Add malloc_sector

kernel/malloc.asm

@@ -86,11 +86,11 @@ malloc_dump:
   pop dx
   ret
 
-; allocate a 16 byte section
+; Allocate a paragraph
 ; out BX ptr
 malloc:
   ; search for a byte that is not 0xFF
-  mov di, 0x0600
+  call malloc_get_table
   mov cx, 0x0200
   mov al, 0xFF
   repe scasb
@@ -119,6 +119,7 @@ malloc:
   mov bx, di
   ret
 
+; Free a paragraph
 ; IN: 0:BX ptr to paragraph to be marked as free
 free:
   call malloc_calc_offsets
@@ -126,6 +127,31 @@ free:
   and byte [bx+di], al
   ret
 
+; Allocate a sector, 512 bytes or 32 paragraphs
+malloc_sector:
+  call malloc_get_table
+  mov cx, 0x0200
+  xor ax, ax
+.continue:
+  repne scasw
+  jne fatal_oom
+
+  ; we need a second word to be 0, otherwise continue search
+  scasw
+  jne .continue
+
+  sub di, 4
+  not ax
+  stosw
+  stosw
+
+  sub di, 0x604
+  mov cl, 7
+  shl di, cl
+
+  xchg bx, di
+  ret
+
 fatal_oom:
   call printf
   db "PANIC OOM", 0x0A, 0x0D, 0x00