lttng-context-prio.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-prio.c
   4  *
   5  * LTTng priority context.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   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/kallsyms.h>
  16 #include <lttng-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_funcptr("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, lttng_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 lttng_channel *chan)
  45 {
  46         int prio;
  47
  48         prio = wrapper_task_prio_sym(current);
  49         lib_ring_buffer_align_ctx(ctx, lttng_alignof(prio));
  50         chan->ops->event_write(ctx, &prio, sizeof(prio));
  51 }
  52
  53 static
  54 void prio_get_value(struct lttng_ctx_field *field,
  55                 struct lttng_probe_ctx *lttng_probe_ctx,
  56                 union lttng_ctx_value *value)
  57 {
  58         value->s64 = wrapper_task_prio_sym(current);
  59 }
  60
  61 int lttng_add_prio_to_ctx(struct lttng_ctx **ctx)
  62 {
  63         struct lttng_ctx_field *field;
  64         int ret;
  65
  66         if (!wrapper_task_prio_sym) {
  67                 ret = wrapper_task_prio_init();
  68                 if (ret)
  69                         return ret;
  70         }
  71
  72         field = lttng_append_context(ctx);
  73         if (!field)
  74                 return -ENOMEM;
  75         if (lttng_find_context(*ctx, "prio")) {
  76                 lttng_remove_context_field(ctx, field);
  77                 return -EEXIST;
  78         }
  79         field->event_field.name = "prio";
  80         field->event_field.type.atype = atype_integer;
  81         field->event_field.type.u.integer.size = sizeof(int) * CHAR_BIT;
  82         field->event_field.type.u.integer.alignment = lttng_alignof(int) * CHAR_BIT;
  83         field->event_field.type.u.integer.signedness = lttng_is_signed_type(int);
  84         field->event_field.type.u.integer.reverse_byte_order = 0;
  85         field->event_field.type.u.integer.base = 10;
  86         field->event_field.type.u.integer.encoding = lttng_encode_none;
  87         field->get_size = prio_get_size;
  88         field->record = prio_record;
  89         field->get_value = prio_get_value;
  90         lttng_context_update(*ctx);
  91         return 0;
  92 }
  93 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);