probes/lttng-kretprobes.c

   1 /*
   2  * probes/lttng-kretprobes.c
   3  *
   4  * LTTng kretprobes 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 <linux/kref.h>
  27 #include "../lttng-events.h"
  28 #include "../wrapper/ringbuffer/frontend_types.h"
  29 #include "../wrapper/vmalloc.h"
  30 #include "../lttng-tracer.h"
  31
  32 enum lttng_kretprobe_type {
  33         EVENT_ENTRY = 0,
  34         EVENT_RETURN = 1,
  35 };
  36
  37 struct lttng_krp {
  38         struct kretprobe krp;
  39         struct lttng_event *event[2];   /* ENTRY and RETURN */
  40         struct kref kref_register;
  41         struct kref kref_alloc;
  42 };
  43
  44 static
  45 int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
  46                               struct pt_regs *regs,
  47                               enum lttng_kretprobe_type type)
  48 {
  49         struct lttng_krp *lttng_krp =
  50                 container_of(krpi->rp, struct lttng_krp, krp);
  51         struct lttng_event *event =
  52                 lttng_krp->event[type];
  53         struct lttng_channel *chan = event->chan;
  54         struct lib_ring_buffer_ctx ctx;
  55         int ret;
  56         struct {
  57                 unsigned long ip;
  58                 unsigned long parent_ip;
  59         } payload;
  60
  61         if (unlikely(!ACCESS_ONCE(chan->session->active)))
  62                 return 0;
  63         if (unlikely(!ACCESS_ONCE(chan->enabled)))
  64                 return 0;
  65         if (unlikely(!ACCESS_ONCE(event->enabled)))
  66                 return 0;
  67
  68         payload.ip = (unsigned long) krpi->rp->kp.addr;
  69         payload.parent_ip = (unsigned long) krpi->ret_addr;
  70
  71         lib_ring_buffer_ctx_init(&ctx, chan->chan, event, sizeof(payload),
  72                                  lttng_alignof(payload), -1);
  73         ret = chan->ops->event_reserve(&ctx, event->id);
  74         if (ret < 0)
  75                 return 0;
  76         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
  77         chan->ops->event_write(&ctx, &payload, sizeof(payload));
  78         chan->ops->event_commit(&ctx);
  79         return 0;
  80 }
  81
  82 static
  83 int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi,
  84                                    struct pt_regs *regs)
  85 {
  86         return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY);
  87 }
  88
  89 static
  90 int lttng_kretprobes_handler_return(struct kretprobe_instance *krpi,
  91                                     struct pt_regs *regs)
  92 {
  93         return _lttng_kretprobes_handler(krpi, regs, EVENT_RETURN);
  94 }
  95
  96 /*
  97  * Create event description
  98  */
  99 static
 100 int lttng_create_kprobe_event(const char *name, struct lttng_event *event,
 101                               enum lttng_kretprobe_type type)
 102 {
 103         struct lttng_event_field *fields;
 104         struct lttng_event_desc *desc;
 105         int ret;
 106         char *alloc_name;
 107         size_t name_len;
 108         const char *suffix = NULL;
 109
 110         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
 111         if (!desc)
 112                 return -ENOMEM;
 113         name_len = strlen(name);
 114         switch (type) {
 115         case EVENT_ENTRY:
 116                 suffix = "_entry";
 117                 break;
 118         case EVENT_RETURN:
 119                 suffix = "_return";
 120                 break;
 121         }
 122         name_len += strlen(suffix);
 123         alloc_name = kmalloc(name_len + 1, GFP_KERNEL);
 124         if (!alloc_name) {
 125                 ret = -ENOMEM;
 126                 goto error_str;
 127         }
 128         strcpy(alloc_name, name);
 129         strcat(alloc_name, suffix);
 130         desc->name = alloc_name;
 131         desc->nr_fields = 2;
 132         desc->fields = fields =
 133                 kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
 134         if (!desc->fields) {
 135                 ret = -ENOMEM;
 136                 goto error_fields;
 137         }
 138         fields[0].name = "ip";
 139         fields[0].type.atype = atype_integer;
 140         fields[0].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
 141         fields[0].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
 142         fields[0].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
 143         fields[0].type.u.basic.integer.reverse_byte_order = 0;
 144         fields[0].type.u.basic.integer.base = 16;
 145         fields[0].type.u.basic.integer.encoding = lttng_encode_none;
 146
 147         fields[1].name = "parent_ip";
 148         fields[1].type.atype = atype_integer;
 149         fields[1].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
 150         fields[1].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
 151         fields[1].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
 152         fields[1].type.u.basic.integer.reverse_byte_order = 0;
 153         fields[1].type.u.basic.integer.base = 16;
 154         fields[1].type.u.basic.integer.encoding = lttng_encode_none;
 155
 156         desc->owner = THIS_MODULE;
 157         event->desc = desc;
 158
 159         return 0;
 160
 161 error_fields:
 162         kfree(desc->name);
 163 error_str:
 164         kfree(desc);
 165         return ret;
 166 }
 167
 168 int lttng_kretprobes_register(const char *name,
 169                            const char *symbol_name,
 170                            uint64_t offset,
 171                            uint64_t addr,
 172                            struct lttng_event *event_entry,
 173                            struct lttng_event *event_return)
 174 {
 175         int ret;
 176         struct lttng_krp *lttng_krp;
 177
 178         /* Kprobes expects a NULL symbol name if unused */
 179         if (symbol_name[0] == '\0')
 180                 symbol_name = NULL;
 181
 182         ret = lttng_create_kprobe_event(name, event_entry, EVENT_ENTRY);
 183         if (ret)
 184                 goto error;
 185         ret = lttng_create_kprobe_event(name, event_return, EVENT_RETURN);
 186         if (ret)
 187                 goto event_return_error;
 188         lttng_krp = kzalloc(sizeof(*lttng_krp), GFP_KERNEL);
 189         if (!lttng_krp)
 190                 goto krp_error;
 191         lttng_krp->krp.entry_handler = lttng_kretprobes_handler_entry;
 192         lttng_krp->krp.handler = lttng_kretprobes_handler_return;
 193         if (symbol_name) {
 194                 char *alloc_symbol;
 195
 196                 alloc_symbol = kstrdup(symbol_name, GFP_KERNEL);
 197                 if (!alloc_symbol) {
 198                         ret = -ENOMEM;
 199                         goto name_error;
 200                 }
 201                 lttng_krp->krp.kp.symbol_name =
 202                         alloc_symbol;
 203                 event_entry->u.kretprobe.symbol_name =
 204                         alloc_symbol;
 205                 event_return->u.kretprobe.symbol_name =
 206                         alloc_symbol;
 207         }
 208         lttng_krp->krp.kp.offset = offset;
 209         lttng_krp->krp.kp.addr = (void *) (unsigned long) addr;
 210
 211         /* Allow probe handler to find event structures */
 212         lttng_krp->event[EVENT_ENTRY] = event_entry;
 213         lttng_krp->event[EVENT_RETURN] = event_return;
 214         event_entry->u.kretprobe.lttng_krp = lttng_krp;
 215         event_return->u.kretprobe.lttng_krp = lttng_krp;
 216
 217         /*
 218          * Both events must be unregistered before the kretprobe is
 219          * unregistered. Same for memory allocation.
 220          */
 221         kref_init(&lttng_krp->kref_alloc);
 222         kref_get(&lttng_krp->kref_alloc);       /* inc refcount to 2 */
 223         kref_init(&lttng_krp->kref_register);
 224         kref_get(&lttng_krp->kref_register);    /* inc refcount to 2 */
 225
 226         /*
 227          * Ensure the memory we just allocated don't trigger page faults.
 228          * Well.. kprobes itself puts the page fault handler on the blacklist,
 229          * but we can never be too careful.
 230          */
 231         wrapper_vmalloc_sync_all();
 232
 233         ret = register_kretprobe(&lttng_krp->krp);
 234         if (ret)
 235                 goto register_error;
 236         return 0;
 237
 238 register_error:
 239         kfree(lttng_krp->krp.kp.symbol_name);
 240 name_error:
 241         kfree(lttng_krp);
 242 krp_error:
 243         kfree(event_return->desc->fields);
 244         kfree(event_return->desc->name);
 245         kfree(event_return->desc);
 246 event_return_error:
 247         kfree(event_entry->desc->fields);
 248         kfree(event_entry->desc->name);
 249         kfree(event_entry->desc);
 250 error:
 251         return ret;
 252 }
 253 EXPORT_SYMBOL_GPL(lttng_kretprobes_register);
 254
 255 static
 256 void _lttng_kretprobes_unregister_release(struct kref *kref)
 257 {
 258         struct lttng_krp *lttng_krp =
 259                 container_of(kref, struct lttng_krp, kref_register);
 260         unregister_kretprobe(&lttng_krp->krp);
 261 }
 262
 263 void lttng_kretprobes_unregister(struct lttng_event *event)
 264 {
 265         kref_put(&event->u.kretprobe.lttng_krp->kref_register,
 266                 _lttng_kretprobes_unregister_release);
 267 }
 268 EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister);
 269
 270 static
 271 void _lttng_kretprobes_release(struct kref *kref)
 272 {
 273         struct lttng_krp *lttng_krp =
 274                 container_of(kref, struct lttng_krp, kref_alloc);
 275         kfree(lttng_krp->krp.kp.symbol_name);
 276 }
 277
 278 void lttng_kretprobes_destroy_private(struct lttng_event *event)
 279 {
 280         kfree(event->desc->fields);
 281         kfree(event->desc->name);
 282         kfree(event->desc);
 283         kref_put(&event->u.kretprobe.lttng_krp->kref_alloc,
 284                 _lttng_kretprobes_release);
 285 }
 286 EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);
 287
 288 MODULE_LICENSE("GPL and additional rights");
 289 MODULE_AUTHOR("Mathieu Desnoyers");
 290 MODULE_DESCRIPTION("Linux Trace Toolkit Kretprobes Support");