lttng-context-pid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-pid.c
   4  *
   5  * LTTng PID 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 pid_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 pid_record(struct lttng_ctx_field *field,
  29                 struct lib_ring_buffer_ctx *ctx,
  30                 struct lttng_channel *chan)
  31 {
  32         pid_t pid;
  33
  34         pid = task_tgid_nr(current);
  35         lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid));
  36         chan->ops->event_write(ctx, &pid, sizeof(pid));
  37 }
  38
  39 static
  40 void pid_get_value(struct lttng_ctx_field *field,
  41                 struct lttng_probe_ctx *lttng_probe_ctx,
  42                 union lttng_ctx_value *value)
  43 {
  44         value->s64 = task_tgid_nr(current);
  45 }
  46
  47 int lttng_add_pid_to_ctx(struct lttng_ctx **ctx)
  48 {
  49         struct lttng_ctx_field *field;
  50
  51         field = lttng_append_context(ctx);
  52         if (!field)
  53                 return -ENOMEM;
  54         if (lttng_find_context(*ctx, "pid")) {
  55                 lttng_remove_context_field(ctx, field);
  56                 return -EEXIST;
  57         }
  58         field->event_field.name = "pid";
  59         field->event_field.type.atype = atype_integer;
  60         field->event_field.type.u.integer.size = sizeof(pid_t) * CHAR_BIT;
  61         field->event_field.type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
  62         field->event_field.type.u.integer.signedness = lttng_is_signed_type(pid_t);
  63         field->event_field.type.u.integer.reverse_byte_order = 0;
  64         field->event_field.type.u.integer.base = 10;
  65         field->event_field.type.u.integer.encoding = lttng_encode_none;
  66         field->get_size = pid_get_size;
  67         field->record = pid_record;
  68         field->get_value = pid_get_value;
  69         lttng_context_update(*ctx);
  70         return 0;
  71 }
  72 EXPORT_SYMBOL_GPL(lttng_add_pid_to_ctx);