lttng-context-hostname.c

   1 /*
   2  * lttng-context-hostname.c
   3  *
   4  * LTTng hostname context.
   5  *
   6  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/slab.h>
  25 #include <linux/sched.h>
  26 #include <linux/utsname.h>
  27 #include "lttng-events.h"
  28 #include "wrapper/ringbuffer/frontend_types.h"
  29 #include "wrapper/vmalloc.h"
  30 #include "lttng-tracer.h"
  31
  32 #define LTTNG_HOSTNAME_CTX_LEN  (__NEW_UTS_LEN + 1)
  33
  34 static
  35 size_t hostname_get_size(size_t offset)
  36 {
  37         size_t size = 0;
  38
  39         size += LTTNG_HOSTNAME_CTX_LEN;
  40         return size;
  41 }
  42
  43 static
  44 void hostname_record(struct lttng_ctx_field *field,
  45                  struct lib_ring_buffer_ctx *ctx,
  46                  struct lttng_channel *chan)
  47 {
  48         struct nsproxy *nsproxy;
  49         struct uts_namespace *ns;
  50         char *hostname;
  51
  52         /*
  53          * No need to take the RCU read-side lock to read current
  54          * nsproxy. (documented in nsproxy.h)
  55          */
  56         nsproxy = current->nsproxy;
  57         if (nsproxy) {
  58                 ns = nsproxy->uts_ns;
  59                 hostname = ns->name.nodename;
  60                 chan->ops->event_write(ctx, hostname,
  61                                 LTTNG_HOSTNAME_CTX_LEN);
  62         } else {
  63                 chan->ops->event_memset(ctx, 0,
  64                                 LTTNG_HOSTNAME_CTX_LEN);
  65         }
  66 }
  67
  68 int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
  69 {
  70         struct lttng_ctx_field *field;
  71
  72         field = lttng_append_context(ctx);
  73         if (!field)
  74                 return -ENOMEM;
  75         if (lttng_find_context(*ctx, "hostname")) {
  76                 lttng_remove_context_field(ctx, field);
  77                 return -EEXIST;
  78         }
  79         field->event_field.name = "hostname";
  80         field->event_field.type.atype = atype_array;
  81         field->event_field.type.u.array.elem_type.atype = atype_integer;
  82         field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;
  83         field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT;
  84         field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char);
  85         field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;
  86         field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;
  87         field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;
  88         field->event_field.type.u.array.length = LTTNG_HOSTNAME_CTX_LEN;
  89
  90         field->get_size = hostname_get_size;
  91         field->record = hostname_record;
  92         wrapper_vmalloc_sync_all();
  93         return 0;
  94 }
  95 EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);
  96
  97 MODULE_LICENSE("GPL and additional rights");
  98 MODULE_AUTHOR("Mathieu Desnoyers");
  99 MODULE_DESCRIPTION("Linux Trace Toolkit Perf Support");