Questions tagged [assembly]
Assembly language questions. Please tag the processor and/or the instruction set you are using, as well as the assembler, a valid set should be like this: ([assembly] [x86] [gnu-assembler] or [att]). Use the [.net-assembly] tag instead for .NET assemblies, [cil] for .NET assembly language, [wasm] for web assembly, and for Java bytecode, use the tag java-bytecode-asm instead.
assembly
44,632
questions
1
vote
1
answer
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RISC-V assembly: global pointer set to a weird value
I am experimenting with RISC-V assembly language on an emulator (qemu64, ubuntu for RISC-V).
Here is a simple program, its function is to convert the instr string to uppercase, outstr is the resulting ...
- 214
0
votes
1
answer
36
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x86 NASM Crash - Iterate over string
How to iterate over individual characters of a string in x86 assembly and print them?
global _main ; declare _main entry point
extern _printf ; extern method
section ....
0
votes
0
answers
40
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How can I disassemble a whole obj file in valid asm, amend some sections of such asm code and reassemble to obj?
Is it possible on Linux to use objdump (or any other utility) to fully disassemble an obj file to asm code, modify such code and then pass the asm to as?
The challenge I have with objdump is that it ...
- 1,428
20
votes
2
answers
1k
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How to prepare stack pointer for bare metal Rust?
I'm trying to write an x86 bootloader and operating system completely in Rust (no separate assembly files, only inline assembly within Rust).
My bootloader works completely as intended within the QEMU ...
- 305
5
votes
1
answer
116
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Logical shift right without dedicated shift instruction
I am working with an assembly language that does not contain either multiply, divide, or bit-shift instructions. I am aware that a left bit-shift can be achieved by just adding the same number to ...
- 73
1
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0
answers
66
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Assembling with gcc gives error operand type mismatch for `cmp' for some integers, not others
This is a weird one. I'm using gcc to assemble a program and I want to know if the value in register rsi fits in 32 bits, so I use this instruction:
cmpq $0xffffffff, %rsi
I get back an error that ...
- 11
-1
votes
1
answer
44
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Does stack work differently in assembly than how it works in C?
I just started learning assembly code. As far as I understand, when a functions calls in assembly code, the main variables are stored to stack from registers and stored back to registers after ...
- 11
1
vote
1
answer
77
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Working with 64-bit products and quotients of 32-bit integers in assembly x86-64
Starting to learn assembly x86-64, I'm writing a program that gets an array of integers and does some calculations on it. The purpose isn't relevant to the question, but the calculations include ...
1
vote
1
answer
44
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E2028: _small_code_ is an undefined reference
I am working on my own bootloader. I want it to print "Hello world". For some reason, I get an error: Error! E2028: small_code is an undefined reference
Hello! I am working on my own ...
0
votes
1
answer
35
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Print the greatest number in assembly programming
Trying to print the greatest number (a & b) by using the below assembly code. But it is printing the "first" (Welcome) message only. I just want to print the "second" (i.e ...
- 387
2
votes
2
answers
53
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Forth: What is the standard way to define a word using machine code?
I wrote a Forth interpreter in Assembler (core set), but is there a standard way to define a Forth word using Assembler instructions or directly machine code?
Example
I want to define "+" (...
- 250
3
votes
1
answer
42
views
Why are multiple B.Cond statements always resolving only one way for variable input?
Utilizing arm64, on qemu.
I want to check whether a user inputted value is negative, positive, or zero. I have a SUBS instruction, followed by three B.Cond instructions. I'm using scanf with a %d ...
- 33
2
votes
0
answers
76
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How does this assembly code perform the source code b = a/3 when a = 2? [duplicate]
I'm trying to trace this C source code (when a = 2):
b = a/3;
To this ARM assembly code (for unsigned 1 byte value):
ldrb r2, [fp, #-6] @ zero_extendqisi2 @ tmp162, a
ldr r3, .L34 @ tmp164,
...
- 21
2
votes
0
answers
45
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(x86_64 NASM) Why is my program returning 0 instead of 256? [duplicate]
This is my first assembly code:
;program name - first.asm
section .data ;stores initialised var
section .bss ;stores uninit var
section .text ;actual code
global _start
_start:
mov eax,1
mov ...
- 21
2
votes
1
answer
50
views
Why does the code show only some white lines when you compiled it?
.MODEL SMALL
.STACK 100h
.DATA
COLUMNA DW ?
FILA DW ?
AVANCEH DW ?
AVANCEV DW ?
.CODE
DETENER_POR_TIEMPO PROC
MOV CX, 2000h
MOV DX, 2000h
MOV BX, 2000h
NOP
RET
DETENER_POR_TIEMPO ...
