probes/lttng-kprobes.c

   1 /*
   2  * probes/lttng-kprobes.c
   3  *
   4  * LTTng kprobes integration module.
   5  *
   6  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/kprobes.h>
  25 #include <linux/slab.h>
  26 #include "../lttng-events.h"
  27 #include "../wrapper/ringbuffer/frontend_types.h"
  28 #include "../wrapper/vmalloc.h"
  29 #include "../lttng-tracer.h"
  30
  31 static
  32 int lttng_kprobes_handler_pre(struct kprobe *p, struct pt_regs *regs)
  33 {
  34         struct lttng_event *event =
  35                 container_of(p, struct lttng_event, u.kprobe.kp);
  36         struct lttng_channel *chan = event->chan;
  37         struct lib_ring_buffer_ctx ctx;
  38         int ret;
  39         unsigned long data = (unsigned long) p->addr;
  40
  41         if (unlikely(!ACCESS_ONCE(chan->session->active)))
  42                 return 0;
  43         if (unlikely(!ACCESS_ONCE(chan->enabled)))
  44                 return 0;
  45         if (unlikely(!ACCESS_ONCE(event->enabled)))
  46                 return 0;
  47
  48         lib_ring_buffer_ctx_init(&ctx, chan->chan, event, sizeof(data),
  49                                  lttng_alignof(data), -1);
  50         ret = chan->ops->event_reserve(&ctx, event->id);
  51         if (ret < 0)
  52                 return 0;
  53         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  54         chan->ops->event_write(&ctx, &data, sizeof(data));
  55         chan->ops->event_commit(&ctx);
  56         return 0;
  57 }
  58
  59 /*
  60  * Create event description
  61  */
  62 static
  63 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  64 {
  65         struct lttng_event_field *field;
  66         struct lttng_event_desc *desc;
  67         int ret;
  68
  69         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  70         if (!desc)
  71                 return -ENOMEM;
  72         desc->name = kstrdup(name, GFP_KERNEL);
  73         if (!desc->name) {
  74                 ret = -ENOMEM;
  75                 goto error_str;
  76         }
  77         desc->nr_fields = 1;
  78         desc->fields = field =
  79                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  80         if (!field) {
  81                 ret = -ENOMEM;
  82                 goto error_field;
  83         }
  84         field->name = "ip";
  85         field->type.atype = atype_integer;
  86         field->type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
  87         field->type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  88         field->type.u.basic.integer.signedness = is_signed_type(unsigned long);
  89         field->type.u.basic.integer.reverse_byte_order = 0;
  90         field->type.u.basic.integer.base = 16;
  91         field->type.u.basic.integer.encoding = lttng_encode_none;
  92         desc->owner = THIS_MODULE;
  93         event->desc = desc;
  94
  95         return 0;
  96
  97 error_field:
  98         kfree(desc->name);
  99 error_str:
 100         kfree(desc);
 101         return ret;
 102 }
 103
 104 int lttng_kprobes_register(const char *name,
 105                            const char *symbol_name,
 106                            uint64_t offset,
 107                            uint64_t addr,
 108                            struct lttng_event *event)
 109 {
 110         int ret;
 111
 112         /* Kprobes expects a NULL symbol name if unused */
 113         if (symbol_name[0] == '\0')
 114                 symbol_name = NULL;
 115
 116         ret = lttng_create_kprobe_event(name, event);
 117         if (ret)
 118                 goto error;
 119         memset(&event->u.kprobe.kp, 0, sizeof(event->u.kprobe.kp));
 120         event->u.kprobe.kp.pre_handler = lttng_kprobes_handler_pre;
 121         if (symbol_name) {
 122                 event->u.kprobe.symbol_name =
 123                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 124                                 GFP_KERNEL);
 125                 if (!event->u.kprobe.symbol_name) {
 126                         ret = -ENOMEM;
 127                         goto name_error;
 128                 }
 129                 memcpy(event->u.kprobe.symbol_name, symbol_name,
 130                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 131                 event->u.kprobe.kp.symbol_name =
 132                         event->u.kprobe.symbol_name;
 133         }
 134         event->u.kprobe.kp.offset = offset;
 135         event->u.kprobe.kp.addr = (void *) (unsigned long) addr;
 136
 137         /*
 138          * Ensure the memory we just allocated don't trigger page faults.
 139          * Well.. kprobes itself puts the page fault handler on the blacklist,
 140          * but we can never be too careful.
 141          */
 142         wrapper_vmalloc_sync_all();
 143
 144         ret = register_kprobe(&event->u.kprobe.kp);
 145         if (ret)
 146                 goto register_error;
 147         return 0;
 148
 149 register_error:
 150         kfree(event->u.kprobe.symbol_name);
 151 name_error:
 152         kfree(event->desc->fields);
 153         kfree(event->desc->name);
 154         kfree(event->desc);
 155 error:
 156         return ret;
 157 }
 158 EXPORT_SYMBOL_GPL(lttng_kprobes_register);
 159
 160 void lttng_kprobes_unregister(struct lttng_event *event)
 161 {
 162         unregister_kprobe(&event->u.kprobe.kp);
 163 }
 164 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister);
 165
 166 void lttng_kprobes_destroy_private(struct lttng_event *event)
 167 {
 168         kfree(event->u.kprobe.symbol_name);
 169         kfree(event->desc->fields);
 170         kfree(event->desc->name);
 171         kfree(event->desc);
 172 }
 173 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_private);
 174
 175 MODULE_LICENSE("GPL and additional rights");
 176 MODULE_AUTHOR("Mathieu Desnoyers");
 177 MODULE_DESCRIPTION("Linux Trace Toolkit Kprobes Support");