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         struct lttng_kernel_notifier_ctx notif_ctx;
  58
  59         if (unlikely(!READ_ONCE(event_notifier->enabled)))
  60                 return 0;
  61
  62         notif_ctx.eval_capture = LTTNG_READ_ONCE(event_notifier->eval_capture);
  63         event_notifier->send_notification(event_notifier, NULL, NULL, &notif_ctx);
  64
  65         return 0;
  66 }
  67
  68 /*
  69  * Create event description
  70  */
  71 static
  72 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  73 {
  74         struct lttng_event_field *field;
  75         struct lttng_event_desc *desc;
  76         int ret;
  77
  78         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  79         if (!desc)
  80                 return -ENOMEM;
  81         desc->name = kstrdup(name, GFP_KERNEL);
  82         if (!desc->name) {
  83                 ret = -ENOMEM;
  84                 goto error_str;
  85         }
  86         desc->nr_fields = 1;
  87         desc->fields = field =
  88                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  89         if (!field) {
  90                 ret = -ENOMEM;
  91                 goto error_field;
  92         }
  93         field->name = "ip";
  94         field->type.type = lttng_kernel_type_integer;
  95         field->type.u.integer.size = sizeof(unsigned long) * CHAR_BIT;
  96         field->type.u.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  97         field->type.u.integer.signedness = lttng_is_signed_type(unsigned long);
  98         field->type.u.integer.reverse_byte_order = 0;
  99         field->type.u.integer.base = 16;
 100         field->type.u.integer.encoding = lttng_encode_none;
 101         desc->owner = THIS_MODULE;
 102         event->desc = desc;
 103
 104         return 0;
 105
 106 error_field:
 107         kfree(desc->name);
 108 error_str:
 109         kfree(desc);
 110         return ret;
 111 }
 112
 113 /*
 114  * Create event_notifier description
 115  */
 116 static
 117 int lttng_create_kprobe_event_notifier(const char *name, struct lttng_event_notifier *event_notifier)
 118 {
 119         struct lttng_event_desc *desc;
 120         int ret;
 121
 122         desc = kzalloc(sizeof(*event_notifier->desc), GFP_KERNEL);
 123         if (!desc)
 124                 return -ENOMEM;
 125         desc->name = kstrdup(name, GFP_KERNEL);
 126         if (!desc->name) {
 127                 ret = -ENOMEM;
 128                 goto error_str;
 129         }
 130         desc->nr_fields = 0;
 131
 132         desc->owner = THIS_MODULE;
 133         event_notifier->desc = desc;
 134
 135         return 0;
 136
 137 error_str:
 138         kfree(desc);
 139         return ret;
 140 }
 141
 142 static
 143 int _lttng_kprobes_register(const char *symbol_name,
 144                            uint64_t offset,
 145                            uint64_t addr,
 146                            struct lttng_kprobe *lttng_kp,
 147                            kprobe_pre_handler_t pre_handler)
 148 {
 149         int ret;
 150
 151         /* Kprobes expects a NULL symbol name if unused */
 152         if (symbol_name[0] == '\0')
 153                 symbol_name = NULL;
 154
 155         memset(&lttng_kp->kp, 0, sizeof(lttng_kp->kp));
 156         lttng_kp->kp.pre_handler = pre_handler;
 157
 158         if (symbol_name) {
 159                 lttng_kp->symbol_name =
 160                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 161                                 GFP_KERNEL);
 162                 if (!lttng_kp->symbol_name) {
 163                         ret = -ENOMEM;
 164                         goto name_error;
 165                 }
 166                 memcpy(lttng_kp->symbol_name, symbol_name,
 167                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 168                 lttng_kp->kp.symbol_name = lttng_kp->symbol_name;
 169         }
 170
 171         lttng_kp->kp.offset = offset;
 172         lttng_kp->kp.addr = (void *) (unsigned long) addr;
 173
 174         /*
 175          * Ensure the memory we just allocated don't notify page faults.
 176          * Well.. kprobes itself puts the page fault handler on the blacklist,
 177          * but we can never be too careful.
 178          */
 179         wrapper_vmalloc_sync_mappings();
 180
 181         ret = register_kprobe(&lttng_kp->kp);
 182         if (ret)
 183                 goto register_error;
 184
 185         return 0;
 186
 187 register_error:
 188         kfree(lttng_kp->symbol_name);
 189 name_error:
 190         return ret;
 191 }
 192
 193 int lttng_kprobes_register_event(const char *name,
 194                            const char *symbol_name,
 195                            uint64_t offset,
 196                            uint64_t addr,
 197                            struct lttng_event *event)
 198 {
 199         int ret;
 200
 201         ret = lttng_create_kprobe_event(name, event);
 202         if (ret)
 203                 goto error;
 204
 205         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 206                 &event->u.kprobe, lttng_kprobes_event_handler_pre);
 207         if (ret)
 208                 goto register_error;
 209
 210         return 0;
 211
 212 register_error:
 213         kfree(event->desc->fields);
 214         kfree(event->desc->name);
 215         kfree(event->desc);
 216 error:
 217         return ret;
 218 }
 219 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event);
 220
 221 int lttng_kprobes_register_event_notifier(const char *symbol_name,
 222                            uint64_t offset,
 223                            uint64_t addr,
 224                            struct lttng_event_notifier *event_notifier)
 225 {
 226         int ret;
 227         ret = lttng_create_kprobe_event_notifier(symbol_name, event_notifier);
 228         if (ret)
 229                 goto error;
 230
 231         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 232                 &event_notifier->u.kprobe, lttng_kprobes_event_notifier_handler_pre);
 233         if (ret)
 234                 goto register_error;
 235
 236         return 0;
 237
 238 register_error:
 239         kfree(event_notifier->desc->name);
 240         kfree(event_notifier->desc);
 241 error:
 242         return ret;
 243 }
 244 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event_notifier);
 245
 246 void lttng_kprobes_unregister_event(struct lttng_event *event)
 247 {
 248         unregister_kprobe(&event->u.kprobe.kp);
 249 }
 250 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event);
 251
 252 void lttng_kprobes_unregister_event_notifier(struct lttng_event_notifier *event_notifier)
 253 {
 254         unregister_kprobe(&event_notifier->u.kprobe.kp);
 255 }
 256 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event_notifier);
 257
 258 void lttng_kprobes_destroy_event_private(struct lttng_event *event)
 259 {
 260         kfree(event->u.kprobe.symbol_name);
 261         kfree(event->desc->fields);
 262         kfree(event->desc->name);
 263         kfree(event->desc);
 264 }
 265 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_private);
 266
 267 void lttng_kprobes_destroy_event_notifier_private(struct lttng_event_notifier *event_notifier)
 268 {
 269         kfree(event_notifier->u.kprobe.symbol_name);
 270         kfree(event_notifier->desc->name);
 271         kfree(event_notifier->desc);
 272 }
 273 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_notifier_private);
 274
 275 MODULE_LICENSE("GPL and additional rights");
 276 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 277 MODULE_DESCRIPTION("LTTng kprobes probes");
 278 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 279         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 280         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 281         LTTNG_MODULES_EXTRAVERSION);