Properly print out the e820 entry types. Make kernel_directory and kernel_page_tables available to all. Add a memory unmap function. Update Makefile.

Makefile

@@ -1,4 +1,5 @@
 CFLAGS = -std=gnu11 -m32 -mgeneral-regs-only -nostdlib -fno-builtin -fno-exceptions -fno-leading-underscore -fno-pie -fno-stack-protector -Wno-pointer-to-int-cast
+CXXFLAGS = -m32 -fno-use-cxa-atexit -nostdlib -fno-builtin -fno-rtti -fno-exceptions -fno-leading-underscore
 LDFLAGS = 
 
 DISK_IMG_FILES = build/kernel/kernel.bin
@@ -50,6 +51,9 @@ build/boot_stage2/stage2.o: src/boot_stage2/main.c
 build/kernel/%.o: src/kernel/%.c
 	gcc $(CFLAGS) -o $@ -c $<
 
+build/kernel/%.o: src/kernel/%.cpp
+	g++ $(CFLAGS) -o $@ -c $<
+
 build/kernel/%.o: src/kernel/%.asm
 	nasm -felf32 $< -o $@
 

src/boot_stage2/main.c

@@ -47,6 +47,21 @@ void mark_unavailble(uint32_t address, uint32_t size) {
   }
 }
 
+char* stringify_type(uint32_t type) {
+  switch (type) {
+    case 1:
+      return "Usable";
+    case 3:
+      return "ACPI Reclaimable";
+    case 4:
+      return "ACPI NVS";
+    case 5:
+      return "Bad memory";
+    default:
+      return "Reserved";
+  }
+}
+
 void main() {
   init_term();
   init_atapio();
@@ -64,7 +79,7 @@ void main() {
 
   for (int i=0; e820_entries[i].length_low != 0 || e820_entries[i].length_high != 0; i++) {
     e820entry entry = e820_entries[i];
-    printf("BIOS-e820: Starting %x%x, length %x%x is %s\n", entry.base_high, entry.base_low, entry.length_high, entry.length_low, entry.type == 1 ? "Available" : "Reserved");
+    printf("BIOS-e820: Starting %x%x, length %x%x is %s\n", entry.base_high, entry.base_low, entry.length_high, entry.length_low, stringify_type(entry.type));
 
     if (entry.type != 1)
       continue;

src/kernel/allocate.h

@@ -4,6 +4,10 @@
 #include "paging.h"
 //void init_allocator();
 
+extern uint8_t* bitmap;
+extern PDE* kernel_page_directory;
+extern PTE** kernel_page_tables;
+
 void set_bit(uint32_t offset, uint8_t* buffer);
 void unset_bit(uint32_t offset, uint8_t* buffer);
 uint8_t get_bit(uint32_t offset, uint8_t* buffer);

src/kernel/kernel.c

@@ -6,6 +6,8 @@
 #include "strings.h"
 #include "atapio.h"
 #include "gdt.h"
+#include "paging.h"
+#include "allocate.h"
 
 int main() {
   init_gdt();
@@ -16,6 +18,8 @@ int main() {
   
   printf("KERNEL OK!\n");
 
+  unmap_4k_virt(0x8000, kernel_page_directory, kernel_page_tables);
+
   init_keyboard();
   
   enable_idt();

src/kernel/paging.c

@@ -44,3 +44,22 @@ void map_many_4k_phys_to_virt(uint32_t physical, uint32_t virtual, PDE* page_dir
   for (int i=0; i<count; i++)
     map_4k_phys_to_virt(physical + 4096*i, virtual + 4096*i, page_directory, page_tables);
 }
+
+void unmap_4k_virt(uint32_t virtual, PDE* page_directory, PTE** page_tables) {
+  split_addr* split = (split_addr*)&virtual;
+
+  ((PTE*)((uint32_t)page_tables[split->pd_index] + 0xbffe0000))[split->pt_index] = (PTE){
+    .address = 0,
+    .available = 0,
+    .global = 0,
+    .accessed = 0,
+    .disable_cache = 0,
+    .dirty = 0,
+    .write_through_cache = 0,
+    .privilege = 0,
+    .present = 0,
+    .read_write = 0,
+
+    .ignored = 0
+  };
+}

src/kernel/paging.h

@@ -34,4 +34,6 @@ typedef struct {
 
 void map_4k_phys_to_virt(uint32_t physical, uint32_t virtual, PDE* page_directory, PTE** page_tables);
 void map_many_4k_phys_to_virt(uint32_t physical, uint32_t virtual, PDE* page_directory, PTE** page_tables, uint32_t count);
+
+void unmap_4k_virt(uint32_t virtual, PDE* page_directory, PTE** page_tables);
 #endif