feat: add Virtual Memory Manager and Virtual Memory Area management

1 files changed, 83 insertions, 0 deletions

diff --git a/na/include/lume/vmm.h b/na/include/lume/vmm.h
new file mode 100644
index 0000000..ea32332
--- /dev/null
+++ b/na/include/lume/vmm.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#pragma once
+
+/*
+ * vmm.h — Virtual Memory Manager
+ *
+ * Managing kernel and user virtual address spaces.
+ * 
+ * Reference: docs/specs/vmm.md
+ */
+
+#include <lume/types.h>
+#include <lume/rbtree.h>
+#include <kernel/sync/spinlock.h>
+
+/* ------------------------------------------------------------------ */
+/*  MI-layer permission flags (architecture-independent)               */
+/*                                                                     */
+/*  These are used by VMA and vmm_map_user / vmm_handle_page_fault.    */
+/*  The pmap MD layer translates them to hardware PTE bits.            */
+/* ------------------------------------------------------------------ */
+inline constexpr uint64 VM_READ  = (1ULL << 0);
+inline constexpr uint64 VM_WRITE = (1ULL << 1);
+inline constexpr uint64 VM_EXEC  = (1ULL << 2);
+inline constexpr uint64 VM_USER  = (1ULL << 3);
+
+/* Forward declarations */
+struct VmSpace;
+struct VmAreaStruct;
+
+/*
+ * Virtual Memory Area (VMA)
+ * Represents a contiguous range [start, end) of uniform permissions.
+ */
+struct VmAreaStruct {
+    uint64 start;           // Start VA (page aligned)
+    uint64 end;             // End VA (exclusive, page aligned)
+    uint64 perm;            // VM_READ | VM_WRITE | VM_EXEC | VM_USER
+    struct rb_node rb;      // Linkage in VmSpace::vma_tree
+    VmSpace* mm;            // Back pointer to the parent address space
+};
+
+/*
+ * Address Space (VmSpace)
+ * Represents a user process's complete virtual memory mapping.
+ *
+ * Lock contract:
+ *   Holds: lock (internal spinlock)
+ *   May acquire: PMM global lock (via pmm_alloc_frame inside page fault)
+ *   Callers must NOT hold: PMM lock (lock ordering: VmSpace -> PMM)
+ */
+struct VmSpace {
+    uint64 root_pa;         // SV39 root page table physical address
+    struct rb_root vma_tree; // Red-black tree of VmAreaStructs
+    Spinlock lock;          // Protects vma_tree mutations
+    
+    // Create a brand new VmSpace (allocates root pagetable)
+    static VmSpace* create();
+    
+    // Destroy VmSpace, unmapping all VMAs and freeing pagetables
+    void destroy();
+};
+
+/* Initialize kernel page table (Phase 1) */
+void vmm_init();
+
+/* Switch AP to the kernel page table built by BSP (Phase 1) */
+void vmm_init_ap();
+
+/* Map MMIO device region to the active kernel page table */
+void vmm_map_kernel_mmio(uint64 pa, uint64 size);
+
+/* User space memory management (VMA & Demand Paging) */
+int vmm_map_user(VmSpace* space, uint64 va, uint64 len, uint64 perm);
+int vmm_unmap_user(VmSpace* space, uint64 va, uint64 len);
+
+/* Handle user page fault (lookup VMA -> allocate frame -> map) */
+int vmm_handle_page_fault(VmSpace* space, uint64 fault_addr, uint64 cause);
+
+/* Clone an address space for fork() */
+VmSpace* vmm_clone(VmSpace* parent_space);