--- /dev/null
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * lttng-context-euid.c
+ *
+ * LTTng effective user ID context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * 2019 Michael Jeanson <mjeanson@efficios.com>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <lttng/events.h>
+#include <lttng/tracer.h>
+#include <ringbuffer/frontend_types.h>
+#include <wrapper/vmalloc.h>
+#include <wrapper/user_namespace.h>
+
+static
+size_t euid_get_size(size_t offset)
+{
+ size_t size = 0;
+
+ size += lib_ring_buffer_align(offset, lttng_alignof(uid_t));
+ size += sizeof(uid_t);
+ return size;
+}
+
+static
+void euid_record(struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ uid_t euid;
+
+ euid = lttng_current_euid();
+ lib_ring_buffer_align_ctx(ctx, lttng_alignof(euid));
+ chan->ops->event_write(ctx, &euid, sizeof(euid));
+}
+
+static
+void euid_get_value(struct lttng_ctx_field *field,
+ struct lttng_probe_ctx *lttng_probe_ctx,
+ union lttng_ctx_value *value)
+{
+ value->s64 = lttng_current_euid();
+}
+
+int lttng_add_euid_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, "euid")) {
+ lttng_remove_context_field(ctx, field);
+ return -EEXIST;
+ }
+ field->event_field.name = "euid";
+ field->event_field.type.atype = atype_integer;
+ field->event_field.type.u.integer.size = sizeof(uid_t) * CHAR_BIT;
+ field->event_field.type.u.integer.alignment = lttng_alignof(uid_t) * CHAR_BIT;
+ field->event_field.type.u.integer.signedness = lttng_is_signed_type(uid_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 = euid_get_size;
+ field->record = euid_record;
+ field->get_value = euid_get_value;
+ lttng_context_update(*ctx);
+ wrapper_vmalloc_sync_mappings();
+ return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_add_euid_to_ctx);