Push more than 4 Bytes

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SilverOne

Joined: 28 Nov 2011
Posts: 1

SilverOne 28 Nov 2011, 14:34

fasm version is 1.69.35

Code:

    ; This works:
    push 'abcd'           ; 4 Bytes
    mov rax,'abcdefgh'
    push rax              ; 8 Bytes over rax

    ; This does not work:
    push 'abcdefgh'       ; Error: value out of range

Shouldn't push allow 8 Byte immediate values in 64bit mode?

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28 Nov 2011, 14:34

revolution
When all else fails, read the source

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

revolution 28 Nov 2011, 14:39

SilverOne wrote:

Shouldn't push allow 8 Byte immediate values in 64bit mode?

Perhaps it should, but the CPU hardware does not support it. fasm properly generates an error since, with the current instruction set, it is impossible to encode a full sized 64-bit push.

If you want this to be changed then I suggest you write to Intel/AMD and ask for them to update the CPU instruction set. Wink

28 Nov 2011, 14:39

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