Recent questions tagged Assembly

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assembly - How to move two 32 bit registers in to one 64 bit?

Let's say that I want to put two 32 bit registers EAX as low 32 bit word and EDX as high 32 bit ... x86-64 instruction that does this operation? 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 - x86 CMP Instruction Difference

Question What is the (non-trivial) difference between the following two x86 instructions? 39 /r CMP r/m32,r32 ... and why this even exists. 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 - Conditional Compilation in assembler (.s) code for iPhone - how?

I have a few lines of assembler arm code in an .s file. Just a few routines i need to call. It works fine when ... ... asm code here ... #endif 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 - relocation truncated to fit r_386_8 against .bss'

When i type ld -m elf_i386 -o loop loop.asm, i get the error stated in the title, any idea what causes it? ... mov dl,$numA mov ah,2 int 21h 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 - invalid effective address calculation

Please look at the following program, the error is invalid effective address calculation and i have mentioned that ... mov ax,0x4c00 int 0x21 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 - execve shellcode linux segmentation fault

Im trying to run this shellcode but it throws me: "Segmentation fault" error The shellcode is the following: ... get no error Thank you 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 properly setup SS, BP and SP in x86 Real Mode?

I want to know how to properly do it, because the way I'm doing it isn't working. When setting the BP register ... 't work. Please give a hand. 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 are the exhaustion characteristics of RDRAND on Ivy Bridge?

After reviewing the Intel Digital Random Number Generator (DRNG) Software Implementation Guide, I have a few ... different information. 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 - Why does GCC subtract the wrong value to the stack pointer when allocating a big array with no subsequent function calls?

Really bizarre gcc quirk. Check this out: main() { int a[100]; a[0]=1; } produces this assembly: 0: ... s "redzone"? What's happening precisely? 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 - "cpuid" before "rdtsc"

Sometimes I encounter code that reads TSC with rdtsc instruction, but calls cpuid right before. Why is calling ... two instructions in sequence? 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 do the abbriviations (Rn, Rd, ...) in the instruction set of ARM mean?

recently i checked the Instruction Set for an ARM Cortex-M3 processor. For example: ADD <Rd>, <Rn>, <Rm> What ... so. But what exactly? 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 - Understanding how `lw` and `sw` actually work in a MIPS program

I'm having bit of a difficulty understanding what sw and lw do in a MIPS program. My understanding of the topic is ... such as sw $t0, 32($s3). 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 - Equivalent for GCC's naked attribute

I've got an application written in pure C, mixed with some functions that contain pure ASM. Naked attribute ... address of such ASM function. 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 use RIP-relative addressing in NASM?

I have an assembly hello world program for Mac OS X that looks like this: global _main section .text _main: mov ... know when to use each one? 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 - reverse engineering c programs

every c program is converted to machine code, if this binary is distributed. Since the instruction set of a ... back the C original program? 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 - Can rip be used with another register with RIP-relative addressing?

I'm familiar with memory references of this form: XXX ptr [base + index * size + displacement] where XXX ... and then offset into that? 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 - LD errors while linking 16-bit real mode code into a Multiboot compliant ELF executable

I'm writing a Multiboot compliant ELF executable containing my 32-bit kernel. My primary problem is that I' ... files /bin Kernel Executable 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 - Storing addresses in a register for MIPS

I have allocated a certain amount of memory and would like to assign the location of this memory to variable ... to access the allocated memory? 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 - Assembling with GCC causes weird relocation error with regards to .data

This is an issue that didn't used to ever occur. I'm pretty convinced it's probably an issue with my ... assembly needs for a long 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 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 ... -DOS). Why is this so? 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 faster: JMP or string of NOPs?

I'm implementing binary translation and have to deal with sequences of NOPs (0x90) with length about 16 opcodes. ... at start of such sequences? 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 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 ... -DOS). Why is this so? 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 faster: JMP or string of NOPs?

I'm implementing binary translation and have to deal with sequences of NOPs (0x90) with length about 16 opcodes. ... at start of such sequences? 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 - Difference between SHL and SAL in 80x86

I have learned how to work with 80x86 assembler, so in bit-wise shift operation, I faced a problem with SAL ... What is the difference of them? 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 does Enum allocate Memory on C?

I'm trying to work with C and Assembly (intelx8086) language. I'm also using one class that was implemented by ... much memory does "enum" take? 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 would happen if the CS segment register is changed? (And how would you do so?)

I read this article: http://static.patater.com/gbaguy/day3pc.htm It includes the sentence DON'T EVER CHANGE CS!! ... ? Why is it so dangerous? See Question&Answers more detail:os...

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

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