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assemblyatt

Iterate stack in AT&T x64 assembly

I have to iterate through the stack to temporary move the values of the words to a register, something like this:

movq    ((i - 3)*8)(%rsp), %esi

or

movq    %rcx, %rbx                # where %rcx is the counter
        subq    $3, %rbx         
        movq    $8, %rax
        mulq    %rbx
        movq    (%rbx)(%rsp), %esi

But obviously, neither of the above works, so how should I change it to make it work?

Solution

  • movl -24(%rsp,%rcx,8),%esi

    Please, read the AT&T syntax documentation (and have it around).

    Personal bias: while usually I don't mind alternatives, in case of x86 assembly I think the MASM quirk mode should be burnt, and AT&T should be used only by compilers as machine format for further compilation/etc, but not by humans. If you insist on using AT&T, go ahead, but I will consider you being a masochist.

    Just to compare, Intel syntax (nasm):
    mov esi,[rsp+rcx*8-24]