src/lttng-context-vtid.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-vtid.c
   4  *
   5  * LTTng vTID 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 <lttng/events-internal.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng/tracer.h>
  18
  19 static
  20 size_t vtid_get_size(size_t offset)
  21 {
  22         size_t size = 0;
  23
  24         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  25         size += sizeof(pid_t);
  26         return size;
  27 }
  28
  29 static
  30 void vtid_record(struct lttng_kernel_ctx_field *field,
  31                  struct lib_ring_buffer_ctx *ctx,
  32                  struct lttng_channel *chan)
  33 {
  34         pid_t vtid;
  35
  36         /*
  37          * nsproxy can be NULL when scheduled out of exit.
  38          */
  39         if (!current->nsproxy)
  40                 vtid = 0;
  41         else
  42                 vtid = task_pid_vnr(current);
  43         lib_ring_buffer_align_ctx(ctx, lttng_alignof(vtid));
  44         chan->ops->event_write(ctx, &vtid, sizeof(vtid));
  45 }
  46
  47 static
  48 void vtid_get_value(struct lttng_kernel_ctx_field *field,
  49                 struct lttng_probe_ctx *lttng_probe_ctx,
  50                 union lttng_ctx_value *value)
  51 {
  52         pid_t vtid;
  53
  54         /*
  55          * nsproxy can be NULL when scheduled out of exit.
  56          */
  57         if (!current->nsproxy)
  58                 vtid = 0;
  59         else
  60                 vtid = task_pid_vnr(current);
  61         value->s64 = vtid;
  62 }
  63
  64 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  65         lttng_kernel_static_event_field("vtid",
  66                 lttng_kernel_static_type_integer_from_type(pid_t, __BYTE_ORDER, 10),
  67                 false, false, false),
  68         vtid_get_size,
  69         NULL,
  70         vtid_record,
  71         vtid_get_value,
  72         NULL, NULL);
  73
  74 int lttng_add_vtid_to_ctx(struct lttng_kernel_ctx **ctx)
  75 {
  76         int ret;
  77
  78         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  79                 return -EEXIST;
  80         ret = lttng_kernel_context_append(ctx, ctx_field);
  81         wrapper_vmalloc_sync_mappings();
  82         return ret;
  83 }
  84 EXPORT_SYMBOL_GPL(lttng_add_vtid_to_ctx);