Add kvmalloc.

Makefile

@@ -26,8 +26,8 @@ LDKERNELFLAGS = --script=script.ld
 endif
 
 OBJECTS = kernel/kstart.o kernel.o console.o drivers/vga.o drivers/uart.o drivers/keyboard.o \
-	cpu/idt.o cpu/gdt.o cpu/swtch.o cpu/vectors.o lib/mem.o proc.o lib/string.o \
-	fs/fs.o drivers/ata.o lib/mem.o lib/string.o proc.o drivers/pit.o
+	cpu/idt.o cpu/gdt.o cpu/swtch.o cpu/vectors.o kernel/mem.o proc.o lib/string.o \
+	fs/fs.o drivers/ata.o lib/string.o proc.o drivers/pit.o kernel/vm.o
 
 run: image.bin
 	qemu-system-i386 -drive format=raw,file=$< -serial mon:stdio
@@ -98,7 +98,7 @@ image.bin: mbr.bin fs.img
 	cat $^ >$@
 
 kernel.bin: $(OBJECTS)
-	$(LD) $(LDFLAGS) $(LDKERNELFLAGS) -o $@ -Ttext 0xf0009000 $^
+	$(LD) $(LDFLAGS) $(LDKERNELFLAGS) -o $@ -Ttext 0x80009000 $^
 
 bootmain.o: bootmain.c
 	$(CC) $(CFLAGS) -Os -c $< -o $@

cpu/gdt.c

@@ -1,5 +1,6 @@
 #include "gdt.h"
 #include "../lib/string.h"
+#include "kernel/mem.h"
 
 #include <stdint.h>
 

cpu/memlayout.h

@@ -1,8 +1,30 @@
 #pragma once
 
-#define KERNBASE 0xf0000000
+#define KERNBASE 0x80000000
 #define PGSIZE   0x1000
 #define PHYSTOP  0x8000000
 
 #define PGROUNDUP(sz)  (((sz)+PGSIZE-1) & ~(PGSIZE-1))
+
+#define PDXSHIFT        22      // offset of PDX in a linear address
+
+#define PXMASK          0x3FF
+
+#ifndef __ASSEMBLER__
+#include <stdint.h>
 #define V2P(a) (((uintptr_t) (a)) - KERNBASE)
+#define P2V(a) ((void *)(((uintptr_t) (a)) + KERNBASE))
+
+// page directory index
+#define PDX(va)         (((uintptr_t)(va) >> PDXSHIFT) & PXMASK)
+#endif
+
+// Page table/directory entry flags.
+#define PTE_P           0x001   // Present
+#define PTE_W           0x002   // Writeable
+#define PTE_U           0x004   // User
+#define PTE_PWT         0x008   // Write-Through
+#define PTE_PCD         0x010   // Cache-Disable
+#define PTE_A           0x020   // Accessed
+#define PTE_D           0x040   // Dirty
+#define PTE_PS          0x080   // Page Size

cpu/x86.h

@@ -11,3 +11,9 @@ stosb(void *addr, unsigned char data, int cnt)
 {
     asm volatile("cld; rep stosb" : : "D"(addr), "c"(cnt), "a"(data) : "memory");
 }
+
+static inline void
+lcr3(uint32_t val)
+{
+  asm volatile("mov %0,%%cr3" : : "r" (val));
+}

drivers/keyboard.c

@@ -3,7 +3,7 @@
 #include "cpu/memlayout.h"
 #include "console.h"
 #include "port.h"
-#include "lib/mem.h"
+#include "kernel/mem.h"
 
 static const char sc_ascii[] = {
     '?', '?', '1', '2', '3', '4', '5', '6',

drivers/vga.c

@@ -1,7 +1,8 @@
 #include "port.h"
 #include "../lib/string.h"
+#include "cpu/memlayout.h"
 
-static char* const video_memory = (char*) 0xb8000;
+static char* const video_memory = (char*) (KERNBASE + 0xb8000);
 
 enum colors16 {
     black = 0,

kernel.c

@@ -1,8 +1,7 @@
-asm(".asciz \"kernel start\\n\"");
-
 #include "console.h"
 #include "cpu/isr.h"
 #include "cpu/gdt.h"
+#include "cpu/memlayout.h"
 #include "drivers/keyboard.h"
 #include "drivers/vga.h"
 #include "drivers/ata.h"
@@ -12,9 +11,14 @@ asm(".asciz \"kernel start\\n\"");
 #include "fs/fs.h"
 #include "lib/string.h"
 #include "proc.h"
+#include "kernel/mem.h"
 
 
 void kmain() {
+    freerange(P2V(1u<<20), P2V(2u<<20)); // 1MB - 2MB
+    kvmalloc();  // map all of physical memory at KERNBASE
+    freerange(P2V(2u<<20), P2V(PHYSTOP));
+
     load_gdt();
     init_keyboard();
     init_pit();

kernel/kstart.S

@@ -24,9 +24,14 @@ _start:
     // Set up the page table for the lowest 4 MiB: PD[0] -> PT
     mov dword ptr [0x1000], 0x2000 | 0x3
 
-    // KERNBASE = 0xF000_0000
-    // Use the same page table for the first 4 MiB after KERNBASE: PD[0x3c0] -> PT
-    mov dword ptr [0x1000 + (0x3c0 * 4)], 0x2000 | 0x3
+    // KERNBASE = 0x8000_0000
+    // Use the same page table for the first 4 MiB after KERNBASE: PD[0x200] -> PT
+    mov dword ptr [0x1000 + ((KERNBASE >> 22) * 4)], 0x2000 | 0x3
+
+    // Enable 4 MiB pages
+    mov eax, cr4
+    or eax, 0x10        // Set the PSE bit (bit 4)
+    mov cr4, eax
 
     // Identity map the first 2 MiB
     mov edi, 0x2000      // Start of the PT

kernel/mem.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stdint.h>
+
+typedef uintptr_t pde_t;
+typedef uintptr_t pte_t;
+
+void* memset(void *dst, unsigned c, uint64_t n);
+
+void freerange(void *vstart, void *vend);
+void* kalloc(void);
+void kfree(char*);
+
+void kvmalloc();

kernel/vm.c

@@ -0,0 +1,18 @@
+#include "mem.h"
+#include "cpu/memlayout.h"
+#include "cpu/x86.h"
+
+pde_t *kvm;
+
+void kvmalloc() {
+    kvm = kalloc();
+    memset(kvm, 0, PGSIZE);
+
+    // Map physical memory to KERNBASE..KERNBASE+PHYSTOP
+    for (uintptr_t pa = 0; pa < PHYSTOP; pa += 4 << 20) {
+        uintptr_t va = KERNBASE + pa;
+        kvm[PDX(va)] = pa | PTE_P | PTE_W | PTE_PS;
+    }
+
+    lcr3(V2P(kvm));
+}

lib/mem.h

@@ -1,5 +0,0 @@
-#pragma once
-
-void freerange(void *vstart, void *vend);
-void* kalloc(void);
-void kfree(char*);

lib/string.h

@@ -4,4 +4,3 @@ typedef unsigned size_t;
 
 void kmemmove(char* dst, char* src, size_t size);
 int strncmp(const char* s1, const char* s2, size_t size);
-void memset(void* b, char c, size_t len);

proc.c

@@ -3,7 +3,7 @@
 #include "fs/fs.h"
 #include "cpu/gdt.h"
 #include "cpu/isr.h"
-#include "lib/mem.h"
+#include "kernel/mem.h"
 #include "lib/string.h"
 #include "console.h"