segment oferrive aclaracion

Author: federicogramos

.gdb_history

@@ -1,12 +1,3 @@
-continue
-quit
-b *0x8000
-continue
-si
-sisi
-si
-exit
-quit
 b *0x8000
 continue
 dashboard
@@ -254,3 +245,12 @@ quit
 b *0x8000
 continue
 quit
+b *0x8000
+continue
+quit
+b *0x8000
+continue
+quit
+b *0x8000
+continue
+quit

asm/bios/mbr.asm

@@ -7,14 +7,9 @@
 ;; -- https://github.com/fysnet/FYSOS/blob/master/boot/embr/embr.asm
 ;; http://www.ctyme.com/intr/rb-0708.htm
 ;; -- https://stanislavs.org/helppc/int_10.html
-
-;; En 16 bits cuando el procesador no es de 16 si no de 32 o 64 pero ejecuta en 
-;; un modo de 16 bits, prestar atencion a algunas instrucciones: jumps por ejemp
-;; lo. El mismo opcode lo interpreta en 32 de una manera y en 16 de otra, saltan
-;; do en cada uno de esos casos a direcciones cercanas pero distintas porque en 
-;; 32 toma operando de 32 y en 16 de 16 (8?) lo cual genera un offset en la dire
-;; ccion de destino. Pero un push de 32 es reconocido en 16 bits y ejecutado cor
-;; rectamente a pesar de estar en modo de 16.
+;;
+;; This mbr is for 32 and 64 bit machines. Will not work fine on 16 bit 8086 or 
+;; 80286 because it uses prefix override for some instructions.
 ;;==============================================================================
 
 
@@ -35,7 +30,6 @@ entry:
 
 	mov [drvNum], dl	;; Bios passes drive number in dl.
 
-	call pushTest
 	call extensionTest
 
 	mov si, msg_load
@@ -89,41 +83,38 @@ notify_ext_not_supported:
 ;;==============================================================================
 
 diskcpy:
-	call readSec	;; Each loop 512 bytes.
+	call cpySec	;; Each loop 512 byte copy.
 	dec ax
 	cmp ax, 0
 	jnz diskcpy
 	ret
 
 
 ;;==============================================================================
-;; readSec | Read a sector from a disk using extended read.
+;; cpySec | Read a sector from a disk using extended read (2TB max disk size)
 ;;==============================================================================
 ;; Arguments:
-;; -- eax: high word of 64 bit sector.
-;; -- ebx: low word of 64 bit sector.
+;; -- ebx: low word of 64 bit src sector (only 32 bits implementation).
 ;; -- {es:cx}: destination address, {seg:offset}
 ;; Returns:
-;; -- eax: high word of next sector.
-;; -- ebx: low word of sector.
-;; -- {es:cx}: p2source + cantBytes2copy
+;; -- ebx: low word of src sector.
+;; -- {es:cx}: p2dest + cantBytes2copy
+;;
+;; No altera registros, excepto los que indica retorna.
+;; Size of source sector received in ebx, so limited to 2^32 sectors (= 2TB).
 ;;==============================================================================
 
-readSec:
-	push eax
+cpySec:
 	push dx
 	push si
 	push di
 
-	xor eax, eax	;; We don't need to load from sectors > 32-bit
-
-.read:
-	push eax		;; Backup sectorNumber.hi
-	push ebx		;; Backup sectorNumber.lo
+.cpy:
+	push ebx		;; Backup sectorNumber.
 	mov di, sp		;; Base of disk address packet.
 
 	;; Build disk address packet.
-	push eax		;; dap10..15 dap.srcLba.hi
+	push dword 0	;; dap10..15 dap.srcLba.hi. No necesario, trunco a 2TB.
 	push ebx		;; dap06..09 dap.srcLba.lo
 	push es			;; dap04..05 dap.dst.seg
 	push cx			;; dap02..03 dap.dst.offset
@@ -132,24 +123,22 @@ readSec:
 
 	mov si, sp
 	mov dl, [drvNum]
-	mov ah, 42h			; EXTENDED READ
-	int 0x13			; http://hdebruijn.soo.dto.tudelft.nl/newpage/interupt/out-0700.htm#0651
+	mov ah, 42h		;; Extended read.
+	int 0x13
 
-	mov sp, di			; remove parameter block from stack
+	mov sp, di		;; Clean stack.
 	pop ebx
-	pop eax				; Restore the sector number
 
-	jnc read_ok			; jump if no error
+	jnc read_ok		; jump if no error
 
 	push ax
-	xor ah, ah			; else, reset and retry
+	xor ah, ah		; else, reset and retry
 	int 0x13
 	pop ax
-	jmp .read
+	jmp .cpy
 
 read_ok:
 	add ebx, 1			; increment next sector with carry
-	adc eax, 0
 	add cx, 512			; Add bytes per sector
 	jnc no_incr_es			; if overflow...
 
@@ -162,27 +151,6 @@ no_incr_es:
 	pop di
 	pop si
 	pop dx
-	pop eax
-
-	ret
-
-
-;;==============================================================================
-;; pushTest | Verifica compatibilidad de opcode push eax en modo 16 bits
-;;==============================================================================
-;; Registers CS, DS, ES, SS, BX, CX, DX are preserved unless
-;; explicitly changed
-;;==============================================================================
-
-pushTest:
-	mov bx, sp
-	push eax
-	sub bx, sp
-	pop eax
-	add [msg_sizeofPush + POSITION_COUNT], bl
-
-	mov si, msg_sizeofPush
-	call print
 
 	ret
 
@@ -199,11 +167,11 @@ extensionTest:
 	call print
 
 	mov ah, 0x41			;; Check extensions present.
-	mov bx, 55AAh			;; Required signature.
+	mov bx, 55aah			;; Required signature.
 	mov dl, [drvNum]
 	int 0x13
 	jc  notify_ext_not_supported
-	cmp bx, 0xAA55
+	cmp bx, 0xaa55
 	jne notify_ext_not_supported
 
 	mov si, msg_ok
@@ -239,9 +207,6 @@ print:
 ;; section .data
 ;;==============================================================================
 
-msg_sizeofPush:	db "16b mode 32b push opcode pushes "
-POSITION_COUNT	equ $ - msg_sizeofPush
-				db "0 bytes", 13, 10, 0
 msg_extSupport:	db "Verifying bios ext support..", 0
 msg_no:			db " no", 13, 10, 0
 msg_load:		db "Reading disk..", 0

obj/mbr.o

@@ -26,6 +26,8 @@ done
 qemu-system-x86_64 $bios_flag -hda img/x64_arq.qcow2 -m 512 \
 	-name "arq64 uefi" $debug_flags  -smp "$cant_cores"
 
+
+
 ### Dejar esto para probar el booteo con bios, luego, agregar flag para seleccionar uno u otro.
 ##qemu-system-x86_64 -hda img/gpt_with_pmbr.qcow2 -m 512 \
 ##	-name "arq64 uefi" $debug_flags  -smp "$cant_cores"