/*
 * 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 <linux/string.h>

#include "trace_probe.h"

#define UPROBE_EVENT_SYSTEM     "uprobes"

struct uprobe_trace_entry_head {
        struct trace_entry      ent;
        unsigned long           vaddr[];
};

#define SIZEOF_TRACE_ENTRY(is_return)                   \
        (sizeof(struct uprobe_trace_entry_head) +       \
         sizeof(unsigned long) * (is_return ? 2 : 1))

#define DATAOF_TRACE_ENTRY(entry, is_return)            \
        ((void*)(entry) + SIZEOF_TRACE_ENTRY(is_return))

struct trace_uprobe_filter {
        rwlock_t                rwlock;
        int                     nr_systemwide;
        struct list_head        perf_events;
};

/*
 * uprobe event core functions
 */
struct trace_uprobe {
        struct list_head                list;
        struct ftrace_event_class       class;
        struct ftrace_event_call        call;
        struct trace_uprobe_filter      filter;
        struct uprobe_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 int 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);
static int uretprobe_dispatcher(struct uprobe_consumer *con,
                                unsigned long func, struct pt_regs *regs);

static inline void init_trace_uprobe_filter(struct trace_uprobe_filter *filter)
{
        rwlock_init(&filter->rwlock);
        filter->nr_systemwide = 0;
        INIT_LIST_HEAD(&filter->perf_events);
}

static inline bool uprobe_filter_is_empty(struct trace_uprobe_filter *filter)
{
        return !filter->nr_systemwide && list_empty(&filter->perf_events);
}

static inline bool is_ret_probe(struct trace_uprobe *tu)
{
        return tu->consumer.ret_handler != NULL;
}

/*
 * Allocate new trace_uprobe and initialize it (including uprobes).
 */
static struct trace_uprobe *
alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret)
{
        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);
        tu->consumer.handler = uprobe_dispatcher;
        if (is_ret)
                tu->consumer.ret_handler = uretprobe_dispatcher;
        init_trace_uprobe_filter(&tu->filter);
        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 int unregister_trace_uprobe(struct trace_uprobe *tu)
{
        int ret;

        ret = unregister_uprobe_event(tu);
        if (ret)
                return ret;

        list_del(&tu->list);
        free_trace_uprobe(tu);
        return 0;
}

/* 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 */
                ret = unregister_trace_uprobe(old_tp);
                if (ret)
                        goto end;
        }

        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|r[:[GRP/]EVENT] PATH:SYMBOL [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, is_return;
        int i, ret;

        inode = NULL;
        ret = 0;
        is_delete = false;
        is_return = false;
        event = NULL;
        group = NULL;

        /* argc must be >= 1 */
        if (argv[0][0] == '-')
                is_delete = true;
        else if (argv[0][0] == 'r')
                is_return = 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) {
                int ret;

                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 */
                ret = unregister_trace_uprobe(tu);
                mutex_unlock(&uprobe_lock);
                return ret;
        }

        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) {
                ret = -EINVAL;
                goto fail_address_parse;
        }

        *arg++ = '\0';
        filename = argv[1];
        ret = kern_path(filename, LOOKUP_FOLLOW, &path);
        if (ret)
                goto fail_address_parse;

        inode = igrab(path.dentry->d_inode);
        path_put(&path);

        if (!inode || !S_ISREG(inode->i_mode)) {
                ret = -EINVAL;
                goto fail_address_parse;
        }

        ret = kstrtoul(arg, 0, &offset);
        if (ret)
                goto fail_address_parse;

        argc -= 2;
        argv += 2;

        /* setup a probe */
        if (!event) {
                char *tail;
                char *ptr;

                tail = kstrdup(kbasename(filename), GFP_KERNEL);
                if (!tail) {
                        ret = -ENOMEM;
                        goto fail_address_parse;
                }

                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, is_return);
        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 or file.\n");

        return ret;
}

static int cleanup_all_probes(void)
{
        struct trace_uprobe *tu;
        int ret = 0;

        mutex_lock(&uprobe_lock);
        while (!list_empty(&uprobe_list)) {
                tu = list_entry(uprobe_list.next, struct trace_uprobe, list);
                ret = unregister_trace_uprobe(tu);
                if (ret)
                        break;
        }
        mutex_unlock(&uprobe_lock);
        return ret;
}

/* 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;
        char c = is_ret_probe(tu) ? 'r' : 'p';
        int i;

        seq_printf(m, "%c:%s/%s", c, 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)
{
        int ret;

        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
                ret = cleanup_all_probes();
                if (ret)
                        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 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,
};

static void uprobe_trace_print(struct trace_uprobe *tu,
                                unsigned long func, struct pt_regs *regs)
{
        struct uprobe_trace_entry_head *entry;
        struct ring_buffer_event *event;
        struct ring_buffer *buffer;
        void *data;
        int size, i;
        struct ftrace_event_call *call = &tu->call;

        size = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
        event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
                                                  size + tu->size, 0, 0);
        if (!event)
                return;

        entry = ring_buffer_event_data(event);
        if (is_ret_probe(tu)) {
                entry->vaddr[0] = func;
                entry->vaddr[1] = instruction_pointer(regs);
                data = DATAOF_TRACE_ENTRY(entry, true);
        } else {
                entry->vaddr[0] = instruction_pointer(regs);
                data = DATAOF_TRACE_ENTRY(entry, false);
        }

        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, 0, 0);
}

/* uprobe handler */
static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
{
        if (!is_ret_probe(tu))
                uprobe_trace_print(tu, 0, regs);
        return 0;
}

static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func,
                                struct pt_regs *regs)
{
        uprobe_trace_print(tu, func, regs);
}

/* 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 *entry;
        struct trace_seq *s = &iter->seq;
        struct trace_uprobe *tu;
        u8 *data;
        int i;

        entry = (struct uprobe_trace_entry_head *)iter->ent;
        tu = container_of(event, struct trace_uprobe, call.event);

        if (is_ret_probe(tu)) {
                if (!trace_seq_printf(s, "%s: (0x%lx <- 0x%lx)", tu->call.name,
                                        entry->vaddr[1], entry->vaddr[0]))
                        goto partial;
                data = DATAOF_TRACE_ENTRY(entry, true);
        } else {
                if (!trace_seq_printf(s, "%s: (0x%lx)", tu->call.name,
                                        entry->vaddr[0]))
                        goto partial;
                data = DATAOF_TRACE_ENTRY(entry, false);
        }

        for (i = 0; i < tu->nr_args; i++) {
                if (!tu->args[i].type->print(s, tu->args[i].name,
                                             data + tu->args[i].offset, entry))
                        goto partial;
        }

        if (trace_seq_puts(s, "\n"))
                return TRACE_TYPE_HANDLED;

partial:
        return TRACE_TYPE_PARTIAL_LINE;
}

static inline bool is_trace_uprobe_enabled(struct trace_uprobe *tu)
{
        return tu->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE);
}

typedef bool (*filter_func_t)(struct uprobe_consumer *self,
                                enum uprobe_filter_ctx ctx,
                                struct mm_struct *mm);

static int
probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
{
        int ret = 0;

        if (is_trace_uprobe_enabled(tu))
                return -EINTR;

        WARN_ON(!uprobe_filter_is_empty(&tu->filter));

        tu->flags |= flag;
        tu->consumer.filter = filter;
        ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
        if (ret)
                tu->flags &= ~flag;

        return ret;
}

static void probe_event_disable(struct trace_uprobe *tu, int flag)
{
        if (!is_trace_uprobe_enabled(tu))
                return;

        WARN_ON(!uprobe_filter_is_empty(&tu->filter));

        uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
        tu->flags &= ~flag;
}

static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
{
        int ret, i, size;
        struct uprobe_trace_entry_head field;
        struct trace_uprobe *tu = event_call->data;

        if (is_ret_probe(tu)) {
                DEFINE_FIELD(unsigned long, vaddr[0], FIELD_STRING_FUNC, 0);
                DEFINE_FIELD(unsigned long, vaddr[1], FIELD_STRING_RETIP, 0);
                size = SIZEOF_TRACE_ENTRY(true);
        } else {
                DEFINE_FIELD(unsigned long, vaddr[0], FIELD_STRING_IP, 0);
                size = SIZEOF_TRACE_ENTRY(false);
        }
        /* 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,
                                         size + 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;

        if (is_ret_probe(tu)) {
                fmt = "(%lx <- %lx)";
                arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
        } else {
                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
static bool
__uprobe_perf_filter(struct trace_uprobe_filter *filter, struct mm_struct *mm)
{
        struct perf_event *event;

        if (filter->nr_systemwide)
                return true;

        list_for_each_entry(event, &filter->perf_events, hw.tp_list) {
                if (event->hw.tp_target->mm == mm)
                        return true;
        }

        return false;
}

static inline bool
uprobe_filter_event(struct trace_uprobe *tu, struct perf_event *event)
{
        return __uprobe_perf_filter(&tu->filter, event->hw.tp_target->mm);
}

static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event)
{
        bool done;

        write_lock(&tu->filter.rwlock);
        if (event->hw.tp_target) {
                /*
                 * event->parent != NULL means copy_process(), we can avoid
                 * uprobe_apply(). current->mm must be probed and we can rely
                 * on dup_mmap() which preserves the already installed bp's.
                 *
                 * attr.enable_on_exec means that exec/mmap will install the
                 * breakpoints we need.
                 */
                done = tu->filter.nr_systemwide ||
                        event->parent || event->attr.enable_on_exec ||
                        uprobe_filter_event(tu, event);
                list_add(&event->hw.tp_list, &tu->filter.perf_events);
        } else {
                done = tu->filter.nr_systemwide;
                tu->filter.nr_systemwide++;
        }
        write_unlock(&tu->filter.rwlock);

        if (!done)
                uprobe_apply(tu->inode, tu->offset, &tu->consumer, true);

        return 0;
}

static int uprobe_perf_close(struct trace_uprobe *tu, struct perf_event *event)
{
        bool done;

        write_lock(&tu->filter.rwlock);
        if (event->hw.tp_target) {
                list_del(&event->hw.tp_list);
                done = tu->filter.nr_systemwide ||
                        (event->hw.tp_target->flags & PF_EXITING) ||
                        uprobe_filter_event(tu, event);
        } else {
                tu->filter.nr_systemwide--;
                done = tu->filter.nr_systemwide;
        }
        write_unlock(&tu->filter.rwlock);

        if (!done)
                uprobe_apply(tu->inode, tu->offset, &tu->consumer, false);

        return 0;
}

static bool uprobe_perf_filter(struct uprobe_consumer *uc,
                                enum uprobe_filter_ctx ctx, struct mm_struct *mm)
{
        struct trace_uprobe *tu;
        int ret;

        tu = container_of(uc, struct trace_uprobe, consumer);
        read_lock(&tu->filter.rwlock);
        ret = __uprobe_perf_filter(&tu->filter, mm);
        read_unlock(&tu->filter.rwlock);

        return ret;
}

static void uprobe_perf_print(struct trace_uprobe *tu,
                                unsigned long func, struct pt_regs *regs)
{
        struct ftrace_event_call *call = &tu->call;
        struct uprobe_trace_entry_head *entry;
        struct hlist_head *head;
        void *data;
        int size, rctx, i;

        size = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
        size = ALIGN(size + tu->size + sizeof(u32), sizeof(u64)) - sizeof(u32);

        preempt_disable();
        head = this_cpu_ptr(call->perf_events);
        if (hlist_empty(head))
                goto out;

        entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
        if (!entry)
                goto out;

        if (is_ret_probe(tu)) {
                entry->vaddr[0] = func;
                entry->vaddr[1] = instruction_pointer(regs);
                data = DATAOF_TRACE_ENTRY(entry, true);
        } else {
                entry->vaddr[0] = instruction_pointer(regs);
                data = DATAOF_TRACE_ENTRY(entry, false);
        }

        for (i = 0; i < tu->nr_args; i++)
                call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);

        perf_trace_buf_submit(entry, size, rctx, 0, 1, regs, head, NULL);
 out:
        preempt_enable();
}

/* uprobe profile handler */
static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
{
        if (!uprobe_perf_filter(&tu->consumer, 0, current->mm))
                return UPROBE_HANDLER_REMOVE;

        if (!is_ret_probe(tu))
                uprobe_perf_print(tu, 0, regs);
        return 0;
}

static void uretprobe_perf_func(struct trace_uprobe *tu, unsigned long func,
                                struct pt_regs *regs)
{
        uprobe_perf_print(tu, func, regs);
}
#endif  /* CONFIG_PERF_EVENTS */

static
int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
{
        struct trace_uprobe *tu = event->data;

        switch (type) {
        case TRACE_REG_REGISTER:
                return probe_event_enable(tu, TP_FLAG_TRACE, NULL);

        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, uprobe_perf_filter);

        case TRACE_REG_PERF_UNREGISTER:
                probe_event_disable(tu, TP_FLAG_PROFILE);
                return 0;

        case TRACE_REG_PERF_OPEN:
                return uprobe_perf_open(tu, data);

        case TRACE_REG_PERF_CLOSE:
                return uprobe_perf_close(tu, data);

#endif
        default:
                return 0;
        }
        return 0;
}

static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
{
        struct trace_uprobe *tu;
        int ret = 0;

        tu = container_of(con, struct trace_uprobe, consumer);
        tu->nhit++;

        if (tu->flags & TP_FLAG_TRACE)
                ret |= uprobe_trace_func(tu, regs);

#ifdef CONFIG_PERF_EVENTS
        if (tu->flags & TP_FLAG_PROFILE)
                ret |= uprobe_perf_func(tu, regs);
#endif
        return ret;
}

static int uretprobe_dispatcher(struct uprobe_consumer *con,
                                unsigned long func, struct pt_regs *regs)
{
        struct trace_uprobe *tu;

        tu = container_of(con, struct trace_uprobe, consumer);

        if (tu->flags & TP_FLAG_TRACE)
                uretprobe_trace_func(tu, func, regs);

#ifdef CONFIG_PERF_EVENTS
        if (tu->flags & TP_FLAG_PROFILE)
                uretprobe_perf_func(tu, func, 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 int unregister_uprobe_event(struct trace_uprobe *tu)
{
        int ret;

        /* tu->event is unregistered in trace_remove_event_call() */
        ret = trace_remove_event_call(&tu->call);
        if (ret)
                return ret;
        kfree(tu->call.print_fmt);
        tu->call.print_fmt = NULL;

        return 0;
}

/* 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);