lttng-context-hostname.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-hostname.c
   4  *
   5  * LTTng hostname 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 <linux/utsname.h>
  14 #include <lttng/lttng-events.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <lttng/lttng-tracer.h>
  17
  18 #define LTTNG_HOSTNAME_CTX_LEN  (__NEW_UTS_LEN + 1)
  19
  20 static
  21 size_t hostname_get_size(size_t offset)
  22 {
  23         size_t size = 0;
  24
  25         size += LTTNG_HOSTNAME_CTX_LEN;
  26         return size;
  27 }
  28
  29 static
  30 void hostname_record(struct lttng_ctx_field *field,
  31                  struct lib_ring_buffer_ctx *ctx,
  32                  struct lttng_channel *chan)
  33 {
  34         struct nsproxy *nsproxy;
  35         struct uts_namespace *ns;
  36         char *hostname;
  37
  38         /*
  39          * No need to take the RCU read-side lock to read current
  40          * nsproxy. (documented in nsproxy.h)
  41          */
  42         nsproxy = current->nsproxy;
  43         if (nsproxy) {
  44                 ns = nsproxy->uts_ns;
  45                 hostname = ns->name.nodename;
  46                 chan->ops->event_write(ctx, hostname,
  47                                 LTTNG_HOSTNAME_CTX_LEN);
  48         } else {
  49                 chan->ops->event_memset(ctx, 0,
  50                                 LTTNG_HOSTNAME_CTX_LEN);
  51         }
  52 }
  53
  54 static
  55 void hostname_get_value(struct lttng_ctx_field *field,
  56                 struct lttng_probe_ctx *lttng_probe_ctx,
  57                 union lttng_ctx_value *value)
  58 {
  59         struct nsproxy *nsproxy;
  60         struct uts_namespace *ns;
  61         char *hostname;
  62
  63         /*
  64          * No need to take the RCU read-side lock to read current
  65          * nsproxy. (documented in nsproxy.h)
  66          */
  67         nsproxy = current->nsproxy;
  68         if (nsproxy) {
  69                 ns = nsproxy->uts_ns;
  70                 hostname = ns->name.nodename;
  71         } else {
  72                 hostname = "";
  73         }
  74         value->str = hostname;
  75 }
  76
  77 static const struct lttng_type hostname_array_elem_type =
  78         __type_integer(char, 0, 0, -1, __BYTE_ORDER, 10, UTF8);
  79
  80 int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
  81 {
  82         struct lttng_ctx_field *field;
  83
  84         field = lttng_append_context(ctx);
  85         if (!field)
  86                 return -ENOMEM;
  87         if (lttng_find_context(*ctx, "hostname")) {
  88                 lttng_remove_context_field(ctx, field);
  89                 return -EEXIST;
  90         }
  91         field->event_field.name = "hostname";
  92         field->event_field.type.atype = atype_array_nestable;
  93         field->event_field.type.u.array_nestable.elem_type =
  94                 &hostname_array_elem_type;
  95         field->event_field.type.u.array_nestable.length = LTTNG_HOSTNAME_CTX_LEN;
  96         field->event_field.type.u.array_nestable.alignment = 0;
  97
  98         field->get_size = hostname_get_size;
  99         field->record = hostname_record;
 100         field->get_value = hostname_get_value;
 101         lttng_context_update(*ctx);
 102         return 0;
 103 }
 104 EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);