stos/amd64: mmu: Implement page mapping

Signed-off-by: Chloe M. <chloe@mensia.org>
2026-06-22 22:35:42 +00:00
parent 532e46c62f
commit 5b30974cb0
2 changed files with 226 additions and 0 deletions
@@ -7,9 +7,186 @@
 */

 #include <hal/mmu.h>
+#include <hal/page.h>
 #include <machine/vas.h>
+#include <mm/pmm.h>
+#include <mm/vmm.h>
 #include <stdef.h>

+/*
+ * Page-Table Entry (PTE) flags
+ *
+ * See Intel SDM Vol 3A, Section 4.5, Table 4-19
+ */
+#define PTE_ADDR_MASK   0x000FFFFFFFFFF000
+#define PTE_P           BIT(0)        /* Present */
+#define PTE_RW          BIT(1)        /* Writable */
+#define PTE_US          BIT(2)        /* User r/w allowed */
+#define PTE_PWT         BIT(3)        /* Page-level write-through */
+#define PTE_PCD         BIT(4)        /* Page-level cache disable */
+#define PTE_ACC         BIT(5)        /* Accessed */
+#define PTE_DIRTY       BIT(6)        /* Dirty (written-to page) */
+#define PTE_PS          BIT(7)        /* Page size */
+#define PTE_GLOBAL      BIT(8)        /* Global; sticky */
+#define PTE_NX          BIT(63)       /* Execute-disable */
+
+/* 57-bit linear addresses */
+#define CR4_LA57 BIT(12)
+
+/*
+ * Valid page levels
+ */
+typedef enum {
+    PAGE_LEVEL_PML1,
+    PAGE_LEVEL_PML2,
+    PAGE_LEVEL_PML3,
+    PAGE_LEVEL_PML4,
+    PAGE_LEVEL_PML5
+} PAGE_LEVEL;
+
+/*
+ * Convert protection flags to PTE flags
+ */
+static inline UQUAD
+MmuProtToPte(UCHAR Prot)
+{
+   switch (Prot) {
+   case PAGE_READONLY:
+        return PTE_P | PTE_NX;
+   case PAGE_READWRITE:
+        return PTE_P | PTE_RW | PTE_NX;
+   case PAGE_READWRITE_X:
+        return PTE_P | PTE_RW;
+   case PAGE_READONLY_X:
+        return PTE_P;
+   }
+
+   return 0;
+}
+
+/*
+ * Returns true if the given pagesize is valid
+ *
+ * @PageSize: Pagesize to check
+ */
+static inline BOOLEAN
+MmuPageSizeValid(MMU_PAGESIZE PageSize)
+{
+    switch (PageSize) {
+    case PAGESIZE_4K:
+        return true;
+    default:
+        return false;
+    }
+}
+
+/*
+ * Obtain the toplevel index
+ */
+static inline PAGE_LEVEL
+MmuTopLevel(VOID)
+{
+    UPTR Cr4;
+
+    ASMV(
+        "mov %%cr4, %0"
+        : "=r" (Cr4)
+        :
+        : "memory"
+    );
+
+    return ISSET(Cr4, CR4_LA57)
+        ? PAGE_LEVEL_PML5
+        : PAGE_LEVEL_PML4;
+}
+
+/*
+ * Invalidate an entry from the TLB
+ *
+ * @Vma: Virtual memory address to flush
+ */
+static inline VOID
+MmuInvlpg(UPTR Vma)
+{
+    ASMV(
+        "invlpg (%0)"
+        :
+        : "r" (Vma)
+        : "memory"
+    );
+}
+
+/*
+ * Obtain the page level index
+ *
+ * @Vma: Virtual memory address
+ * @Level: Page level
+ */
+static inline UQUAD
+MmuLevelIndex(UPTR Vma, PAGE_LEVEL Level)
+{
+    switch (Level) {
+    case PAGE_LEVEL_PML1: return (Vma >> 12)  & 0x1FF;
+    case PAGE_LEVEL_PML2: return (Vma >> 21) & 0x1FF;
+    case PAGE_LEVEL_PML3: return (Vma >> 30) & 0x1FF;
+    case PAGE_LEVEL_PML4: return (Vma >> 39) & 0x1FF;
+    case PAGE_LEVEL_PML5: return (Vma >> 48) & 0x1FF;
+    default: return 0;
+    }
+}
+
+/*
+ * Extract a page table entry at a specific level
+ *
+ * @Vas:    Virtual address space containing top-level
+ * @Vma:    Virtual memory address used as key
+ * @Level:  Level to extract
+ * @Alloc:  If true, allocate unset entries
+ */
+static UPTR *
+MmuExtractLevel(MMU_VAS *Vas, UPTR Vma, PAGE_LEVEL Level, BOOLEAN Alloc)
+{
+    MM_PFN AllocPfn;
+    UPTR Pma, *PageMap;
+    PAGE_LEVEL CurrentLevel;
+    USHORT Index;
+
+    if (Vas == NULL) {
+        return NULL;
+    }
+
+    CurrentLevel = MmuTopLevel();
+    PageMap = PMA_TO_VMA((Vas->Cr3 & PTE_ADDR_MASK));
+
+    while (CurrentLevel > Level) {
+        Index = MmuLevelIndex(Vma, CurrentLevel);
+
+        if (ISSET(PageMap[Index], PTE_P)) {
+            Pma = PageMap[Index] & PTE_ADDR_MASK;
+            PageMap = PMA_TO_VMA(Pma);
+            --CurrentLevel;
+            continue;
+        }
+
+        if (!Alloc) {
+            return NULL;
+        }
+
+        AllocPfn = MmRequestFrame();
+        if (AllocPfn == 0) {
+            return NULL;
+        }
+
+        Pma = AllocPfn << LOG2_PAGESIZE;
+        PageMap[Index] = Pma | (PTE_P | PTE_RW | PTE_US);
+
+        PageMap = PMA_TO_VMA(Pma);
+        --CurrentLevel;
+    }
+
+    return PageMap;
+}
+
 VOID
 HalMmuReadVas(MMU_VAS *Result)
 {
@@ -39,3 +216,28 @@ HalMmuWriteVas(MMU_VAS *Vas)
        : "memory"
    );
 }
+
+ST_STATUS
+HalMmuMapSingle(MMU_VAS *Vas, UPTR Vma, UPTR Pma, USHORT Flags, MMU_PAGESIZE PagSize)
+{
+    UPTR *PageTable;
+    USIZE PteFlags;
+    USHORT Index;
+
+    if (Vas == NULL) {
+        return STATUS_INVALID_PARAM;
+    }
+
+    PageTable = MmuExtractLevel(Vas, Vma, PAGE_LEVEL_PML1, true);
+    if (PageTable == NULL) {
+        return STATUS_NO_MEMORY;
+    }
+
+    PteFlags = MmuProtToPte(Flags);
+    Index = MmuLevelIndex(Vma, PAGE_LEVEL_PML1);
+
+    /* Map the entry and flush the TLB */
+    PageTable[Index] = Pma | PteFlags;
+    MmuInvlpg(Vma);
+    return STATUS_SUCCESS;
+}