X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-mnt-ns.c;fp=liblttng-ust%2Flttng-context-mnt-ns.c;h=d54c42aa093ae1e2c2a310bc7af09abe69eb3fb3;hb=0a5755a3dc6533557037a06800839733b6ee5378;hp=0000000000000000000000000000000000000000;hpb=82df14e46c733a9e0906cf7a11299d83d160e1a0;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-context-mnt-ns.c b/liblttng-ust/lttng-context-mnt-ns.c
new file mode 100644
index 00000000..d54c42aa
--- /dev/null
+++ b/liblttng-ust/lttng-context-mnt-ns.c
@@ -0,0 +1,139 @@
+/*
+ * lttng-context-mnt-ns.c
+ *
+ * LTTng UST mnt namespace context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *               2019 Michael Jeanson <mjeanson@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
+ */
+
+#define _LGPL_SOURCE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <lttng/ust-events.h>
+#include <lttng/ust-tracer.h>
+#include <lttng/ringbuffer-config.h>
+
+#include "ns.h"
+
+/*
+ * We cache the result to ensure we don't stat(2) the proc filesystem on
+ * each event. The mount namespace is global to the process.
+ */
+static ino_t cached_mnt_ns = NS_INO_UNINITIALIZED;
+
+static
+ino_t get_mnt_ns(void)
+{
+	struct stat sb;
+	ino_t mnt_ns;
+
+	mnt_ns = CMM_LOAD_SHARED(cached_mnt_ns);
+
+	/*
+	 * If the cache is populated, do nothing and return the
+	 * cached inode number.
+	 */
+	if (caa_likely(mnt_ns != NS_INO_UNINITIALIZED))
+		return mnt_ns;
+
+	/*
+	 * At this point we have to populate the cache, set the initial
+	 * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
+	 * number from the proc filesystem, this is the value we will
+	 * cache.
+	 */
+	mnt_ns = NS_INO_UNAVAILABLE;
+
+	if (stat("/proc/self/ns/mnt", &sb) == 0) {
+		mnt_ns = sb.st_ino;
+	}
+
+	/*
+	 * And finally, store the inode number in the cache.
+	 */
+	CMM_STORE_SHARED(cached_mnt_ns, mnt_ns);
+
+	return mnt_ns;
+}
+
+/*
+ * The mnt namespace can change for 3 reasons
+ *  * clone(2) called with CLONE_NEWNS
+ *  * setns(2) called with the fd of a different mnt ns
+ *  * unshare(2) called with CLONE_NEWNS
+ */
+void lttng_context_mnt_ns_reset(void)
+{
+	CMM_STORE_SHARED(cached_mnt_ns, NS_INO_UNINITIALIZED);
+}
+
+static
+size_t mnt_ns_get_size(struct lttng_ctx_field *field, size_t offset)
+{
+	size_t size = 0;
+
+	size += lib_ring_buffer_align(offset, lttng_alignof(ino_t));
+	size += sizeof(ino_t);
+	return size;
+}
+
+static
+void mnt_ns_record(struct lttng_ctx_field *field,
+		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
+		 struct lttng_channel *chan)
+{
+	ino_t mnt_ns;
+
+	mnt_ns = get_mnt_ns();
+	lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns));
+	chan->ops->event_write(ctx, &mnt_ns, sizeof(mnt_ns));
+}
+
+static
+void mnt_ns_get_value(struct lttng_ctx_field *field,
+		struct lttng_ctx_value *value)
+{
+	value->u.s64 = get_mnt_ns();
+}
+
+int lttng_add_mnt_ns_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, "mnt_ns")) {
+		lttng_remove_context_field(ctx, field);
+		return -EEXIST;
+	}
+	field->event_field.name = "mnt_ns";
+	field->event_field.type.atype = atype_integer;
+	field->event_field.type.u.basic.integer.size = sizeof(ino_t) * CHAR_BIT;
+	field->event_field.type.u.basic.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT;
+	field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(ino_t);
+	field->event_field.type.u.basic.integer.reverse_byte_order = 0;
+	field->event_field.type.u.basic.integer.base = 10;
+	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
+	field->get_size = mnt_ns_get_size;
+	field->record = mnt_ns_record;
+	field->get_value = mnt_ns_get_value;
+	lttng_context_update(*ctx);
+	return 0;
+}