tracing: Provide trace events interface for uprobes

Implements trace_event support for uprobes. In its current form
it can be used to put probes at a specified offset in a file and
dump the required registers when the code flow reaches the
probed address.

The following example shows how to dump the instruction pointer
and %ax a register at the probed text address.  Here we are
trying to probe zfree in /bin/zsh:

 # cd /sys/kernel/debug/tracing/
 # cat /proc/`pgrep  zsh`/maps | grep /bin/zsh | grep r-xp
 00400000-0048a000 r-xp 00000000 08:03 130904 /bin/zsh
 # objdump -T /bin/zsh | grep -w zfree
 0000000000446420 g    DF .text  0000000000000012  Base
 zfree # echo 'p /bin/zsh:0x46420 %ip %ax' > uprobe_events
 # cat uprobe_events
 p:uprobes/p_zsh_0x46420 /bin/zsh:0x0000000000046420
 # echo 1 > events/uprobes/enable
 # sleep 20
 # echo 0 > events/uprobes/enable
 # cat trace
 # tracer: nop
 #
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
              zsh-24842 [006] 258544.995456: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
              zsh-24842 [007] 258545.000270: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
              zsh-24842 [002] 258545.043929: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
              zsh-24842 [004] 258547.046129: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120411103043.GB29437@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

7 files changed, 823 insertions, 6 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index ce5a5c54ac8f..ea4bff6295fc 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -386,6 +386,22 @@ config KPROBE_EVENT
           This option is also required by perf-probe subcommand of perf tools.
           If you want to use perf tools, this option is strongly recommended.
 
+config UPROBE_EVENT
+        bool "Enable uprobes-based dynamic events"
+        depends on ARCH_SUPPORTS_UPROBES
+        depends on MMU
+        select UPROBES
+        select PROBE_EVENTS
+        select TRACING
+        default n
+        help
+          This allows the user to add tracing events on top of userspace
+          dynamic events (similar to tracepoints) on the fly via the trace
+          events interface. Those events can be inserted wherever uprobes
+          can probe, and record various registers.
+          This option is required if you plan to use perf-probe subcommand
+          of perf tools on user space applications.
+
 config PROBE_EVENTS
         def_bool n
 
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index fa10d5ca5ab1..1734c03e048b 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -62,5 +62,6 @@ ifeq ($(CONFIG_TRACING),y)
 obj-$(CONFIG_KGDB_KDB) += trace_kdb.o
 endif
 obj-$(CONFIG_PROBE_EVENTS) += trace_probe.o
+obj-$(CONFIG_UPROBE_EVENT) += trace_uprobe.o
 
 libftrace-y := ftrace.o
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 95059f091a24..1bcdbec95a11 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -103,6 +103,11 @@ struct kretprobe_trace_entry_head {
         unsigned long           ret_ip;
 };
 
+struct uprobe_trace_entry_head {
+        struct trace_entry      ent;
+        unsigned long           ip;
+};
+
 /*
  * trace_flag_type is an enumeration that holds different
  * states when a trace occurs. These are:
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index f8b777367d8e..b31d3d5699fe 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -525,7 +525,7 @@ static int create_trace_probe(int argc, char **argv)
 
                 /* Parse fetch argument */
                 ret = traceprobe_parse_probe_arg(arg, &tp->size, &tp->args[i],
-                                                                is_return);
+                                                is_return, true);
                 if (ret) {
                         pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
                         goto error;
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 8e526b9286e9..daa9980153af 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -550,7 +550,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
 
 /* Recursive argument parser */
 static int parse_probe_arg(char *arg, const struct fetch_type *t,
-                     struct fetch_param *f, bool is_return)
+                     struct fetch_param *f, bool is_return, bool is_kprobe)
 {
         unsigned long param;
         long offset;
@@ -558,6 +558,11 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
         int ret;
 
         ret = 0;
+
+        /* Until uprobe_events supports only reg arguments */
+        if (!is_kprobe && arg[0] != '%')
+                return -EINVAL;
+
         switch (arg[0]) {
         case '$':
                 ret = parse_probe_vars(arg + 1, t, f, is_return);
@@ -619,7 +624,8 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
                                 return -ENOMEM;
 
                         dprm->offset = offset;
-                        ret = parse_probe_arg(arg, t2, &dprm->orig, is_return);
+                        ret = parse_probe_arg(arg, t2, &dprm->orig, is_return,
+                                                        is_kprobe);
                         if (ret)
                                 kfree(dprm);
                         else {
@@ -677,7 +683,7 @@ static int __parse_bitfield_probe_arg(const char *bf,
 
 /* String length checking wrapper */
 int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
-                struct probe_arg *parg, bool is_return)
+                struct probe_arg *parg, bool is_return, bool is_kprobe)
 {
         const char *t;
         int ret;
@@ -703,7 +709,7 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
         }
         parg->offset = *size;
         *size += parg->type->size;
-        ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
+        ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return, is_kprobe);
 
         if (ret >= 0 && t != NULL)
                 ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch);
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 2df9a18e0252..933708677814 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -66,6 +66,7 @@
 #define TP_FLAG_TRACE           1
 #define TP_FLAG_PROFILE         2
 #define TP_FLAG_REGISTERED      4
+#define TP_FLAG_UPROBE          8
 
 
 /* data_rloc: data relative location, compatible with u32 */
@@ -143,7 +144,7 @@ static inline int is_good_name(const char *name)
 }
 
 extern int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
-                   struct probe_arg *parg, bool is_return);
+                   struct probe_arg *parg, bool is_return, bool is_kprobe);
 
 extern int traceprobe_conflict_field_name(const char *name,
                                struct probe_arg *args, int narg);
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
new file mode 100644
index 000000000000..2b36ac68549e
--- /dev/null
+++ b/kernel/trace/trace_uprobe.c
@@ -0,0 +1,788 @@
+/*
+ * uprobes-based tracing events
+ *
+ * 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
+ *
+ * Copyright (C) IBM Corporation, 2010-2012
+ * Author:      Srikar Dronamraju <srikar@linux.vnet.ibm.com>
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/uprobes.h>
+#include <linux/namei.h>
+
+#include "trace_probe.h"
+
+#define UPROBE_EVENT_SYSTEM     "uprobes"
+
+/*
+ * uprobe event core functions
+ */
+struct trace_uprobe;
+struct uprobe_trace_consumer {
+        struct uprobe_consumer          cons;
+        struct trace_uprobe             *tu;
+};
+
+struct trace_uprobe {
+        struct list_head                list;
+        struct ftrace_event_class       class;
+        struct ftrace_event_call        call;
+        struct uprobe_trace_consumer    *consumer;
+        struct inode                    *inode;
+        char                            *filename;
+        unsigned long                   offset;
+        unsigned long                   nhit;
+        unsigned int                    flags;  /* For TP_FLAG_* */
+        ssize_t                         size;   /* trace entry size */
+        unsigned int                    nr_args;
+        struct probe_arg                args[];
+};
+
+#define SIZEOF_TRACE_UPROBE(n)                  \
+        (offsetof(struct trace_uprobe, args) +  \
+        (sizeof(struct probe_arg) * (n)))
+
+static int register_uprobe_event(struct trace_uprobe *tu);
+static void unregister_uprobe_event(struct trace_uprobe *tu);
+
+static DEFINE_MUTEX(uprobe_lock);
+static LIST_HEAD(uprobe_list);
+
+static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs);
+
+/*
+ * Allocate new trace_uprobe and initialize it (including uprobes).
+ */
+static struct trace_uprobe *
+alloc_trace_uprobe(const char *group, const char *event, int nargs)
+{
+        struct trace_uprobe *tu;
+
+        if (!event || !is_good_name(event))
+                return ERR_PTR(-EINVAL);
+
+        if (!group || !is_good_name(group))
+                return ERR_PTR(-EINVAL);
+
+        tu = kzalloc(SIZEOF_TRACE_UPROBE(nargs), GFP_KERNEL);
+        if (!tu)
+                return ERR_PTR(-ENOMEM);
+
+        tu->call.class = &tu->class;
+        tu->call.name = kstrdup(event, GFP_KERNEL);
+        if (!tu->call.name)
+                goto error;
+
+        tu->class.system = kstrdup(group, GFP_KERNEL);
+        if (!tu->class.system)
+                goto error;
+
+        INIT_LIST_HEAD(&tu->list);
+        return tu;
+
+error:
+        kfree(tu->call.name);
+        kfree(tu);
+
+        return ERR_PTR(-ENOMEM);
+}
+
+static void free_trace_uprobe(struct trace_uprobe *tu)
+{
+        int i;
+
+        for (i = 0; i < tu->nr_args; i++)
+                traceprobe_free_probe_arg(&tu->args[i]);
+
+        iput(tu->inode);
+        kfree(tu->call.class->system);
+        kfree(tu->call.name);
+        kfree(tu->filename);
+        kfree(tu);
+}
+
+static struct trace_uprobe *find_probe_event(const char *event, const char *group)
+{
+        struct trace_uprobe *tu;
+
+        list_for_each_entry(tu, &uprobe_list, list)
+                if (strcmp(tu->call.name, event) == 0 &&
+                    strcmp(tu->call.class->system, group) == 0)
+                        return tu;
+
+        return NULL;
+}
+
+/* Unregister a trace_uprobe and probe_event: call with locking uprobe_lock */
+static void unregister_trace_uprobe(struct trace_uprobe *tu)
+{
+        list_del(&tu->list);
+        unregister_uprobe_event(tu);
+        free_trace_uprobe(tu);
+}
+
+/* Register a trace_uprobe and probe_event */
+static int register_trace_uprobe(struct trace_uprobe *tu)
+{
+        struct trace_uprobe *old_tp;
+        int ret;
+
+        mutex_lock(&uprobe_lock);
+
+        /* register as an event */
+        old_tp = find_probe_event(tu->call.name, tu->call.class->system);
+        if (old_tp)
+                /* delete old event */
+                unregister_trace_uprobe(old_tp);
+
+        ret = register_uprobe_event(tu);
+        if (ret) {
+                pr_warning("Failed to register probe event(%d)\n", ret);
+                goto end;
+        }
+
+        list_add_tail(&tu->list, &uprobe_list);
+
+end:
+        mutex_unlock(&uprobe_lock);
+
+        return ret;
+}
+
+/*
+ * Argument syntax:
+ *  - Add uprobe: p[:[GRP/]EVENT] PATH:SYMBOL[+offs] [FETCHARGS]
+ *
+ *  - Remove uprobe: -:[GRP/]EVENT
+ */
+static int create_trace_uprobe(int argc, char **argv)
+{
+        struct trace_uprobe *tu;
+        struct inode *inode;
+        char *arg, *event, *group, *filename;
+        char buf[MAX_EVENT_NAME_LEN];
+        struct path path;
+        unsigned long offset;
+        bool is_delete;
+        int i, ret;
+
+        inode = NULL;
+        ret = 0;
+        is_delete = false;
+        event = NULL;
+        group = NULL;
+
+        /* argc must be >= 1 */
+        if (argv[0][0] == '-')
+                is_delete = true;
+        else if (argv[0][0] != 'p') {
+                pr_info("Probe definition must be started with 'p', 'r' or" " '-'.\n");
+                return -EINVAL;
+        }
+
+        if (argv[0][1] == ':') {
+                event = &argv[0][2];
+                arg = strchr(event, '/');
+
+                if (arg) {
+                        group = event;
+                        event = arg + 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 = UPROBE_EVENT_SYSTEM;
+
+        if (is_delete) {
+                if (!event) {
+                        pr_info("Delete command needs an event name.\n");
+                        return -EINVAL;
+                }
+                mutex_lock(&uprobe_lock);
+                tu = find_probe_event(event, group);
+
+                if (!tu) {
+                        mutex_unlock(&uprobe_lock);
+                        pr_info("Event %s/%s doesn't exist.\n", group, event);
+                        return -ENOENT;
+                }
+                /* delete an event */
+                unregister_trace_uprobe(tu);
+                mutex_unlock(&uprobe_lock);
+                return 0;
+        }
+
+        if (argc < 2) {
+                pr_info("Probe point is not specified.\n");
+                return -EINVAL;
+        }
+        if (isdigit(argv[1][0])) {
+                pr_info("probe point must be have a filename.\n");
+                return -EINVAL;
+        }
+        arg = strchr(argv[1], ':');
+        if (!arg)
+                goto fail_address_parse;
+
+        *arg++ = '\0';
+        filename = argv[1];
+        ret = kern_path(filename, LOOKUP_FOLLOW, &path);
+        if (ret)
+                goto fail_address_parse;
+
+        ret = strict_strtoul(arg, 0, &offset);
+        if (ret)
+                goto fail_address_parse;
+
+        inode = igrab(path.dentry->d_inode);
+
+        argc -= 2;
+        argv += 2;
+
+        /* setup a probe */
+        if (!event) {
+                char *tail = strrchr(filename, '/');
+                char *ptr;
+
+                ptr = kstrdup((tail ? tail + 1 : filename), GFP_KERNEL);
+                if (!ptr) {
+                        ret = -ENOMEM;
+                        goto fail_address_parse;
+                }
+
+                tail = ptr;
+                ptr = strpbrk(tail, ".-_");
+                if (ptr)
+                        *ptr = '\0';
+
+                snprintf(buf, MAX_EVENT_NAME_LEN, "%c_%s_0x%lx", 'p', tail, offset);
+                event = buf;
+                kfree(tail);
+        }
+
+        tu = alloc_trace_uprobe(group, event, argc);
+        if (IS_ERR(tu)) {
+                pr_info("Failed to allocate trace_uprobe.(%d)\n", (int)PTR_ERR(tu));
+                ret = PTR_ERR(tu);
+                goto fail_address_parse;
+        }
+        tu->offset = offset;
+        tu->inode = inode;
+        tu->filename = kstrdup(filename, GFP_KERNEL);
+
+        if (!tu->filename) {
+                pr_info("Failed to allocate filename.\n");
+                ret = -ENOMEM;
+                goto error;
+        }
+
+        /* parse arguments */
+        ret = 0;
+        for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
+                /* Increment count for freeing args in error case */
+                tu->nr_args++;
+
+                /* Parse argument name */
+                arg = strchr(argv[i], '=');
+                if (arg) {
+                        *arg++ = '\0';
+                        tu->args[i].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);
+                        tu->args[i].name = kstrdup(buf, GFP_KERNEL);
+                }
+
+                if (!tu->args[i].name) {
+                        pr_info("Failed to allocate argument[%d] name.\n", i);
+                        ret = -ENOMEM;
+                        goto error;
+                }
+
+                if (!is_good_name(tu->args[i].name)) {
+                        pr_info("Invalid argument[%d] name: %s\n", i, tu->args[i].name);
+                        ret = -EINVAL;
+                        goto error;
+                }
+
+                if (traceprobe_conflict_field_name(tu->args[i].name, tu->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, &tu->size, &tu->args[i], false, false);
+                if (ret) {
+                        pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
+                        goto error;
+                }
+        }
+
+        ret = register_trace_uprobe(tu);
+        if (ret)
+                goto error;
+        return 0;
+
+error:
+        free_trace_uprobe(tu);
+        return ret;
+
+fail_address_parse:
+        if (inode)
+                iput(inode);
+
+        pr_info("Failed to parse address.\n");
+
+        return ret;
+}
+
+static void cleanup_all_probes(void)
+{
+        struct trace_uprobe *tu;
+
+        mutex_lock(&uprobe_lock);
+        while (!list_empty(&uprobe_list)) {
+                tu = list_entry(uprobe_list.next, struct trace_uprobe, list);
+                unregister_trace_uprobe(tu);
+        }
+        mutex_unlock(&uprobe_lock);
+}
+
+/* Probes listing interfaces */
+static void *probes_seq_start(struct seq_file *m, loff_t *pos)
+{
+        mutex_lock(&uprobe_lock);
+        return seq_list_start(&uprobe_list, *pos);
+}
+
+static void *probes_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+        return seq_list_next(v, &uprobe_list, pos);
+}
+
+static void probes_seq_stop(struct seq_file *m, void *v)
+{
+        mutex_unlock(&uprobe_lock);
+}
+
+static int probes_seq_show(struct seq_file *m, void *v)
+{
+        struct trace_uprobe *tu = v;
+        int i;
+
+        seq_printf(m, "p:%s/%s", tu->call.class->system, tu->call.name);
+        seq_printf(m, " %s:0x%p", tu->filename, (void *)tu->offset);
+
+        for (i = 0; i < tu->nr_args; i++)
+                seq_printf(m, " %s=%s", tu->args[i].name, tu->args[i].comm);
+
+        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 ssize_t probes_write(struct file *file, const char __user *buffer,
+                            size_t count, loff_t *ppos)
+{
+        return traceprobe_probes_write(file, buffer, count, ppos, create_trace_uprobe);
+}
+
+static const struct file_operations uprobe_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_uprobe *tu = v;
+
+        seq_printf(m, "  %s %-44s %15lu\n", tu->filename, tu->call.name, tu->nhit);
+        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 uprobe_profile_ops = {
+        .owner          = THIS_MODULE,
+        .open           = profile_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
+/* uprobe handler */
+static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
+{
+        struct uprobe_trace_entry_head *entry;
+        struct ring_buffer_event *event;
+        struct ring_buffer *buffer;
+        u8 *data;
+        int size, i, pc;
+        unsigned long irq_flags;
+        struct ftrace_event_call *call = &tu->call;
+
+        tu->nhit++;
+
+        local_save_flags(irq_flags);
+        pc = preempt_count();
+
+        size = sizeof(*entry) + tu->size;
+
+        event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
+                                                  size, irq_flags, pc);
+        if (!event)
+                return;
+
+        entry = ring_buffer_event_data(event);
+        entry->ip = uprobe_get_swbp_addr(task_pt_regs(current));
+        data = (u8 *)&entry[1];
+        for (i = 0; i < tu->nr_args; i++)
+                call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);
+
+        if (!filter_current_check_discard(buffer, call, entry, event))
+                trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
+}
+
+/* Event entry printers */
+static enum print_line_t
+print_uprobe_event(struct trace_iterator *iter, int flags, struct trace_event *event)
+{
+        struct uprobe_trace_entry_head *field;
+        struct trace_seq *s = &iter->seq;
+        struct trace_uprobe *tu;
+        u8 *data;
+        int i;
+
+        field = (struct uprobe_trace_entry_head *)iter->ent;
+        tu = container_of(event, struct trace_uprobe, call.event);
+
+        if (!trace_seq_printf(s, "%s: (", tu->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;
+
+        data = (u8 *)&field[1];
+        for (i = 0; i < tu->nr_args; i++) {
+                if (!tu->args[i].type->print(s, tu->args[i].name,
+                                             data + tu->args[i].offset, field))
+                        goto partial;
+        }
+
+        if (trace_seq_puts(s, "\n"))
+                return TRACE_TYPE_HANDLED;
+
+partial:
+        return TRACE_TYPE_PARTIAL_LINE;
+}
+
+static int probe_event_enable(struct trace_uprobe *tu, int flag)
+{
+        struct uprobe_trace_consumer *utc;
+        int ret = 0;
+
+        if (!tu->inode || tu->consumer)
+                return -EINTR;
+
+        utc = kzalloc(sizeof(struct uprobe_trace_consumer), GFP_KERNEL);
+        if (!utc)
+                return -EINTR;
+
+        utc->cons.handler = uprobe_dispatcher;
+        utc->cons.filter = NULL;
+        ret = uprobe_register(tu->inode, tu->offset, &utc->cons);
+        if (ret) {
+                kfree(utc);
+                return ret;
+        }
+
+        tu->flags |= flag;
+        utc->tu = tu;
+        tu->consumer = utc;
+
+        return 0;
+}
+
+static void probe_event_disable(struct trace_uprobe *tu, int flag)
+{
+        if (!tu->inode || !tu->consumer)
+                return;
+
+        uprobe_unregister(tu->inode, tu->offset, &tu->consumer->cons);
+        tu->flags &= ~flag;
+        kfree(tu->consumer);
+        tu->consumer = NULL;
+}
+
+static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
+{
+        int ret, i;
+        struct uprobe_trace_entry_head field;
+        struct trace_uprobe *tu = (struct trace_uprobe *)event_call->data;
+
+        DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
+        /* Set argument names as fields */
+        for (i = 0; i < tu->nr_args; i++) {
+                ret = trace_define_field(event_call, tu->args[i].type->fmttype,
+                                         tu->args[i].name,
+                                         sizeof(field) + tu->args[i].offset,
+                                         tu->args[i].type->size,
+                                         tu->args[i].type->is_signed,
+                                         FILTER_OTHER);
+
+                if (ret)
+                        return ret;
+        }
+        return 0;
+}
+
+#define LEN_OR_ZERO             (len ? len - pos : 0)
+static int __set_print_fmt(struct trace_uprobe *tu, char *buf, int len)
+{
+        const char *fmt, *arg;
+        int i;
+        int pos = 0;
+
+        fmt = "(%lx)";
+        arg = "REC->" FIELD_STRING_IP;
+
+        /* When len=0, we just calculate the needed length */
+
+        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);
+
+        for (i = 0; i < tu->nr_args; i++) {
+                pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
+                                tu->args[i].name, tu->args[i].type->fmt);
+        }
+
+        pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
+
+        for (i = 0; i < tu->nr_args; i++) {
+                pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
+                                tu->args[i].name);
+        }
+
+        return pos;     /* return the length of print_fmt */
+}
+#undef LEN_OR_ZERO
+
+static int set_print_fmt(struct trace_uprobe *tu)
+{
+        char *print_fmt;
+        int len;
+
+        /* First: called with 0 length to calculate the needed length */
+        len = __set_print_fmt(tu, NULL, 0);
+        print_fmt = kmalloc(len + 1, GFP_KERNEL);
+        if (!print_fmt)
+                return -ENOMEM;
+
+        /* Second: actually write the @print_fmt */
+        __set_print_fmt(tu, print_fmt, len + 1);
+        tu->call.print_fmt = print_fmt;
+
+        return 0;
+}
+
+#ifdef CONFIG_PERF_EVENTS
+/* uprobe profile handler */
+static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
+{
+        struct ftrace_event_call *call = &tu->call;
+        struct uprobe_trace_entry_head *entry;
+        struct hlist_head *head;
+        u8 *data;
+        int size, __size, i;
+        int rctx;
+
+        __size = sizeof(*entry) + tu->size;
+        size = ALIGN(__size + sizeof(u32), sizeof(u64));
+        size -= sizeof(u32);
+        if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
+                return;
+
+        preempt_disable();
+
+        entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
+        if (!entry)
+                goto out;
+
+        entry->ip = uprobe_get_swbp_addr(task_pt_regs(current));
+        data = (u8 *)&entry[1];
+        for (i = 0; i < tu->nr_args; i++)
+                call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);
+
+        head = this_cpu_ptr(call->perf_events);
+        perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head);
+
+ out:
+        preempt_enable();
+}
+#endif  /* CONFIG_PERF_EVENTS */
+
+static
+int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
+{
+        struct trace_uprobe *tu = (struct trace_uprobe *)event->data;
+
+        switch (type) {
+        case TRACE_REG_REGISTER:
+                return probe_event_enable(tu, TP_FLAG_TRACE);
+
+        case TRACE_REG_UNREGISTER:
+                probe_event_disable(tu, TP_FLAG_TRACE);
+                return 0;
+
+#ifdef CONFIG_PERF_EVENTS
+        case TRACE_REG_PERF_REGISTER:
+                return probe_event_enable(tu, TP_FLAG_PROFILE);
+
+        case TRACE_REG_PERF_UNREGISTER:
+                probe_event_disable(tu, TP_FLAG_PROFILE);
+                return 0;
+#endif
+        default:
+                return 0;
+        }
+        return 0;
+}
+
+static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
+{
+        struct uprobe_trace_consumer *utc;
+        struct trace_uprobe *tu;
+
+        utc = container_of(con, struct uprobe_trace_consumer, cons);
+        tu = utc->tu;
+        if (!tu || tu->consumer != utc)
+                return 0;
+
+        if (tu->flags & TP_FLAG_TRACE)
+                uprobe_trace_func(tu, regs);
+
+#ifdef CONFIG_PERF_EVENTS
+        if (tu->flags & TP_FLAG_PROFILE)
+                uprobe_perf_func(tu, regs);
+#endif
+        return 0;
+}
+
+static struct trace_event_functions uprobe_funcs = {
+        .trace          = print_uprobe_event
+};
+
+static int register_uprobe_event(struct trace_uprobe *tu)
+{
+        struct ftrace_event_call *call = &tu->call;
+        int ret;
+
+        /* Initialize ftrace_event_call */
+        INIT_LIST_HEAD(&call->class->fields);
+        call->event.funcs = &uprobe_funcs;
+        call->class->define_fields = uprobe_event_define_fields;
+
+        if (set_print_fmt(tu) < 0)
+                return -ENOMEM;
+
+        ret = register_ftrace_event(&call->event);
+        if (!ret) {
+                kfree(call->print_fmt);
+                return -ENODEV;
+        }
+        call->flags = 0;
+        call->class->reg = trace_uprobe_register;
+        call->data = tu;
+        ret = trace_add_event_call(call);
+
+        if (ret) {
+                pr_info("Failed to register uprobe event: %s\n", call->name);
+                kfree(call->print_fmt);
+                unregister_ftrace_event(&call->event);
+        }
+
+        return ret;
+}
+
+static void unregister_uprobe_event(struct trace_uprobe *tu)
+{
+        /* tu->event is unregistered in trace_remove_event_call() */
+        trace_remove_event_call(&tu->call);
+        kfree(tu->call.print_fmt);
+        tu->call.print_fmt = NULL;
+}
+
+/* Make a trace interface for controling probe points */
+static __init int init_uprobe_trace(void)
+{
+        struct dentry *d_tracer;
+
+        d_tracer = tracing_init_dentry();
+        if (!d_tracer)
+                return 0;
+
+        trace_create_file("uprobe_events", 0644, d_tracer,
+                                    NULL, &uprobe_events_ops);
+        /* Profile interface */
+        trace_create_file("uprobe_profile", 0444, d_tracer,
+                                    NULL, &uprobe_profile_ops);
+        return 0;
+}
+
+fs_initcall(init_uprobe_trace);