--- /dev/null
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * lttng-context-hostname.c
+ *
+ * LTTng hostname context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/utsname.h>
+#include <lttng/events.h>
+#include <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;
+
+ /*
+ * No need to take the RCU read-side lock to read current
+ * nsproxy. (documented in nsproxy.h)
+ */
+ nsproxy = current->nsproxy;
+ 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);
+ }
+}
+
+static
+void hostname_get_value(struct lttng_ctx_field *field,
+ struct lttng_probe_ctx *lttng_probe_ctx,
+ union lttng_ctx_value *value)
+{
+ struct nsproxy *nsproxy;
+ struct uts_namespace *ns;
+ char *hostname;
+
+ /*
+ * No need to take the RCU read-side lock to read current
+ * nsproxy. (documented in nsproxy.h)
+ */
+ nsproxy = current->nsproxy;
+ if (nsproxy) {
+ ns = nsproxy->uts_ns;
+ hostname = ns->name.nodename;
+ } else {
+ hostname = "";
+ }
+ value->str = hostname;
+}
+
+static const struct lttng_type hostname_array_elem_type =
+ __type_integer(char, 0, 0, -1, __BYTE_ORDER, 10, UTF8);
+
+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_nestable;
+ field->event_field.type.u.array_nestable.elem_type =
+ &hostname_array_elem_type;
+ field->event_field.type.u.array_nestable.length = LTTNG_HOSTNAME_CTX_LEN;
+ field->event_field.type.u.array_nestable.alignment = 0;
+
+ field->get_size = hostname_get_size;
+ field->record = hostname_record;
+ field->get_value = hostname_get_value;
+ lttng_context_update(*ctx);
+ wrapper_vmalloc_sync_mappings();
+ return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_add_hostname_to_ctx);