| 1 | /* |
| 2 | * probes/lttng-ftrace.c |
| 3 | * |
| 4 | * LTTng function tracer integration module. |
| 5 | * |
| 6 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 7 | * |
| 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. |
| 12 | * |
| 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. |
| 17 | * |
| 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 |
| 21 | */ |
| 22 | |
| 23 | /* |
| 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). |
| 27 | * |
| 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. |
| 31 | */ |
| 32 | |
| 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" |
| 41 | |
| 42 | static |
| 43 | void lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data) |
| 44 | { |
| 45 | struct lttng_event *event = *data; |
| 46 | struct lttng_channel *chan = event->chan; |
| 47 | struct lib_ring_buffer_ctx ctx; |
| 48 | struct { |
| 49 | unsigned long ip; |
| 50 | unsigned long parent_ip; |
| 51 | } payload; |
| 52 | int ret; |
| 53 | |
| 54 | if (unlikely(!ACCESS_ONCE(chan->session->active))) |
| 55 | return; |
| 56 | if (unlikely(!ACCESS_ONCE(chan->enabled))) |
| 57 | return; |
| 58 | if (unlikely(!ACCESS_ONCE(event->enabled))) |
| 59 | return; |
| 60 | |
| 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); |
| 64 | if (ret < 0) |
| 65 | return; |
| 66 | payload.ip = ip; |
| 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); |
| 71 | return; |
| 72 | } |
| 73 | |
| 74 | /* |
| 75 | * Create event description |
| 76 | */ |
| 77 | static |
| 78 | int lttng_create_ftrace_event(const char *name, struct lttng_event *event) |
| 79 | { |
| 80 | struct lttng_event_field *fields; |
| 81 | struct lttng_event_desc *desc; |
| 82 | int ret; |
| 83 | |
| 84 | desc = kzalloc(sizeof(*event->desc), GFP_KERNEL); |
| 85 | if (!desc) |
| 86 | return -ENOMEM; |
| 87 | desc->name = kstrdup(name, GFP_KERNEL); |
| 88 | if (!desc->name) { |
| 89 | ret = -ENOMEM; |
| 90 | goto error_str; |
| 91 | } |
| 92 | desc->nr_fields = 2; |
| 93 | desc->fields = fields = |
| 94 | kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL); |
| 95 | if (!desc->fields) { |
| 96 | ret = -ENOMEM; |
| 97 | goto error_fields; |
| 98 | } |
| 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; |
| 107 | |
| 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; |
| 116 | |
| 117 | desc->owner = THIS_MODULE; |
| 118 | event->desc = desc; |
| 119 | |
| 120 | return 0; |
| 121 | |
| 122 | error_fields: |
| 123 | kfree(desc->name); |
| 124 | error_str: |
| 125 | kfree(desc); |
| 126 | return ret; |
| 127 | } |
| 128 | |
| 129 | static |
| 130 | struct ftrace_probe_ops lttng_ftrace_ops = { |
| 131 | .func = lttng_ftrace_handler, |
| 132 | }; |
| 133 | |
| 134 | int lttng_ftrace_register(const char *name, |
| 135 | const char *symbol_name, |
| 136 | struct lttng_event *event) |
| 137 | { |
| 138 | int ret; |
| 139 | |
| 140 | ret = lttng_create_ftrace_event(name, event); |
| 141 | if (ret) |
| 142 | goto error; |
| 143 | |
| 144 | event->u.ftrace.symbol_name = kstrdup(symbol_name, GFP_KERNEL); |
| 145 | if (!event->u.ftrace.symbol_name) |
| 146 | goto name_error; |
| 147 | |
| 148 | /* Ensure the memory we just allocated don't trigger page faults */ |
| 149 | wrapper_vmalloc_sync_all(); |
| 150 | |
| 151 | ret = wrapper_register_ftrace_function_probe(event->u.ftrace.symbol_name, |
| 152 | <tng_ftrace_ops, event); |
| 153 | if (ret < 0) |
| 154 | goto register_error; |
| 155 | return 0; |
| 156 | |
| 157 | register_error: |
| 158 | kfree(event->u.ftrace.symbol_name); |
| 159 | name_error: |
| 160 | kfree(event->desc->name); |
| 161 | kfree(event->desc); |
| 162 | error: |
| 163 | return ret; |
| 164 | } |
| 165 | EXPORT_SYMBOL_GPL(lttng_ftrace_register); |
| 166 | |
| 167 | void lttng_ftrace_unregister(struct lttng_event *event) |
| 168 | { |
| 169 | wrapper_unregister_ftrace_function_probe(event->u.ftrace.symbol_name, |
| 170 | <tng_ftrace_ops, event); |
| 171 | } |
| 172 | EXPORT_SYMBOL_GPL(lttng_ftrace_unregister); |
| 173 | |
| 174 | void lttng_ftrace_destroy_private(struct lttng_event *event) |
| 175 | { |
| 176 | kfree(event->u.ftrace.symbol_name); |
| 177 | kfree(event->desc->fields); |
| 178 | kfree(event->desc->name); |
| 179 | kfree(event->desc); |
| 180 | } |
| 181 | EXPORT_SYMBOL_GPL(lttng_ftrace_destroy_private); |
| 182 | |
| 183 | int lttng_ftrace_init(void) |
| 184 | { |
| 185 | wrapper_vmalloc_sync_all(); |
| 186 | return 0; |
| 187 | } |
| 188 | module_init(lttng_ftrace_init) |
| 189 | |
| 190 | /* |
| 191 | * Ftrace takes care of waiting for a grace period (RCU sched) at probe |
| 192 | * unregistration, and disables preemption around probe call. |
| 193 | */ |
| 194 | void lttng_ftrace_exit(void) |
| 195 | { |
| 196 | } |
| 197 | module_exit(lttng_ftrace_exit) |
| 198 | |
| 199 | MODULE_LICENSE("GPL and additional rights"); |
| 200 | MODULE_AUTHOR("Mathieu Desnoyers"); |
| 201 | MODULE_DESCRIPTION("Linux Trace Toolkit Ftrace Support"); |
| 202 | MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "." |
| 203 | __stringify(LTTNG_MODULES_MINOR_VERSION) "." |
| 204 | __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION) |
| 205 | LTTNG_MODULES_EXTRAVERSION); |