Questions tagged [masm]
MASM is Microsoft's Macro Assembler tool for converting assembly language to object code. It processes x86 instructions and pseudo instructions written in "Intel syntax". MASM is the standard low-level language for all MSDOS and Windows environments and is currently being supported in the 32-bit and 64-bit versions.
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ASM: MASM, NASM, FASM?
I have done ARM assembly programming and I would like to learn the Intel Assembler. I keep hearing all these different F/M/N/ASMs mentioned- but I am unsure how they related to what I wish to achieve?
...
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votes
3
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x86, difference between BYTE and BYTE PTR
What is the difference between these two lines? What PTR changes here?
;first
mov BYTE [ecx], 0
;second
mov BYTE PTR [ecx], 0
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27
votes
1
answer
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external assembly file in visual studio
I searched and found I can not use __asm in x64 in visual studio. Instead I have to use an external assembly file.
How can I add external assembly file to my win32 console project?
How can compile ...
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24
votes
4
answers
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MOV src, dest (or) MOV dest, src?
MOV is probably the first instruction everyone learns while learning ASM.
Just now I encountered a book Assembly Language Programming in GNU/Linux for IA32 Architectures By Rajat Moona which says: (...
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23
votes
6
answers
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What does OFFSET in 16 bit assembly code mean?
I am going through some example assembly code for 16-bit real mode.
I've come across the lines:
mov bx, cs
mov ds, bx
mov si, OFFSET value1
pop es
mov di, OFFSET ...
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18
votes
3
answers
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Difference between lea and offset
ar db "Defference $"
What's the difference between
mov dx,offset ar
and
lea dx,ar
I think both are doing same work, but what is the difference between these two
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18
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2
answers
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dword ptr usage confusion
In assembly language if we use
mov eax, dword ptr[ebx]
then it means copy the value pointed by ebx (ebx contains the address value, not the actual value, this instruction copies the actual value in ...
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16
votes
1
answer
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Multiple line comments in MASM assembly
Is there a way to comment multiple lines in assembly?
I am using Masm32 v9.
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15
votes
7
answers
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MASM under Linux?
Is there a way that I use MASM under Linux. Even tough NASM is quite popular under Linux, it still differs for some instruction style on code.
15
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2
answers
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What is meaning of .model small in 8086 programs?
I am a beginner in 8086 assembly language. I can understand the logic used in the program and write small programs myself. But I just want to know what this does:
.model small
.stack 300h
What is ...
- 187
14
votes
2
answers
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Floating Point Program gives Invalid Result
RECENT EDIT
I am trying to run this floating point Quadratic Equation program on x86 MASM. This code is found in the Kip Irvine x86 textbook and I want to see how it works visually. The following ...
- 605
13
votes
2
answers
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Assembly Segments in opcodes
I noticed that in Assembly segments are used in opcodes.
Example:
MOV DWORD PTR SS:[EBP-30],30
I think that "PTR SS:" is used to specify that EBP-30 comes from the stack? (SS: stack segment)
Am I ...
- 858
13
votes
3
answers
14k
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Making assembly function inline in x64 Visual Studio
I know that MSVC compiler in x64 mode does not support inline assembly snippets of code, and in order to use assembly code you have to define your function in some external my_asm_funcs.asm file like ...
- 540
13
votes
1
answer
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MASM Fixing 64 bit Truncation in a DLL
I am working with the Adobe Flash ocx by loading it into my C++ program. The ocx is supposed to be 64 bit but for some reason it has issues when I compile with the x64 platform. I have read up on ...
- 1,607
12
votes
2
answers
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Referencing the contents of a memory location. (x86 addressing modes)
I have a memory location that contains a character that I want to compare with another character (and it's not at the top of the stack so I can't just pop it). How do I reference the contents of a ...
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12
votes
2
answers
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error LNK2001: unresolved external symbol _MessageBox
I am trying to create a helloworld program using only masm and not masm32 libs. Here is the code snippet:
.386
.model flat, stdcall
option casemap :none
extrn MessageBox : PROC
extrn ExitProcess : ...
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12
votes
1
answer
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Confusing brackets in MASM32
I am trying to get to grips with MASM32 and am confused by the following:
I thought that brackets were used for indirection so if I have the a pre-defined variable
.data
item dd 42
then
mov ...
- 2,136
12
votes
1
answer
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NASM is pure assembly, but MASM is high level Assembly? [closed]
I'm learning assembly, motivation being able to reverse engineer. I'm trying to find the assembler I should begin with, so that I can then find tutorials and start writing some assembly.
I came to ...
- 2,337
11
votes
3
answers
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masm division overflow
I'm trying divide two numbers in assembly. I'm working out of the Irvine assembly for intel computers book and I can't make division work for the life of me.
Here's my code
.code
main PROC
call ...
11
votes
5
answers
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Force visual studio to always 'rebuild all' when debugging
Edit: Basically what I need is for visual studio to always rebuild all when I hit debug.
I'm currently using visual studio to compile my assembly programs, using MASM and in general it's working fine....
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10
votes
3
answers
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JMP to absolute address (op codes)
I'm trying to code a exe packer/protector as a way of learning more about assembler, c++, and how PE files work. I've currently got it working so the section containing the EP is XORed with a key and ...
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10
votes
2
answers
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Difference between `bx` and `bp`?
What is the difference between bx and bp in assembly? Example here:
mov bx, 1h
mov bp, 1h
Do they reference to the same memory? Is it the same with ss and sp?
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10
votes
1
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Assembly programming - WinAsm vs Visual Studio 2017
I'm here to ask you some stuff about VS2017.
In the past I had used WinAsm for MASM and I never got problems with it.
However, when I'm trying to do something with MASM in VS2017, I always gonna get ...
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10
votes
1
answer
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x86 assembly equ vs =
I am taking a class in x86 assembly language and it's starting to move rather fast. There is one thing that the book keeps doing without mentioning how it works, and that is using the equ and = ...
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10
votes
2
answers
542
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Infected compiler, or malfunction?
I've encountered something very strange, and things just don't add up.
First of all, I posted this here because I'm not sure if this has anything to do with computer virusses at all. And if it does, ...
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10
votes
3
answers
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Outputting Hello World in MASM using WIN32 Functions
Contents
Intro
Code
Assembling and Running
Miscellaneous
Question
1. Intro
This isn't a question per se (though there is one at the bottom) but a HelloWorld app for people on StackOverflow to ...
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10
votes
2
answers
2k
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Why doesn't MS-DOS initialize the DS and ES registers?
Why does the initialization of the DS and ES registers has to be done manually by the programmer?
For example:
MOV AX, DTSEG
MOV DS, AX
On the other hand, the CS and SS registers are initialized ...
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9
votes
3
answers
5k
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Assembly language for Reverse Engineering [closed]
What should I choose NASM or MASM for learning assembly. I want to learn assembly, motivation being Reverse Engineering.
So that when I disassemble some executable, I can understand the code by ...
- 2,337
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votes
3
answers
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How are dw and dd different from db directives for strings?
Let's say I want to define a initialized variable string before running my assembly program (in section .data). The variable I chose to create is called Digits and it is a string that contains all the ...
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votes
1
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Returning a __m128d from MASM procedure to a C caller
I am porting a function from inline assembly to MASM in Visual Studio 2013 and am having trouble getting a return value out of it.
Here is the C caller and the assembly function prototype:
extern "...
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8
votes
2
answers
7k
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Quick, beginner MASM register question - DX:AX
I am currently studying for an exam I'll have on x86 assembly.
I didn't have much luck googling for ":", too common of a punctuation mark :/
IDIV - Signed Integer Division
Usage: IDIV ...
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votes
3
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Detecting architecture at compile time from MASM/MASM64
How can I detect at compile time from an ASM source file if the target architecture is I386 or AMD64?
I am using masm(ml.exe)/masm64(ml64.exe) to assemble file32.asm and file64.asm. It would be nice ...
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votes
8
answers
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Taking an Assembly Course, Stuck in DOS!
I'm taking a course on Microprocessor Programming as part of my Electronic Engineering degree. Unfortunately, in the labs, we have to work in DOS using MASM.
Now, I don't really find DOS a hindrance, ...
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8
votes
3
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2k
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Assembly language - Stack machine
I am learning assembly language in my spare time to become a better developer.
I understand the difference between stack-based machines and register-based machines at a conceptual level, but I am ...
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votes
2
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__cdecl, __stdcall and __fastcall are all called the exact same way?
I am using Visual C++ 2010, and MASM as my x64-Assembler.
This is my C++ code:
// include directive
#include "stdafx.h"
// functions
extern "C" int Asm();
extern "C" int (convention) sum(int x, int ...
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8
votes
2
answers
14k
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bt assembly instruction
I have quesetion about bt assembly instruction. I have excerpted part of book to provide context. Please see last example, bt Testme, bx. Why does that copy TestMe+8? Shouldn't it copy TestMe+65?
...
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8
votes
2
answers
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Write a maximum of two instructions to clear, set and complement some bits in the AL register
You are required to write a maximum of two instructions in assembly to do the following:
Clear bits 0 and 7 of register AL, i.e. make them 0
Set bits 3 and 4 of register AL, i.e. make them 1.
...
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8
votes
2
answers
7k
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Why can't I change the value of a segment register? (MASM)
I decided to teach myself assembly language.
I have realized that my program will not compile if I attempt to change the value of any segment register.
Every article that I have found says that I ...
- 123k
8
votes
3
answers
9k
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TSL instruction reference
I want to use "TSL" instruction in assembly , but it has no reference for understand .in some articles this instruction is introduced for mutual exclusion problem but it has no reference or complete ...
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8
votes
1
answer
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Move quadword between xmm and general-purpose register in ml64?
In a simple program written for Microsoft's x64 assembler, I want to move a 64-bit value between an SSE register (say xmm0) and a general-purpose register (say rcx), as in <Intel syntax in MASM>:...
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2
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What is the difference between MASM.exe and ml.exe?
When i install masm assembler, it asked to install Microsoft visual c++ 2005 express edition. I installed it. Now i can find only "ml.exe". Where is masm.exe?
Even i tried in cmd by typing masm.exe, ...
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Call C standard library function from asm in Visual Studio
I have a problem with calling C function from asm project created in visual studio (Win10 x64, Visual Studio 2015). Project consist of one asm file:
.586
.model flat, stdcall
option casemap:none
...
- 1,311
7
votes
3
answers
8k
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Les instruction purpose?
What is purpose of les instruction in assembly?
Why do we need to load es segment and a register? Book gives following example:
les bx, p ; Load p into ES:BX
mov es:[bx], al ; ...
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7
votes
3
answers
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Assembly Language (x86): How to create a loop to calculate Fibonacci sequence
I am programming assembly language (x86) in MASM using Visual Studio 2013 Ultimate. I am trying to use an array to calculate a Fibonacci sequence for n elements using an array. In other words, I am ...
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7
votes
2
answers
3k
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x86 register flag abbreviations
I'm currently studying assembly language.
In Microsoft visual studio 2017, I wanted to check the current status of the register flags.
I wanted to know what each register flag abbreviation stands ...
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votes
2
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Assembly difference between TASM and MASM
I am learning TASM at University, but information regarding TASM on the web seems to be very limited. I have found more information on MASM.
My question is, what is the different between MASM and ...
- 11k
7
votes
2
answers
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Injecting 64 Bit DLL using code cave
I'm trying to inject a 64 Bit DLL into 64 Bit Process (explorer for the matter).
I've tried using Remote-thread\Window Hooks techniques but some Anti-Viruses detects my loader as a false positive.
...
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7
votes
3
answers
24k
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How do I use a buffer in an assembly procedure?
So, I understand the general abstract concept of a buffer: it's an allocation in memory that holds data before it gets processed. I'm trying to complete a homework problem which requires me to write ...
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7
votes
3
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Difference between masm32 and masm?
I am trying to learn assembly for windows and see that there are 2 assemblers:
masm : https://www.microsoft.com/downloads/en/details.aspx?FamilyID=7a1c9da0-0510-44a2-b042-7ef370530c64
masm32 : http:...
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