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 /*
  11  * Ftrace function tracer does not seem to provide synchronization between probe
  12  * teardown and callback execution. Therefore, we make this module permanently
  13  * loaded (unloadable).
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/ftrace.h>
  18 #include <linux/slab.h>
  19 #include "../ltt-events.h"
  20 #include "../wrapper/ringbuffer/frontend_types.h"
  21 #include "../wrapper/ftrace.h"
  22 #include "../wrapper/vmalloc.h"
  23 #include "../ltt-tracer.h"
  24
  25 static
  26 void lttng_ftrace_handler(unsigned long ip, unsigned long parent_ip, void **data)
  27 {
  28         struct ltt_event *event = *data;
  29         struct ltt_channel *chan = event->chan;
  30         struct lib_ring_buffer_ctx ctx;
  31         struct {
  32                 unsigned long ip;
  33                 unsigned long parent_ip;
  34         } payload;
  35         int ret;
  36
  37         if (!ACCESS_ONCE(chan->session->active))
  38                 return;
  39         lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL,
  40                                  sizeof(payload), ltt_alignof(payload), -1);
  41         ret = chan->ops->event_reserve(&ctx);
  42         if (ret < 0)
  43                 return;
  44         payload.ip = ip;
  45         payload.parent_ip = parent_ip;
  46         lib_ring_buffer_align_ctx(&ctx, ltt_alignof(payload));
  47         chan->ops->event_write(&ctx, &payload, sizeof(payload));
  48         chan->ops->event_commit(&ctx);
  49         return;
  50 }
  51
  52 /*
  53  * Create event description
  54  */
  55 static
  56 int lttng_create_ftrace_event(const char *name, struct ltt_event *event)
  57 {
  58         struct lttng_event_field *fields;
  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 = 2;
  71         desc->fields = fields =
  72                 kzalloc(2 * sizeof(struct lttng_event_field), GFP_KERNEL);
  73         if (!desc->fields) {
  74                 ret = -ENOMEM;
  75                 goto error_fields;
  76         }
  77         fields[0].name = "ip";
  78         fields[0].type.atype = atype_integer;
  79         fields[0].type.u.basic.integer.size = sizeof(unsigned long);
  80         fields[0].type.u.basic.integer.alignment = ltt_alignof(unsigned long);
  81         fields[0].type.u.basic.integer.signedness = 0;
  82         fields[0].type.u.basic.integer.reverse_byte_order = 0;
  83         fields[0].type.u.basic.integer.base = 16;
  84         fields[0].type.u.basic.integer.encoding = lttng_encode_none;
  85
  86         fields[1].name = "parent_ip";
  87         fields[1].type.atype = atype_integer;
  88         fields[1].type.u.basic.integer.size = sizeof(unsigned long);
  89         fields[1].type.u.basic.integer.alignment = ltt_alignof(unsigned long);
  90         fields[1].type.u.basic.integer.signedness = 0;
  91         fields[1].type.u.basic.integer.reverse_byte_order = 0;
  92         fields[1].type.u.basic.integer.base = 16;
  93         fields[1].type.u.basic.integer.encoding = lttng_encode_none;
  94
  95         event->desc = desc;
  96
  97         return 0;
  98
  99 error_fields:
 100         kfree(desc->name);
 101 error_str:
 102         kfree(desc);
 103         return ret;
 104 }
 105
 106 static
 107 struct ftrace_probe_ops lttng_ftrace_ops = {
 108         .func = lttng_ftrace_handler,
 109 };
 110
 111 int lttng_ftrace_register(const char *name,
 112                           const char *symbol_name,
 113                           struct ltt_event *event)
 114 {
 115         int ret;
 116
 117         ret = lttng_create_ftrace_event(name, event);
 118         if (ret)
 119                 goto error;
 120
 121         event->u.ftrace.symbol_name = kstrdup(name, GFP_KERNEL);
 122         if (!event->u.ftrace.symbol_name)
 123                 goto name_error;
 124
 125         /* Ensure the memory we just allocated don't trigger page faults */
 126         wrapper_vmalloc_sync_all();
 127
 128         ret = wrapper_register_ftrace_function_probe(event->u.ftrace.symbol_name,
 129                         &lttng_ftrace_ops, event);
 130         if (ret)
 131                 goto register_error;
 132         return 0;
 133
 134 register_error:
 135         kfree(event->u.ftrace.symbol_name);
 136 name_error:
 137         kfree(event->desc->name);
 138         kfree(event->desc);
 139 error:
 140         return ret;
 141 }
 142 EXPORT_SYMBOL_GPL(lttng_ftrace_register);
 143
 144 void lttng_ftrace_unregister(struct ltt_event *event)
 145 {
 146         wrapper_unregister_ftrace_function_probe(event->u.ftrace.symbol_name,
 147                         &lttng_ftrace_ops, event);
 148         kfree(event->u.ftrace.symbol_name);
 149         kfree(desc->fields);
 150         kfree(event->desc->name);
 151         kfree(event->desc);
 152 }
 153 EXPORT_SYMBOL_GPL(lttng_ftrace_unregister);
 154
 155 /* This module is permanent. */
 156 int lttng_ftrace_init(void)
 157 {
 158         wrapper_vmalloc_sync_all();
 159         return 0;
 160 }
 161 module_init(lttng_ftrace_init)
 162
 163 MODULE_LICENSE("GPL and additional rights");
 164 MODULE_AUTHOR("Mathieu Desnoyers");
 165 MODULE_DESCRIPTION("Linux Trace Toolkit Ftrace Support");