probes/lttng-kprobes.c

   1 /*
   2  * probes/lttng-kprobes.c
   3  *
   4  * LTTng kprobes integration module.
   5  *
   6  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/kprobes.h>
  25 #include <linux/slab.h>
  26 #include <lttng-events.h>
  27 #include <wrapper/ringbuffer/frontend_types.h>
  28 #include <wrapper/vmalloc.h>
  29 #include <wrapper/irqflags.h>
  30 #include <lttng-tracer.h>
  31
  32 static
  33 int lttng_kprobes_handler_pre(struct kprobe *p, struct pt_regs *regs)
  34 {
  35         struct lttng_event *event =
  36                 container_of(p, struct lttng_event, u.kprobe.kp);
  37         struct lttng_probe_ctx lttng_probe_ctx = {
  38                 .event = event,
  39                 .interruptible = !lttng_regs_irqs_disabled(regs),
  40         };
  41         struct lttng_channel *chan = event->chan;
  42         struct lib_ring_buffer_ctx ctx;
  43         int ret;
  44         unsigned long data = (unsigned long) p->addr;
  45
  46         if (unlikely(!READ_ONCE(chan->session->active)))
  47                 return 0;
  48         if (unlikely(!READ_ONCE(chan->enabled)))
  49                 return 0;
  50         if (unlikely(!READ_ONCE(event->enabled)))
  51                 return 0;
  52
  53         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),
  54                                  lttng_alignof(data), -1);
  55         ret = chan->ops->event_reserve(&ctx, event->id);
  56         if (ret < 0)
  57                 return 0;
  58         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  59         chan->ops->event_write(&ctx, &data, sizeof(data));
  60         chan->ops->event_commit(&ctx);
  61         return 0;
  62 }
  63
  64 /*
  65  * Create event description
  66  */
  67 static
  68 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  69 {
  70         struct lttng_event_field *field;
  71         struct lttng_event_desc *desc;
  72         int ret;
  73
  74         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  75         if (!desc)
  76                 return -ENOMEM;
  77         desc->name = kstrdup(name, GFP_KERNEL);
  78         if (!desc->name) {
  79                 ret = -ENOMEM;
  80                 goto error_str;
  81         }
  82         desc->nr_fields = 1;
  83         desc->fields = field =
  84                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  85         if (!field) {
  86                 ret = -ENOMEM;
  87                 goto error_field;
  88         }
  89         field->name = "ip";
  90         field->type.atype = atype_integer;
  91         field->type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
  92         field->type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  93         field->type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
  94         field->type.u.basic.integer.reverse_byte_order = 0;
  95         field->type.u.basic.integer.base = 16;
  96         field->type.u.basic.integer.encoding = lttng_encode_none;
  97         desc->owner = THIS_MODULE;
  98         event->desc = desc;
  99
 100         return 0;
 101
 102 error_field:
 103         kfree(desc->name);
 104 error_str:
 105         kfree(desc);
 106         return ret;
 107 }
 108
 109 int lttng_kprobes_register(const char *name,
 110                            const char *symbol_name,
 111                            uint64_t offset,
 112                            uint64_t addr,
 113                            struct lttng_event *event)
 114 {
 115         int ret;
 116
 117         /* Kprobes expects a NULL symbol name if unused */
 118         if (symbol_name[0] == '\0')
 119                 symbol_name = NULL;
 120
 121         ret = lttng_create_kprobe_event(name, event);
 122         if (ret)
 123                 goto error;
 124         memset(&event->u.kprobe.kp, 0, sizeof(event->u.kprobe.kp));
 125         event->u.kprobe.kp.pre_handler = lttng_kprobes_handler_pre;
 126         if (symbol_name) {
 127                 event->u.kprobe.symbol_name =
 128                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 129                                 GFP_KERNEL);
 130                 if (!event->u.kprobe.symbol_name) {
 131                         ret = -ENOMEM;
 132                         goto name_error;
 133                 }
 134                 memcpy(event->u.kprobe.symbol_name, symbol_name,
 135                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 136                 event->u.kprobe.kp.symbol_name =
 137                         event->u.kprobe.symbol_name;
 138         }
 139         event->u.kprobe.kp.offset = offset;
 140         event->u.kprobe.kp.addr = (void *) (unsigned long) addr;
 141
 142         /*
 143          * Ensure the memory we just allocated don't trigger page faults.
 144          * Well.. kprobes itself puts the page fault handler on the blacklist,
 145          * but we can never be too careful.
 146          */
 147         wrapper_vmalloc_sync_all();
 148
 149         ret = register_kprobe(&event->u.kprobe.kp);
 150         if (ret)
 151                 goto register_error;
 152         return 0;
 153
 154 register_error:
 155         kfree(event->u.kprobe.symbol_name);
 156 name_error:
 157         kfree(event->desc->fields);
 158         kfree(event->desc->name);
 159         kfree(event->desc);
 160 error:
 161         return ret;
 162 }
 163 EXPORT_SYMBOL_GPL(lttng_kprobes_register);
 164
 165 void lttng_kprobes_unregister(struct lttng_event *event)
 166 {
 167         unregister_kprobe(&event->u.kprobe.kp);
 168 }
 169 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister);
 170
 171 void lttng_kprobes_destroy_private(struct lttng_event *event)
 172 {
 173         kfree(event->u.kprobe.symbol_name);
 174         kfree(event->desc->fields);
 175         kfree(event->desc->name);
 176         kfree(event->desc);
 177 }
 178 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_private);
 179
 180 MODULE_LICENSE("GPL and additional rights");
 181 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 182 MODULE_DESCRIPTION("LTTng kprobes probes");
 183 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 184         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 185         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 186         LTTNG_MODULES_EXTRAVERSION);