src/probes/lttng-kretprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * probes/lttng-kretprobes.c
   4  *
   5  * LTTng kretprobes integration module.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <wrapper/kprobes.h>
  12 #include <linux/slab.h>
  13 #include <linux/kref.h>
  14 #include <lttng/events.h>
  15 #include <lttng/events-internal.h>
  16 #include <ringbuffer/frontend_types.h>
  17 #include <wrapper/vmalloc.h>
  18 #include <wrapper/irqflags.h>
  19 #include <lttng/tracer.h>
  20 #include <blacklist/kprobes.h>
  21
  22 enum lttng_kretprobe_type {
  23         EVENT_ENTRY     = 0,
  24         EVENT_EXIT      = 1,
  25 };
  26
  27 struct lttng_krp {
  28         struct kretprobe krp;
  29         struct lttng_kernel_event_common *event[2];     /* ENTRY and EXIT */
  30         struct kref kref_register;
  31         struct kref kref_alloc;
  32 };
  33
  34 static
  35 int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
  36                               struct pt_regs *regs,
  37                               enum lttng_kretprobe_type type)
  38 {
  39         struct lttng_krp *lttng_krp =
  40                 container_of(lttng_get_kretprobe(krpi), struct lttng_krp, krp);
  41         struct lttng_kernel_event_common *event = lttng_krp->event[type];
  42         struct lttng_kernel_probe_ctx lttng_probe_ctx = {
  43                 .event = event,
  44                 .interruptible = !lttng_regs_irqs_disabled(regs),
  45         };
  46         struct {
  47                 unsigned long ip;
  48                 unsigned long parent_ip;
  49         } payload;
  50
  51         switch (event->type) {
  52         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  53         {
  54                 struct lttng_kernel_event_recorder *event_recorder =
  55                         container_of(event, struct lttng_kernel_event_recorder, parent);
  56                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  57
  58                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.session->active)))
  59                         return 0;
  60                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.enabled)))
  61                         return 0;
  62                 break;
  63         }
  64         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:  /* Fall-through. */
  65         default:
  66                 WARN_ON_ONCE(1);
  67         }
  68
  69         if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
  70                 return 0;
  71
  72         switch (event->type) {
  73         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  74         {
  75                 struct lttng_kernel_event_recorder *event_recorder =
  76                         container_of(event, struct lttng_kernel_event_recorder, parent);
  77                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  78                 struct lttng_kernel_ring_buffer_ctx ctx;
  79                 int ret;
  80
  81                 payload.ip = (unsigned long) lttng_get_kretprobe(krpi)->kp.addr;
  82                 payload.parent_ip = (unsigned long) krpi->ret_addr;
  83
  84                 lib_ring_buffer_ctx_init(&ctx, event_recorder, sizeof(payload),
  85                                          lttng_alignof(payload), &lttng_probe_ctx);
  86                 ret = chan->ops->event_reserve(&ctx);
  87                 if (ret < 0)
  88                         return 0;
  89                 chan->ops->event_write(&ctx, &payload, sizeof(payload), lttng_alignof(payload));
  90                 chan->ops->event_commit(&ctx);
  91                 break;
  92         }
  93         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:  /* Fall-through. */
  94         default:
  95                 WARN_ON_ONCE(1);
  96         }
  97         return 0;
  98 }
  99
 100 static
 101 int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi,
 102                                    struct pt_regs *regs)
 103 {
 104         return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY);
 105 }
 106
 107 static
 108 int lttng_kretprobes_handler_exit(struct kretprobe_instance *krpi,
 109                                   struct pt_regs *regs)
 110 {
 111         return _lttng_kretprobes_handler(krpi, regs, EVENT_EXIT);
 112 }
 113
 114 static const struct lttng_kernel_event_field *event_fields[] = {
 115         lttng_kernel_static_event_field("ip",
 116                 lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
 117                 false, false, false),
 118         lttng_kernel_static_event_field("parent_ip",
 119                 lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
 120                 false, false, false),
 121 };
 122
 123 static const struct lttng_kernel_tracepoint_class tp_class = {
 124         .nr_fields = ARRAY_SIZE(event_fields),
 125         .fields = event_fields,
 126 };
 127
 128 /*
 129  * Create event description
 130  */
 131 static
 132 int lttng_create_kprobe_event(const char *name, struct lttng_kernel_event_recorder *event_recorder,
 133                               enum lttng_kretprobe_type type)
 134 {
 135         struct lttng_kernel_event_desc *desc;
 136         char *alloc_name;
 137         size_t name_len;
 138         const char *suffix = NULL;
 139         int ret;
 140
 141         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
 142         if (!desc)
 143                 return -ENOMEM;
 144         name_len = strlen(name);
 145         switch (type) {
 146         case EVENT_ENTRY:
 147                 suffix = "_entry";
 148                 break;
 149         case EVENT_EXIT:
 150                 suffix = "_exit";
 151                 break;
 152         }
 153         name_len += strlen(suffix);
 154         alloc_name = kmalloc(name_len + 1, GFP_KERNEL);
 155         if (!alloc_name) {
 156                 ret = -ENOMEM;
 157                 goto error_str;
 158         }
 159         strcpy(alloc_name, name);
 160         strcat(alloc_name, suffix);
 161         desc->event_name = alloc_name;
 162         desc->tp_class = &tp_class;
 163         desc->owner = THIS_MODULE;
 164         event_recorder->priv->parent.desc = desc;
 165
 166         return 0;
 167
 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_kernel_event_recorder *event_recorder_entry,
 178                            struct lttng_kernel_event_recorder *event_recorder_exit)
 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_recorder_entry, EVENT_ENTRY);
 188         if (ret)
 189                 goto error;
 190         ret = lttng_create_kprobe_event(name, event_recorder_exit, EVENT_EXIT);
 191         if (ret)
 192                 goto event_exit_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_exit;
 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_recorder_entry->priv->parent.u.kretprobe.symbol_name =
 209                         alloc_symbol;
 210                 event_recorder_exit->priv->parent.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_recorder_entry->parent;
 218         lttng_krp->event[EVENT_EXIT] = &event_recorder_exit->parent;
 219         event_recorder_entry->priv->parent.u.kretprobe.lttng_krp = lttng_krp;
 220         event_recorder_exit->priv->parent.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_mappings();
 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_recorder_exit->priv->parent.desc->event_name);
 249         kfree(event_recorder_exit->priv->parent.desc);
 250 event_exit_error:
 251         kfree(event_recorder_entry->priv->parent.desc->event_name);
 252         kfree(event_recorder_entry->priv->parent.desc);
 253 error:
 254         return ret;
 255 }
 256 EXPORT_SYMBOL_GPL(lttng_kretprobes_register);
 257
 258 static
 259 void _lttng_kretprobes_unregister_release(struct kref *kref)
 260 {
 261         struct lttng_krp *lttng_krp =
 262                 container_of(kref, struct lttng_krp, kref_register);
 263         unregister_kretprobe(&lttng_krp->krp);
 264 }
 265
 266 void lttng_kretprobes_unregister(struct lttng_kernel_event_recorder *event_recorder)
 267 {
 268         kref_put(&event_recorder->priv->parent.u.kretprobe.lttng_krp->kref_register,
 269                 _lttng_kretprobes_unregister_release);
 270 }
 271 EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister);
 272
 273 static
 274 void _lttng_kretprobes_release(struct kref *kref)
 275 {
 276         struct lttng_krp *lttng_krp =
 277                 container_of(kref, struct lttng_krp, kref_alloc);
 278         kfree(lttng_krp->krp.kp.symbol_name);
 279 }
 280
 281 void lttng_kretprobes_destroy_private(struct lttng_kernel_event_recorder *event_recorder)
 282 {
 283         kfree(event_recorder->priv->parent.desc->event_name);
 284         kfree(event_recorder->priv->parent.desc);
 285         kref_put(&event_recorder->priv->parent.u.kretprobe.lttng_krp->kref_alloc,
 286                 _lttng_kretprobes_release);
 287 }
 288 EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);
 289
 290 int lttng_kretprobes_event_enable_state(struct lttng_kernel_event_common *event,
 291                 int enable)
 292 {
 293         struct lttng_kernel_event_common *event_exit;
 294         struct lttng_krp *lttng_krp;
 295
 296         if (event->priv->instrumentation != LTTNG_KERNEL_ABI_KRETPROBE) {
 297                 return -EINVAL;
 298         }
 299         if (event->enabled == enable) {
 300                 return -EBUSY;
 301         }
 302         lttng_krp = event->priv->u.kretprobe.lttng_krp;
 303         event_exit = lttng_krp->event[EVENT_EXIT];
 304         WRITE_ONCE(event->enabled, enable);
 305         WRITE_ONCE(event_exit->enabled, enable);
 306         return 0;
 307 }
 308 EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state);
 309
 310 MODULE_LICENSE("GPL and additional rights");
 311 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 312 MODULE_DESCRIPTION("LTTng kretprobes probes");
 313 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 314         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 315         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 316         LTTNG_MODULES_EXTRAVERSION);