--- /dev/null
+/*
+ * lttng-context-time-ns.c
+ *
+ * LTTng UST time namespace context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * 2020 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 <stddef.h>
+#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 <lttng/ust-tid.h>
+#include <urcu/tls-compat.h>
+#include "lttng-tracer-core.h"
+#include "ns.h"
+
+
+/*
+ * We cache the result to ensure we don't stat(2) the proc filesystem on
+ * each event.
+ */
+static DEFINE_URCU_TLS_INIT(ino_t, cached_time_ns, NS_INO_UNINITIALIZED);
+
+static
+ino_t get_time_ns(void)
+{
+ struct stat sb;
+ ino_t time_ns;
+
+ time_ns = CMM_LOAD_SHARED(URCU_TLS(cached_time_ns));
+
+ /*
+ * If the cache is populated, do nothing and return the
+ * cached inode number.
+ */
+ if (caa_likely(time_ns != NS_INO_UNINITIALIZED))
+ return time_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.
+ */
+ time_ns = NS_INO_UNAVAILABLE;
+
+ /*
+ * /proc/thread-self was introduced in kernel v3.17
+ */
+ if (stat("/proc/thread-self/ns/time", &sb) == 0) {
+ time_ns = sb.st_ino;
+ } else {
+ char proc_ns_path[LTTNG_PROC_NS_PATH_MAX];
+
+ if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX,
+ "/proc/self/task/%d/ns/time",
+ lttng_gettid()) >= 0) {
+
+ if (stat(proc_ns_path, &sb) == 0) {
+ time_ns = sb.st_ino;
+ }
+ }
+ }
+
+ /*
+ * And finally, store the inode number in the cache.
+ */
+ CMM_STORE_SHARED(URCU_TLS(cached_time_ns), time_ns);
+
+ return time_ns;
+}
+
+/*
+ * The time namespace can change for 2 reasons
+ * * setns(2) called with the fd of a different time ns
+ * * clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWTIME flag
+ */
+void lttng_context_time_ns_reset(void)
+{
+ CMM_STORE_SHARED(URCU_TLS(cached_time_ns), NS_INO_UNINITIALIZED);
+}
+
+static
+size_t time_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 time_ns_record(struct lttng_ctx_field *field,
+ struct lttng_ust_lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ ino_t time_ns;
+
+ time_ns = get_time_ns();
+ lib_ring_buffer_align_ctx(ctx, lttng_alignof(time_ns));
+ chan->ops->event_write(ctx, &time_ns, sizeof(time_ns));
+}
+
+static
+void time_ns_get_value(struct lttng_ctx_field *field,
+ struct lttng_ctx_value *value)
+{
+ value->u.s64 = get_time_ns();
+}
+
+int lttng_add_time_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, "time_ns")) {
+ lttng_remove_context_field(ctx, field);
+ return -EEXIST;
+ }
+ field->event_field.name = "time_ns";
+ field->event_field.type.atype = atype_integer;
+ field->event_field.type.u.integer.size = sizeof(ino_t) * CHAR_BIT;
+ field->event_field.type.u.integer.alignment = lttng_alignof(ino_t) * CHAR_BIT;
+ field->event_field.type.u.integer.signedness = lttng_is_signed_type(ino_t);
+ field->event_field.type.u.integer.reverse_byte_order = 0;
+ field->event_field.type.u.integer.base = 10;
+ field->event_field.type.u.integer.encoding = lttng_encode_none;
+ field->get_size = time_ns_get_size;
+ field->record = time_ns_record;
+ field->get_value = time_ns_get_value;
+ lttng_context_update(*ctx);
+ return 0;
+}
+
+/*
+ * * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ * */
+void lttng_fixup_time_ns_tls(void)
+{
+ asm volatile ("" : : "m" (URCU_TLS(cached_time_ns)));
+}
projects / lttng-ust.git / commitdiff
