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_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(!READ_ONCE(chan->session->active)))
  35                 return 0;
  36         if (unlikely(!READ_ONCE(chan->enabled)))
  37                 return 0;
  38         if (unlikely(!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 int lttng_kprobes_register(const char *name,
  98                            const char *symbol_name,
  99                            uint64_t offset,
 100                            uint64_t addr,
 101                            struct lttng_event *event)
 102 {
 103         int ret;
 104
 105         /* Kprobes expects a NULL symbol name if unused */
 106         if (symbol_name[0] == '\0')
 107                 symbol_name = NULL;
 108
 109         ret = lttng_create_kprobe_event(name, event);
 110         if (ret)
 111                 goto error;
 112         memset(&event->u.kprobe.kp, 0, sizeof(event->u.kprobe.kp));
 113         event->u.kprobe.kp.pre_handler = lttng_kprobes_handler_pre;
 114         if (symbol_name) {
 115                 event->u.kprobe.symbol_name =
 116                         kzalloc(LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char),
 117                                 GFP_KERNEL);
 118                 if (!event->u.kprobe.symbol_name) {
 119                         ret = -ENOMEM;
 120                         goto name_error;
 121                 }
 122                 memcpy(event->u.kprobe.symbol_name, symbol_name,
 123                        LTTNG_KERNEL_SYM_NAME_LEN * sizeof(char));
 124                 event->u.kprobe.kp.symbol_name =
 125                         event->u.kprobe.symbol_name;
 126         }
 127         event->u.kprobe.kp.offset = offset;
 128         event->u.kprobe.kp.addr = (void *) (unsigned long) addr;
 129
 130         /*
 131          * Ensure the memory we just allocated don't trigger page faults.
 132          * Well.. kprobes itself puts the page fault handler on the blacklist,
 133          * but we can never be too careful.
 134          */
 135         wrapper_vmalloc_sync_mappings();
 136
 137         ret = register_kprobe(&event->u.kprobe.kp);
 138         if (ret)
 139                 goto register_error;
 140         return 0;
 141
 142 register_error:
 143         kfree(event->u.kprobe.symbol_name);
 144 name_error:
 145         kfree(event->desc->fields);
 146         kfree(event->desc->name);
 147         kfree(event->desc);
 148 error:
 149         return ret;
 150 }
 151 EXPORT_SYMBOL_GPL(lttng_kprobes_register);
 152
 153 void lttng_kprobes_unregister(struct lttng_event *event)
 154 {
 155         unregister_kprobe(&event->u.kprobe.kp);
 156 }
 157 EXPORT_SYMBOL_GPL(lttng_kprobes_unregister);
 158
 159 void lttng_kprobes_destroy_private(struct lttng_event *event)
 160 {
 161         kfree(event->u.kprobe.symbol_name);
 162         kfree(event->desc->fields);
 163         kfree(event->desc->name);
 164         kfree(event->desc);
 165 }
 166 EXPORT_SYMBOL_GPL(lttng_kprobes_destroy_private);
 167
 168 MODULE_LICENSE("GPL and additional rights");
 169 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 170 MODULE_DESCRIPTION("LTTng kprobes probes");
 171 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 172         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 173         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 174         LTTNG_MODULES_EXTRAVERSION);