From 567e09f7e9c8c7fa5899d0f755398ef392d893b3 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sun, 15 Sep 2019 17:26:09 +0000
Subject: [PATCH] Bootloader: parse cmdline field

---
 boot/floppy.asm | 104 ++++++++++++++++++++++++++++++------------------
 1 file changed, 65 insertions(+), 39 deletions(-)

diff --git a/boot/floppy.asm b/boot/floppy.asm
index 1453f4e..3005cba 100644
--- a/boot/floppy.asm
+++ b/boot/floppy.asm
@@ -1,17 +1,24 @@
 ; Memory layout:
-%define mbr     0x00600 ; 1 sector
-%define self	0x00800 ; 1 sector
-%define fattab  0x01000 ; variable size
-%define rootdir 0x06000 ; variable size
-%define psp     0x07B00 ; 0x100 bytes
-%define prog    0x07C00 ; 64k - psp
+%define mbr       0x00600 ; 1 sector
+%define self      0x00800 ; 1 sector
+%define fattab    0x01000 ; variable size
+%define rootdir   0x06000 ; variable size
+%define psp       (prog - 0x100)
+%define prog      0x07C00
+
+%define filename  (psp + 0x5C + 1)
+%define arguments (psp + 0x81)
 
 org self
 
+jmp short init
+
+cluster_offset:
+  dw 0
+
+times (0x0B - ($-$$)) db 0
+
 fdc:
-.jmp:
-  jmp short main
-  times (0x0B - ($-$$)) db 0
 .ss:
   dw 0x200	; sector size
 .sc:
@@ -49,7 +56,7 @@ fdc:
   db "FAT12"
   times (62 - ($-$$)) db " "
 
-main:
+init:
   cli
 
   ; Stack grows down from PSP + 64k
@@ -66,10 +73,9 @@ main:
   mov cx, 0x100
   rep movsw
 
-  ; Jump into relocated code
-  jmp 0:.relocated
-.relocated:
+  jmp 0:main
 
+main:
   mov [fdc.drv], dl ; save drive number in fd
   sti
 
@@ -98,26 +104,12 @@ main:
   ; clusters start after rootdir
   mov [cluster_offset], ax
 
+  call parse_cmdline
+
   call load_file
-  mov bp, 0x0032
+  mov bp, 0x3332
   jc error
 
-  ; get length of arguments
-  mov cx, 0x007F
-  mov di, arguments
-  xor ax, ax
-  repne scasb
-  dec di
-  sub di, arguments
-  mov cx, di
-
-  ; setup arguments field
-  mov [psp+0x080], cl
-  mov di, 0x081
-  mov si, arguments
-  rep movsb
-  mov BYTE [di], 0x0D
-
   ; setup int 19h call at 0000, and push its address to stack
   mov WORD [psp], 0x19CD
   push sp
@@ -142,7 +134,7 @@ main:
 load_sectors:
   ; fail instantly if reading sectors > 16 bit
   test dx, dx
-  mov bp, 0x0030
+  mov bp, 0x3330
   jnz error
 
 .loop:
@@ -162,7 +154,7 @@ load_sectors:
   mov dl, [cs:fdc.drv] ; driver number
   mov ax, 0x0201 ; ah=0x02 al=0x01
   int 0x13
-  mov bp, 0x0031
+  mov bp, 0x3331
   jc error
 
   pop dx
@@ -186,6 +178,7 @@ load_file:
   je read_clusters
   add si, 0x20
   loop .loop
+  stc
   ret
 
 ; Compares the FAT dirent against [filename]
@@ -252,14 +245,47 @@ error:
   int 0x16
   int 0x19
 
-cluster_offset:
-  dw 0
+parse_cmdline:
+  mov si, cmdline
+  mov di, filename
+.cleanout:
+  push di
+  mov cx, 0x0A
+  mov al, 0x20
+  rep stosb
+  pop di
+.base_loop:
+  call .read
+  cmp al, 0x2E
+  je .ext_start
+  cmp al, 0x20
+  je .args_start
+  stosb
+  jmp .base_loop
+.ext_start:
+  mov di, (filename + 8)
+.ext_loop:
+  call .read
+  cmp al, 0x20
+  je .args_start
+  stosb
+  jmp .ext_loop
+.args_start:
+  mov di, (psp + 0x81)
+.args_loop:
+  call .read
+  stosb
+  jmp .args_loop
+.read:
+  lodsb
+  test al, al
+  jnz .ret
+  pop ax
+.ret:
+  ret
 
-filename:
-  db "KERNEL  COM"
-
-arguments:
-  db "", 0
+cmdline:
+  db "KERNEL.COM /?", 0
 
 times (0x1FE - ($-$$)) db 0