8956e540e1c8a0a01255c61d88203b9727ed9092
[lttng-modules.git] / src / 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 <lttng/events-internal.h>
16 #include <ringbuffer/frontend_types.h>
17 #include <wrapper/vmalloc.h>
18 #include <lttng/tracer.h>
19
20 #define LTTNG_HOSTNAME_CTX_LEN (__NEW_UTS_LEN + 1)
21
22 static
23 size_t hostname_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
24 {
25 size_t size = 0;
26
27 size += LTTNG_HOSTNAME_CTX_LEN;
28 return size;
29 }
30
31 static
32 void hostname_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
33 struct lttng_kernel_ring_buffer_ctx *ctx,
34 struct lttng_kernel_channel_buffer *chan)
35 {
36 struct nsproxy *nsproxy;
37 struct uts_namespace *ns;
38 char *hostname;
39
40 /*
41 * No need to take the RCU read-side lock to read current
42 * nsproxy. (documented in nsproxy.h)
43 */
44 nsproxy = current->nsproxy;
45 if (nsproxy) {
46 ns = nsproxy->uts_ns;
47 hostname = ns->name.nodename;
48 chan->ops->event_write(ctx, hostname,
49 LTTNG_HOSTNAME_CTX_LEN);
50 } else {
51 chan->ops->event_memset(ctx, 0,
52 LTTNG_HOSTNAME_CTX_LEN);
53 }
54 }
55
56 static
57 void hostname_get_value(void *priv,
58 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
59 struct lttng_ctx_value *value)
60 {
61 struct nsproxy *nsproxy;
62 struct uts_namespace *ns;
63 char *hostname;
64
65 /*
66 * No need to take the RCU read-side lock to read current
67 * nsproxy. (documented in nsproxy.h)
68 */
69 nsproxy = current->nsproxy;
70 if (nsproxy) {
71 ns = nsproxy->uts_ns;
72 hostname = ns->name.nodename;
73 } else {
74 hostname = "";
75 }
76 value->u.str = hostname;
77 }
78
79 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
80 lttng_kernel_static_event_field("hostname",
81 lttng_kernel_static_type_array_text(LTTNG_HOSTNAME_CTX_LEN),
82 false, false, false),
83 hostname_get_size,
84 hostname_record,
85 hostname_get_value,
86 NULL, NULL);
87
88 int lttng_add_hostname_to_ctx(struct lttng_kernel_ctx **ctx)
89 {
90 int ret;
91
92 if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
93 return -EEXIST;
94 ret = lttng_kernel_context_append(ctx, ctx_field);
95 wrapper_vmalloc_sync_mappings();
96 return ret;
97 }
98 EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);
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