Add namespace contexts

[lttng-modules.git] / lttng-context-mnt-ns.c

diff --git a/lttng-context-mnt-ns.c b/lttng-context-mnt-ns.c
new file mode 100644 (file)
index 0000000..98d5b8e
--- /dev/null
+++ b/lttng-context-mnt-ns.c
@@ -0,0 +1,105 @@
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
+ * lttng-context-mnt-ns.c
+ *
+ * LTTng mount namespace context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *               2019 Michael Jeanson <mjeanson@efficios.com>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <lttng-events.h>
+#include <wrapper/ringbuffer/frontend_types.h>
+#include <wrapper/vmalloc.h>
+#include <wrapper/namespace.h>
+#include <lttng-tracer.h>
+
+#if !defined(LTTNG_MNT_NS_MISSING_HEADER) && \
+       (LINUX_VERSION_CODE >= KERNEL_VERSION(3,8,0))
+
+#include <../fs/mount.h>
+
+static
+size_t mnt_ns_get_size(size_t offset)
+{
+       size_t size = 0;
+
+       size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
+       size += sizeof(unsigned int);
+       return size;
+}
+
+static
+void mnt_ns_record(struct lttng_ctx_field *field,
+                struct lib_ring_buffer_ctx *ctx,
+                struct lttng_channel *chan)
+{
+       unsigned int mnt_ns_inum = 0;
+
+       /*
+        * nsproxy can be NULL when scheduled out of exit.
+        *
+        * As documented in 'linux/nsproxy.h' namespaces access rules, no
+        * precautions should be taken when accessing the current task's
+        * namespaces, just dereference the pointers.
+        */
+       if (current->nsproxy)
+               mnt_ns_inum = current->nsproxy->mnt_ns->lttng_ns_inum;
+
+       lib_ring_buffer_align_ctx(ctx, lttng_alignof(mnt_ns_inum));
+       chan->ops->event_write(ctx, &mnt_ns_inum, sizeof(mnt_ns_inum));
+}
+
+static
+void mnt_ns_get_value(struct lttng_ctx_field *field,
+               struct lttng_probe_ctx *lttng_probe_ctx,
+               union lttng_ctx_value *value)
+{
+       unsigned int mnt_ns_inum = 0;
+
+       /*
+        * nsproxy can be NULL when scheduled out of exit.
+        *
+        * As documented in 'linux/nsproxy.h' namespaces access rules, no
+        * precautions should be taken when accessing the current task's
+        * namespaces, just dereference the pointers.
+        */
+       if (current->nsproxy)
+               mnt_ns_inum = current->nsproxy->mnt_ns->lttng_ns_inum;
+
+       value->s64 = mnt_ns_inum;
+}
+
+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(unsigned int) * CHAR_BIT;
+       field->event_field.type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT;
+       field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int);
+       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);
+       wrapper_vmalloc_sync_all();
+       return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_add_mnt_ns_to_ctx);
+
+#endif