Memory management

src/kernel/memory/memory.c

@@ -0,0 +1,37 @@
+#include <stdint.h>
+#include <memory.h>
+#include <debug.h>
+#include <multiboot.h>
+
+
+uint64_t kernel_P4;
+
+void memory_init()
+{
+    kernel_P4 = (uint64_t)&BootP4;
+
+    uint64_t start, end;
+    uint32_t type, i = 0;
+    debug_info("Parsing memory map\n");
+    while(!multiboot_get_memory_area(i++, &start, &end, &type))
+    {
+        debug("0x%016x-0x%016x (%d)\n", start, end, type);
+
+        for(uint64_t p = start; p < end; p += PAGE_SIZE)
+        {
+            if(p >= V2P(&kernel_start) && p < V2P(&kernel_end))
+                continue;
+
+            uint64_t vaddr = (uint64_t)P2V(p);
+            uint64_t page = vmm_get_page(kernel_P4, vaddr);
+            if(page == (uint64_t)-1 || !(page & PAGE_PRESENT))
+            {
+                uint16_t flags = PAGE_WRITE | PAGE_PRESENT;
+                vmm_set_page(kernel_P4, vaddr, p, flags);
+            }
+
+            if(type == MMAP_FREE)
+                pmm_free(p);
+        }
+    }
+}

src/kernel/memory/pmm.c

@@ -0,0 +1,26 @@
+#include <stdint.h>
+#include <memory.h>
+
+// Physical address of next page
+uint64_t next = 0;
+
+void pmm_free(uint64_t page)
+{
+    *(uint64_t *)P2V(page) = next;
+    next = page;
+}
+
+uint64_t pmm_alloc()
+{
+    if(!next) return 0;
+    uint64_t page = next;
+    next = *(uint64_t *)P2V(page);
+    return page;
+}
+
+uint64_t pmm_calloc()
+{
+    uint64_t page = pmm_alloc();
+    memset(P2V(page), 0, PAGE_SIZE);
+    return page;
+}

src/kernel/memory/vmm.c

@@ -0,0 +1,94 @@
+#include <stdint.h>
+#include <memory.h>
+#include <debug.h>
+
+#define FLAGS_MASK (PAGE_SIZE-1)
+#define MASK_FLAGS(addr) ((uint64_t)addr & ~FLAGS_MASK)
+
+#define PRESENT(p) (p & PAGE_PRESENT)
+
+#define PT(ptr) ((uint64_t *)P2V(MASK_FLAGS(ptr)))
+
+#define P4E(P4, addr) (PT(P4)[P4_OFFSET(addr)])
+#define P3E(P4, addr) (PT(P4E(P4, addr))[P3_OFFSET(addr)])
+#define P2E(P4, addr) (PT(P3E(P4, addr))[P2_OFFSET(addr)])
+#define P1E(P4, addr) (PT(P2E(P4, addr))[P1_OFFSET(addr)])
+
+
+static int P1_exists(uint64_t P4, uint64_t addr)
+{
+
+    if (P4 && PRESENT(P4E(P4, addr)) && PRESENT(P3E(P4, addr)) && PRESENT(P2E(P4, addr)))
+        return 1;
+    return 0;
+}
+
+static int touch_P1(uint64_t P4, uint64_t addr, uint16_t flags)
+{
+    if (!P4) return -1;
+
+    if(!PRESENT(P4E(P4, addr)) && (!(P4E(P4,addr) = pmm_calloc())))
+        return -1;
+    P4E(P4, addr) |= flags | PAGE_PRESENT;
+
+    if(!PRESENT(P3E(P4, addr)) && (!(P3E(P4, addr) = pmm_calloc())))
+        return -1;
+    P3E(P4, addr) |= flags | PAGE_PRESENT;
+
+    if(!PRESENT(P2E(P4, addr)) && (!(P2E(P4, addr) = pmm_calloc())))
+        return -1;
+    P2E(P4, addr) |= flags | PAGE_PRESENT;
+
+    return 0;
+}
+
+uint64_t vmm_get_page(uint64_t P4, uint64_t addr)
+{
+    if(P1_exists(P4, addr))
+        return P1E(P4, addr);
+    return -1;
+}
+
+int vmm_set_page(uint64_t P4, uint64_t addr, uint64_t page, uint16_t flags)
+{
+    if(!P1_exists(P4, addr))
+        if(touch_P1(P4, addr, flags))
+            return -1;
+
+    P1E(P4, addr) = page | flags;
+    return 0;
+}
+
+void vmm_clear_page(uint64_t P4, uint64_t addr, int free)
+{
+    if(!P1_exists(P4, addr))
+        return;
+
+    uint64_t *pt;
+
+    P1E(P4, addr) = 0;
+
+    if(!free)
+        return;
+
+    pt = PT(P2E(P4, addr));
+    for(int i = 0; i < ENTRIES_PER_PT; i++)
+        if(pt[i])
+            return;
+    pmm_free(MASK_FLAGS(P2E(P4, addr)));
+    P2E(P4, addr) = 0;
+
+    pt = PT(P3E(P4, addr));
+    for(int i = 0; i < ENTRIES_PER_PT; i++)
+        if(pt[i])
+            return;
+    pmm_free(MASK_FLAGS(P3E(P4, addr)));
+    P3E(P4, addr) = 0;
+
+    pt = PT(P4E(P4, addr));
+    for(int i = 0; i < ENTRIES_PER_PT; i++)
+        if(pt[i])
+            return;
+    pmm_free(MASK_FLAGS(P4E(P4, addr)));
+    P4E(P4, addr) = 0;
+}