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_common *event = event_priv->pub;
  27         struct lttng_kernel_probe_ctx lttng_probe_ctx = {
  28                 .event = event,
  29                 .interruptible = !lttng_regs_irqs_disabled(regs),
  30         };
  31         unsigned long data = (unsigned long) p->addr;
  32
  33         switch (event->type) {
  34         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  35         {
  36                 struct lttng_kernel_event_recorder_private *event_recorder_priv =
  37                         container_of(event_priv, struct lttng_kernel_event_recorder_private, parent);
  38                 struct lttng_kernel_event_recorder *event_recorder =
  39                         event_recorder_priv->pub;
  40                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  41
  42                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.session->active)))
  43                         return 0;
  44                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.enabled)))
  45                         return 0;
  46                 break;
  47         }
  48         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:
  49                 break;
  50         default:
  51                 WARN_ON_ONCE(1);
  52         }
  53
  54         if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
  55                 return 0;
  56
  57         switch (event->type) {
  58         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  59         {
  60                 struct lttng_kernel_event_recorder *event_recorder =
  61                         container_of(event, struct lttng_kernel_event_recorder, parent);
  62                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  63                 struct lttng_kernel_ring_buffer_ctx ctx;
  64                 int ret;
  65
  66                 lib_ring_buffer_ctx_init(&ctx, event_recorder, sizeof(data),
  67                                          lttng_alignof(data), &lttng_probe_ctx);
  68                 ret = chan->ops->event_reserve(&ctx);
  69                 if (ret < 0)
  70                         return 0;
  71                 chan->ops->event_write(&ctx, &data, sizeof(data), lttng_alignof(data));
  72                 chan->ops->event_commit(&ctx);
  73                 break;
  74         }
  75         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:
  76         {
  77                 struct lttng_kernel_event_notifier *event_notifier =
  78                         container_of(event, struct lttng_kernel_event_notifier, parent);
  79                 struct lttng_kernel_notification_ctx notif_ctx;
  80
  81                 notif_ctx.eval_capture = LTTNG_READ_ONCE(event_notifier->eval_capture);
  82                 event_notifier->notification_send(event_notifier, NULL, NULL, &notif_ctx);
  83                 break;
  84         }
  85         default:
  86                 WARN_ON_ONCE(1);
  87         }
  88         return 0;
  89 }
  90
  91 static const struct lttng_kernel_event_field *event_fields[] = {
  92         lttng_kernel_static_event_field("ip",
  93                 lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
  94                 false, false, false),
  95 };
  96
  97 static const struct lttng_kernel_tracepoint_class tp_class = {
  98         .nr_fields = ARRAY_SIZE(event_fields),
  99         .fields = event_fields,
 100 };
 101
 102 /*
 103  * Create event description
 104  */
 105 static
 106 int lttng_create_kprobe_event(const char *name, struct lttng_kernel_event_common *event)
 107 {
 108         struct lttng_kernel_event_desc *desc;
 109         int ret;
 110
 111         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
 112         if (!desc)
 113                 return -ENOMEM;
 114         desc->tp_class = &tp_class;
 115         desc->event_name = kstrdup(name, GFP_KERNEL);
 116         if (!desc->event_name) {
 117                 ret = -ENOMEM;
 118                 goto error_str;
 119         }
 120         desc->owner = THIS_MODULE;
 121         event->priv->desc = desc;
 122
 123         return 0;
 124
 125 error_str:
 126         kfree(desc);
 127         return ret;
 128 }
 129
 130 static
 131 int _lttng_kprobes_register(const char *symbol_name,
 132                            uint64_t offset,
 133                            uint64_t addr,
 134                            struct lttng_kprobe *lttng_kp,
 135                            kprobe_pre_handler_t pre_handler)
 136 {
 137         int ret;
 138
 139         /* Kprobes expects a NULL symbol name if unused */
 140         if (symbol_name[0] == '\0')
 141                 symbol_name = NULL;
 142
 143         memset(&lttng_kp->kp, 0, sizeof(lttng_kp->kp));
 144         lttng_kp->kp.pre_handler = pre_handler;
 145
 146         if (symbol_name) {
 147                 lttng_kp->symbol_name =
 148                         kzalloc(LTTNG_KERNEL_ABI_SYM_NAME_LEN * sizeof(char),
 149                                 GFP_KERNEL);
 150                 if (!lttng_kp->symbol_name) {
 151                         ret = -ENOMEM;
 152                         goto name_error;
 153                 }
 154                 memcpy(lttng_kp->symbol_name, symbol_name,
 155                        LTTNG_KERNEL_ABI_SYM_NAME_LEN * sizeof(char));
 156                 lttng_kp->kp.symbol_name = lttng_kp->symbol_name;
 157         }
 158
 159         lttng_kp->kp.offset = offset;
 160         lttng_kp->kp.addr = (void *) (unsigned long) addr;
 161
 162         /*
 163          * Ensure the memory we just allocated don't notify page faults.
 164          * Well.. kprobes itself puts the page fault handler on the blacklist,
 165          * but we can never be too careful.
 166          */
 167         wrapper_vmalloc_sync_mappings();
 168
 169         ret = register_kprobe(&lttng_kp->kp);
 170         if (ret)
 171                 goto register_error;
 172
 173         return 0;
 174
 175 register_error:
 176         kfree(lttng_kp->symbol_name);
 177 name_error:
 178         return ret;
 179 }
 180
 181 int lttng_kprobes_register_event(const char *name,
 182                            const char *symbol_name,
 183                            uint64_t offset,
 184                            uint64_t addr,
 185                            struct lttng_kernel_event_common *event)
 186 {
 187         int ret;
 188
 189         ret = lttng_create_kprobe_event(name, event);
 190         if (ret)
 191                 goto error;
 192
 193         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 194                 &event->priv->u.kprobe, lttng_kprobes_event_handler_pre);
 195         if (ret)
 196                 goto register_error;
 197
 198         return 0;
 199
 200 register_error:
 201         kfree(event->priv->desc->event_name);
 202         kfree(event->priv->desc);
 203 error:
 204         return ret;
 205 }
 206 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event);
 207
 208 void lttng_kprobes_unregister_event(struct lttng_kernel_event_common *event)
 209 {
 210         unregister_kprobe(&event->priv->u.kprobe.kp);
 211 }
 212 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event);
 213
 214 void lttng_kprobes_destroy_event_private(struct lttng_kernel_event_common *event)
 215 {
 216         kfree(event->priv->u.kprobe.symbol_name);
 217         kfree(event->priv->desc->event_name);
 218         kfree(event->priv->desc);
 219 }
 220 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_private);
 221
 222 MODULE_LICENSE("GPL and additional rights");
 223 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 224 MODULE_DESCRIPTION("LTTng kprobes probes");
 225 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 226         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 227         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 228         LTTNG_MODULES_EXTRAVERSION);