Questions by index of massive and procedures

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Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 00:35

What syntax of handling to element of massive?

mov si, 2
mov ax, mas[si] (MASM version?)

doesn't work.

What syntax of procedure and where may I read about procedures in FASM?

09 Nov 2013, 00:35

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 09 Nov 2013, 03:29

Try this:

Code:

mov ax,[si+mas]

09 Nov 2013, 03:29

Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 08:00

I try to write first and last elements to variables, but have some troubles
like this:

Quote:

error: operand sizes do not match.

or this this

Quote:

error: invalid operand.

if use movsx

Code:

xor eax,eax
lea dx, [mas]
mov edi, 10
mov esi, 1
movsx ax, [esi+mas]
mov [a], ax
movsx ax, [edi+mas]
mov [b], ax

09 Nov 2013, 08:00

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 09 Nov 2013, 08:10

How have you defined mas?

09 Nov 2013, 08:10

Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 08:18

revolution wrote:

How have you defined mas?

db, ten elements

09 Nov 2013, 08:18

RIxRIpt

Joined: 18 Apr 2013
Posts: 50

RIxRIpt 09 Nov 2013, 08:43

You are trying to mov byte to ax (word)

Code:

mov al, [(e)si + mas]

Or if you want to get 2 bytes in ax:

Code:

mov ax, word[(e)si + mas]

09 Nov 2013, 08:43

Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 09:03

Code:

mov ax, word[(e)si + mas]

Quote:

error: invalid address.

It's just appel to elements of array, what's wrong the syntax to this o.O

09 Nov 2013, 09:03

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 09 Nov 2013, 09:07

Just use si.

Code:

mov ax,word[si+mas]

09 Nov 2013, 09:07

Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 09:12

this is have no effect, look:

Description:
Filesize:	51.92 KB
Viewed:	9811 Time(s)

09 Nov 2013, 09:12

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 09 Nov 2013, 09:19

If you are using a PE file then you will need to use the 32-bit registers for addressing. Use ESI.

09 Nov 2013, 09:19

Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 09:32

If Array have 10 symbols, how many positions need to shift to appeal to last element?

09 Nov 2013, 09:32

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 09 Nov 2013, 09:50

Satansoft wrote:

If Array have 10 symbols, how many positions need to shift to appeal to last element?

In programming, everything is counted from 0. If you want to read the last word from your 10 bytes array, use:

Code:

mov  esi, mas
mov  ax, word [esi+8]

Or even more simple:

Code:

mov  ax, word [mas+8]

Using registers as an address worths only if you need to cycle through the array.

P.S. BTW, where are you from? Naming an array "масив" talks about some of the slavonic languages. Smile

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Last edited by JohnFound on 09 Nov 2013, 10:28; edited 1 time in total

09 Nov 2013, 09:50

Satansoft

Joined: 09 Nov 2013
Posts: 7

Satansoft 09 Nov 2013, 10:08

Thx to all helpers.

Quote:

Naming an array "масив" is a talks about Slavonic language.

Have no Slavonic language, it's an a group of languages.

Quote:

where are you from?

Greetings from Ukraine :3

09 Nov 2013, 10:08

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 09 Nov 2013, 10:29

Satansoft wrote:

Greetings from Ukraine :3

Welcome in the assembly world. Wink

_________________
Tox ID: 48C0321ADDB2FE5F644BB5E3D58B0D58C35E5BCBC81D7CD333633FEDF1047914A534256478D9

09 Nov 2013, 10:29

Bargest

Joined: 09 Feb 2012
Posts: 79
Location: Russia

Bargest 09 Nov 2013, 16:44

Do you really want to get WORD from array? It's defined as 'db', so reading by words will give you values as 406h, 609h, 92Bh, etc. I think you should use AL:

Code:

mov al, [mas + 9]

09 Nov 2013, 16:44

ejamesr

Joined: 04 Feb 2011
Posts: 52
Location: Provo, Utah, USA

ejamesr 09 Nov 2013, 17:19

Try any of these:

Code:

; When mas is a global variable (as in your example), the following will work
mov  al, [mas + 9]

;-- OR --

mov  edx, mas
mov  al, [edx+9]


; But when 'mas' is a stack-based variable, you should use 'lea':
lea  edx, [mas]         ; also works when 'mas' is global
mov  al, [edx + 9]

09 Nov 2013, 17:19

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