probes/lttng-ftrace.c

   1 /*
   2  * (C) Copyright        2009-2011 -
   3  *              Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * LTTng function tracer integration module.
   6  *
   7  * Dual LGPL v2.1/GPL v2 license.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/ftrace.h>
  12 #include <linux/slab.h>
  13 #include "../ltt-events.h"
  14 #include "../wrapper/ringbuffer/frontend_types.h"
  15 #include "../ltt-tracer.h"
  16
  17 static
  18 int lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data)
  19 {
  20         struct ltt_event *event = *data;
  21         struct ltt_channel *chan = event->chan;
  22         struct lib_ring_buffer_ctx ctx;
  23         struct {
  24                 unsigned long ip;
  25                 unsigned long parent_ip;
  26         } payload;
  27         int ret;
  28
  29         if (!ACCESS_ONCE(chan->session->active))
  30                 return 0;
  31         lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL,
  32                                  sizeof(payload), ltt_alignof(payload), -1);
  33         ret = chan->ops->event_reserve(&ctx);
  34         if (ret < 0)
  35                 return 0;
  36         payload.ip = ip;
  37         payload.parent_ip = parent_ip;
  38         lib_ring_buffer_align_ctx(&ctx, ltt_alignof(payload));
  39         chan->ops->event_write(&ctx, &payload, sizeof(payload));
  40         chan->ops->event_commit(&ctx);
  41         return 0;
  42 }
  43
  44 /*
  45  * Create event description
  46  */
  47 static
  48 int lttng_create_ftrace_event(const char *name, struct ltt_event *event)
  49 {
  50         struct lttng_event_field *fields;
  51         struct lttng_event_desc *desc;
  52         int ret;
  53
  54         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  55         if (!desc)
  56                 return -ENOMEM;
  57         desc->name = kstrdup(name, GFP_KERNEL);
  58         if (!desc->name) {
  59                 ret = -ENOMEM;
  60                 goto error_str;
  61         }
  62         desc->nr_fields = 2;
  63         desc->fields = fields =
  64                 kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
  65         fields[0].name = "ip";
  66         fields[0].type.atype = atype_integer;
  67         fields[0].type.u.basic.integer.size = sizeof(unsigned long);
  68         fields[0].type.u.basic.integer.alignment = ltt_alignof(unsigned long);
  69         fields[0].type.u.basic.integer.signedness = 0;
  70         fields[0].type.u.basic.integer.reverse_byte_order = 0;
  71         fields[0].type.u.basic.integer.base = 16;
  72         fields[0].type.u.basic.integer.encoding = lttng_encode_none;
  73
  74         fields[1].name = "parent_ip";
  75         fields[1].type.atype = atype_integer;
  76         fields[1].type.u.basic.integer.size = sizeof(unsigned long);
  77         fields[1].type.u.basic.integer.alignment = ltt_alignof(unsigned long);
  78         fields[1].type.u.basic.integer.signedness = 0;
  79         fields[1].type.u.basic.integer.reverse_byte_order = 0;
  80         fields[1].type.u.basic.integer.base = 16;
  81         fields[1].type.u.basic.integer.encoding = lttng_encode_none;
  82
  83         event->desc = desc;
  84
  85         return 0;
  86
  87 error_str:
  88         kfree(desc);
  89         return ret;
  90 }
  91
  92 static
  93 struct ftrace_probe_ops lttng_ftrace_ops = {
  94         .func = lttng_ftrace_handler,
  95 };
  96
  97 int lttng_ftrace_register(const char *name,
  98                           const char *symbol_name,
  99                           struct ltt_event *event)
 100 {
 101         int ret;
 102
 103         ret = lttng_create_ftrace_event(name, event);
 104         if (ret)
 105                 goto error;
 106
 107         event->u.ftrace.symbol_name = kstrdup(name, GFP_KERNEL);
 108         if (!event->u.ftrace.symbol_name)
 109                 goto name_error;
 110
 111         ret = register_ftrace_function_probe(symbol_name,
 112                         &lttng_ftrace_ops, event);
 113         if (ret)
 114                 goto register_error;
 115         return 0;
 116
 117 register_error:
 118         kfree(event->u.ftrace.symbol_name);
 119 name_error:
 120         kfree(event->desc->name);
 121         kfree(event->desc);
 122 error:
 123         return ret;
 124 }
 125 EXPORT_SYMBOL_GPL(lttng_ftrace_register);
 126
 127 void lttng_ftrace_unregister(struct ltt_event *event)
 128 {
 129         unregister_ftrace_function_probe(event->u.ftrace.symbol_name,
 130                         &lttng_ftrace_ops, event);
 131         kfree(event->u.ftrace.symbol_name);
 132         kfree(event->desc->name);
 133         kfree(event->desc);
 134 }
 135 EXPORT_SYMBOL_GPL(lttng_ftrace_unregister);
 136
 137 MODULE_LICENSE("GPL and additional rights");
 138 MODULE_AUTHOR("Mathieu Desnoyers");
 139 MODULE_DESCRIPTION("Linux Trace Toolkit Ftrace Support");