feat: implement user-kernel memory copy functions with validation

1 files changed, 27 insertions, 0 deletions

diff --git a/na/include/lume/uaccess.h b/na/include/lume/uaccess.h
new file mode 100644
index 0000000..5a9ed71
--- /dev/null
+++ b/na/include/lume/uaccess.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#pragma once
+
+/*
+ * User-space memory access — safe copy routines.
+ *
+ * Phase 2: Software page-table validation.
+ * Phase 3+: Exception Table (zero-cost happy path).
+ *
+ * Reference: docs/specs/syscall.md §8
+ */
+
+#include <lume/types.h>
+
+/* Copy len bytes from user address to kernel buffer.
+ * Returns 0 on success, -EFAULT if user address is invalid. */
+int copy_from_user(void* kernel_dst, uint64 user_src, uint64 len);
+
+/* Copy len bytes from kernel buffer to user address.
+ * Returns 0 on success, -EFAULT if user address is invalid. */
+int copy_to_user(uint64 user_dst, const void* kernel_src, uint64 len);
+
+/* Copy NUL-terminated string from user space.
+ * Returns string length (excluding NUL) or -EFAULT. */
+int64 strncpy_from_user(char* kernel_dst, uint64 user_src, uint64 max_len);