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/events.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng/tracer.h>
  18
  19 #define LTTNG_HOSTNAME_CTX_LEN  (__NEW_UTS_LEN + 1)
  20
  21 static
  22 size_t hostname_get_size(size_t offset)
  23 {
  24         size_t size = 0;
  25
  26         size += LTTNG_HOSTNAME_CTX_LEN;
  27         return size;
  28 }
  29
  30 static
  31 void hostname_record(struct lttng_ctx_field *field,
  32                  struct lib_ring_buffer_ctx *ctx,
  33                  struct lttng_channel *chan)
  34 {
  35         struct nsproxy *nsproxy;
  36         struct uts_namespace *ns;
  37         char *hostname;
  38
  39         /*
  40          * No need to take the RCU read-side lock to read current
  41          * nsproxy. (documented in nsproxy.h)
  42          */
  43         nsproxy = current->nsproxy;
  44         if (nsproxy) {
  45                 ns = nsproxy->uts_ns;
  46                 hostname = ns->name.nodename;
  47                 chan->ops->event_write(ctx, hostname,
  48                                 LTTNG_HOSTNAME_CTX_LEN);
  49         } else {
  50                 chan->ops->event_memset(ctx, 0,
  51                                 LTTNG_HOSTNAME_CTX_LEN);
  52         }
  53 }
  54
  55 static
  56 void hostname_get_value(struct lttng_ctx_field *field,
  57                 struct lttng_probe_ctx *lttng_probe_ctx,
  58                 union lttng_ctx_value *value)
  59 {
  60         struct nsproxy *nsproxy;
  61         struct uts_namespace *ns;
  62         char *hostname;
  63
  64         /*
  65          * No need to take the RCU read-side lock to read current
  66          * nsproxy. (documented in nsproxy.h)
  67          */
  68         nsproxy = current->nsproxy;
  69         if (nsproxy) {
  70                 ns = nsproxy->uts_ns;
  71                 hostname = ns->name.nodename;
  72         } else {
  73                 hostname = "";
  74         }
  75         value->str = hostname;
  76 }
  77
  78 static const struct lttng_type hostname_array_elem_type =
  79         __type_integer(char, 0, 0, -1, __BYTE_ORDER, 10, UTF8);
  80
  81 int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
  82 {
  83         struct lttng_ctx_field *field;
  84
  85         field = lttng_append_context(ctx);
  86         if (!field)
  87                 return -ENOMEM;
  88         if (lttng_find_context(*ctx, "hostname")) {
  89                 lttng_remove_context_field(ctx, field);
  90                 return -EEXIST;
  91         }
  92         field->event_field.name = "hostname";
  93         field->event_field.type.atype = atype_array_nestable;
  94         field->event_field.type.u.array_nestable.elem_type =
  95                 &hostname_array_elem_type;
  96         field->event_field.type.u.array_nestable.length = LTTNG_HOSTNAME_CTX_LEN;
  97         field->event_field.type.u.array_nestable.alignment = 0;
  98
  99         field->get_size = hostname_get_size;
 100         field->record = hostname_record;
 101         field->get_value = hostname_get_value;
 102         lttng_context_update(*ctx);
 103         wrapper_vmalloc_sync_mappings();
 104         return 0;
 105 }
 106 EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);