strchr(symname, '.');
+		if (!p)
+			return true;
+		*p = '\0';
+		addr = (unsigned long)kprobe_lookup_name(symname, 0);
+		if (addr)
+			return __within_notrace_func(addr);
+	}
+
+	return true;
+}
+#else
+#define within_notrace_func(tk)	(false)
+#endif
+
+/* Internal register function - just handle k*probes and flags */
+static int __register_trace_kprobe(struct trace_kprobe *tk)
+{
+	int i, ret;
+
+	if (trace_probe_is_registered(&tk->tp))
+		return -EINVAL;
+
+	if (within_notrace_func(tk)) {
+		pr_warn("Could not probe notrace function %s\n",
+			trace_kprobe_symbol(tk));
+		return -EINVAL;
+	}
+
+	for (i = 0; i < tk->tp.nr_args; i++)
+		traceprobe_update_arg(&tk->tp.args[i]);
+
+	/* Set/clear disabled flag according to tp->flag */
+	if (trace_probe_is_enabled(&tk->tp))
+		tk->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
+	else
+		tk->rp.kp.flags |= KPROBE_FLAG_DISABLED;
+
+	if (trace_kprobe_is_return(tk))
+		ret = register_kretprobe(&tk->rp);
+	else
+		ret = register_kprobe(&tk->rp.kp);
+
+	if (ret == 0) {
+		tk->tp.flags |= TP_FLAG_REGISTERED;
+	} else if (ret == -EILSEQ) {
+		pr_warn("Probing address(0x%p) is not an instruction boundary.\n",
+			tk->rp.kp.addr);
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+/* Internal unregister function - just handle k*probes and flags */
+static void __unregister_trace_kprobe(struct trace_kprobe *tk)
+{
+	if (trace_probe_is_registered(&tk->tp)) {
+		if (trace_kprobe_is_return(tk))
+			unregister_kretprobe(&tk->rp);
+		else
+			unregister_kprobe(&tk->rp.kp);
+		tk->tp.flags &= ~TP_FLAG_REGISTERED;
+		/* Cleanup kprobe for reuse */
+		if (tk->rp.kp.symbol_name)
+			tk->rp.kp.addr = NULL;
+	}
+}
+
+/* Unregister a trace_probe and probe_event: call with locking probe_lock */
+static int unregister_trace_kprobe(struct trace_kprobe *tk)
+{
+	/* Enabled event can not be unregistered */
+	if (trace_probe_is_enabled(&tk->tp))
+		return -EBUSY;
+
+	/* Will fail if probe is being used by ftrace or perf */
+	if (unregister_kprobe_event(tk))
+		return -EBUSY;
+
+	__unregister_trace_kprobe(tk);
+	list_del(&tk->list);
+
+	return 0;
+}
+
+/* Register a trace_probe and probe_event */
+static int register_trace_kprobe(struct trace_kprobe *tk)
+{
+	struct trace_kprobe *old_tk;
+	int ret;
+
+	mutex_lock(&probe_lock);
+
+	/* Delete old (same name) event if exist */
+	old_tk = find_trace_kprobe(trace_event_name(&tk->tp.call),
+			tk->tp.call.class->system);
+	if (old_tk) {
+		ret = unregister_trace_kprobe(old_tk);
+		if (ret < 0)
+			goto end;
+		free_trace_kprobe(old_tk);
+	}
+
+	/* Register new event */
+	ret = register_kprobe_event(tk);
+	if (ret) {
+		pr_warn("Failed to register probe event(%d)\n", ret);
+		goto end;
+	}
+
+	/* Register k*probe */
+	ret = __register_trace_kprobe(tk);
+	if (ret == -ENOENT && !trace_kprobe_module_exist(tk)) {
+		pr_warn("This probe might be able to register after target module is loaded. Continue.\n");
+		ret = 0;
+	}
+
+	if (ret < 0)
+		unregister_kprobe_event(tk);
+	else
+		list_add_tail(&tk->list, &probe_list);
+
+end:
+	mutex_unlock(&probe_lock);
+	return ret;
+}
+
+/* Module notifier call back, checking event on the module */
+static int trace_kprobe_module_callback(struct notifier_block *nb,
+				       unsigned long val, void *data)
+{
+	struct module *mod = data;
+	struct trace_kprobe *tk;
+	int ret;
+
+	if (val != MODULE_STATE_COMING)
+		return NOTIFY_DONE;
+
+	/* Update probes on coming module */
+	mutex_lock(&probe_lock);
+	list_for_each_entry(tk, &probe_list, list) {
+		if (trace_kprobe_within_module(tk, mod)) {
+			/* Don't need to check busy - this should have gone. */
+			__unregister_trace_kprobe(tk);
+			ret = __register_trace_kprobe(tk);
+			if (ret)
+				pr_warn("Failed to re-register probe %s on %s: %d\n",
+					trace_event_name(&tk->tp.call),
+					mod->name, ret);
+		}
+	}
+	mutex_unlock(&probe_lock);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block trace_kprobe_module_nb = {
+	.notifier_call = trace_kprobe_module_callback,
+	.priority = 1	/* Invoked after kprobe module callback */
+};
+
+/* Convert certain expected symbols into '_' when generating event names */
+static inline void sanitize_event_name(char *name)
+{
+	while (*name++ != '\0')
+		if (*name == ':' || *name == '.')
+			*name = '_';
+}
+
+static int create_trace_kprobe(int argc, char **argv)
+{
+	/*
+	 * Argument syntax:
+	 *  - Add kprobe:
+	 *      p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS]
+	 *  - Add kretprobe:
+	 *      r[MAXACTIVE][:[GRP/]EVENT] [MOD:]KSYM[+0] [FETCHARGS]
+	 * Fetch args:
+	 *  $retval	: fetch return value
+	 *  $stack	: fetch stack address
+	 *  $stackN	: fetch Nth of stack (N:0-)
+	 *  $comm       : fetch current task comm
+	 *  @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
+	 * Dereferencing memory fetch:
+	 *  +|-offs(ARG) : fetch memory at ARG +|- offs address.
+	 * Alias name of args:
+	 *  NAME=FETCHARG : set NAME as alias of FETCHARG.
+	 * Type of args:
+	 *  FETCHARG:TYPE : use TYPE instead of unsigned long.
+	 */
+	struct trace_kprobe *tk;
+	int i, ret = 0;
+	bool is_return = false, is_delete = false;
+	char *symbol = NULL, *event = NULL, *group = NULL;
+	int maxactive = 0;
+	char *arg;
+	long offset = 0;
+	void *addr = NULL;
+	char buf[MAX_EVENT_NAME_LEN];
+
+	/* argc must be >= 1 */
+	if (argv[0][0] == 'p')
+		is_return = false;
+	else if (argv[0][0] == 'r')
+		is_return = true;
+	else if (argv[0][0] == '-')
+		is_delete = true;
+	else {
+		pr_info("Probe definition must be started with 'p', 'r' or"
+			" '-'.\n");
+		return -EINVAL;
+	}
+
+	event = strchr(&argv[0][1], ':');
+	if (event) {
+		event[0] = '\0';
+		event++;
+	}
+	if (is_return && isdigit(argv[0][1])) {
+		ret = kstrtouint(&argv[0][1], 0, &maxactive);
+		if (ret) {
+			pr_info("Failed to parse maxactive.\n");
+			return ret;
+		}
+		/* kretprobes instances are iterated over via a list. The
+		 * maximum should stay reasonable.
+		 */
+		if (maxactive > KRETPROBE_MAXACTIVE_MAX) {
+			pr_info("Maxactive is too big (%d > %d).\n",
+				maxactive, KRETPROBE_MAXACTIVE_MAX);
+			return -E2BIG;
+		}
+	}
+
+	if (event) {
+		if (strchr(event, '/')) {
+			group = event;
+			event = strchr(group, '/') + 1;
+			event[-1] = '\0';
+			if (strlen(group) == 0) {
+				pr_info("Group name is not specified\n");
+				return -EINVAL;
+			}
+		}
+		if (strlen(event) == 0) {
+			pr_info("Event name is not specified\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;
+		}
+		mutex_lock(&probe_lock);
+		tk = find_trace_kprobe(event, group);
+		if (!tk) {
+			mutex_unlock(&probe_lock);
+			pr_info("Event %s/%s doesn't exist.\n", group, event);
+			return -ENOENT;
+		}
+		/* delete an event */
+		ret = unregister_trace_kprobe(tk);
+		if (ret == 0)
+			free_trace_kprobe(tk);
+		mutex_unlock(&probe_lock);
+		return ret;
+	}
+
+	if (argc < 2) {
+		pr_info("Probe point is not specified.\n");
+		return -EINVAL;
+	}
+
+	/* try to parse an address. if that fails, try to read the
+	 * input as a symbol. */
+	if (kstrtoul(argv[1], 0, (unsigned long *)&addr)) {
+		/* a symbol specified */
+		symbol = argv[1];
+		/* TODO: support .init module functions */
+		ret = traceprobe_split_symbol_offset(symbol, &offset);
+		if (ret || offset < 0 || offset > UINT_MAX) {
+			pr_info("Failed to parse either an address or a symbol.\n");
+			return ret;
+		}
+		/* Defer the ENOENT case until register kprobe */
+		if (offset && is_return &&
+		    kprobe_on_func_entry(NULL, symbol, offset) == -EINVAL) {
+			pr_info("Given offset is not valid for return probe.\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);
+		sanitize_event_name(buf);
+		event = buf;
+	}
+	tk = alloc_trace_kprobe(group, event, addr, symbol, offset, maxactive,
+			       argc, is_return);
+	if (IS_ERR(tk)) {
+		pr_info("Failed to allocate trace_probe.(%d)\n",
+			(int)PTR_ERR(tk));
+		return PTR_ERR(tk);
+	}
+
+	/* parse arguments */
+	ret = 0;
+	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
+		struct probe_arg *parg = &tk->tp.args[i];
+
+		/* Increment count for freeing args in error case */
+		tk->tp.nr_args++;
+
+		/* Parse argument name */
+		arg = strchr(argv[i], '=');
+		if (arg) {
+			*arg++ = '\0';
+			parg->name = kstrdup(argv[i], GFP_KERNEL);
+		} else {
+			arg = argv[i];
+			/* If argument name is omitted, set "argN" */
+			snprintf(buf, MAX_EVENT_NAME_LEN, "arg%d", i + 1);
+			parg->name = kstrdup(buf, GFP_KERNEL);
+		}
+
+		if (!parg->name) {
+			pr_info("Failed to allocate argument[%d] name.\n", i);
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		if (!is_good_name(parg->name)) {
+			pr_info("Invalid argument[%d] name: %s\n",
+				i, parg->name);
+			ret = -EINVAL;
+			goto error;
+		}
+
+		if (traceprobe_conflict_field_name(parg->name,
+							tk->tp.args, i)) {
+			pr_info("Argument[%d] name '%s' conflicts with "
+				"another field.\n", i, argv[i]);
+			ret = -EINVAL;
+			goto error;
+		}
+
+		/* Parse fetch argument */
+		ret = traceprobe_parse_probe_arg(arg, &tk->tp.size, parg,
+						is_return, true,
+						kprobes_fetch_type_table);
+		if (ret) {
+			pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
+			goto error;
+		}
+	}
+
+	ret = register_trace_kprobe(tk);
+	if (ret)
+		goto error;
+	return 0;
+
+error:
+	free_trace_kprobe(tk);
+	return ret;
+}
+
+static int release_all_trace_kprobes(void)
+{
+	struct trace_kprobe *tk;
+	int ret = 0;
+
+	mutex_lock(&probe_lock);
+	/* Ensure no probe is in use. */
+	list_for_each_entry(tk, &probe_list, list)
+		if (trace_probe_is_enabled(&tk->tp)) {
+			ret = -EBUSY;
+			goto end;
+		}
+	/* TODO: Use batch unregistration */
+	while (!list_empty(&probe_list)) {
+		tk = list_entry(probe_list.next, struct trace_kprobe, list);
+		ret = unregister_trace_kprobe(tk);
+		if (ret)
+			goto end;
+		free_trace_kprobe(tk);
+	}
+
+end:
+	mutex_unlock(&probe_lock);
+
+	return ret;
+}
+
+/* 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_kprobe *tk = v;
+	int i;
+
+	seq_putc(m, trace_kprobe_is_return(tk) ? 'r' : 'p');
+	if (trace_kprobe_is_return(tk) && tk->rp.maxactive)
+		seq_printf(m, "%d", tk->rp.maxactive);
+	seq_printf(m, ":%s/%s", tk->tp.call.class->system,
+			trace_event_name(&tk->tp.call));
+
+	if (!tk->symbol)
+		seq_printf(m, " 0x%p", tk->rp.kp.addr);
+	else if (tk->rp.kp.offset)
+		seq_printf(m, " %s+%u", trace_kprobe_symbol(tk),
+			   tk->rp.kp.offset);
+	else
+		seq_printf(m, " %s", trace_kprobe_symbol(tk));
+
+	for (i = 0; i < tk->tp.nr_args; i++)
+		seq_printf(m, " %s=%s", tk->tp.args[i].name, tk->tp.args[i].comm);
+	seq_putc(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)
+{
+	int ret;
+
+	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
+		ret = release_all_trace_kprobes();
+		if (ret < 0)
+			return ret;
+	}
+
+	return seq_open(file, &probes_seq_op);
+}
+
+static ssize_t probes_write(struct file *file, const char __user *buffer,
+			    size_t count, loff_t *ppos)
+{
+	return trace_parse_run_command(file, buffer, count, ppos,
+				       create_trace_kprobe);
+}
+
+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_kprobe *tk = v;
+
+	seq_printf(m, "  %-44s %15lu %15lu\n",
+		   trace_event_name(&tk->tp.call),
+		   trace_kprobe_nhit(tk),
+		   tk->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 nokprobe_inline void
+__kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,
+		    struct trace_event_file *trace_file)
+{
+	struct kprobe_trace_entry_head *entry;
+	struct ring_buffer_event *event;
+	struct ring_buffer *buffer;
+	int size, dsize, pc;
+	unsigned long irq_flags;
+	struct trace_event_call *call = &tk->tp.call;
+
+	WARN_ON(call != trace_file->event_call);
+
+	if (trace_trigger_soft_disabled(trace_file))
+		return;
+
+	local_save_flags(irq_flags);
+	pc = preempt_count();
+
+	dsize = __get_data_size(&tk->tp, regs);
+	size = sizeof(*entry) + tk->tp.size + dsize;
+
+	event = trace_event_buffer_lock_reserve(&buffer, trace_file,
+						call->event.type,
+						size, irq_flags, pc);
+	if (!event)
+		return;
+
+	entry = ring_buffer_event_data(event);
+	entry->ip = (unsigned long)tk->rp.kp.addr;
+	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+
+	event_trigger_unlock_commit_regs(trace_file, buffer, event,
+					 entry, irq_flags, pc, regs);
+}
+
+static void
+kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs)
+{
+	struct event_file_link *link;
+
+	list_for_each_entry_rcu(link, &tk->tp.files, list)
+		__kprobe_trace_func(tk, regs, link->file);
+}
+NOKPROBE_SYMBOL(kprobe_trace_func);
+
+/* Kretprobe handler */
+static nokprobe_inline void
+__kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
+		       struct pt_regs *regs,
+		       struct trace_event_file *trace_file)
+{
+	struct kretprobe_trace_entry_head *entry;
+	struct ring_buffer_event *event;
+	struct ring_buffer *buffer;
+	int size, pc, dsize;
+	unsigned long irq_flags;
+	struct trace_event_call *call = &tk->tp.call;
+
+	WARN_ON(call != trace_file->event_call);
+
+	if (trace_trigger_soft_disabled(trace_file))
+		return;
+
+	local_save_flags(irq_flags);
+	pc = preempt_count();
+
+	dsize = __get_data_size(&tk->tp, regs);
+	size = sizeof(*entry) + tk->tp.size + dsize;
+
+	event = trace_event_buffer_lock_reserve(&buffer, trace_file,
+						call->event.type,
+						size, irq_flags, pc);
+	if (!event)
+		return;
+
+	entry = ring_buffer_event_data(event);
+	entry->func = (unsigned long)tk->rp.kp.addr;
+	entry->ret_ip = (unsigned long)ri->ret_addr;
+	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+
+	event_trigger_unlock_commit_regs(trace_file, buffer, event,
+					 entry, irq_flags, pc, regs);
+}
+
+static void
+kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
+		     struct pt_regs *regs)
+{
+	struct event_file_link *link;
+
+	list_for_each_entry_rcu(link, &tk->tp.files, list)
+		__kretprobe_trace_func(tk, ri, regs, link->file);
+}
+NOKPROBE_SYMBOL(kretprobe_trace_func);
+
+/* Event entry printers */
+static enum print_line_t
+print_kprobe_event(struct trace_iterator *iter, int flags,
+		   struct trace_event *event)
+{
+	struct kprobe_trace_entry_head *field;
+	struct trace_seq *s = &iter->seq;
+	struct trace_probe *tp;
+	u8 *data;
+	int i;
+
+	field = (struct kprobe_trace_entry_head *)iter->ent;
+	tp = container_of(event, struct trace_probe, call.event);
+
+	trace_seq_printf(s, "%s: (", trace_event_name(&tp->call));
+
+	if (!seq_print_ip_sym(s, field->ip, flags | TRACE_ITER_SYM_OFFSET))
+		goto out;
+
+	trace_seq_putc(s, ')');
+
+	data = (u8 *)&field[1];
+	for (i = 0; i < tp->nr_args; i++)
+		if (!tp->args[i].type->print(s, tp->args[i].name,
+					     data + tp->args[i].offset, field))
+			goto out;
+
+	trace_seq_putc(s, '\n');
+ out:
+	return trace_handle_return(s);
+}
+
+static enum print_line_t
+print_kretprobe_event(struct trace_iterator *iter, int flags,
+		      struct trace_event *event)
+{
+	struct kretprobe_trace_entry_head *field;
+	struct trace_seq *s = &iter->seq;
+	struct trace_probe *tp;
+	u8 *data;
+	int i;
+
+	field = (struct kretprobe_trace_entry_head *)iter->ent;
+	tp = container_of(event, struct trace_probe, call.event);
+
+	trace_seq_printf(s, "%s: (", trace_event_name(&tp->call));
+
+	if (!seq_print_ip_sym(s, field->ret_ip, flags | TRACE_ITER_SYM_OFFSET))
+		goto out;
+
+	trace_seq_puts(s, " <- ");
+
+	if (!seq_print_ip_sym(s, field->func, flags & ~TRACE_ITER_SYM_OFFSET))
+		goto out;
+
+	trace_seq_putc(s, ')');
+
+	data = (u8 *)&field[1];
+	for (i = 0; i < tp->nr_args; i++)
+		if (!tp->args[i].type->print(s, tp->args[i].name,
+					     data + tp->args[i].offset, field))
+			goto out;
+
+	trace_seq_putc(s, '\n');
+
+ out:
+	return trace_handle_return(s);
+}
+
+
+static int kprobe_event_define_fields(struct trace_event_call *event_call)
+{
+	int ret, i;
+	struct kprobe_trace_entry_head field;
+	struct trace_kprobe *tk = (struct trace_kprobe *)event_call->data;
+
+	DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
+	/* Set argument names as fields */
+	for (i = 0; i < tk->tp.nr_args; i++) {
+		struct probe_arg *parg = &tk->tp.args[i];
+
+		ret = trace_define_field(event_call, parg->type->fmttype,
+					 parg->name,
+					 sizeof(field) + parg->offset,
+					 parg->type->size,
+					 parg->type->is_signed,
+					 FILTER_OTHER);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static int kretprobe_event_define_fields(struct trace_event_call *event_call)
+{
+	int ret, i;
+	struct kretprobe_trace_entry_head field;
+	struct trace_kprobe *tk = (struct trace_kprobe *)event_call->data;
+
+	DEFINE_FIELD(unsigned long, func, FIELD_STRING_FUNC, 0);
+	DEFINE_FIELD(unsigned long, ret_ip, FIELD_STRING_RETIP, 0);
+	/* Set argument names as fields */
+	for (i = 0; i < tk->tp.nr_args; i++) {
+		struct probe_arg *parg = &tk->tp.args[i];
+
+		ret = trace_define_field(event_call, parg->type->fmttype,
+					 parg->name,
+					 sizeof(field) + parg->offset,
+					 parg->type->size,
+					 parg->type->is_signed,
+					 FILTER_OTHER);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+#ifdef CONFIG_PERF_EVENTS
+
+/* Kprobe profile handler */
+static int
+kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
+{
+	struct trace_event_call *call = &tk->tp.call;
+	struct kprobe_trace_entry_head *entry;
+	struct hlist_head *head;
+	int size, __size, dsize;
+	int rctx;
+
+	if (bpf_prog_array_valid(call)) {
+		unsigned long orig_ip = instruction_pointer(regs);
+		int ret;
+
+		ret = trace_call_bpf(call, regs);
+
+		/*
+		 * We need to check and see if we modified the pc of the
+		 * pt_regs, and if so return 1 so that we don't do the
+		 * single stepping.
+		 */
+		if (orig_ip != instruction_pointer(regs))
+			return 1;
+		if (!ret)
+			return 0;
+	}
+
+	head = this_cpu_ptr(call->perf_events);
+	if (hlist_empty(head))
+		return 0;
+
+	dsize = __get_data_size(&tk->tp, regs);
+	__size = sizeof(*entry) + tk->tp.size + dsize;
+	size = ALIGN(__size + sizeof(u32), sizeof(u64));
+	size -= sizeof(u32);
+
+	entry = perf_trace_buf_alloc(size, NULL, &rctx);
+	if (!entry)
+		return 0;
+
+	entry->ip = (unsigned long)tk->rp.kp.addr;
+	memset(&entry[1], 0, dsize);
+	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+	perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
+			      head, NULL);
+	return 0;
+}
+NOKPROBE_SYMBOL(kprobe_perf_func);
+
+/* Kretprobe profile handler */
+static void
+kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
+		    struct pt_regs *regs)
+{
+	struct trace_event_call *call = &tk->tp.call;
+	struct kretprobe_trace_entry_head *entry;
+	struct hlist_head *head;
+	int size, __size, dsize;
+	int rctx;
+
+	if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
+		return;
+
+	head = this_cpu_ptr(call->perf_events);
+	if (hlist_empty(head))
+		return;
+
+	dsize = __get_data_size(&tk->tp, regs);
+	__size = sizeof(*entry) + tk->tp.size + dsize;
+	size = ALIGN(__size + sizeof(u32), sizeof(u64));
+	size -= sizeof(u32);
+
+	entry = perf_trace_buf_alloc(size, NULL, &rctx);
+	if (!entry)
+		return;
+
+	entry->func = (unsigned long)tk->rp.kp.addr;
+	entry->ret_ip = (unsigned long)ri->ret_addr;
+	store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+	perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
+			      head, NULL);
+}
+NOKPROBE_SYMBOL(kretprobe_perf_func);
+
+int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
+			const char **symbol, u64 *probe_offset,
+			u64 *probe_addr, bool perf_type_tracepoint)
+{
+	const char *pevent = trace_event_name(event->tp_event);
+	const char *group = event->tp_event->class->system;
+	struct trace_kprobe *tk;
+
+	if (perf_type_tracepoint)
+		tk = find_trace_kprobe(pevent, group);
+	else
+		tk = event->tp_event->data;
+	if (!tk)
+		return -EINVAL;
+
+	*fd_type = trace_kprobe_is_return(tk) ? BPF_FD_TYPE_KRETPROBE
+					      : BPF_FD_TYPE_KPROBE;
+	if (tk->symbol) {
+		*symbol = tk->symbol;
+		*probe_offset = tk->rp.kp.offset;
+		*probe_addr = 0;
+	} else {
+		*symbol = NULL;
+		*probe_offset = 0;
+		*probe_addr = (unsigned long)tk->rp.kp.addr;
+	}
+	return 0;
+}
+#endif	/* CONFIG_PERF_EVENTS */
+
+/*
+ * called by perf_trace_init() or __ftrace_set_clr_event() under event_mutex.
+ *
+ * kprobe_trace_self_tests_init() does enable_trace_probe/disable_trace_probe
+ * lockless, but we can't race with this __init function.
+ */
+static int kprobe_register(struct trace_event_call *event,
+			   enum trace_reg type, void *data)
+{
+	struct trace_kprobe *tk = (struct trace_kprobe *)event->data;
+	struct trace_event_file *file = data;
+
+	switch (type) {
+	case TRACE_REG_REGISTER:
+		return enable_trace_kprobe(tk, file);
+	case TRACE_REG_UNREGISTER:
+		return disable_trace_kprobe(tk, file);
+
+#ifdef CONFIG_PERF_EVENTS
+	case TRACE_REG_PERF_REGISTER:
+		return enable_trace_kprobe(tk, NULL);
+	case TRACE_REG_PERF_UNREGISTER:
+		return disable_trace_kprobe(tk, NULL);
+	case TRACE_REG_PERF_OPEN:
+	case TRACE_REG_PERF_CLOSE:
+	case TRACE_REG_PERF_ADD:
+	case TRACE_REG_PERF_DEL:
+		return 0;
+#endif
+	}
+	return 0;
+}
+
+static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
+{
+	struct trace_kprobe *tk = container_of(kp, struct trace_kprobe, rp.kp);
+	int ret = 0;
+
+	raw_cpu_inc(*tk->nhit);
+
+	if (tk->tp.flags & TP_FLAG_TRACE)
+		kprobe_trace_func(tk, regs);
+#ifdef CONFIG_PERF_EVENTS
+	if (tk->tp.flags & TP_FLAG_PROFILE)
+		ret = kprobe_perf_func(tk, regs);
+#endif
+	return ret;
+}
+NOKPROBE_SYMBOL(kprobe_dispatcher);
+
+static int
+kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+	struct trace_kprobe *tk = container_of(ri->rp, struct trace_kprobe, rp);
+
+	raw_cpu_inc(*tk->nhit);
+
+	if (tk->tp.flags & TP_FLAG_TRACE)
+		kretprobe_trace_func(tk, ri, regs);
+#ifdef CONFIG_PERF_EVENTS
+	if (tk->tp.flags & TP_FLAG_PROFILE)
+		kretprobe_perf_func(tk, ri, regs);
+#endif
+	return 0;	/* We don't tweek kernel, so just return 0 */
+}
+NOKPROBE_SYMBOL(kretprobe_dispatcher);
+
+static struct trace_event_functions kretprobe_funcs = {
+	.trace		= print_kretprobe_event
+};
+
+static struct trace_event_functions kprobe_funcs = {
+	.trace		= print_kprobe_event
+};
+
+static inline void init_trace_event_call(struct trace_kprobe *tk,
+					 struct trace_event_call *call)
+{
+	INIT_LIST_HEAD(&call->class->fields);
+	if (trace_kprobe_is_return(tk)) {
+		call->event.funcs = &kretprobe_funcs;
+		call->class->define_fields = kretprobe_event_define_fields;
+	} else {
+		call->event.funcs = &kprobe_funcs;
+		call->class->define_fields = kprobe_event_define_fields;
+	}
+
+	call->flags = TRACE_EVENT_FL_KPROBE;
+	call->class->reg = kprobe_register;
+	call->data = tk;
+}
+
+static int register_kprobe_event(struct trace_kprobe *tk)
+{
+	struct trace_event_call *call = &tk->tp.call;
+	int ret = 0;
+
+	init_trace_event_call(tk, call);
+
+	if (set_print_fmt(&tk->tp, trace_kprobe_is_return(tk)) < 0)
+		return -ENOMEM;
+	ret = register_trace_event(&call->event);
+	if (!ret) {
+		kfree(call->print_fmt);
+		return -ENODEV;
+	}
+	ret = trace_add_event_call(call);
+	if (ret) {
+		pr_info("Failed to register kprobe event: %s\n",
+			trace_event_name(call));
+		kfree(call->print_fmt);
+		unregister_trace_event(&call->event);
+	}
+	return ret;
+}
+
+static int unregister_kprobe_event(struct trace_kprobe *tk)
+{
+	int ret;
+
+	/* tp->event is unregistered in trace_remove_event_call() */
+	ret = trace_remove_event_call(&tk->tp.call);
+	if (!ret)
+		kfree(tk->tp.call.print_fmt);
+	return ret;
+}
+
+#ifdef CONFIG_PERF_EVENTS
+/* create a trace_kprobe, but don't add it to global lists */
+struct trace_event_call *
+create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
+			  bool is_return)
+{
+	struct trace_kprobe *tk;
+	int ret;
+	char *event;
+
+	/*
+	 * local trace_kprobes are not added to probe_list, so they are never
+	 * searched in find_trace_kprobe(). Therefore, there is no concern of
+	 * duplicated name here.
+	 */
+	event = func ? func : "DUMMY_EVENT";
+
+	tk = alloc_trace_kprobe(KPROBE_EVENT_SYSTEM, event, (void *)addr, func,
+				offs, 0 /* maxactive */, 0 /* nargs */,
+				is_return);
+
+	if (IS_ERR(tk)) {
+		pr_info("Failed to allocate trace_probe.(%d)\n",
+			(int)PTR_ERR(tk));
+		return ERR_CAST(tk);
+	}
+
+	init_trace_event_call(tk, &tk->tp.call);
+
+	if (set_print_fmt(&tk->tp, trace_kprobe_is_return(tk)) < 0) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	ret = __register_trace_kprobe(tk);
+	if (ret < 0) {
+		kfree(tk->tp.call.print_fmt);
+		goto error;
+	}
+
+	return &tk->tp.call;
+error:
+	free_trace_kprobe(tk);
+	return ERR_PTR(ret);
+}
+
+void destroy_local_trace_kprobe(struct trace_event_call *event_call)
+{
+	struct trace_kprobe *tk;
+
+	tk = container_of(event_call, struct trace_kprobe, tp.call);
+
+	if (trace_probe_is_enabled(&tk->tp)) {
+		WARN_ON(1);
+		return;
+	}
+
+	__unregister_trace_kprobe(tk);
+
+	kfree(tk->tp.call.print_fmt);
+	free_trace_kprobe(tk);
+}
+#endif /* CONFIG_PERF_EVENTS */
+
+/* Make a tracefs interface for controlling probe points */
+static __init int init_kprobe_trace(void)
+{
+	struct dentry *d_tracer;
+	struct dentry *entry;
+
+	if (register_module_notifier(&trace_kprobe_module_nb))
+		return -EINVAL;
+
+	d_tracer = tracing_init_dentry();
+	if (IS_ERR(d_tracer))
+		return 0;
+
+	entry = tracefs_create_file("kprobe_events", 0644, d_tracer,
+				    NULL, &kprobe_events_ops);
+
+	/* Event list interface */
+	if (!entry)
+		pr_warn("Could not create tracefs 'kprobe_events' entry\n");
+
+	/* Profile interface */
+	entry = tracefs_create_file("kprobe_profile", 0444, d_tracer,
+				    NULL, &kprobe_profile_ops);
+
+	if (!entry)
+		pr_warn("Could not create tracefs 'kprobe_profile' entry\n");
+	return 0;
+}
+fs_initcall(init_kprobe_trace);
+
+
+#ifdef CONFIG_FTRACE_STARTUP_TEST
+static __init struct trace_event_file *
+find_trace_probe_file(struct trace_kprobe *tk, struct trace_array *tr)
+{
+	struct trace_event_file *file;
+
+	list_for_each_entry(file, &tr->events, list)
+		if (file->event_call == &tk->tp.call)
+			return file;
+
+	return NULL;
+}
+
+/*
+ * Nobody but us can call enable_trace_kprobe/disable_trace_kprobe at this
+ * stage, we can do this lockless.
+ */
+static __init int kprobe_trace_self_tests_init(void)
+{
+	int ret, warn = 0;
+	int (*target)(int, int, int, int, int, int);
+	struct trace_kprobe *tk;
+	struct trace_event_file *file;
+
+	if (tracing_is_disabled())
+		return -ENODEV;
+
+	target = kprobe_trace_selftest_target;
+
+	pr_info("Testing kprobe tracing: ");
+
+	ret = trace_run_command("p:testprobe kprobe_trace_selftest_target "
+				"$stack $stack0 +0($stack)",
+				create_trace_kprobe);
+	if (WARN_ON_ONCE(ret)) {
+		pr_warn("error on probing function entry.\n");
+		warn++;
+	} else {
+		/* Enable trace point */
+		tk = find_trace_kprobe("testprobe", KPROBE_EVENT_SYSTEM);
+		if (WARN_ON_ONCE(tk == NULL)) {
+			pr_warn("error on getting new probe.\n");
+			warn++;
+		} else {
+			file = find_trace_probe_file(tk, top_trace_array());
+			if (WARN_ON_ONCE(file == NULL)) {
+				pr_warn("error on getting probe file.\n");
+				warn++;
+			} else
+				enable_trace_kprobe(tk, file);
+		}
+	}
+
+	ret = trace_run_command("r:testprobe2 kprobe_trace_selftest_target "
+				"$retval", create_trace_kprobe);
+	if (WARN_ON_ONCE(ret)) {
+		pr_warn("error on probing function return.\n");
+		warn++;
+	} else {
+		/* Enable trace point */
+		tk = find_trace_kprobe("testprobe2", KPROBE_EVENT_SYSTEM);
+		if (WARN_ON_ONCE(tk == NULL)) {
+			pr_warn("error on getting 2nd new probe.\n");
+			warn++;
+		} else {
+			file = find_trace_probe_file(tk, top_trace_array());
+			if (WARN_ON_ONCE(file == NULL)) {
+				pr_warn("error on getting probe file.\n");
+				warn++;
+			} else
+				enable_trace_kprobe(tk, file);
+		}
+	}
+
+	if (warn)
+		goto end;
+
+	ret = target(1, 2, 3, 4, 5, 6);
+
+	/*
+	 * Not expecting an error here, the check is only to prevent the
+	 * optimizer from removing the call to target() as otherwise there
+	 * are no side-effects and the call is never performed.
+	 */
+	if (ret != 21)
+		warn++;
+
+	/* Disable trace points before removing it */
+	tk = find_trace_kprobe("testprobe", KPROBE_EVENT_SYSTEM);
+	if (WARN_ON_ONCE(tk == NULL)) {
+		pr_warn("error on getting test probe.\n");
+		warn++;
+	} else {
+		if (trace_kprobe_nhit(tk) != 1) {
+			pr_warn("incorrect number of testprobe hits\n");
+			warn++;
+		}
+
+		file = find_trace_probe_file(tk, top_trace_array());
+		if (WARN_ON_ONCE(file == NULL)) {
+			pr_warn("error on getting probe file.\n");
+			warn++;
+		} else
+			disable_trace_kprobe(tk, file);
+	}
+
+	tk = find_trace_kprobe("testprobe2", KPROBE_EVENT_SYSTEM);
+	if (WARN_ON_ONCE(tk == NULL)) {
+		pr_warn("error on getting 2nd test probe.\n");
+		warn++;
+	} else {
+		if (trace_kprobe_nhit(tk) != 1) {
+			pr_warn("incorrect number of testprobe2 hits\n");
+			warn++;
+		}
+
+		file = find_trace_probe_file(tk, top_trace_array());
+		if (WARN_ON_ONCE(file == NULL)) {
+			pr_warn("error on getting probe file.\n");
+			warn++;
+		} else
+			disable_trace_kprobe(tk, file);
+	}
+
+	ret = trace_run_command("-:testprobe", create_trace_kprobe);
+	if (WARN_ON_ONCE(ret)) {
+		pr_warn("error on deleting a probe.\n");
+		warn++;
+	}
+
+	ret = trace_run_command("-:testprobe2", create_trace_kprobe);
+	if (WARN_ON_ONCE(ret)) {
+		pr_warn("error on deleting a probe.\n");
+		warn++;
+	}
+
+end:
+	release_all_trace_kprobes();
+	/*
+	 * Wait for the optimizer work to finish. Otherwise it might fiddle
+	 * with probes in already freed __init text.
+	 */
+	wait_for_kprobe_optimizer();
+	if (warn)
+		pr_cont("NG: Some tests are failed. Please check them.\n");
+	else
+		pr_cont("OK\n");
+	return 0;
+}
+
+late_initcall(kprobe_trace_self_tests_init);
+
+#endif