refactor: promote new architecture to repository root

Archive the deprecated implementation under lume-legacy, make the new kernel the default root-level build, and update repository entry points without changing kernel behavior.

1 files changed, 62 insertions, 0 deletions

diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
new file mode 100644
index 0000000..7b9f155
--- /dev/null
+++ b/arch/riscv/include/asm/page.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#ifndef _ASM_RISCV_PAGE_H
+#define _ASM_RISCV_PAGE_H
+
+/*
+ * RISC-V page / virtual-memory layout constants.
+ *
+ * Mirrors the subset of Linux arch/riscv/include/asm/page.h that LumeOS's
+ * early boot path needs:
+ *   - PAGE_SIZE / PAGE_SHIFT / PAGE_MASK
+ *   - PAGE_OFFSET (start of the higher-half direct map)
+ *   - KERNEL_LINK_ADDR (link-time VA of _start)
+ *   - SV39 PTE flag bits
+ *   - PTRS_PER_PGD (512 for SV39)
+ *
+ * Values match Linux RISC-V SV39 defaults so that struct kernel_mapping
+ * (filled by setup_vm in arch/riscv/mm/init.cc) carries the same numeric
+ * relations Linux's mm/init.c maintains.
+ */
+
+#define PAGE_SHIFT      12
+#define PAGE_SIZE       (1UL << PAGE_SHIFT)
+#define PAGE_MASK       (~(PAGE_SIZE - 1))
+
+/* Higher-half base of the kernel direct map.  Bottom of the SV39 supervisor
+ * address space minus the unmapped guard region.  Identical to Linux's
+ * CONFIG_PAGE_OFFSET default on RV64. */
+#define PAGE_OFFSET     0xFFFFFFC000000000UL
+
+/* Where _start was linked.  OpenSBI hands control to PHYS_BASE; the kernel
+ * runs at KERNEL_LINK_ADDR after relocate_enable_mmu jumps to higher-half. */
+#define PHYS_BASE       0x80200000UL
+#define KERNEL_LINK_ADDR 0xFFFFFFC080200000UL
+
+/* SATP mode field — SV39 = 8, shifted to bits [63:60]. */
+#define SATP_MODE_SV39  (8UL << 60)
+
+#define PTRS_PER_PGD    512
+
+/* 1 GB superpage size — entry.S used to build the early page table with
+ * these; setup_vm in arch/riscv/mm/init.cc now does the same. */
+#define PGDIR_SHIFT     30
+#define PGDIR_SIZE      (1UL << PGDIR_SHIFT)
+#define PGDIR_MASK      (~(PGDIR_SIZE - 1))
+
+/* SV39 PTE flag bits (one byte). */
+#define _PAGE_PRESENT   (1UL << 0)  /* aka VALID — historic Linux name */
+#define _PAGE_READ      (1UL << 1)
+#define _PAGE_WRITE     (1UL << 2)
+#define _PAGE_EXEC      (1UL << 3)
+#define _PAGE_USER      (1UL << 4)
+#define _PAGE_GLOBAL    (1UL << 5)
+#define _PAGE_ACCESSED  (1UL << 6)
+#define _PAGE_DIRTY     (1UL << 7)
+
+#define PAGE_KERNEL_EXEC \
+        (_PAGE_PRESENT | _PAGE_READ | _PAGE_WRITE | _PAGE_EXEC | \
+         _PAGE_ACCESSED | _PAGE_DIRTY)
+
+#endif /* _ASM_RISCV_PAGE_H */