src/probes/lttng-kprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * probes/lttng-kprobes.c
   4  *
   5  * LTTng kprobes integration module.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/kprobes.h>
  12 #include <linux/slab.h>
  13 #include <lttng/events.h>
  14 #include <ringbuffer/frontend_types.h>
  15 #include <wrapper/vmalloc.h>
  16 #include <wrapper/irqflags.h>
  17 #include <lttng/tracer.h>
  18 #include <blacklist/kprobes.h>
  19
  20 static
  21 int lttng_kprobes_event_handler_pre(struct kprobe *p, struct pt_regs *regs)
  22 {
  23         struct lttng_event *event =
  24                 container_of(p, struct lttng_event, u.kprobe.kp);
  25         struct lttng_probe_ctx lttng_probe_ctx = {
  26                 .event = event,
  27                 .interruptible = !lttng_regs_irqs_disabled(regs),
  28         };
  29         struct lttng_channel *chan = event->chan;
  30         struct lib_ring_buffer_ctx ctx;
  31         int ret;
  32         unsigned long data = (unsigned long) p->addr;
  33
  34         if (unlikely(!LTTNG_READ_ONCE(chan->session->active)))
  35                 return 0;
  36         if (unlikely(!LTTNG_READ_ONCE(chan->enabled)))
  37                 return 0;
  38         if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
  39                 return 0;
  40
  41         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),
  42                                  lttng_alignof(data), -1);
  43         ret = chan->ops->event_reserve(&ctx, event->id);
  44         if (ret < 0)
  45                 return 0;
  46         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  47         chan->ops->event_write(&ctx, &data, sizeof(data));
  48         chan->ops->event_commit(&ctx);
  49         return 0;
  50 }
  51
  52 static
  53 int lttng_kprobes_event_notifier_handler_pre(struct kprobe *p, struct pt_regs *regs)
  54 {
  55         struct lttng_event_notifier *event_notifier =
  56                 container_of(p, struct lttng_event_notifier, u.kprobe.kp);
  57
  58         if (unlikely(!READ_ONCE(event_notifier->enabled)))
  59                 return 0;
  60
  61         event_notifier->send_notification(event_notifier, NULL, NULL);
  62
  63         return 0;
  64 }
  65
  66 /*
  67  * Create event description
  68  */
  69 static
  70 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  71 {
  72         struct lttng_event_field *field;
  73         struct lttng_event_desc *desc;
  74         int ret;
  75
  76         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  77         if (!desc)
  78                 return -ENOMEM;
  79         desc->name = kstrdup(name, GFP_KERNEL);
  80         if (!desc->name) {
  81                 ret = -ENOMEM;
  82                 goto error_str;
  83         }
  84         desc->nr_fields = 1;
  85         desc->fields = field =
  86                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  87         if (!field) {
  88                 ret = -ENOMEM;
  89                 goto error_field;
  90         }
  91         field->name = "ip";
  92         field->type.atype = atype_integer;
  93         field->type.u.integer.size = sizeof(unsigned long) * CHAR_BIT;
  94         field->type.u.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  95         field->type.u.integer.signedness = lttng_is_signed_type(unsigned long);
  96         field->type.u.integer.reverse_byte_order = 0;
  97         field->type.u.integer.base = 16;
  98         field->type.u.integer.encoding = lttng_encode_none;
  99         desc->owner = THIS_MODULE;
 100         event->desc = desc;
 101
 102         return 0;
 103
 104 error_field:
 105         kfree(desc->name);
 106 error_str:
 107         kfree(desc);
 108         return ret;
 109 }
 110
 111 /*
 112  * Create event_notifier description
 113  */
 114 static
 115 int lttng_create_kprobe_event_notifier(const char *name, struct lttng_event_notifier *event_notifier)
 116 {
 117         struct lttng_event_desc *desc;
 118         int ret;
 119
 120         desc = kzalloc(sizeof(*event_notifier->desc), GFP_KERNEL);
 121         if (!desc)
 122                 return -ENOMEM;
 123         desc->name = kstrdup(name, GFP_KERNEL);
 124         if (!desc->name) {
 125                 ret = -ENOMEM;
 126                 goto error_str;
 127         }
 128         desc->nr_fields = 0;
 129
 130         desc->owner = THIS_MODULE;
 131         event_notifier->desc = desc;
 132
 133         return 0;
 134
 135 error_str:
 136         kfree(desc);
 137         return ret;
 138 }
 139
 140 static
 141 int _lttng_kprobes_register(const char *symbol_name,
 142                            uint64_t offset,
 143                            uint64_t addr,
 144                            struct lttng_kprobe *lttng_kp,
 145                            kprobe_pre_handler_t pre_handler)
 146 {
 147         int ret;
 148
 149         /* Kprobes expects a NULL symbol name if unused */
 150         if (symbol_name[0] == '\0')
 151                 symbol_name = NULL;
 152
 153         memset(&lttng_kp->kp, 0, sizeof(lttng_kp->kp));
 154         lttng_kp->kp.pre_handler = pre_handler;
 155
 156         if (symbol_name) {
 157                 lttng_kp->symbol_name =
 158                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 159                                 GFP_KERNEL);
 160                 if (!lttng_kp->symbol_name) {
 161                         ret = -ENOMEM;
 162                         goto name_error;
 163                 }
 164                 memcpy(lttng_kp->symbol_name, symbol_name,
 165                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 166                 lttng_kp->kp.symbol_name = lttng_kp->symbol_name;
 167         }
 168
 169         lttng_kp->kp.offset = offset;
 170         lttng_kp->kp.addr = (void *) (unsigned long) addr;
 171
 172         /*
 173          * Ensure the memory we just allocated don't event_notifier page faults.
 174          * Well.. kprobes itself puts the page fault handler on the blacklist,
 175          * but we can never be too careful.
 176          */
 177         wrapper_vmalloc_sync_mappings();
 178
 179         ret = register_kprobe(&lttng_kp->kp);
 180         if (ret)
 181                 goto register_error;
 182
 183         return 0;
 184
 185 register_error:
 186         kfree(lttng_kp->symbol_name);
 187 name_error:
 188         return ret;
 189 }
 190
 191 int lttng_kprobes_register_event(const char *name,
 192                            const char *symbol_name,
 193                            uint64_t offset,
 194                            uint64_t addr,
 195                            struct lttng_event *event)
 196 {
 197         int ret;
 198
 199         ret = lttng_create_kprobe_event(name, event);
 200         if (ret)
 201                 goto error;
 202
 203         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 204                 &event->u.kprobe, lttng_kprobes_event_handler_pre);
 205         if (ret)
 206                 goto register_error;
 207
 208         return 0;
 209
 210 register_error:
 211         kfree(event->desc->fields);
 212         kfree(event->desc->name);
 213         kfree(event->desc);
 214 error:
 215         return ret;
 216 }
 217 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event);
 218
 219 int lttng_kprobes_register_event_notifier(const char *symbol_name,
 220                            uint64_t offset,
 221                            uint64_t addr,
 222                            struct lttng_event_notifier *event_notifier)
 223 {
 224         int ret;
 225         ret = lttng_create_kprobe_event_notifier(symbol_name, event_notifier);
 226         if (ret)
 227                 goto error;
 228
 229         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 230                 &event_notifier->u.kprobe, lttng_kprobes_event_notifier_handler_pre);
 231         if (ret)
 232                 goto register_error;
 233
 234         return 0;
 235
 236 register_error:
 237         kfree(event_notifier->desc->name);
 238         kfree(event_notifier->desc);
 239 error:
 240         return ret;
 241 }
 242 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event_notifier);
 243
 244 void lttng_kprobes_unregister_event(struct lttng_event *event)
 245 {
 246         unregister_kprobe(&event->u.kprobe.kp);
 247 }
 248 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event);
 249
 250 void lttng_kprobes_unregister_event_notifier(struct lttng_event_notifier *event_notifier)
 251 {
 252         unregister_kprobe(&event_notifier->u.kprobe.kp);
 253 }
 254 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event_notifier);
 255
 256 void lttng_kprobes_destroy_event_private(struct lttng_event *event)
 257 {
 258         kfree(event->u.kprobe.symbol_name);
 259         kfree(event->desc->fields);
 260         kfree(event->desc->name);
 261         kfree(event->desc);
 262 }
 263 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_private);
 264
 265 void lttng_kprobes_destroy_event_notifier_private(struct lttng_event_notifier *event_notifier)
 266 {
 267         kfree(event_notifier->u.kprobe.symbol_name);
 268         kfree(event_notifier->desc->name);
 269         kfree(event_notifier->desc);
 270 }
 271 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_notifier_private);
 272
 273 MODULE_LICENSE("GPL and additional rights");
 274 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 275 MODULE_DESCRIPTION("LTTng kprobes probes");
 276 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 277         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 278         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 279         LTTNG_MODULES_EXTRAVERSION);