int 19h

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Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 13 Jan 2008, 17:11

I tell you what i will do, i like problems like this, so if we put our heads together we can fix it, so i will do some tests and get back to you Smile

13 Jan 2008, 17:11

Vov4ik

Joined: 20 May 2007
Posts: 28
Location: USSR, Moscow Region

Vov4ik 13 Jan 2008, 17:26

I tried to write a stub to int13 today, as i said earlier. It replaces HDDs, reads MBR from 80h HDD end executes it. But... it hangs. I tried to debug it, stub works correctly, reading of MBR passes well. Debugger hangs when MBR jumps to its copy at 0000:0600, i think because it overwrites some DOS handlers. (DOS handles int13 too, it adds some stub to BIOS handler). This is a source of my program and binary file.
Sorry, i still prefer TASM in ideal mode for DOS.

Description:	A program with commented source.	Download
Filename:	INT13CH.ZIP
Filesize:	1.49 KB
Downloaded:	411 Time(s)

_________________
MicroSoft? is that some kind of a toilet paper?
Sorry for my English . . .

13 Jan 2008, 17:26

edfed

Joined: 20 Feb 2006
Posts: 4354
Location: Now

edfed 13 Jan 2008, 17:31

So , it shall restore the original bios before execution.
but how to make it? i suppose it's overwriten by DOS and OSes.

13 Jan 2008, 17:31

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 13 Jan 2008, 21:39

I have done some tests, it works fine in MiniDos, but in real Dos it freezers, i even rewritten all the interrupts form 32 to 256 to hook to a set ISR, but just the same.
I will do some more tests.

Why do you not write a floppy bootsector that comes up with a menu and asks what OS you want to boot.
It can than run your code to boot to hdd1 etc.
You can do a warm boot with this code

Code:

;Warm Boot By Dex (untested)        xor   ax,ax            ;*SET FLAG FOR WARM REBOOT*        mov   ds,ax            ; dos flags memory segment address        mov   si,0x0472        ; dos reboot type flag offset        mov   cx,0x1234        ; warm boot indicator        mov   word[ds:si],cx   ; set the flag                               ;*WARM REBOOT*        db    0xea             ; Machine language to jump to                               ; address FFFF:0000 (reboot)        dw    0x0000        dw    0xffff           ; No return required                               ; we're rebooting!        jmp $                    ; Just incase

You can then run the above code from Dos.

Last edited by Dex4u on 14 Jan 2008, 05:20; edited 1 time in total

13 Jan 2008, 21:39

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 13 Jan 2008, 22:16

Dex, why not just "jmp $FFFF:0"?

13 Jan 2008, 22:16

edfed

Joined: 20 Feb 2006
Posts: 4354
Location: Now

edfed 13 Jan 2008, 23:32

because it cannot work for CD, i never tryed to rewrite the boot sector of a CD-R. can you do that?

13 Jan 2008, 23:32

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 14 Jan 2008, 03:43

LocoDelAssembly wrote:

Dex, why not just "jmp $FFFF:0"?

By adding the first bit of the code, it does a warm boot (or cold boot, if you mov cx,0x0000).

@edfed, From my point of view, when booting from a CD-R, i use a bootable floppy image, as it's set to floppy emulation.

14 Jan 2008, 03:43

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 14 Jan 2008, 04:05

I should be more specific Razz

I mean why don't you use just the instruction instead of hard coding it with DBs.

14 Jan 2008, 04:05

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 14 Jan 2008, 05:18

LocoDelAssembly wrote:

I should be more specific I mean why don't you use just the instruction instead of hard coding it with DBs.

Oh i see

, because it looks cool Wink

, its common for this type of jump to be done like this.

14 Jan 2008, 05:18

edfed

Joined: 20 Feb 2006
Posts: 4354
Location: Now

edfed 14 Jan 2008, 15:13

finally, i think that making a menu on boot sector is the solution to adopt.
this menu then launch the boot we need.

14 Jan 2008, 15:13

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 14 Jan 2008, 21:53

I have read that calling this will help

Code:

        mov ah,0Dh                   ; Disk Reset        int 21h                      ; causes SmartDrv 4.x to write cache        mov ax, 40h                  ; set up segment addressing        mov ds,ax        or  byte [ds:17h],0Ch        ; Same as pressing CTRL+ALT        mov ax,0x4f53                ; 53h = DEL scan code        int 15h                      ; EMM386 sees this & shuts down

See here: http://www.freedos.org/freedos/news/technote/217.html

14 Jan 2008, 21:53

System86

Joined: 15 Aug 2007
Posts: 77

System86 15 Jan 2008, 00:53

The simplest way to reboot, that works for both real mode and protected mode, is to write 0xFE to port 64h. Jumping to 0xFFFF:0x0000 is another way, but only works in real mode. For both cases, if the value at 0040h:0072h is 1234h, a warm boot will occur, if it is 0, a cold boot will occur. Other ways of reseting a CPU include generating a triple fault (by enabling pmode, lidt with size of IDT being 0, and generating an interrupt), using APM, ACPI, and INT 15h/AH=4Fh.

15 Jan 2008, 00:53

rugxulo

Joined: 09 Aug 2005
Posts: 2341
Location: Usono (aka, USA)

rugxulo 25 Jan 2008, 06:45

Not sure if this is what you want, but take a look at these (all except Gujin are written in asm):

25 Jan 2008, 06:45

bitRAKE

Joined: 21 Jul 2003
Posts: 4178
Location: vpcmpistri

bitRAKE 30 Jan 2008, 03:02

INT $18, is the correct way to return to BIOS for next boot device - at least with modern BIOS. I can boot to my USB stick and work with play OS and then INT $18 to boot harddrive.

http://www.phoenix.com/NR/rdonlyres/56E38DE2-3E6F-4743-835F-B4A53726ABED/0/specsbbs101.pdf

30 Jan 2008, 03:02

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