lttng-context-tid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-tid.c
   4  *
   5  * LTTng TID 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/lttng-events.h>
  14 #include <ringbuffer/frontend_types.h>
  15 #include <lttng/lttng-tracer.h>
  16
  17 static
  18 size_t tid_get_size(size_t offset)
  19 {
  20         size_t size = 0;
  21
  22         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  23         size += sizeof(pid_t);
  24         return size;
  25 }
  26
  27 static
  28 void tid_record(struct lttng_ctx_field *field,
  29                  struct lib_ring_buffer_ctx *ctx,
  30                  struct lttng_channel *chan)
  31 {
  32         pid_t tid;
  33
  34         tid = task_pid_nr(current);
  35         lib_ring_buffer_align_ctx(ctx, lttng_alignof(tid));
  36         chan->ops->event_write(ctx, &tid, sizeof(tid));
  37 }
  38
  39 static
  40 void tid_get_value(struct lttng_ctx_field *field,
  41                 struct lttng_probe_ctx *lttng_probe_ctx,
  42                 union lttng_ctx_value *value)
  43 {
  44         pid_t tid;
  45
  46         tid = task_pid_nr(current);
  47         value->s64 = tid;
  48 }
  49
  50 int lttng_add_tid_to_ctx(struct lttng_ctx **ctx)
  51 {
  52         struct lttng_ctx_field *field;
  53
  54         field = lttng_append_context(ctx);
  55         if (!field)
  56                 return -ENOMEM;
  57         if (lttng_find_context(*ctx, "tid")) {
  58                 lttng_remove_context_field(ctx, field);
  59                 return -EEXIST;
  60         }
  61         field->event_field.name = "tid";
  62         field->event_field.type.atype = atype_integer;
  63         field->event_field.type.u.integer.size = sizeof(pid_t) * CHAR_BIT;
  64         field->event_field.type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
  65         field->event_field.type.u.integer.signedness = lttng_is_signed_type(pid_t);
  66         field->event_field.type.u.integer.reverse_byte_order = 0;
  67         field->event_field.type.u.integer.base = 10;
  68         field->event_field.type.u.integer.encoding = lttng_encode_none;
  69         field->get_size = tid_get_size;
  70         field->record = tid_record;
  71         field->get_value = tid_get_value;
  72         lttng_context_update(*ctx);
  73         return 0;
  74 }
  75 EXPORT_SYMBOL_GPL(lttng_add_tid_to_ctx);