2 * probes/lttng-ftrace.c
4 * LTTng function tracer integration module.
6 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; only
11 * version 2.1 of the License.
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * Ftrace function tracer does not seem to provide synchronization between probe
25 * teardown and callback execution. Therefore, we make this module permanently
26 * loaded (unloadable).
28 * TODO: Move to register_ftrace_function() (which is exported for
29 * modules) for Linux >= 3.0. It is faster (only enables the selected
30 * functions), and will stay there.
33 #include <linux/module.h>
34 #include <linux/ftrace.h>
35 #include <linux/slab.h>
36 #include "../lttng-events.h"
37 #include "../wrapper/ringbuffer/frontend_types.h"
38 #include "../wrapper/ftrace.h"
39 #include "../wrapper/vmalloc.h"
40 #include "../lttng-tracer.h"
43 void lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data)
45 struct lttng_event *event = *data;
46 struct lttng_channel *chan = event->chan;
47 struct lib_ring_buffer_ctx ctx;
50 unsigned long parent_ip;
54 if (unlikely(!ACCESS_ONCE(chan->session->active)))
56 if (unlikely(!ACCESS_ONCE(chan->enabled)))
58 if (unlikely(!ACCESS_ONCE(event->enabled)))
61 lib_ring_buffer_ctx_init(&ctx, chan->chan, event,
62 sizeof(payload), lttng_alignof(payload), -1);
63 ret = chan->ops->event_reserve(&ctx, event->id);
67 payload.parent_ip = parent_ip;
68 lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
69 chan->ops->event_write(&ctx, &payload, sizeof(payload));
70 chan->ops->event_commit(&ctx);
75 * Create event description
78 int lttng_create_ftrace_event(const char *name, struct lttng_event *event)
80 struct lttng_event_field *fields;
81 struct lttng_event_desc *desc;
84 desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
87 desc->name = kstrdup(name, GFP_KERNEL);
93 desc->fields = fields =
94 kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
99 fields[0].name = "ip";
100 fields[0].type.atype = atype_integer;
101 fields[0].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
102 fields[0].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
103 fields[0].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
104 fields[0].type.u.basic.integer.reverse_byte_order = 0;
105 fields[0].type.u.basic.integer.base = 16;
106 fields[0].type.u.basic.integer.encoding = lttng_encode_none;
108 fields[1].name = "parent_ip";
109 fields[1].type.atype = atype_integer;
110 fields[1].type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT;
111 fields[1].type.u.basic.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
112 fields[1].type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long);
113 fields[1].type.u.basic.integer.reverse_byte_order = 0;
114 fields[1].type.u.basic.integer.base = 16;
115 fields[1].type.u.basic.integer.encoding = lttng_encode_none;
117 desc->owner = THIS_MODULE;
130 struct ftrace_probe_ops lttng_ftrace_ops = {
131 .func = lttng_ftrace_handler,
134 int lttng_ftrace_register(const char *name,
135 const char *symbol_name,
136 struct lttng_event *event)
140 ret = lttng_create_ftrace_event(name, event);
144 event->u.ftrace.symbol_name = kstrdup(symbol_name, GFP_KERNEL);
145 if (!event->u.ftrace.symbol_name)
148 /* Ensure the memory we just allocated don't trigger page faults */
149 wrapper_vmalloc_sync_all();
151 ret = wrapper_register_ftrace_function_probe(event->u.ftrace.symbol_name,
152 <tng_ftrace_ops, event);
158 kfree(event->u.ftrace.symbol_name);
160 kfree(event->desc->name);
165 EXPORT_SYMBOL_GPL(lttng_ftrace_register);
167 void lttng_ftrace_unregister(struct lttng_event *event)
169 wrapper_unregister_ftrace_function_probe(event->u.ftrace.symbol_name,
170 <tng_ftrace_ops, event);
172 EXPORT_SYMBOL_GPL(lttng_ftrace_unregister);
174 void lttng_ftrace_destroy_private(struct lttng_event *event)
176 kfree(event->u.ftrace.symbol_name);
177 kfree(event->desc->fields);
178 kfree(event->desc->name);
181 EXPORT_SYMBOL_GPL(lttng_ftrace_destroy_private);
183 int lttng_ftrace_init(void)
185 wrapper_vmalloc_sync_all();
188 module_init(lttng_ftrace_init)
191 * Ftrace takes care of waiting for a grace period (RCU sched) at probe
192 * unregistration, and disables preemption around probe call.
194 void lttng_ftrace_exit(void)
197 module_exit(lttng_ftrace_exit)
199 MODULE_LICENSE("GPL and additional rights");
200 MODULE_AUTHOR("Mathieu Desnoyers");
201 MODULE_DESCRIPTION("Linux Trace Toolkit Ftrace Support");