Memory management

src/kernel/boot/kmain.c

@@ -30,17 +30,9 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
 
     debug_info("Kernel loaded with command line: \"%s\" by <%s>\n", kernel_boot_data.commandline, kernel_boot_data.bootloader);
 
-    debug_info("Memory areas:\n");
-    size_t index = 0;
-    uintptr_t start, end;
-    uint32_t type;
-    while(!multiboot_get_memory_area(index++, &start, &end, &type))
-    {
-        debug_info("%d %x-%x\n", type, start, end);
-    }
-    bind_interrupt(0, divbyzero);
+    memory_init();
 
-    debug("Hello, world!");
+    bind_interrupt(0, divbyzero);
 
     // Force a divide by zero error
     divide(5, 0);

src/kernel/include/memory.h

@@ -2,31 +2,54 @@
 
 #define KERNEL_OFFSET 0xFFFFFF8000000000
 
-#ifdef __ASSEMBLER__
-#define V2P(a) ((a) - KERNEL_OFFSET)
-#define P2V(a) ((a) + KERNEL_OFFSET)
-#else
-#include <stdint.h>
-#define V2P(a) ((uintptr_t)(a) &~KERNEL_OFFSET)
-#define P2V(a) ((void *)((uintptr_t)(a) | KERNEL_OFFSET))
-
-#define incptr(p, n) ((void *)(((uintptr_t)(p)) + (n)))
-#endif
-
-
 #define PAGE_PRESENT 0x001
 #define PAGE_WRITE 0x002
 
 #define PAGE_SIZE 0x1000
 #define ENTRIES_PER_PT 512
 
-#ifndef __ASSEMBLER__
-#include <stddef.h>
+#ifdef __ASSEMBLER__
+    #define V2P(a) ((a) - KERNEL_OFFSET)
+    #define P2V(a) ((a) + KERNEL_OFFSET)
+#else
+    #include <stdint.h>
+    #include <stddef.h>
+    #define V2P(a) ((uintptr_t)(a) &~KERNEL_OFFSET)
+    #define P2V(a) ((void *)((uintptr_t)(a) | KERNEL_OFFSET))
 
-void *memcpy(void *dst, const void *src, size_t n);
-void *memset(void *s, int c, size_t n);
-void *memmove(void *dest, const void *src, size_t n);
-int memcmp(const void *s1, const void *s2, size_t n);
-size_t strlen(const char *s);
+    #define incptr(p, n) ((void *)(((uintptr_t)(p)) + (n)))
+
+    #define P1_OFFSET(a) (((a)>>12) & 0x1FF)
+    #define P2_OFFSET(a) (((a)>>21) & 0x1FF)
+    #define P3_OFFSET(a) (((a)>>30) & 0x1FF)
+    #define P4_OFFSET(a) (((a)>>39) & 0x1FF)
+
+    // memory/memory.c
+    void memory_init();
+    extern uint64_t kernel_P4;
+
+    // memory/vmm.c
+    void vmm_init();
+    uint64_t vmm_get_page(uint64_t P4, uint64_t addr);
+    int vmm_set_page(uint64_t P4, uint64_t addr, uint64_t page, uint16_t flags);
+    void vmm_clear_page(uint64_t P4, uint64_t addr, int free);
+
+    // memory/pmm.c
+    void pmm_free(uint64_t page);
+    uint64_t pmm_alloc();
+    uint64_t pmm_calloc();
+
+    // memory/string.c
+    void *memcpy(void *dst, const void *src, size_t n);
+    void *memset(void *s, int c, size_t n);
+    void *memmove(void *dest, const void *src, size_t n);
+    int memcmp(const void *s1, const void *s2, size_t n);
+    size_t strlen(const char *s);
+
+    // Link.ld
+    extern int kernel_start, kernel_end;
+
+    // boot/boot_PT.s
+    extern uint64_t BootP4;
 
 #endif

src/kernel/include/multiboot.h

@@ -22,6 +22,8 @@ struct kernel_boot_data_st{
     void *mmap;
 };
 
+#define MMAP_FREE 1
+
 extern struct kernel_boot_data_st kernel_boot_data;
 
 int multiboot_init(uint64_t magic, void *mboot_info);

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;
+}