tracing: Add kprobe-based event tracer

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)
  sa    : Fetch stack address.
  @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/kprobetrace.txt in the next patch for details.

Changes from v13:
 - Support 'sa' for stack address.
 - Use call->data instead of container_of() macro.

[fweisbec@gmail.com: Fixed conflict against latest tracing/core]

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Przemysław Pawełczyk <przemyslaw@pawelczyk.it>
Cc: Roland McGrath <roland@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
LKML-Reference: <20090813203510.31965.29123.stgit@localhost.localdomain>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

5 files changed, 1263 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 06be85a7ef8c..fb5fbf75f279 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -411,6 +411,18 @@ 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 844164dca90a..7c00a1ec1496 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -54,5 +54,6 @@ obj-$(CONFIG_EVENT_TRACING) += trace_export.o
 obj-$(CONFIG_FTRACE_SYSCALLS) += trace_syscalls.o
 obj-$(CONFIG_EVENT_PROFILE) += trace_event_profile.o
 obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
+obj-$(CONFIG_KPROBE_TRACER) += trace_kprobe.o
 
 libftrace-y := ftrace.o
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 654fd657bd03..667f832d16b7 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -38,6 +38,8 @@ enum trace_type {
         TRACE_KMEM_FREE,
         TRACE_POWER,
         TRACE_BLK,
+        TRACE_KPROBE,
+        TRACE_KRETPROBE,
 
         __TRACE_LAST_TYPE,
 };
@@ -205,6 +207,30 @@ struct syscall_trace_exit {
         unsigned long           ret;
 };
 
+struct kprobe_trace_entry {
+        struct trace_entry      ent;
+        unsigned long           ip;
+        int                     nargs;
+        unsigned long           args[];
+};
+
+#define SIZEOF_KPROBE_TRACE_ENTRY(n)                    \
+        (offsetof(struct kprobe_trace_entry, args) +    \
+        (sizeof(unsigned long) * (n)))
+
+struct kretprobe_trace_entry {
+        struct trace_entry      ent;
+        unsigned long           func;
+        unsigned long           ret_ip;
+        int                     nargs;
+        unsigned long           args[];
+};
+
+#define SIZEOF_KRETPROBE_TRACE_ENTRY(n)                 \
+        (offsetof(struct kretprobe_trace_entry, args) + \
+        (sizeof(unsigned long) * (n)))
+
+
 
 /*
  * trace_flag_type is an enumeration that holds different
@@ -317,6 +343,10 @@ extern void __ftrace_bad_type(void);
                           TRACE_KMEM_ALLOC);    \
                 IF_ASSIGN(var, ent, struct kmemtrace_free_entry,        \
                           TRACE_KMEM_FREE);     \
+                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 e74f0906ab1a..186b598a1f11 100644
--- a/kernel/trace/trace_event_types.h
+++ b/kernel/trace/trace_event_types.h
@@ -175,4 +175,22 @@ 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_ZERO(unsigned long, 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_ZERO(unsigned long, 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 000000000000..0c4f00aafb92
--- /dev/null
+++ b/kernel/trace/trace_kprobe.c
@@ -0,0 +1,1202 @@
+/*
+ * kprobe based kernel tracer
+ *
+ * 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 "trace.h"
+#include "trace_output.h"
+
+#define TRACE_KPROBE_ARGS 6
+#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 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_ip(struct pt_regs *regs, void *dummy)
+{
+        return instruction_pointer(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_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 int)((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_stack_address)
+                ret = snprintf(buf, n, "sa");
+        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 = trace_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 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 */
+                if (arg[1] == 'a') {
+                        ff->func = fetch_stack_address;
+                        ff->data = NULL;
+                } else {
+                        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
+         *  sa  : fetch stack 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];
+
+        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 < 0) {
+                        pr_warning("Argument%d decoding error(%d).\n", i, ret);
+                        return ret;
+                }
+                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_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,
+};
+
+/* 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_KPROBE_TRACE_ENTRY(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_KRETPROBE_TRACE_ENTRY(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 = (struct trace_probe *)call->data;
+
+        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 = (struct trace_probe *)call->data;
+
+        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, \
+                                         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;
+        char buf[MAX_ARGSTR_LEN + 1];
+        struct trace_probe *tp = (struct trace_probe *)event_call->data;
+
+        ret = trace_define_common_fields(event_call);
+        if (!ret)
+                return ret;
+
+        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 < 0)
+                        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 = (struct trace_probe *)event_call->data;
+
+        ret = trace_define_common_fields(event_call);
+        if (!ret)
+                return ret;
+
+        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 < 0)
+                        return ret;
+                DEFINE_FIELD(unsigned long, args[i], buf, 0);
+        }
+        return 0;
+}
+
+static int __probe_event_show_format(struct trace_seq *s,
+                                     struct trace_probe *tp, const char *fmt,
+                                     const char *arg)
+{
+        int i, ret;
+        char buf[MAX_ARGSTR_LEN + 1];
+
+        /* Show aliases */
+        for (i = 0; i < tp->nr_args; i++) {
+                ret = trace_arg_string(buf, MAX_ARGSTR_LEN, &tp->args[i]);
+                if (ret < 0)
+                        return ret;
+                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 int)offsetof(typeof(field), item),\
+                                (unsigned int)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 = (struct trace_probe *)call->data;
+
+        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(s, tp, "%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 = (struct trace_probe *)call->data;
+
+        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(s, tp, "%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;
+        call->data = tp;
+        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