Author Topic: movntq does not appear to be supported  (Read 2638 times)

nobody

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movntq does not appear to be supported
« on: April 03, 2009, 02:52:13 PM »
Hi,

First time caller here.

I have the following code in my test asm program:

movntq [EDI     ], mm1;

When I trying debug however, movntq does not appear to be used but another set of instructions is instead inserted in its place.

I'm using NASM version 2.06rc1.

Is this correct?

nobody

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Re: movntq does not appear to be supported
« Reply #1 on: April 03, 2009, 07:52:56 PM »
Please post your list file (nasm -l x.lst x.asm), so that we can see the resulting opcodes.

Are you sure that you're using the same mode both, at assembly time (NASM) and run-time (debugger)?
For example, you're not assembling this MOVNTQ in 16-bit mode, but then running it in 32-bit mode, right?

nobody

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Re: movntq does not appear to be supported
« Reply #2 on: April 07, 2009, 01:18:24 PM »
I do not think i'm running in a different mode but I may be wrong.

Let me explain what I have done. Firstly I have created an assembly file containing the following:

global TestMovntq;
export TestMovntq;

segment code public use32 class=CODE

..start:
dllstart:
   mov eax, 1;
   ret 12    ;

TestMovntq:
   push ebp;
   mov ebp, esp;
   ; load parameters
   mov esi, [ebp+12]; second argument in call (source)
   mov edi, [ebp+8];

movq mm0, [esi];
   movntq [edi], mm0;

emms;

pop ebp;

ret 8;

Now this builds with nasm -fobj -l TestMovntq1.lst TestMovntq1.Asm

and links with alink -oPE -dll TestMovntq1.

THis all builds and links with no errors. I subsequently load the dll at runtime in a Borland c++ application and call the function TestMovntq(__int64 *Src, __int64 *Dest);

The Src is successfuly copied to the dest but, when I look in Borlands debugger window I see the following:

push ebp
mov ebp,esp
mov esi,[ebp+0x0c]
mov edi,[ebp+0x08]
movq mm0,[esi]
db 2
pop es
emms
pop ebp
ret 0x0008

Is there something that I have fundamentally not understood? Or is this a bug?

Here is the contents of the lst file:

1                                  global TestMovntq;
     2                                  export TestMovntq;
     3
     4                                  segment code public use32 class=CODE
     5
     6                                  ..start:
     7                                  dllstart:
     8 00000000 B801000000                 mov eax, 1;
     9 00000005 C20C00                     ret 12    ;
    10
    11                                  TestMovntq:
    12 00000008 55                         push ebp;
    13 00000009 89E5                       mov ebp, esp;
    14                                     ; load parameters
    15 0000000B 8B750C                     mov esi, [ebp+12]; second argument in call (source)
    16 0000000E 8B7D08                     mov edi, [ebp+8];
    17
    18 00000011 0F6F06                     movq mm0, [esi];
    19 00000014 0FE707                     movntq [edi], mm0;
    20
    21 00000017 0F77                       emms;
    22
    23 00000019 5D                         pop ebp;
    24
    25 0000001A C20800                     ret 8;


Thanks for any help

Offline Frank Kotler

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Re: movntq does not appear to be supported
« Reply #3 on: April 07, 2009, 02:53:38 PM »
I think you've discovered a bug, alright, but in Borland's debugger, not Nasm. The Nasm output looks right to me. I don't know where the "db 2" came from - disassembling in 16-bit mode *does* turn up a "pop es"...

I don't think it's Nasm's problem. What's Ollydbg think about it?

Best,
Frank