multiple regs in push with error: illegal instruction

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catafest

Joined: 05 Aug 2010
Posts: 129

catafest 22 Jun 2021, 20:22

Can you help me with this error and why this is happened ? Thank you.

Code:

[mythcat@desk fasm]$ ./fasm 001.fasm 001
flat assembler  version 1.73.27  (16384 kilobytes memory)
source\Linux\system.inc [104]:
        push    esi edi ebp
processed: push esi edi ebp
error: illegal instruction.

The source code in FASM is:

Code:

format  ELF64

include 'source\Linux\system.inc'
...

22 Jun 2021, 20:22

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20300
Location: In your JS exploiting you and your system

revolution 23 Jun 2021, 00:36

In 64-bit mode (ELF64) it is not possible to push a 32-bit value.

You can only push 16-bit and 64-bit values.

Code:

use64
push ax ; okay
push rax ; okay
push eax ; invalid, cannot be encoded in 64-bit mode

23 Jun 2021, 00:36

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