src/probes/lttng-uprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * probes/lttng-uprobes.c
   4  *
   5  * LTTng uprobes integration module.
   6  *
   7  * Copyright (C) 2013 Yannick Brosseau <yannick.brosseau@gmail.com>
   8  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  *
  10  */
  11
  12 #include <wrapper/fdtable.h>
  13 #include <linux/list.h>
  14 #include <linux/module.h>
  15 #include <linux/namei.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <lttng/events.h>
  19 #include <lttng/tracer.h>
  20 #include <wrapper/irqflags.h>
  21 #include <ringbuffer/frontend_types.h>
  22 #include <wrapper/uprobes.h>
  23 #include <wrapper/vmalloc.h>
  24
  25 static
  26 int lttng_uprobes_event_handler_pre(struct uprobe_consumer *uc, struct pt_regs *regs)
  27 {
  28         struct lttng_uprobe_handler *uprobe_handler =
  29                 container_of(uc, struct lttng_uprobe_handler, up_consumer);
  30         struct lttng_event *event = uprobe_handler->u.event;
  31         struct lttng_probe_ctx lttng_probe_ctx = {
  32                 .event = event,
  33                 .interruptible = !lttng_regs_irqs_disabled(regs),
  34         };
  35         struct lttng_channel *chan = event->chan;
  36         struct lib_ring_buffer_ctx ctx;
  37         int ret;
  38
  39         struct {
  40                 unsigned long ip;
  41         } payload;
  42
  43         if (unlikely(!LTTNG_READ_ONCE(chan->session->active)))
  44                 return 0;
  45         if (unlikely(!LTTNG_READ_ONCE(chan->enabled)))
  46                 return 0;
  47         if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
  48                 return 0;
  49
  50         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx,
  51                 sizeof(payload), lttng_alignof(payload), -1);
  52
  53         ret = chan->ops->event_reserve(&ctx, event->id);
  54         if (ret < 0)
  55                 return 0;
  56
  57         /* Event payload. */
  58         payload.ip = (unsigned long)instruction_pointer(regs);
  59
  60         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
  61         chan->ops->event_write(&ctx, &payload, sizeof(payload));
  62         chan->ops->event_commit(&ctx);
  63         return 0;
  64 }
  65
  66 static
  67 int lttng_uprobes_event_notifier_handler_pre(struct uprobe_consumer *uc, struct pt_regs *regs)
  68 {
  69         struct lttng_uprobe_handler *uprobe_handler =
  70                 container_of(uc, struct lttng_uprobe_handler, up_consumer);
  71         struct lttng_event_notifier *event_notifier = uprobe_handler->u.event_notifier;
  72         struct lttng_kernel_notifier_ctx notif_ctx;
  73
  74         if (unlikely(!READ_ONCE(event_notifier->enabled)))
  75                 return 0;
  76
  77         notif_ctx.eval_capture = LTTNG_READ_ONCE(event_notifier->eval_capture);
  78         event_notifier->send_notification(event_notifier, NULL, NULL, &notif_ctx);
  79         return 0;
  80 }
  81
  82 static const struct lttng_kernel_type_common *event_type =
  83         lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16);
  84
  85 /*
  86  * Create event description.
  87  */
  88 static
  89 int lttng_create_uprobe_event(const char *name, struct lttng_event *event)
  90 {
  91         const struct lttng_kernel_event_field **fieldp_array;
  92         struct lttng_kernel_event_field *field;
  93         struct lttng_kernel_event_desc *desc;
  94         int ret;
  95
  96         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
  97         if (!desc)
  98                 return -ENOMEM;
  99         desc->event_name = kstrdup(name, GFP_KERNEL);
 100         if (!desc->event_name) {
 101                 ret = -ENOMEM;
 102                 goto error_str;
 103         }
 104         desc->nr_fields = 1;
 105         fieldp_array = kzalloc(1 * sizeof(struct lttng_kernel_event_field *), GFP_KERNEL);
 106         if (!fieldp_array) {
 107                 ret = -ENOMEM;
 108                 goto error_fieldp_array;
 109         }
 110         desc->fields = fieldp_array;
 111         desc->fields[0] = field =
 112                 kzalloc(sizeof(struct lttng_kernel_event_field), GFP_KERNEL);
 113         if (!field) {
 114                 ret = -ENOMEM;
 115                 goto error_field;
 116         }
 117         field->name = "ip";
 118         field->type = event_type;
 119         desc->owner = THIS_MODULE;
 120         event->desc = desc;
 121
 122         return 0;
 123
 124 error_field:
 125         kfree(fieldp_array);
 126 error_fieldp_array:
 127         kfree(desc->event_name);
 128 error_str:
 129         kfree(desc);
 130         return ret;
 131 }
 132
 133 /*
 134  * Create event_notifier description.
 135  */
 136 static
 137 int lttng_create_uprobe_event_notifier(const char *name, struct lttng_event_notifier *event_notifier)
 138 {
 139         struct lttng_kernel_event_desc *desc;
 140         int ret;
 141
 142         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
 143         if (!desc)
 144                 return -ENOMEM;
 145         desc->event_name = kstrdup(name, GFP_KERNEL);
 146         if (!desc->event_name) {
 147                 ret = -ENOMEM;
 148                 goto error_str;
 149         }
 150
 151         desc->nr_fields = 0;
 152
 153         desc->owner = THIS_MODULE;
 154         event_notifier->desc = desc;
 155
 156         return 0;
 157
 158 error_str:
 159         kfree(desc);
 160         return ret;
 161 }
 162
 163 /*
 164  * Returns the inode struct from the current task and an fd. The inode is
 165  * grabbed by this function and must be put once we are done with it using
 166  * iput().
 167  */
 168 static struct inode *get_inode_from_fd(int fd)
 169 {
 170         struct file *file;
 171         struct inode *inode;
 172
 173         rcu_read_lock();
 174         /*
 175          * Returns the file backing the given fd. Needs to be done inside an RCU
 176          * critical section.
 177          */
 178         file = lttng_lookup_fd_rcu(fd);
 179         if (file == NULL) {
 180                 printk(KERN_WARNING "LTTng: Cannot access file backing the fd(%d)\n", fd);
 181                 inode = NULL;
 182                 goto error;
 183         }
 184
 185         /* Grab a reference on the inode. */
 186         inode = igrab(file->f_path.dentry->d_inode);
 187         if (inode == NULL)
 188                 printk(KERN_WARNING "LTTng: Cannot grab a reference on the inode.\n");
 189 error:
 190         rcu_read_unlock();
 191         return inode;
 192 }
 193
 194
 195 static
 196 int lttng_uprobes_add_callsite(struct lttng_uprobe *uprobe,
 197         struct lttng_kernel_event_callsite __user *callsite,
 198         int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs),
 199         void *priv_data)
 200 {
 201         int ret = 0;
 202         struct lttng_uprobe_handler *uprobe_handler;
 203
 204         if (!priv_data) {
 205                 ret = -EINVAL;
 206                 goto end;
 207         }
 208
 209         uprobe_handler = kzalloc(sizeof(struct lttng_uprobe_handler), GFP_KERNEL);
 210         if (!uprobe_handler) {
 211                 printk(KERN_WARNING "LTTng: Error allocating uprobe_handler");
 212                 ret = -ENOMEM;
 213                 goto end;
 214         }
 215
 216         /* Ensure the memory we just allocated don't notify page faults. */
 217         wrapper_vmalloc_sync_mappings();
 218
 219         uprobe_handler->u.event = priv_data;
 220         uprobe_handler->up_consumer.handler = handler;
 221
 222         ret = copy_from_user(&uprobe_handler->offset, &callsite->u.uprobe.offset, sizeof(uint64_t));
 223         if (ret) {
 224                 goto register_error;
 225         }
 226
 227         ret = wrapper_uprobe_register(uprobe->inode,
 228                       uprobe_handler->offset, &uprobe_handler->up_consumer);
 229         if (ret) {
 230                 printk(KERN_WARNING "LTTng: Error registering probe on inode %lu "
 231                        "and offset 0x%llx\n", uprobe->inode->i_ino,
 232                        uprobe_handler->offset);
 233                 ret = -1;
 234                 goto register_error;
 235         }
 236
 237         list_add(&uprobe_handler->node, &uprobe->head);
 238
 239         return ret;
 240
 241 register_error:
 242         kfree(uprobe_handler);
 243 end:
 244         return ret;
 245 }
 246
 247 int lttng_uprobes_event_add_callsite(struct lttng_event *event,
 248         struct lttng_kernel_event_callsite __user *callsite)
 249 {
 250         return lttng_uprobes_add_callsite(&event->u.uprobe, callsite,
 251                 lttng_uprobes_event_handler_pre, event);
 252 }
 253 EXPORT_SYMBOL_GPL(lttng_uprobes_event_add_callsite);
 254
 255 int lttng_uprobes_event_notifier_add_callsite(struct lttng_event_notifier *event_notifier,
 256         struct lttng_kernel_event_callsite __user *callsite)
 257 {
 258         return lttng_uprobes_add_callsite(&event_notifier->u.uprobe, callsite,
 259                 lttng_uprobes_event_notifier_handler_pre, event_notifier);
 260 }
 261 EXPORT_SYMBOL_GPL(lttng_uprobes_event_notifier_add_callsite);
 262
 263 static
 264 int lttng_uprobes_register(struct lttng_uprobe *uprobe, int fd)
 265 {
 266         int ret = 0;
 267         struct inode *inode;
 268
 269         inode = get_inode_from_fd(fd);
 270         if (!inode) {
 271                 printk(KERN_WARNING "LTTng: Cannot get inode from fd\n");
 272                 ret = -EBADF;
 273                 goto inode_error;
 274         }
 275         uprobe->inode = inode;
 276         INIT_LIST_HEAD(&uprobe->head);
 277
 278 inode_error:
 279         return ret;
 280 }
 281
 282 int lttng_uprobes_register_event(const char *name, int fd, struct lttng_event *event)
 283 {
 284         int ret = 0;
 285
 286         ret = lttng_create_uprobe_event(name, event);
 287         if (ret)
 288                 goto error;
 289
 290         ret = lttng_uprobes_register(&event->u.uprobe, fd);
 291         if (ret)
 292                 goto register_error;
 293
 294         return 0;
 295
 296 register_error:
 297         kfree(event->desc->event_name);
 298         kfree(event->desc);
 299 error:
 300         return ret;
 301 }
 302 EXPORT_SYMBOL_GPL(lttng_uprobes_register_event);
 303
 304 int lttng_uprobes_register_event_notifier(const char *name, int fd,
 305                 struct lttng_event_notifier *event_notifier)
 306 {
 307         int ret = 0;
 308
 309         ret = lttng_create_uprobe_event_notifier(name, event_notifier);
 310         if (ret)
 311                 goto error;
 312
 313         ret = lttng_uprobes_register(&event_notifier->u.uprobe, fd);
 314         if (ret)
 315                 goto register_error;
 316
 317         return 0;
 318
 319 register_error:
 320         kfree(event_notifier->desc->event_name);
 321         kfree(event_notifier->desc);
 322 error:
 323         return ret;
 324 }
 325 EXPORT_SYMBOL_GPL(lttng_uprobes_register_event_notifier);
 326
 327 static
 328 void lttng_uprobes_unregister(struct inode *inode, struct list_head *head)
 329 {
 330         struct lttng_uprobe_handler *iter, *tmp;
 331
 332         /*
 333          * Iterate over the list of handler, remove each handler from the list
 334          * and free the struct.
 335          */
 336         list_for_each_entry_safe(iter, tmp, head, node) {
 337                 wrapper_uprobe_unregister(inode, iter->offset, &iter->up_consumer);
 338                 list_del(&iter->node);
 339                 kfree(iter);
 340         }
 341
 342 }
 343
 344 void lttng_uprobes_unregister_event(struct lttng_event *event)
 345 {
 346         lttng_uprobes_unregister(event->u.uprobe.inode, &event->u.uprobe.head);
 347 }
 348 EXPORT_SYMBOL_GPL(lttng_uprobes_unregister_event);
 349
 350 void lttng_uprobes_unregister_event_notifier(struct lttng_event_notifier *event_notifier)
 351 {
 352         lttng_uprobes_unregister(event_notifier->u.uprobe.inode, &event_notifier->u.uprobe.head);
 353 }
 354 EXPORT_SYMBOL_GPL(lttng_uprobes_unregister_event_notifier);
 355
 356 void lttng_uprobes_destroy_event_private(struct lttng_event *event)
 357 {
 358         iput(event->u.uprobe.inode);
 359         kfree(event->desc->fields[0]);
 360         kfree(event->desc->fields);
 361         kfree(event->desc->event_name);
 362         kfree(event->desc);
 363 }
 364 EXPORT_SYMBOL_GPL(lttng_uprobes_destroy_event_private);
 365
 366 void lttng_uprobes_destroy_event_notifier_private(struct lttng_event_notifier *event_notifier)
 367 {
 368         iput(event_notifier->u.uprobe.inode);
 369         kfree(event_notifier->desc->event_name);
 370         kfree(event_notifier->desc);
 371 }
 372 EXPORT_SYMBOL_GPL(lttng_uprobes_destroy_event_notifier_private);
 373
 374 MODULE_LICENSE("GPL and additional rights");
 375 MODULE_AUTHOR("Yannick Brosseau");
 376 MODULE_DESCRIPTION("Linux Trace Toolkit Uprobes Support");