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 <wrapper/irqflags.h>
  31 #include <lttng-tracer.h>
  32
  33 enum lttng_kretprobe_type {
  34         EVENT_ENTRY = 0,
  35         EVENT_RETURN = 1,
  36 };
  37
  38 struct lttng_krp {
  39         struct kretprobe krp;
  40         struct lttng_event *event[2];   /* ENTRY and RETURN */
  41         struct kref kref_register;
  42         struct kref kref_alloc;
  43 };
  44
  45 static
  46 int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
  47                               struct pt_regs *regs,
  48                               enum lttng_kretprobe_type type)
  49 {
  50         struct lttng_krp *lttng_krp =
  51                 container_of(krpi->rp, struct lttng_krp, krp);
  52         struct lttng_event *event =
  53                 lttng_krp->event[type];
  54         struct lttng_probe_ctx lttng_probe_ctx = {
  55                 .event = event,
  56                 .interruptible = !lttng_regs_irqs_disabled(regs),
  57         };
  58         struct lttng_channel *chan = event->chan;
  59         struct lib_ring_buffer_ctx ctx;
  60         int ret;
  61         struct {
  62                 unsigned long ip;
  63                 unsigned long parent_ip;
  64         } payload;
  65
  66         if (unlikely(!READ_ONCE(chan->session->active)))
  67                 return 0;
  68         if (unlikely(!READ_ONCE(chan->enabled)))
  69                 return 0;
  70         if (unlikely(!READ_ONCE(event->enabled)))
  71                 return 0;
  72
  73         payload.ip = (unsigned long) krpi->rp->kp.addr;
  74         payload.parent_ip = (unsigned long) krpi->ret_addr;
  75
  76         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(payload),
  77                                  lttng_alignof(payload), -1);
  78         ret = chan->ops->event_reserve(&ctx, event->id);
  79         if (ret < 0)
  80                 return 0;
  81         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
  82         chan->ops->event_write(&ctx, &payload, sizeof(payload));
  83         chan->ops->event_commit(&ctx);
  84         return 0;
  85 }
  86
  87 static
  88 int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi,
  89                                    struct pt_regs *regs)
  90 {
  91         return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY);
  92 }
  93
  94 static
  95 int lttng_kretprobes_handler_return(struct kretprobe_instance *krpi,
  96                                     struct pt_regs *regs)
  97 {
  98         return _lttng_kretprobes_handler(krpi, regs, EVENT_RETURN);
  99 }
 100
 101 /*
 102  * Create event description
 103  */
 104 static
 105 int lttng_create_kprobe_event(const char *name, struct lttng_event *event,
 106                               enum lttng_kretprobe_type type)
 107 {
 108         struct lttng_event_field *fields;
 109         struct lttng_event_desc *desc;
 110         int ret;
 111         char *alloc_name;
 112         size_t name_len;
 113         const char *suffix = NULL;
 114
 115         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
 116         if (!desc)
 117                 return -ENOMEM;
 118         name_len = strlen(name);
 119         switch (type) {
 120         case EVENT_ENTRY:
 121                 suffix = "_entry";
 122                 break;
 123         case EVENT_RETURN:
 124                 suffix = "_return";
 125                 break;
 126         }
 127         name_len += strlen(suffix);
 128         alloc_name = kmalloc(name_len + 1, GFP_KERNEL);
 129         if (!alloc_name) {
 130                 ret = -ENOMEM;
 131                 goto error_str;
 132         }
 133         strcpy(alloc_name, name);
 134         strcat(alloc_name, suffix);
 135         desc->name = alloc_name;
 136         desc->nr_fields = 2;
 137         desc->fields = fields =
 138                 kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
 139         if (!desc->fields) {
 140                 ret = -ENOMEM;
 141                 goto error_fields;
 142         }
 143         fields[0].name = "ip";
 144         fields[0].type.atype = atype_integer;
 145         fields[0].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
 146         fields[0].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
 147         fields[0].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
 148         fields[0].type.u.basic.integer.reverse_byte_order = 0;
 149         fields[0].type.u.basic.integer.base = 16;
 150         fields[0].type.u.basic.integer.encoding = lttng_encode_none;
 151
 152         fields[1].name = "parent_ip";
 153         fields[1].type.atype = atype_integer;
 154         fields[1].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
 155         fields[1].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
 156         fields[1].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
 157         fields[1].type.u.basic.integer.reverse_byte_order = 0;
 158         fields[1].type.u.basic.integer.base = 16;
 159         fields[1].type.u.basic.integer.encoding = lttng_encode_none;
 160
 161         desc->owner = THIS_MODULE;
 162         event->desc = desc;
 163
 164         return 0;
 165
 166 error_fields:
 167         kfree(desc->name);
 168 error_str:
 169         kfree(desc);
 170         return ret;
 171 }
 172
 173 int lttng_kretprobes_register(const char *name,
 174                            const char *symbol_name,
 175                            uint64_t offset,
 176                            uint64_t addr,
 177                            struct lttng_event *event_entry,
 178                            struct lttng_event *event_return)
 179 {
 180         int ret;
 181         struct lttng_krp *lttng_krp;
 182
 183         /* Kprobes expects a NULL symbol name if unused */
 184         if (symbol_name[0] == '\0')
 185                 symbol_name = NULL;
 186
 187         ret = lttng_create_kprobe_event(name, event_entry, EVENT_ENTRY);
 188         if (ret)
 189                 goto error;
 190         ret = lttng_create_kprobe_event(name, event_return, EVENT_RETURN);
 191         if (ret)
 192                 goto event_return_error;
 193         lttng_krp = kzalloc(sizeof(*lttng_krp), GFP_KERNEL);
 194         if (!lttng_krp)
 195                 goto krp_error;
 196         lttng_krp->krp.entry_handler = lttng_kretprobes_handler_entry;
 197         lttng_krp->krp.handler = lttng_kretprobes_handler_return;
 198         if (symbol_name) {
 199                 char *alloc_symbol;
 200
 201                 alloc_symbol = kstrdup(symbol_name, GFP_KERNEL);
 202                 if (!alloc_symbol) {
 203                         ret = -ENOMEM;
 204                         goto name_error;
 205                 }
 206                 lttng_krp->krp.kp.symbol_name =
 207                         alloc_symbol;
 208                 event_entry->u.kretprobe.symbol_name =
 209                         alloc_symbol;
 210                 event_return->u.kretprobe.symbol_name =
 211                         alloc_symbol;
 212         }
 213         lttng_krp->krp.kp.offset = offset;
 214         lttng_krp->krp.kp.addr = (void *) (unsigned long) addr;
 215
 216         /* Allow probe handler to find event structures */
 217         lttng_krp->event[EVENT_ENTRY] = event_entry;
 218         lttng_krp->event[EVENT_RETURN] = event_return;
 219         event_entry->u.kretprobe.lttng_krp = lttng_krp;
 220         event_return->u.kretprobe.lttng_krp = lttng_krp;
 221
 222         /*
 223          * Both events must be unregistered before the kretprobe is
 224          * unregistered. Same for memory allocation.
 225          */
 226         kref_init(&lttng_krp->kref_alloc);
 227         kref_get(&lttng_krp->kref_alloc);       /* inc refcount to 2, no overflow. */
 228         kref_init(&lttng_krp->kref_register);
 229         kref_get(&lttng_krp->kref_register);    /* inc refcount to 2, no overflow. */
 230
 231         /*
 232          * Ensure the memory we just allocated don't trigger page faults.
 233          * Well.. kprobes itself puts the page fault handler on the blacklist,
 234          * but we can never be too careful.
 235          */
 236         wrapper_vmalloc_sync_all();
 237
 238         ret = register_kretprobe(&lttng_krp->krp);
 239         if (ret)
 240                 goto register_error;
 241         return 0;
 242
 243 register_error:
 244         kfree(lttng_krp->krp.kp.symbol_name);
 245 name_error:
 246         kfree(lttng_krp);
 247 krp_error:
 248         kfree(event_return->desc->fields);
 249         kfree(event_return->desc->name);
 250         kfree(event_return->desc);
 251 event_return_error:
 252         kfree(event_entry->desc->fields);
 253         kfree(event_entry->desc->name);
 254         kfree(event_entry->desc);
 255 error:
 256         return ret;
 257 }
 258 EXPORT_SYMBOL_GPL(lttng_kretprobes_register);
 259
 260 static
 261 void _lttng_kretprobes_unregister_release(struct kref *kref)
 262 {
 263         struct lttng_krp *lttng_krp =
 264                 container_of(kref, struct lttng_krp, kref_register);
 265         unregister_kretprobe(&lttng_krp->krp);
 266 }
 267
 268 void lttng_kretprobes_unregister(struct lttng_event *event)
 269 {
 270         kref_put(&event->u.kretprobe.lttng_krp->kref_register,
 271                 _lttng_kretprobes_unregister_release);
 272 }
 273 EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister);
 274
 275 static
 276 void _lttng_kretprobes_release(struct kref *kref)
 277 {
 278         struct lttng_krp *lttng_krp =
 279                 container_of(kref, struct lttng_krp, kref_alloc);
 280         kfree(lttng_krp->krp.kp.symbol_name);
 281 }
 282
 283 void lttng_kretprobes_destroy_private(struct lttng_event *event)
 284 {
 285         kfree(event->desc->fields);
 286         kfree(event->desc->name);
 287         kfree(event->desc);
 288         kref_put(&event->u.kretprobe.lttng_krp->kref_alloc,
 289                 _lttng_kretprobes_release);
 290 }
 291 EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);
 292
 293 int lttng_kretprobes_event_enable_state(struct lttng_event *event,
 294                 int enable)
 295 {
 296         struct lttng_event *event_return;
 297         struct lttng_krp *lttng_krp;
 298
 299         if (event->instrumentation != LTTNG_KERNEL_KRETPROBE) {
 300                 return -EINVAL;
 301         }
 302         if (event->enabled == enable) {
 303                 return -EBUSY;
 304         }
 305         lttng_krp = event->u.kretprobe.lttng_krp;
 306         event_return = lttng_krp->event[EVENT_RETURN];
 307         WRITE_ONCE(event->enabled, enable);
 308         WRITE_ONCE(event_return->enabled, enable);
 309         return 0;
 310 }
 311 EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state);
 312
 313 MODULE_LICENSE("GPL and additional rights");
 314 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 315 MODULE_DESCRIPTION("LTTng kretprobes probes");
 316 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 317         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 318         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 319         LTTNG_MODULES_EXTRAVERSION);