--- /dev/null
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * lttng-context-ppid.c
+ *
+ * LTTng PPID context.
+ *
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/syscalls.h>
+#include <lttng/events.h>
+#include <ringbuffer/frontend_types.h>
+#include <wrapper/vmalloc.h>
+#include <lttng/tracer.h>
+
+static
+size_t ppid_get_size(size_t offset)
+{
+ size_t size = 0;
+
+ size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
+ size += sizeof(pid_t);
+ return size;
+}
+
+static
+void ppid_record(struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ pid_t ppid;
+
+ /*
+ * TODO: when we eventually add RCU subsystem instrumentation,
+ * taking the rcu read lock here will trigger RCU tracing
+ * recursively. We should modify the kernel synchronization so
+ * it synchronizes both for RCU and RCU sched, and rely on
+ * rcu_read_lock_sched_notrace.
+ */
+ rcu_read_lock();
+ ppid = task_tgid_nr(current->real_parent);
+ rcu_read_unlock();
+ lib_ring_buffer_align_ctx(ctx, lttng_alignof(ppid));
+ chan->ops->event_write(ctx, &ppid, sizeof(ppid));
+}
+
+static
+void ppid_get_value(struct lttng_ctx_field *field,
+ struct lttng_probe_ctx *lttng_probe_ctx,
+ union lttng_ctx_value *value)
+{
+ pid_t ppid;
+
+ /*
+ * TODO: when we eventually add RCU subsystem instrumentation,
+ * taking the rcu read lock here will trigger RCU tracing
+ * recursively. We should modify the kernel synchronization so
+ * it synchronizes both for RCU and RCU sched, and rely on
+ * rcu_read_lock_sched_notrace.
+ */
+ rcu_read_lock();
+ ppid = task_tgid_nr(current->real_parent);
+ rcu_read_unlock();
+ value->s64 = ppid;
+}
+
+int lttng_add_ppid_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, "ppid")) {
+ lttng_remove_context_field(ctx, field);
+ return -EEXIST;
+ }
+ field->event_field.name = "ppid";
+ field->event_field.type.atype = atype_integer;
+ field->event_field.type.u.integer.size = sizeof(pid_t) * CHAR_BIT;
+ field->event_field.type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
+ field->event_field.type.u.integer.signedness = lttng_is_signed_type(pid_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 = ppid_get_size;
+ field->record = ppid_record;
+ field->get_value = ppid_get_value;
+ lttng_context_update(*ctx);
+ wrapper_vmalloc_sync_mappings();
+ return 0;
+}
+EXPORT_SYMBOL_GPL(lttng_add_ppid_to_ctx);