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/lttng-events.h>
  14 #include <ringbuffer/frontend_types.h>
  15 #include <wrapper/irqflags.h>
  16 #include <lttng/lttng-tracer.h>
  17
  18 static
  19 int lttng_kprobes_handler_pre(struct kprobe *p, struct pt_regs *regs)
  20 {
  21         struct lttng_event *event =
  22                 container_of(p, struct lttng_event, u.kprobe.kp);
  23         struct lttng_probe_ctx lttng_probe_ctx = {
  24                 .event = event,
  25                 .interruptible = !lttng_regs_irqs_disabled(regs),
  26         };
  27         struct lttng_channel *chan = event->chan;
  28         struct lib_ring_buffer_ctx ctx;
  29         int ret;
  30         unsigned long data = (unsigned long) p->addr;
  31
  32         if (unlikely(!READ_ONCE(chan->session->active)))
  33                 return 0;
  34         if (unlikely(!READ_ONCE(chan->enabled)))
  35                 return 0;
  36         if (unlikely(!READ_ONCE(event->enabled)))
  37                 return 0;
  38
  39         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),
  40                                  lttng_alignof(data), -1);
  41         ret = chan->ops->event_reserve(&ctx, event->id);
  42         if (ret < 0)
  43                 return 0;
  44         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(data));
  45         chan->ops->event_write(&ctx, &data, sizeof(data));
  46         chan->ops->event_commit(&ctx);
  47         return 0;
  48 }
  49
  50 /*
  51  * Create event description
  52  */
  53 static
  54 int lttng_create_kprobe_event(const char *name, struct lttng_event *event)
  55 {
  56         struct lttng_event_field *field;
  57         struct lttng_event_desc *desc;
  58         int ret;
  59
  60         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  61         if (!desc)
  62                 return -ENOMEM;
  63         desc->name = kstrdup(name, GFP_KERNEL);
  64         if (!desc->name) {
  65                 ret = -ENOMEM;
  66                 goto error_str;
  67         }
  68         desc->nr_fields = 1;
  69         desc->fields = field =
  70                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  71         if (!field) {
  72                 ret = -ENOMEM;
  73                 goto error_field;
  74         }
  75         field->name = "ip";
  76         field->type.atype = atype_integer;
  77         field->type.u.integer.size = sizeof(unsigned long) * CHAR_BIT;
  78         field->type.u.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  79         field->type.u.integer.signedness = lttng_is_signed_type(unsigned long);
  80         field->type.u.integer.reverse_byte_order = 0;
  81         field->type.u.integer.base = 16;
  82         field->type.u.integer.encoding = lttng_encode_none;
  83         desc->owner = THIS_MODULE;
  84         event->desc = desc;
  85
  86         return 0;
  87
  88 error_field:
  89         kfree(desc->name);
  90 error_str:
  91         kfree(desc);
  92         return ret;
  93 }
  94
  95 int lttng_kprobes_register(const char *name,
  96                            const char *symbol_name,
  97                            uint64_t offset,
  98                            uint64_t addr,
  99                            struct lttng_event *event)
 100 {
 101         int ret;
 102
 103         /* Kprobes expects a NULL symbol name if unused */
 104         if (symbol_name[0] == '\0')
 105                 symbol_name = NULL;
 106
 107         ret = lttng_create_kprobe_event(name, event);
 108         if (ret)
 109                 goto error;
 110         memset(&event->u.kprobe.kp, 0, sizeof(event->u.kprobe.kp));
 111         event->u.kprobe.kp.pre_handler = lttng_kprobes_handler_pre;
 112         if (symbol_name) {
 113                 event->u.kprobe.symbol_name =
 114                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 115                                 GFP_KERNEL);
 116                 if (!event->u.kprobe.symbol_name) {
 117                         ret = -ENOMEM;
 118                         goto name_error;
 119                 }
 120                 memcpy(event->u.kprobe.symbol_name, symbol_name,
 121                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 122                 event->u.kprobe.kp.symbol_name =
 123                         event->u.kprobe.symbol_name;
 124         }
 125         event->u.kprobe.kp.offset = offset;
 126         event->u.kprobe.kp.addr = (void *) (unsigned long) addr;
 127
 128         ret = register_kprobe(&event->u.kprobe.kp);
 129         if (ret)
 130                 goto register_error;
 131         return 0;
 132
 133 register_error:
 134         kfree(event->u.kprobe.symbol_name);
 135 name_error:
 136         kfree(event->desc->fields);
 137         kfree(event->desc->name);
 138         kfree(event->desc);
 139 error:
 140         return ret;
 141 }
 142 EXPORT_SYMBOL_GPL(lttng_kprobes_register);
 143
 144 void lttng_kprobes_unregister(struct lttng_event *event)
 145 {
 146         unregister_kprobe(&event->u.kprobe.kp);
 147 }
 148 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister);
 149
 150 void lttng_kprobes_destroy_private(struct lttng_event *event)
 151 {
 152         kfree(event->u.kprobe.symbol_name);
 153         kfree(event->desc->fields);
 154         kfree(event->desc->name);
 155         kfree(event->desc);
 156 }
 157 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_private);
 158
 159 MODULE_LICENSE("GPL and additional rights");
 160 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 161 MODULE_DESCRIPTION("LTTng kprobes probes");
 162 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 163         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 164         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 165         LTTNG_MODULES_EXTRAVERSION);