feat: add Virtual Memory Manager and Virtual Memory Area management

1 files changed, 124 insertions, 0 deletions

diff --git a/na/mm/vmm.cc b/na/mm/vmm.cc
new file mode 100644
index 0000000..54e9b15
--- /dev/null
+++ b/na/mm/vmm.cc
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * vmm.cc — Virtual Memory Manager (Phase 1: Kernel Page Table)
+ *
+ * Builds a fine-grained kernel page table (4KB pages, precise
+ * permissions per section), activates it, and retires the early_pgdir
+ * identity mapping from entry.S.
+ *
+ * This module is machine-independent (MI).  All architecture-specific
+ * page table manipulation goes through the pmap:: namespace.
+ *
+ * Reference: docs/specs/vmm.md
+ */
+
+#include <lume/types.h>
+#include <lume/addr.h>
+#include <lume/pmm.h>
+#include <lume/panic.h>
+#include <lume/fdt.h>
+#include <lume/vmm.h>
+#include <arch/pmap.h>
+#include <arch/mmu.h>
+
+/* Linker-exported section boundaries (virtual addresses) */
+extern "C" char _stext[], _etext[];
+extern "C" char _srodata[], _erodata[];
+extern "C" char _sdata[], _edata[];
+extern "C" char _sbss[], _ebss[];
+extern "C" char _kernel_end[];
+
+/* Global kernel page table root PA */
+static uint64 g_kernel_pgtbl = 0;
+
+/* Convert a linker symbol to PA. Handles both VA and PA cases. */
+static inline uint64 sym_to_pa(const void *sym)
+{
+    return ensure_pa(reinterpret_cast<uint64>(sym));
+}
+
+/* Map a PA range into the kernel page table with given permissions.
+ * All addresses must be page-aligned. Panics on failure. */
+static void map_range(uint64 root, uint64 pa_start, uint64 pa_end, uint64 perm)
+{
+    for (uint64 pa = pa_start; pa < pa_end; pa += kPageSize) {
+        uint64 va = pa_to_va(pa);
+        int ret = pmap::map(root, va, pa, perm | pmap::PTE_G);
+        if (ret != 0)
+            kernel_panic("vmm_init: pmap::map failed");
+    }
+}
+
+
+
+void vmm_init()
+{
+    /* 1. Allocate new root page table */
+    uint64 root = pmap::create();
+    if (!root)
+        kernel_panic("vmm_init: failed to create root page table");
+
+    /* 2. Compute PA boundaries of each kernel section */
+    uint64 text_start  = page_align_down(sym_to_pa(_stext));
+    uint64 text_end    = page_align_up(sym_to_pa(_etext));
+    uint64 ro_start    = page_align_down(sym_to_pa(_srodata));
+    uint64 ro_end      = page_align_up(sym_to_pa(_erodata));
+    uint64 data_start  = page_align_down(sym_to_pa(_sdata));
+    uint64 bss_end     = page_align_up(sym_to_pa(_ebss));
+
+    /* Memory extent from PMM */
+    uint64 mem_base = pmm_get_mem_base();
+    uint64 mem_end  = mem_base + pmm_get_mem_size();
+
+    /* 3. Map kernel .text (RX) */
+    map_range(root, text_start, text_end,
+              pmap::PTE_R | pmap::PTE_X);
+
+    /* 4. Map .rodata (R) */
+    map_range(root, ro_start, ro_end,
+              pmap::PTE_R);
+
+    /* 5. Map .data + .bss (RW) */
+    map_range(root, data_start, bss_end,
+              pmap::PTE_R | pmap::PTE_W);
+
+    /* 6. Map remaining physical memory after kernel (RW)
+     * This covers frame_map, slab objects, and all free pages. */
+    uint64 after_kernel = page_align_up(sym_to_pa(_kernel_end));
+    if (after_kernel < mem_end) {
+        map_range(root, after_kernel, mem_end,
+                  pmap::PTE_R | pmap::PTE_W);
+    }
+    /* 7. MMIO regions will be mapped later via vmm_map_kernel_mmio by architecture/drivers */
+
+    /* 8. Activate the new page table */
+    pmap::activate(root);
+
+    g_kernel_pgtbl = root;
+}
+
+void vmm_init_ap()
+{
+    /* AP just switches to the kernel page table built by BSP */
+    if (!g_kernel_pgtbl)
+        kernel_panic("vmm_init_ap: kernel page table not ready");
+    pmap::activate(g_kernel_pgtbl);
+}
+
+void vmm_map_kernel_mmio(uint64 pa, uint64 size)
+{
+    if (!g_kernel_pgtbl)
+        kernel_panic("vmm_map_kernel_mmio: kernel page table not ready");
+    
+    uint64 aligned_pa = page_align_down(pa);
+    uint64 aligned_size = page_align_up(pa + size) - aligned_pa;
+    
+    map_range(g_kernel_pgtbl, aligned_pa, aligned_pa + aligned_size,
+              pmap::PTE_R | pmap::PTE_W | pmap::PTE_G);
+    arch::mmu::flush_tlb_all();
+}
+
+
+