lttng-context-prio.c

   1 /*
   2  * (C) Copyright        2009-2011 -
   3  *              Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * LTTng priority context.
   6  *
   7  * Dual LGPL v2.1/GPL v2 license.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/sched.h>
  13 #include "ltt-events.h"
  14 #include "wrapper/ringbuffer/frontend_types.h"
  15 #include "wrapper/vmalloc.h"
  16 #include "ltt-tracer.h"
  17
  18 static
  19 int (*wrapper_task_prio_sym)(struct task_struct *t);
  20
  21 int wrapper_task_prio_init(void)
  22 {
  23         wrapper_task_prio_sym = (void *) kallsyms_lookup_name("task_prio");
  24         if (!wrapper_task_prio_sym) {
  25                 printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
  26                 return -EINVAL;
  27         }
  28         return 0;
  29 }
  30
  31 static
  32 size_t prio_get_size(size_t offset)
  33 {
  34         size_t size = 0;
  35
  36         size += lib_ring_buffer_align(offset, ltt_alignof(int));
  37         size += sizeof(int);
  38         return size;
  39 }
  40
  41 static
  42 void prio_record(struct lttng_ctx_field *field,
  43                 struct lib_ring_buffer_ctx *ctx,
  44                 struct ltt_channel *chan)
  45 {
  46         int prio;
  47
  48         prio = wrapper_task_prio_sym(current);
  49         lib_ring_buffer_align_ctx(ctx, ltt_alignof(prio));
  50         chan->ops->event_write(ctx, &prio, sizeof(prio));
  51 }
  52
  53 int lttng_add_prio_to_ctx(struct lttng_ctx **ctx)
  54 {
  55         struct lttng_ctx_field *field;
  56         int ret;
  57
  58         if (!wrapper_task_prio_sym) {
  59                 ret = wrapper_task_prio_init();
  60                 if (ret)
  61                         return ret;
  62         }
  63
  64         field = lttng_append_context(ctx);
  65         if (!field)
  66                 return -ENOMEM;
  67         field->event_field.name = "prio";
  68         field->event_field.type.atype = atype_integer;
  69         field->event_field.type.u.basic.integer.size = sizeof(int) * CHAR_BIT;
  70         field->event_field.type.u.basic.integer.alignment = ltt_alignof(int) * CHAR_BIT;
  71         field->event_field.type.u.basic.integer.signedness = is_signed_type(int);
  72         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  73         field->event_field.type.u.basic.integer.base = 10;
  74         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  75         field->get_size = prio_get_size;
  76         field->record = prio_record;
  77         wrapper_vmalloc_sync_all();
  78         return 0;
  79 }
  80 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);
  81
  82 MODULE_LICENSE("GPL and additional rights");
  83 MODULE_AUTHOR("Mathieu Desnoyers");
  84 MODULE_DESCRIPTION("Linux Trace Toolkit Priority Context");