Recent questions tagged assembly

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assembly - Tiny C Compiler's generated code emits extra (unnecessary?) NOPs and JMPs

Can someone explain why this code: #include <stdio.h> int main() { return 0; } when compiled with tcc using ... executable using TCC 0.9.26. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Problem switching to v8086 mode from 32-bit protected mode by setting EFLAGS.VM to 1

I'm in 32-bit protected mode running at current privilege level (CPL=0). I'm trying to enter v8086 mode by ... : qemu-system-i386 -fda v86.bin See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Is it possible to decode x86-64 instructions in reverse?

I was wondering if it is possible to decode x86-64 instructions in reverse? I need this for a runtime ... do this by reverse decoding. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Printing an integer with x86 32-bit Linux sys_write (NASM)

I'm new to this forum. I have a little experience with high-level languages (really little). Nearly one month ago I ... address (or does it?) ?? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why function parameter occupy at least 4 bytes stack on x86?

Function parameter is allocated with at least 4 bytes via push/pop if they are allocated in stack on x86. This ... [esp+3], para4 call func See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Avr asm label*2

Hi i am new in avr asm programming,in the example below, i have few questions: 1) Is it label: 8 bit or ... db "Hello world", 0 lpm Thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Errors on assembling ARM asm on an x86 PC with GCC or `as`

So I have been doing an assembly tutorial, and I got stuck in the very beginning. Project name: asmtut.s The ... help me what could cause this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Linking Android C-code and ARM Assembler

I have written an Android app. It uses a main C-code module and a linked-in C-code module. Now I want ... module. Anyone have a simple example? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Create .SO files on Linux without using PIC (position independent code) (x86 32bit)

As far as I know, x86 assembly code is very much constrained by the limited amount of registers. When I learnt ... when compiling a .so-file? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Variable bit shift

I'm looking to shift a register bits n times to the left specified with another register. For example, something ... not known at assemble-time? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why did the compiler put an instruction after the MIPS "j" instruction that returns from a function?

I'm looking at some compiler output for a MIPS platform and struggling to understand how a function returns and ... executed after the jump?! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - How to use character literals in GNU GAS to replace numbers?

For example, I'd like to write something like 'a' instead of 0x61 like I can in C. The manual mentions them ... I'm not sure I understood. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Increasing Efficiency of binary -> gray code for 8086

I am a beginner in assembly and This is a code that I designed to convert from binary and to gray, and ... but it is affecting the output. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Reading a single-key input on Linux (without waiting for return) using x86_64 sys_call

I want to make Linux just take 1 keystroke from keyboard using sys_read, but sys_read just wait until i pressed ... to 8 input from keyboard. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - SSE/SIMD shift with one-byte element size / granularity?

As you know we have below Shift instructions in SIMD SSE: PSLL(W-D-Q) and PSRL(W-D-Q) There's no ... vectors of 8bit values (single bytes)? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Is ARM (not Thumb) supported on WinPhone8 at all?

I'm facing a weird issue, somewhat similar to this. I have a Windows Phone 8 native DLL project, mostly C+ ... device; that could be the reason. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Gas altmacro macro with a percent sign in a default parameter fails with "% operator needs absolute expression"

I want to create a macro like the following: .altmacro .macro assert_eq a, b=%eax LOCAL ok #... .endm To be used ... use %? GAS version: 2.23.52 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - NASM TO GAS: counterpart of resw in GAS

I am tasked to convert my assembly program which uses NASM to GAS. Unfortunately there are lots of mismatched ... this statement min resw 1 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - 32 bit registers act as 8 bit ones

I've been having the strangest problem. In x86 assembly, the 32 bit registers (eax, ebx, etc.) have been ... 8 bit ones, in ANY situation? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Generating random numbers using the interrupt of clock

I need to generate 5 random numbers, for that purpose i used the interrupt of clock: mov ah,2ch int ... problem using interrupts please help. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Where is -32768 coming from?

This is LC3 Assembly code I am working with .ORIG x3000 LOOP LDI R0, KBSR BRzp LOOP From LC3 Assembly, ... has received a new character. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Can assembled ASM code result in more than a single possible way (except for offset values)?

I don't know x86 ASM very well, but I'm rather comfortable with SHARP-z80, and I know by experience that ... is affected by surrounding C code. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Avoiding 0xFF bytes in shellcode using CALL to read RIP?

I'm trying to write a decoder stub and I'm running into a restriction on 0xFF as a bad character. I'm using ... in my machine code are: 00 FF See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - During an x86 software interrupt, when exactly is a context switch made?

I am asking this because I am trying to implement interrupts in my toy kernel. So, I know that when an ... not sure where else I should. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why does the lw instruction's second argument take in both an offset and regSource?

So the lw instruction is in the following format: lw RegDest, Offset(RegSource). Why does the second argument take ... e. only register source)? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - What is the most efficient way to support CMGT with 64bit signed comparisons on ARMv7a with Neon?

This question was originally posed for SSE2 here. Since every single algorithm overlapped with ARMv7a+NEON's ... into WebAssembly SIMD. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - ARM MOV and MVN operand

I'm trying to write code to do two things: return a 1 to register r2 if my value is presentable as a constant ... , 0x3fc, 0x100, 0xff, 0 END See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Cube root on x87 FPU using Newton-Raphson method

I am trying to write an assembly program using the 8086 processor that will find the cube root of a number. ... ; exit ret main ENDP END See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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