How I can define 256 bit variable?

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SergeASM

Joined: 13 Nov 2015
Posts: 21

SergeASM 12 Mar 2016, 08:05

Hello all,

sorry for troubling, I can't find answer in search.

Code:

align 32
qq1 dq ?
    dq ?
[...]
vmovdqa ymm0,qqword[qq1]

Can I define one variable of 256 bit?

Serge

12 Mar 2016, 08:05

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19069
Location: In your JS exploiting you and your system

revolution 12 Mar 2016, 08:16

Code:

vmovdqa ymm0,qqword ptr qq1

12 Mar 2016, 08:16

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19069
Location: In your JS exploiting you and your system

revolution 12 Mar 2016, 08:19

Update: This also works

Code:

qq1 dq ?,?,?,?
vmovdqa ymm0,qqword ptr qq1
label qq2 qqword at $$
vmovdqa ymm0,[qq2]

Last edited by revolution on 12 Mar 2016, 09:25; edited 1 time in total

12 Mar 2016, 08:19

SergeASM

Joined: 13 Nov 2015
Posts: 21

SergeASM 12 Mar 2016, 09:17

Thanks but you've defined a label, but not 256 bit variable. Smile

Suppose I want to define a 256 bit constant like:

qq1 qq 12345678901234567890123456789012h

Why there is no definition qq?

12 Mar 2016, 09:17

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19069
Location: In your JS exploiting you and your system

revolution 12 Mar 2016, 09:22

Fasm doesn't support more than 64 bit numbers at this time. Also, the CPUs don't support more than 64 bit numbers at this time.

BTW: There is no such thing as a 256 bit number when talking about native CPU instructions, you have to use multiples of 64 bit numbers. The fact that the current batch of CPUs allow defining multiples of 64 bit numbers in parallel doesn't alter the fact that they still can only work with a maximum of 64 bit numbers in any ALU or FPU execution unit.

12 Mar 2016, 09:22

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