Add userspace namespace contexts

[deliverable/lttng-ust.git] / liblttng-ust / lttng-context-pid-ns.c

diff --git a/liblttng-ust/lttng-context-pid-ns.c b/liblttng-ust/lttng-context-pid-ns.c
new file mode 100644 (file)
index 0000000..1581fb3
--- /dev/null
+++ b/liblttng-ust/lttng-context-pid-ns.c
@@ -0,0 +1,142 @@
+/*
+ * lttng-context-pid-ns.c
+ *
+ * LTTng UST pid 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 PID namespace is global to the process.
+ */
+static ino_t cached_pid_ns = NS_INO_UNINITIALIZED;
+
+static
+ino_t get_pid_ns(void)
+{
+       struct stat sb;
+       ino_t pid_ns;
+
+       pid_ns = CMM_LOAD_SHARED(cached_pid_ns);
+
+       /*
+        * If the cache is populated, do nothing and return the
+        * cached inode number.
+        */
+       if (caa_likely(pid_ns != NS_INO_UNINITIALIZED))
+               return pid_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.
+        */
+       pid_ns = NS_INO_UNAVAILABLE;
+
+       if (stat("/proc/self/ns/pid", &sb) == 0) {
+               pid_ns = sb.st_ino;
+       }
+
+       /*
+        * And finally, store the inode number in the cache.
+        */
+       CMM_STORE_SHARED(cached_pid_ns, pid_ns);
+
+       return pid_ns;
+}
+
+/*
+ * A process's PID namespace membership is determined when the process is
+ * created and cannot be changed thereafter.
+ *
+ * The pid namespace can change only on clone(2) / fork(2) :
+ *  - clone(2) with the CLONE_NEWPID flag
+ *  - clone(2) / fork(2) after a call to unshare(2) with the CLONE_NEWPID flag
+ *  - clone(2) / fork(2) after a call to setns(2) with a PID namespace fd
+ */
+void lttng_context_pid_ns_reset(void)
+{
+       CMM_STORE_SHARED(cached_pid_ns, NS_INO_UNINITIALIZED);
+}
+
+static
+size_t pid_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 pid_ns_record(struct lttng_ctx_field *field,
+                struct lttng_ust_lib_ring_buffer_ctx *ctx,
+                struct lttng_channel *chan)
+{
+       ino_t pid_ns;
+
+       pid_ns = get_pid_ns();
+       lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid_ns));
+       chan->ops->event_write(ctx, &pid_ns, sizeof(pid_ns));
+}
+
+static
+void pid_ns_get_value(struct lttng_ctx_field *field,
+               struct lttng_ctx_value *value)
+{
+       value->u.s64 = get_pid_ns();
+}
+
+int lttng_add_pid_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, "pid_ns")) {
+               lttng_remove_context_field(ctx, field);
+               return -EEXIST;
+       }
+       field->event_field.name = "pid_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 = pid_ns_get_size;
+       field->record = pid_ns_record;
+       field->get_value = pid_ns_get_value;
+       lttng_context_update(*ctx);
+       return 0;
+}