Version 2.7.7
[lttng-modules.git] / lttng-context-hostname.c
CommitLineData
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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
34static
35size_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
43static
44void 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
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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;
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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 }
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66}
67
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68static
69void hostname_get_value(struct lttng_ctx_field *field,
70 union lttng_ctx_value *value)
71{
72 struct nsproxy *nsproxy;
73 struct uts_namespace *ns;
74 char *hostname;
75
76 /*
77 * No need to take the RCU read-side lock to read current
78 * nsproxy. (documented in nsproxy.h)
79 */
80 nsproxy = current->nsproxy;
81 if (nsproxy) {
82 ns = nsproxy->uts_ns;
83 hostname = ns->name.nodename;
84 } else {
85 hostname = "";
86 }
87 value->str = hostname;
88}
89
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90int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
91{
92 struct lttng_ctx_field *field;
93
94 field = lttng_append_context(ctx);
95 if (!field)
96 return -ENOMEM;
97 if (lttng_find_context(*ctx, "hostname")) {
98 lttng_remove_context_field(ctx, field);
99 return -EEXIST;
100 }
101 field->event_field.name = "hostname";
102 field->event_field.type.atype = atype_array;
103 field->event_field.type.u.array.elem_type.atype = atype_integer;
104 field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;
105 field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT;
06254b0f 106 field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char);
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107 field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;
108 field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;
109 field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;
110 field->event_field.type.u.array.length = LTTNG_HOSTNAME_CTX_LEN;
111
112 field->get_size = hostname_get_size;
113 field->record = hostname_record;
f127e61e 114 field->get_value = hostname_get_value;
a9dd15da 115 lttng_context_update(*ctx);
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116 wrapper_vmalloc_sync_all();
117 return 0;
118}
119EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);
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