From b5cc332a02a0a35e3d5d4f1eb8206897430d6bb3 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sun, 1 Sep 2019 13:46:48 +0000
Subject: [PATCH] Remove malloc, pursue a more DOS-like MM approach

---
 kernel/main.asm   |  12 +---
 kernel/malloc.asm | 172 ----------------------------------------------
 2 files changed, 2 insertions(+), 182 deletions(-)
 delete mode 100644 kernel/malloc.asm

diff --git a/kernel/main.asm b/kernel/main.asm
index 9f21611..c3c6da9 100644
--- a/kernel/main.asm
+++ b/kernel/main.asm
@@ -73,15 +73,11 @@ start:
   xor ax, ax
   mov ds, ax
   mov es, ax
-  ; setup code + data stack
   mov ss, ax
-  mov sp, ax
-  mov bp, sp
+  mov sp, 0x800
+  mov di, sp
 
   call announce
-  call malloc_reset
-
-  call malloc_dump
 
   cli
 .halt:
@@ -91,13 +87,9 @@ start:
 %include "printf.inc"
 %include "print.asm"
 
-%include "popcnt.asm"
-
 %include "intr.asm"
 %include "debug.asm"
 
-%include "malloc.asm"
-
 times 512 nop
 
 align 512
diff --git a/kernel/malloc.asm b/kernel/malloc.asm
deleted file mode 100644
index f451c1c..0000000
--- a/kernel/malloc.asm
+++ /dev/null
@@ -1,172 +0,0 @@
-; All these functions assume DS=0 and ES=0
-
-malloc_reserve:
-  push bx
-  call malloc_mark_allocated
-  pop bx
-  add bx, 0x10
-  loop malloc_reserve
-  ret
-
-malloc_reset:
-  xor ax, ax
-  mov es, ax
-  call malloc_get_table
-  mov cx, 0x100 ; 256 words
-  rep stosw
-
-  ; reserve IVT and BDA, the extra data area and this table itself
-  xor bx, bx
-  mov cx, 0x80
-  call malloc_reserve
-
-  ; reserve location for chainloaded boot sector
-  mov bx, 0x7C00
-  mov cx, 0x20
-  call malloc_reserve
-  ret
-
-; Input:
-;   0:BX - ptr to mem paragraph
-; Output:
-;   AL	- bitmask for byte in table
-;   BX  - offset in table
-malloc_calc_offsets:
-  ; ch is bit offset
-  ; cl is operand for bit shifts
-  push cx
-
-  ; strip last 4 bits (offset within paragraph)
-  mov cl, 4
-  shr bx, cl
-
-  ; backup the next 3 bits of bx (wll be bit offset)
-  mov ch, bl
-  and ch, 0x07
-
-  ; calculate byte offset by shifting off 3 bits
-  mov cl, 3
-  shr bx, cl
-
-  ; setup bit mask in al, shifted by bit offset
-  mov al, 0x01
-  mov cl, ch
-  shl al, cl
-
-  pop cx
-  ; fallthrough to setup DI
-
-malloc_get_table:
-  mov di, 0x0600
-  ret
-
-; IN: 0:BX ptr to paragraph to be marked as allocated
-malloc_mark_allocated:
-  call malloc_calc_offsets
-  or byte [bx+di], al
-  ret
-
-malloc_dump:
-  call malloc_get_table
-  mov si, di
-  mov cx, 0x200
-  xor dx, dx
-.loop:
-  lodsb
-  call print8
-  xor ah, ah
-  call popcnt
-  add dx, ax
-  loop .loop
-  mov cl, 6
-  shr dx, cl
-  push dx
-  call printf
-  db " data %UkB", 0x0A, 0x0D, 0x00
-  pop dx
-  ret
-
-; Allocate a paragraph
-; out BX ptr
-malloc:
-  ; search for a byte that is not 0xFF
-  call malloc_get_table
-  mov cx, 0x0200
-  mov al, 0xFF
-  repe scasb
-  je fatal_oom
-  dec di
-  mov al, [es:di]
-
-  sub di, 0x0600
-  mov cl, 3
-  shl di, cl
-  jmp .ishere
-
-  ; advance one bit each time
-.nextbit:
-  inc di
-  shr al, 1
-.ishere:
-  test al, 1
-  jnz .nextbit
-
-  mov cl, 4
-  shl di, cl
-
-  mov bx, di
-  call malloc_mark_allocated
-  mov bx, di
-  ret
-
-; Free a paragraph
-; IN: 0:BX ptr to paragraph to be marked as free
-free:
-  call malloc_calc_offsets
-  not al
-  and byte [bx+di], al
-  ret
-
-; Allocate a sector, 512 bytes or 32 paragraphs
-; OUT BX ptr to sector
-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
-
-; Free a sector
-; IN BX ptr to sector
-free_sector:
-  call malloc_calc_offsets
-  xor ax, ax
-  add di, bx
-  stosw
-  stosw
-  ret
-
-fatal_oom:
-  call printf
-  db "PANIC OOM", 0x0A, 0x0D, 0x00
-  clip
-.loop:
-  hlt
-  jmp .loop