probes/lttng-kprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
   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 <wrapper/ringbuffer/frontend_types.h>
  15 #include <wrapper/vmalloc.h>
  16 #include <wrapper/irqflags.h>
  17 #include <lttng-tracer.h>
  18
  19 static
  20 int lttng_kprobes_handler_pre(struct kprobe *p, struct pt_regs *regs)
  21 {
  22         struct lttng_event *event =
  23                 container_of(p, struct lttng_event, u.kprobe.kp);
  24         struct lttng_probe_ctx lttng_probe_ctx = {
  25                 .event = event,
  26                 .interruptible = !lttng_regs_irqs_disabled(regs),
  27         };
  28         struct lttng_channel *chan = event->chan;
  29         struct lib_ring_buffer_ctx ctx;
  30         int ret;
  31         unsigned long data = (unsigned long) p->addr;
  32
  33         if (unlikely(!READ_ONCE(chan->session->active)))
  34                 return 0;
  35         if (unlikely(!READ_ONCE(chan->enabled)))
  36                 return 0;
  37         if (unlikely(!READ_ONCE(event->enabled)))
  38                 return 0;
  39
  40         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),
  41                                  lttng_alignof(data), -1);
  42         ret = chan->ops->event_reserve(&ctx, event->id);
  43         if (ret < 0)
  44                 return 0;
  45         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  46         chan->ops->event_write(&ctx, &data, sizeof(data));
  47         chan->ops->event_commit(&ctx);
  48         return 0;
  49 }
  50
  51 /*
  52  * Create event description
  53  */
  54 static
  55 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  56 {
  57         struct lttng_event_field *field;
  58         struct lttng_event_desc *desc;
  59         int ret;
  60
  61         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  62         if (!desc)
  63                 return -ENOMEM;
  64         desc->name = kstrdup(name, GFP_KERNEL);
  65         if (!desc->name) {
  66                 ret = -ENOMEM;
  67                 goto error_str;
  68         }
  69         desc->nr_fields = 1;
  70         desc->fields = field =
  71                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  72         if (!field) {
  73                 ret = -ENOMEM;
  74                 goto error_field;
  75         }
  76         field->name = "ip";
  77         field->type.atype = atype_integer;
  78         field->type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
  79         field->type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  80         field->type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
  81         field->type.u.basic.integer.reverse_byte_order = 0;
  82         field->type.u.basic.integer.base = 16;
  83         field->type.u.basic.integer.encoding = lttng_encode_none;
  84         desc->owner = THIS_MODULE;
  85         event->desc = desc;
  86
  87         return 0;
  88
  89 error_field:
  90         kfree(desc->name);
  91 error_str:
  92         kfree(desc);
  93         return ret;
  94 }
  95
  96 int lttng_kprobes_register(const char *name,
  97                            const char *symbol_name,
  98                            uint64_t offset,
  99                            uint64_t addr,
 100                            struct lttng_event *event)
 101 {
 102         int ret;
 103
 104         /* Kprobes expects a NULL symbol name if unused */
 105         if (symbol_name[0] == '\0')
 106                 symbol_name = NULL;
 107
 108         ret = lttng_create_kprobe_event(name, event);
 109         if (ret)
 110                 goto error;
 111         memset(&event->u.kprobe.kp, 0, sizeof(event->u.kprobe.kp));
 112         event->u.kprobe.kp.pre_handler = lttng_kprobes_handler_pre;
 113         if (symbol_name) {
 114                 event->u.kprobe.symbol_name =
 115                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 116                                 GFP_KERNEL);
 117                 if (!event->u.kprobe.symbol_name) {
 118                         ret = -ENOMEM;
 119                         goto name_error;
 120                 }
 121                 memcpy(event->u.kprobe.symbol_name, symbol_name,
 122                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 123                 event->u.kprobe.kp.symbol_name =
 124                         event->u.kprobe.symbol_name;
 125         }
 126         event->u.kprobe.kp.offset = offset;
 127         event->u.kprobe.kp.addr = (void *) (unsigned long) addr;
 128
 129         /*
 130          * Ensure the memory we just allocated don't trigger page faults.
 131          * Well.. kprobes itself puts the page fault handler on the blacklist,
 132          * but we can never be too careful.
 133          */
 134         wrapper_vmalloc_sync_all();
 135
 136         ret = register_kprobe(&event->u.kprobe.kp);
 137         if (ret)
 138                 goto register_error;
 139         return 0;
 140
 141 register_error:
 142         kfree(event->u.kprobe.symbol_name);
 143 name_error:
 144         kfree(event->desc->fields);
 145         kfree(event->desc->name);
 146         kfree(event->desc);
 147 error:
 148         return ret;
 149 }
 150 EXPORT_SYMBOL_GPL(lttng_kprobes_register);
 151
 152 void lttng_kprobes_unregister(struct lttng_event *event)
 153 {
 154         unregister_kprobe(&event->u.kprobe.kp);
 155 }
 156 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister);
 157
 158 void lttng_kprobes_destroy_private(struct lttng_event *event)
 159 {
 160         kfree(event->u.kprobe.symbol_name);
 161         kfree(event->desc->fields);
 162         kfree(event->desc->name);
 163         kfree(event->desc);
 164 }
 165 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_private);
 166
 167 MODULE_LICENSE("GPL and additional rights");
 168 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 169 MODULE_DESCRIPTION("LTTng kprobes probes");
 170 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 171         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 172         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 173         LTTNG_MODULES_EXTRAVERSION);