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src/arch/x86_64/mem/vmm.c

@@ -0,0 +1,115 @@
+#include "vmm.h"
+#include "pmm.h"
+#include "x86_64/panic.h"
+
+#define PML4_INDEX(addr) (((addr) >> 39) & 0x1FF)
+#define PDPT_INDEX(addr) (((addr) >> 30) & 0x1FF)
+#define PD_INDEX(addr) (((addr) >> 21) & 0x1FF)
+
+#define PTE_MASK 0x000FFFFFFFFFF000ULL
+
+#define PTE_PRESENT (1ULL << 0)
+#define PTE_WRITABLE (1ULL << 1)
+#define PTE_USER (1ULL << 2)
+#define PTE_PS (1ULL << 7)
+
+extern u64 pml4[];
+
+static u64 create_pte(u64 physical_address)
+{
+    if (physical_address & (PAGE_SIZE - 1))
+    {
+        printf("Physical address not page aligned (0x%x)\n", physical_address);
+        panic("Failed to create PTE");
+    }
+
+    return (physical_address & PTE_MASK) | PTE_PRESENT | PTE_WRITABLE | PTE_PS;
+}
+
+void vmm_map(u64 virtual_address, u64 physical_address)
+{
+    u64 pml4_idx = PML4_INDEX(virtual_address);
+    u64 pdpt_idx = PDPT_INDEX(virtual_address);
+    u64 pd_idx = PD_INDEX(virtual_address);
+
+    u64 pdpt = pml4[pml4_idx];
+    if (!(pdpt & PTE_PRESENT))
+    {
+        // todo(nub31): Dynamically create a pdpt table
+        printf("PDPT not present at PML4 index %u\n", pml4_idx);
+        panic("Failed to map virtual to physical page");
+    }
+
+    u64* pdpt_phys = (u64*)(pdpt & PTE_MASK);
+    u64 pd = pdpt_phys[pdpt_idx];
+    if (!(pd & PTE_PRESENT))
+    {
+        // todo(nub31): Dynamically create a pd table
+        printf("PD not present at PDPT index %u\n", pdpt_idx);
+        panic("Failed to map virtual to physical page");
+    }
+
+    u64* pd_phys = (u64*)(pd & PTE_MASK);
+    u64 entry = pd_phys[pd_idx];
+
+    if (entry & PTE_PRESENT)
+    {
+        printf("Virtual address 0x%x is already mapped\n", virtual_address);
+        panic("Failed to map virtual to physical page");
+    }
+
+    pd_phys[pd_idx] = create_pte(physical_address);
+}
+
+u64 vmm_unmap(u64 virtual_address)
+{
+    u64 pml4_idx = PML4_INDEX(virtual_address);
+    u64 pdpt_idx = PDPT_INDEX(virtual_address);
+    u64 pd_idx = PD_INDEX(virtual_address);
+
+    u64 pdpt_entry = pml4[pml4_idx];
+    if (!(pdpt_entry & PTE_PRESENT))
+    {
+        printf("PDPT not present at PML4 index %llu\n", pml4_idx);
+        panic("Failed to unmap virtual address");
+    }
+
+    u64* pdpt_phys = (u64*)(pdpt_entry & PTE_MASK);
+    u64 pd_entry = pdpt_phys[pdpt_idx];
+    if (!(pd_entry & PTE_PRESENT))
+    {
+        printf("PD not present at PDPT index %llu\n", pdpt_idx);
+        panic("Failed to unmap virtual address");
+    }
+
+    u64* pd_phys = (u64*)(pd_entry & PTE_MASK);
+    if (!(pd_phys[pd_idx] & PTE_PRESENT))
+    {
+        printf("Virtual address 0x%llx is not mapped\n", virtual_address);
+        panic("Failed to unmap virtual address");
+    }
+    u64 phys = pd_phys[pd_idx] & PTE_MASK;
+    pd_phys[pd_idx] = 0;
+
+    __asm__ volatile("invlpg (%0)" : : "r"(virtual_address) : "memory");
+
+    return phys;
+}
+
+void* vmm_alloc(u64 virtual_address)
+{
+    u64 phys = pmm_alloc();
+    if (!phys)
+    {
+        panic("Out of physical memory");
+    }
+
+    vmm_map(virtual_address, phys);
+    return (void*)virtual_address;
+}
+
+void vmm_free(u64 virtual_address)
+{
+    u64 phys = vmm_unmap(virtual_address);
+    pmm_free(phys);
+}