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 static
  69 void hostname_get_value(struct lttng_ctx_field *field,
  70                 struct lttng_probe_ctx *lttng_probe_ctx,
  71                 union lttng_ctx_value *value)
  72 {
  73         struct nsproxy *nsproxy;
  74         struct uts_namespace *ns;
  75         char *hostname;
  76
  77         /*
  78          * No need to take the RCU read-side lock to read current
  79          * nsproxy. (documented in nsproxy.h)
  80          */
  81         nsproxy = current->nsproxy;
  82         if (nsproxy) {
  83                 ns = nsproxy->uts_ns;
  84                 hostname = ns->name.nodename;
  85         } else {
  86                 hostname = "";
  87         }
  88         value->str = hostname;
  89 }
  90
  91 int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
  92 {
  93         struct lttng_ctx_field *field;
  94
  95         field = lttng_append_context(ctx);
  96         if (!field)
  97                 return -ENOMEM;
  98         if (lttng_find_context(*ctx, "hostname")) {
  99                 lttng_remove_context_field(ctx, field);
 100                 return -EEXIST;
 101         }
 102         field->event_field.name = "hostname";
 103         field->event_field.type.atype = atype_array;
 104         field->event_field.type.u.array.elem_type.atype = atype_integer;
 105         field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;
 106         field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT;
 107         field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char);
 108         field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;
 109         field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;
 110         field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;
 111         field->event_field.type.u.array.length = LTTNG_HOSTNAME_CTX_LEN;
 112
 113         field->get_size = hostname_get_size;
 114         field->record = hostname_record;
 115         field->get_value = hostname_get_value;
 116         lttng_context_update(*ctx);
 117         wrapper_vmalloc_sync_all();
 118         return 0;
 119 }
 120 EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);