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 #include <blacklist/kprobes.h>
  32
  33 static
  34 int lttng_kprobes_handler_pre(struct kprobe *p, struct pt_regs *regs)
  35 {
  36         struct lttng_event *event =
  37                 container_of(p, struct lttng_event, u.kprobe.kp);
  38         struct lttng_probe_ctx lttng_probe_ctx = {
  39                 .event = event,
  40                 .interruptible = !lttng_regs_irqs_disabled(regs),
  41         };
  42         struct lttng_channel *chan = event->chan;
  43         struct lib_ring_buffer_ctx ctx;
  44         int ret;
  45         unsigned long data = (unsigned long) p->addr;
  46
  47         if (unlikely(!READ_ONCE(chan->session->active)))
  48                 return 0;
  49         if (unlikely(!READ_ONCE(chan->enabled)))
  50                 return 0;
  51         if (unlikely(!READ_ONCE(event->enabled)))
  52                 return 0;
  53
  54         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),
  55                                  lttng_alignof(data), -1);
  56         ret = chan->ops->event_reserve(&ctx, event->id);
  57         if (ret < 0)
  58                 return 0;
  59         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  60         chan->ops->event_write(&ctx, &data, sizeof(data));
  61         chan->ops->event_commit(&ctx);
  62         return 0;
  63 }
  64
  65 /*
  66  * Create event description
  67  */
  68 static
  69 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  70 {
  71         struct lttng_event_field *field;
  72         struct lttng_event_desc *desc;
  73         int ret;
  74
  75         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  76         if (!desc)
  77                 return -ENOMEM;
  78         desc->name = kstrdup(name, GFP_KERNEL);
  79         if (!desc->name) {
  80                 ret = -ENOMEM;
  81                 goto error_str;
  82         }
  83         desc->nr_fields = 1;
  84         desc->fields = field =
  85                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  86         if (!field) {
  87                 ret = -ENOMEM;
  88                 goto error_field;
  89         }
  90         field->name = "ip";
  91         field->type.atype = atype_integer;
  92         field->type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
  93         field->type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  94         field->type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
  95         field->type.u.basic.integer.reverse_byte_order = 0;
  96         field->type.u.basic.integer.base = 16;
  97         field->type.u.basic.integer.encoding = lttng_encode_none;
  98         desc->owner = THIS_MODULE;
  99         event->desc = desc;
 100
 101         return 0;
 102
 103 error_field:
 104         kfree(desc->name);
 105 error_str:
 106         kfree(desc);
 107         return ret;
 108 }
 109
 110 int lttng_kprobes_register(const char *name,
 111                            const char *symbol_name,
 112                            uint64_t offset,
 113                            uint64_t addr,
 114                            struct lttng_event *event)
 115 {
 116         int ret;
 117
 118         /* Kprobes expects a NULL symbol name if unused */
 119         if (symbol_name[0] == '\0')
 120                 symbol_name = NULL;
 121
 122         ret = lttng_create_kprobe_event(name, event);
 123         if (ret)
 124                 goto error;
 125         memset(&event->u.kprobe.kp, 0, sizeof(event->u.kprobe.kp));
 126         event->u.kprobe.kp.pre_handler = lttng_kprobes_handler_pre;
 127         if (symbol_name) {
 128                 event->u.kprobe.symbol_name =
 129                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 130                                 GFP_KERNEL);
 131                 if (!event->u.kprobe.symbol_name) {
 132                         ret = -ENOMEM;
 133                         goto name_error;
 134                 }
 135                 memcpy(event->u.kprobe.symbol_name, symbol_name,
 136                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 137                 event->u.kprobe.kp.symbol_name =
 138                         event->u.kprobe.symbol_name;
 139         }
 140         event->u.kprobe.kp.offset = offset;
 141         event->u.kprobe.kp.addr = (void *) (unsigned long) addr;
 142
 143         /*
 144          * Ensure the memory we just allocated don't trigger page faults.
 145          * Well.. kprobes itself puts the page fault handler on the blacklist,
 146          * but we can never be too careful.
 147          */
 148         wrapper_vmalloc_sync_all();
 149
 150         ret = register_kprobe(&event->u.kprobe.kp);
 151         if (ret)
 152                 goto register_error;
 153         return 0;
 154
 155 register_error:
 156         kfree(event->u.kprobe.symbol_name);
 157 name_error:
 158         kfree(event->desc->fields);
 159         kfree(event->desc->name);
 160         kfree(event->desc);
 161 error:
 162         return ret;
 163 }
 164 EXPORT_SYMBOL_GPL(lttng_kprobes_register);
 165
 166 void lttng_kprobes_unregister(struct lttng_event *event)
 167 {
 168         unregister_kprobe(&event->u.kprobe.kp);
 169 }
 170 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister);
 171
 172 void lttng_kprobes_destroy_private(struct lttng_event *event)
 173 {
 174         kfree(event->u.kprobe.symbol_name);
 175         kfree(event->desc->fields);
 176         kfree(event->desc->name);
 177         kfree(event->desc);
 178 }
 179 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_private);
 180
 181 MODULE_LICENSE("GPL and additional rights");
 182 MODULE_AUTHOR("Mathieu Desnoyers");
 183 MODULE_DESCRIPTION("Linux Trace Toolkit Kprobes Support");
 184 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 185         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 186         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 187         LTTNG_MODULES_EXTRAVERSION);