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 /*
  53  * Create event description
  54  */
  55 static
  56 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  57 {
  58         struct lttng_event_field *field;
  59         struct lttng_event_desc *desc;
  60         int ret;
  61
  62         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  63         if (!desc)
  64                 return -ENOMEM;
  65         desc->name = kstrdup(name, GFP_KERNEL);
  66         if (!desc->name) {
  67                 ret = -ENOMEM;
  68                 goto error_str;
  69         }
  70         desc->nr_fields = 1;
  71         desc->fields = field =
  72                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  73         if (!field) {
  74                 ret = -ENOMEM;
  75                 goto error_field;
  76         }
  77         field->name = "ip";
  78         field->type.atype = atype_integer;
  79         field->type.u.integer.size = sizeof(unsigned long) * CHAR_BIT;
  80         field->type.u.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  81         field->type.u.integer.signedness = lttng_is_signed_type(unsigned long);
  82         field->type.u.integer.reverse_byte_order = 0;
  83         field->type.u.integer.base = 16;
  84         field->type.u.integer.encoding = lttng_encode_none;
  85         desc->owner = THIS_MODULE;
  86         event->desc = desc;
  87
  88         return 0;
  89
  90 error_field:
  91         kfree(desc->name);
  92 error_str:
  93         kfree(desc);
  94         return ret;
  95 }
  96
  97 static
  98 int _lttng_kprobes_register(const char *symbol_name,
  99                            uint64_t offset,
 100                            uint64_t addr,
 101                            struct lttng_kprobe *lttng_kp,
 102                            kprobe_pre_handler_t pre_handler)
 103 {
 104         int ret;
 105
 106         /* Kprobes expects a NULL symbol name if unused */
 107         if (symbol_name[0] == '\0')
 108                 symbol_name = NULL;
 109
 110         memset(&lttng_kp->kp, 0, sizeof(lttng_kp->kp));
 111         lttng_kp->kp.pre_handler = pre_handler;
 112
 113         if (symbol_name) {
 114                 lttng_kp->symbol_name =
 115                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 116                                 GFP_KERNEL);
 117                 if (!lttng_kp->symbol_name) {
 118                         ret = -ENOMEM;
 119                         goto name_error;
 120                 }
 121                 memcpy(lttng_kp->symbol_name, symbol_name,
 122                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 123                 lttng_kp->kp.symbol_name = lttng_kp->symbol_name;
 124         }
 125
 126         lttng_kp->kp.offset = offset;
 127         lttng_kp->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_mappings();
 135
 136         ret = register_kprobe(&lttng_kp->kp);
 137         if (ret)
 138                 goto register_error;
 139
 140         return 0;
 141
 142 register_error:
 143         kfree(lttng_kp->symbol_name);
 144 name_error:
 145         return ret;
 146 }
 147
 148 int lttng_kprobes_register_event(const char *name,
 149                            const char *symbol_name,
 150                            uint64_t offset,
 151                            uint64_t addr,
 152                            struct lttng_event *event)
 153 {
 154         int ret;
 155
 156         ret = lttng_create_kprobe_event(name, event);
 157         if (ret)
 158                 goto error;
 159
 160         ret = _lttng_kprobes_register(symbol_name, offset, addr,
 161                 &event->u.kprobe, lttng_kprobes_event_handler_pre);
 162         if (ret)
 163                 goto register_error;
 164
 165         return 0;
 166
 167 register_error:
 168         kfree(event->desc->fields);
 169         kfree(event->desc->name);
 170         kfree(event->desc);
 171 error:
 172         return ret;
 173 }
 174 EXPORT_SYMBOL_GPL(lttng_kprobes_register_event);
 175
 176 void lttng_kprobes_unregister_event(struct lttng_event *event)
 177 {
 178         unregister_kprobe(&event->u.kprobe.kp);
 179 }
 180 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister_event);
 181
 182 void lttng_kprobes_destroy_event_private(struct lttng_event *event)
 183 {
 184         kfree(event->u.kprobe.symbol_name);
 185         kfree(event->desc->fields);
 186         kfree(event->desc->name);
 187         kfree(event->desc);
 188 }
 189 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_event_private);
 190
 191 MODULE_LICENSE("GPL and additional rights");
 192 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 193 MODULE_DESCRIPTION("LTTng kprobes probes");
 194 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 195         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 196         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 197         LTTNG_MODULES_EXTRAVERSION);