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 <lttng/events-internal.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <wrapper/irqflags.h>
  18 #include <lttng/tracer.h>
  19 #include <blacklist/kprobes.h>
  20
  21 static
  22 int lttng_kprobes_event_handler_pre(struct kprobe *p, struct pt_regs *regs)
  23 {
  24         struct lttng_kernel_event_common_private *event_priv =
  25                 container_of(p, struct lttng_kernel_event_common_private, u.kprobe.kp);
  26         struct lttng_kernel_event_recorder_private *event_recorder_priv =
  27                 container_of(event_priv, struct lttng_kernel_event_recorder_private, parent);
  28         struct lttng_kernel_event_recorder *event_recorder =
  29                 event_recorder_priv->pub;
  30         struct lttng_probe_ctx lttng_probe_ctx = {
  31                 .event = event_recorder,
  32                 .interruptible = !lttng_regs_irqs_disabled(regs),
  33         };
  34         struct lttng_channel *chan = event_recorder->chan;
  35         struct lib_ring_buffer_ctx ctx;
  36         int ret;
  37         unsigned long data = (unsigned long) p->addr;
  38
  39         if (unlikely(!LTTNG_READ_ONCE(chan->session->active)))
  40                 return 0;
  41         if (unlikely(!LTTNG_READ_ONCE(chan->enabled)))
  42                 return 0;
  43         if (unlikely(!LTTNG_READ_ONCE(event_recorder->parent.enabled)))
  44                 return 0;
  45
  46         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),
  47                                  lttng_alignof(data), -1);
  48         ret = chan->ops->event_reserve(&ctx, event_recorder->priv->id);
  49         if (ret < 0)
  50                 return 0;
  51         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  52         chan->ops->event_write(&ctx, &data, sizeof(data));
  53         chan->ops->event_commit(&ctx);
  54         return 0;
  55 }
  56
  57 static
  58 int lttng_kprobes_event_notifier_handler_pre(struct kprobe *p, struct pt_regs *regs)
  59 {
  60         struct lttng_kernel_event_common_private *event_priv =
  61                 container_of(p, struct lttng_kernel_event_common_private, u.kprobe.kp);
  62         struct lttng_kernel_event_notifier_private *event_notifier_priv =
  63                 container_of(event_priv, struct lttng_kernel_event_notifier_private, parent);
  64         struct lttng_kernel_event_notifier *event_notifier =
  65                 event_notifier_priv->pub;
  66         struct lttng_kernel_notification_ctx notif_ctx;
  67
  68         if (unlikely(!READ_ONCE(event_notifier->parent.enabled)))
  69                 return 0;
  70
  71         notif_ctx.eval_capture = LTTNG_READ_ONCE(event_notifier->eval_capture);
  72         event_notifier->notification_send(event_notifier, NULL, NULL, &notif_ctx);
  73
  74         return 0;
  75 }
  76
  77 static const struct lttng_kernel_type_common *event_type =
  78         lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16);
  79
  80 /*
  81  * Create event description
  82  */
  83 static
  84 int lttng_create_kprobe_event(const char *name, struct lttng_kernel_event_recorder *event_recorder)
  85 {
  86         const struct lttng_kernel_event_field **fieldp_array;
  87         struct lttng_kernel_event_field *field;
  88         struct lttng_kernel_event_desc *desc;
  89         int ret;
  90
  91         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
  92         if (!desc)
  93                 return -ENOMEM;
  94         desc->event_name = kstrdup(name, GFP_KERNEL);
  95         if (!desc->event_name) {
  96                 ret = -ENOMEM;
  97                 goto error_str;
  98         }
  99         desc->nr_fields = 1;
 100         fieldp_array = kzalloc(1 * sizeof(struct lttng_kernel_event_field *), GFP_KERNEL);
 101         if (!fieldp_array) {
 102                 ret = -ENOMEM;
 103                 goto error_fieldp_array;
 104         }
 105         desc->fields = fieldp_array;
 106         desc->fields[0] = field =
 107                 kzalloc(sizeof(struct lttng_kernel_event_field), GFP_KERNEL);
 108         if (!field) {
 109                 ret = -ENOMEM;
 110                 goto error_field;
 111         }
 112         field->name = "ip";
 113         field->type = event_type;
 114         desc->owner = THIS_MODULE;
 115         event_recorder->priv->parent.desc = desc;
 116
 117         return 0;
 118
 119 error_field:
 120         kfree(fieldp_array);
 121 error_fieldp_array:
 122         kfree(desc->event_name);
 123 error_str:
 124         kfree(desc);
 125         return ret;
 126 }
 127
 128 /*
 129  * Create event_notifier description
 130  */
 131 static
 132 int lttng_create_kprobe_event_notifier(const char *name, struct lttng_kernel_event_notifier *event_notifier)
 133 {
 134         struct lttng_kernel_event_desc *desc;
 135         int ret;
 136
 137         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
 138         if (!desc)
 139                 return -ENOMEM;
 140         desc->event_name = kstrdup(name, GFP_KERNEL);
 141         if (!desc->event_name) {
 142                 ret = -ENOMEM;
 143                 goto error_str;
 144         }
 145         desc->nr_fields = 0;
 146
 147         desc->owner = THIS_MODULE;
 148         event_notifier->priv->parent.desc = desc;
 149
 150         return 0;
 151
 152 error_str:
 153         kfree(desc);
 154         return ret;
 155 }
 156
 157 static
 158 int _lttng_kprobes_register(const char *symbol_name,
 159                            uint64_t offset,
 160                            uint64_t addr,
 161                            struct lttng_kprobe *lttng_kp,
 162                            kprobe_pre_handler_t pre_handler)
 163 {
 164         int ret;
 165
 166         /* Kprobes expects a NULL symbol name if unused */
 167         if (symbol_name[0] == '\0')
 168                 symbol_name = NULL;
 169
 170         memset(&lttng_kp->kp, 0, sizeof(lttng_kp->kp));
 171         lttng_kp->kp.pre_handler = pre_handler;
 172
 173         if (symbol_name) {
 174                 lttng_kp->symbol_name =
 175                         kzalloc(LTTNG_KERNEL_ABI_SYM_NAME_LEN * sizeof(char),
 176                                 GFP_KERNEL);
 177                 if (!lttng_kp->symbol_name) {
 178                         ret = -ENOMEM;
 179                         goto name_error;
 180                 }
 181                 memcpy(lttng_kp->symbol_name, symbol_name,
 182                        LTTNG_KERNEL_ABI_SYM_NAME_LEN * sizeof(char));
 183                 lttng_kp->kp.symbol_name = lttng_kp->symbol_name;
 184         }
 185
 186         lttng_kp->kp.offset = offset;
 187         lttng_kp->kp.addr = (void *) (unsigned long) addr;
 188
 189         /*
 190          * Ensure the memory we just allocated don't notify page faults.
 191          * Well.. kprobes itself puts the page fault handler on the blacklist,
 192          * but we can never be too careful.
 193          */
 194         wrapper_vmalloc_sync_mappings();
 195
 196         ret = register_kprobe(&lttng_kp->kp);
 197         if (ret)
 198                 goto register_error;
 199
 200         return 0;
 201
 202 register_error:
 203         kfree(lttng_kp->symbol_name);
 204 name_error:
 205         return ret;
 206 }
 207
 208 int lttng_kprobes_register_event(const char *name,
 209                            const char *symbol_name,
 210                            uint64_t offset,
 211                            uint64_t addr,
 212                            struct lttng_kernel_event_recorder *event_recorder)
 213 {
 214         int ret;
 215
 216         ret = lttng_create_kprobe_event(name, event_recorder);
 217         if (ret)
 218                 goto error;
 219
 220         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 221                 &event_recorder->priv->parent.u.kprobe, lttng_kprobes_event_handler_pre);
 222         if (ret)
 223                 goto register_error;
 224
 225         return 0;
 226
 227 register_error:
 228         kfree(event_recorder->priv->parent.desc->fields);
 229         kfree(event_recorder->priv->parent.desc->event_name);
 230         kfree(event_recorder->priv->parent.desc);
 231 error:
 232         return ret;
 233 }
 234 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event);
 235
 236 int lttng_kprobes_register_event_notifier(const char *symbol_name,
 237                            uint64_t offset,
 238                            uint64_t addr,
 239                            struct lttng_kernel_event_notifier *event_notifier)
 240 {
 241         int ret;
 242         ret = lttng_create_kprobe_event_notifier(symbol_name, event_notifier);
 243         if (ret)
 244                 goto error;
 245
 246         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 247                 &event_notifier->priv->parent.u.kprobe, lttng_kprobes_event_notifier_handler_pre);
 248         if (ret)
 249                 goto register_error;
 250
 251         return 0;
 252
 253 register_error:
 254         kfree(event_notifier->priv->parent.desc->event_name);
 255         kfree(event_notifier->priv->parent.desc);
 256 error:
 257         return ret;
 258 }
 259 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event_notifier);
 260
 261 void lttng_kprobes_unregister_event(struct lttng_kernel_event_recorder *event_recorder)
 262 {
 263         unregister_kprobe(&event_recorder->priv->parent.u.kprobe.kp);
 264 }
 265 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event);
 266
 267 void lttng_kprobes_unregister_event_notifier(struct lttng_kernel_event_notifier *event_notifier)
 268 {
 269         unregister_kprobe(&event_notifier->priv->parent.u.kprobe.kp);
 270 }
 271 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event_notifier);
 272
 273 void lttng_kprobes_destroy_event_private(struct lttng_kernel_event_recorder *event_recorder)
 274 {
 275         kfree(event_recorder->priv->parent.u.kprobe.symbol_name);
 276         kfree(event_recorder->priv->parent.desc->fields[0]);
 277         kfree(event_recorder->priv->parent.desc->fields);
 278         kfree(event_recorder->priv->parent.desc->event_name);
 279         kfree(event_recorder->priv->parent.desc);
 280 }
 281 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_private);
 282
 283 void lttng_kprobes_destroy_event_notifier_private(struct lttng_kernel_event_notifier *event_notifier)
 284 {
 285         kfree(event_notifier->priv->parent.u.kprobe.symbol_name);
 286         kfree(event_notifier->priv->parent.desc->event_name);
 287         kfree(event_notifier->priv->parent.desc);
 288 }
 289 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_notifier_private);
 290
 291 MODULE_LICENSE("GPL and additional rights");
 292 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 293 MODULE_DESCRIPTION("LTTng kprobes probes");
 294 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 295         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 296         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 297         LTTNG_MODULES_EXTRAVERSION);