Support the hostname context

[lttng-modules.git] / lttng-context-hostname.c

diff --git a/lttng-context-hostname.c b/lttng-context-hostname.c
new file mode 100644 (file)
index 0000000..e38340b
--- /dev/null
+++ b/lttng-context-hostname.c
@@ -0,0 +1,97 @@
+/*
+ * lttng-context-hostname.c
+ *
+ * LTTng hostname context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/utsname.h>
+#include "lttng-events.h"
+#include "wrapper/ringbuffer/frontend_types.h"
+#include "wrapper/vmalloc.h"
+#include "lttng-tracer.h"
+
+#define LTTNG_HOSTNAME_CTX_LEN (__NEW_UTS_LEN + 1)
+
+static
+size_t hostname_get_size(size_t offset)
+{
+       size_t size = 0;
+
+       size += LTTNG_HOSTNAME_CTX_LEN;
+       return size;
+}
+
+static
+void hostname_record(struct lttng_ctx_field *field,
+                struct lib_ring_buffer_ctx *ctx,
+                struct lttng_channel *chan)
+{
+       struct nsproxy *nsproxy;
+       struct uts_namespace *ns;
+       char *hostname;
+
+       rcu_read_lock();
+       nsproxy = task_nsproxy(current);
+       if (nsproxy) {
+               ns = nsproxy->uts_ns;
+               hostname = ns->name.nodename;
+               chan->ops->event_write(ctx, hostname,
+                               LTTNG_HOSTNAME_CTX_LEN);
+       } else {
+               chan->ops->event_memset(ctx, 0,
+                               LTTNG_HOSTNAME_CTX_LEN);
+       }
+       rcu_read_unlock();
+}
+
+int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
+{
+       struct lttng_ctx_field *field;
+
+       field = lttng_append_context(ctx);
+       if (!field)
+               return -ENOMEM;
+       if (lttng_find_context(*ctx, "hostname")) {
+               lttng_remove_context_field(ctx, field);
+               return -EEXIST;
+       }
+       field->event_field.name = "hostname";
+       field->event_field.type.atype = atype_array;
+       field->event_field.type.u.array.elem_type.atype = atype_integer;
+       field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT;
+       field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT;
+       field->event_field.type.u.array.elem_type.u.basic.integer.signedness = is_signed_type(char);
+       field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0;
+       field->event_field.type.u.array.elem_type.u.basic.integer.base = 10;
+       field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8;
+       field->event_field.type.u.array.length = LTTNG_HOSTNAME_CTX_LEN;
+
+       field->get_size = hostname_get_size;
+       field->record = hostname_record;
+       wrapper_vmalloc_sync_all();
+       return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Linux Trace Toolkit Perf Support");