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 "lttng-events.h"
  14 #include "wrapper/ringbuffer/frontend_types.h"
  15 #include "wrapper/vmalloc.h"
  16 #include "wrapper/kallsyms.h"
  17 #include "lttng-tracer.h"
  18
  19 static
  20 int (*wrapper_task_prio_sym)(struct task_struct *t);
  21
  22 int wrapper_task_prio_init(void)
  23 {
  24         wrapper_task_prio_sym = (void *) kallsyms_lookup_funcptr("task_prio");
  25         if (!wrapper_task_prio_sym) {
  26                 printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
  27                 return -EINVAL;
  28         }
  29         return 0;
  30 }
  31
  32 static
  33 size_t prio_get_size(size_t offset)
  34 {
  35         size_t size = 0;
  36
  37         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  38         size += sizeof(int);
  39         return size;
  40 }
  41
  42 static
  43 void prio_record(struct lttng_ctx_field *field,
  44                 struct lib_ring_buffer_ctx *ctx,
  45                 struct lttng_channel *chan)
  46 {
  47         int prio;
  48
  49         prio = wrapper_task_prio_sym(current);
  50         lib_ring_buffer_align_ctx(ctx, lttng_alignof(prio));
  51         chan->ops->event_write(ctx, &prio, sizeof(prio));
  52 }
  53
  54 int lttng_add_prio_to_ctx(struct lttng_ctx **ctx)
  55 {
  56         struct lttng_ctx_field *field;
  57         int ret;
  58
  59         if (!wrapper_task_prio_sym) {
  60                 ret = wrapper_task_prio_init();
  61                 if (ret)
  62                         return ret;
  63         }
  64
  65         field = lttng_append_context(ctx);
  66         if (!field)
  67                 return -ENOMEM;
  68         if (lttng_find_context(*ctx, "prio")) {
  69                 lttng_remove_context_field(ctx, field);
  70                 return -EEXIST;
  71         }
  72         field->event_field.name = "prio";
  73         field->event_field.type.atype = atype_integer;
  74         field->event_field.type.u.basic.integer.size = sizeof(int) * CHAR_BIT;
  75         field->event_field.type.u.basic.integer.alignment = lttng_alignof(int) * CHAR_BIT;
  76         field->event_field.type.u.basic.integer.signedness = is_signed_type(int);
  77         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  78         field->event_field.type.u.basic.integer.base = 10;
  79         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  80         field->get_size = prio_get_size;
  81         field->record = prio_record;
  82         wrapper_vmalloc_sync_all();
  83         return 0;
  84 }
  85 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);
  86
  87 MODULE_LICENSE("GPL and additional rights");
  88 MODULE_AUTHOR("Mathieu Desnoyers");
  89 MODULE_DESCRIPTION("Linux Trace Toolkit Priority Context");