Memory bitmap generated

boot.asm

@@ -8,7 +8,7 @@ bpOEMid db "XNOE    "
 
 bpBytesPerSector dw 512
 bpSectorsPerCluster db 1
-bpReservedSectors dw 10 ; We should reserve 10 sectors. Boot sector + stage2
+bpReservedSectors dw 32 ; We should reserve some sectors. Boot sector + stage2
 bpNoFATs db 2
 bpRootDirEntries dw 256
 bpLVSectors dw 8586
@@ -50,14 +50,14 @@ bootcode:
 
   mov ax, 2 ; Begin with the 2nd sector
   call prep_i13
-  mov al, 9 ; Load the next 9 sectors (4.5k)
+  mov al, 31 ; Load the next 9 sectors (4.5k)
   int 13h
 
   ; We need to get the memory configuration from the BIOS now
   ; To do this we can use int 15h eax=e820h
-  ; We will load the e820 data to 0x10000
+  ; We will load the e820 data to 0x20000
 
-  mov ax, 1000h
+  mov ax, 2000h
   mov es, ax
   xor di, di
   xor ebx, ebx

src/boot_stage2/main.c

@@ -1,15 +1,75 @@
 #include "../kernel/atapio.h"
 #include "../kernel/screenstuff.h"
 
+typedef struct {
+  uint32_t base_low;
+  uint32_t base_high;
+  uint32_t length_low;
+  uint32_t length_high;
+  uint32_t type;
+  uint32_t acpi3_extended;
+}__attribute__((packed)) e820entry;
+
+void set_bit(uint32_t offset, uint8_t* buffer) {
+    uint32_t index = offset / 8;
+    uint32_t bit = offset % 8;
+
+    buffer[index] |= (1<<(7 - bit));
+}
 
 void main() {
     init_term();
     init_atapio();
 
+    // e820 memory map exists at 0x20000
+    e820entry* e820_entries = 0x20000;
+
+    uint8_t* bitmap = 0x100000;
+
+    // Zero out the bitmap.
+    for (int i=0; i<0x20000; i++)
+        bitmap[i] = 0;
+    // Ensure the bitmap data is clear
+
+    for (int i=0; i<0x20000; i++)
+        if (bitmap[i])
+            printf("Found data in bitmap at %x!\n", (bitmap+i));
+
+    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");
+
+        if (entry.type != 1)
+            continue;
+        
+        uint32_t base = entry.base_low;
+        uint32_t length = entry.length_low;
+
+        if (base % 4096) { 
+            // Memory isn't page aligned, we need to fix that.
+            uint32_t add_offset = 4096 - (base % 4096);
+            if (length > add_offset) {
+                base += add_offset;
+                length -= add_offset;
+            }
+        }
+        uint32_t page_index = base / 4096;
+
+        printf("Page Index: %d\nLength (Pages): %d\n", page_index, length / 4096);
+
+        for (int j=0; length > 4096; length -= 4096, j++) {
+            uint32_t index = (page_index+j) / 8;
+            uint32_t bit = (page_index+j) % 8;
+
+            bitmap[index] |= (1<<(7 - bit));
+        }
+    }
+
     uint8_t* kernel_location = 0x80000;
     load_file("KERNEL  BIN", kernel_location);
 
     printf("Stage2 success!\n");
 
+    while (1);
     ((void(*)(void))kernel_location)();
 }

src/kernel/screenstuff.c

@@ -71,8 +71,9 @@ int int_to_decimal(unsigned int number, char* string_buffer) {
 
 char dec_to_hex[16] = "0123456789abcdef";
 int int_to_hex(unsigned int number, char* string_buffer) { 
-  for (int i=0; i<9; i++)
-    string_buffer[i] = 0;
+  for (int i=0; i<8; i++)
+    string_buffer[i] = '0';
+  string_buffer[8] = 0;
   
   int index = 7;
   unsigned int acc = number;
@@ -128,7 +129,7 @@ void printf(const char* string, ...) {
         case 'x':
           char hex_buffer[8];
           offset = int_to_hex(va_arg(ptr, int), hex_buffer);
-          printf(hex_buffer + offset);
+          printf(hex_buffer);
           break;
         case 's':
           printf(va_arg(ptr, const char*));