Recent questions tagged assembly

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assembly - x86 LOCK question on multi-core CPUs

Is it true that the x86 ASM "LOCK" command prefix causes all cores to freeze while the instruction following "LOCK" ... if this is true or not. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why does Intel hide internal RISC core in their processors?

Starting with Pentium Pro (P6 microarchitecture), Intel redesigned it's microprocessors and used internal RISC core under ... , SSE4 and others. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - How do I write letter-initiated hexadecimal numbers in masm code?

I am currently editing several macros consisting of MASM code. They all look similar to this: Primary MACRO Key ... numbers in this case? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why is my MIPS base converter printing out the values from a previous loop after the current values?

I'm very new to MIPS and this has me completely baffled. I made a program to convert bases and it works ... like to input another number? " See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why is no value returned if a function does not explicity use 'ret'

I have the following program: SECTION .text main: mov ebx, 10 mov ecx, 50 repeat: inc ebx loop repeat mov eax, ... then returns 0. Why is that? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Do terms like direct/indirect addressing mode actual exists in the Intel x86 manuals

To give a little bit of background, I wanted to study how x86 instructions are encoded/decoded manually. I came ... to them in the manuals. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why do we need to disambiguate when adding an immediate value to a value at a memory address

Explains that unless we specify a size operator (such as byte or dword) when adding an immediate value to a ... version 2.11.08 Architecture x86 See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Does cmpxchg write destination cache line on failure? If not, is it better than xchg for spinlock?

I assume simple spinlock that does not go to OS waiting for the purposes of this question. I see that simple ... to cmpxchg, not in general. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - gas: too many memory reference

When compiling the following instruction: movl 4(%ebp), 8(%ebp) I got: too many memory reference. What's wrong with it? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Can I add 64bit constants to 64bit registers?

At my 64bit Intel machine following code works: mov rdi, 1 << 40 add r10, rdi and this quite ... : signed dword immediate exceeds bounds See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - How to print a character in Linux x86 NASM?

I'm trying to print a single character or a number using NASM, targeting an x86 GNU/Linux architecture. Here's the ... . What am I doing wrong? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Optimize for fast multiplication but slow addition: FMA and doubledouble

When I first got a Haswell processor I tried implementing FMA to determine the Mandelbrot set. The main algorithm ... , 32(%rdi) vzeroupper ret See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Load from a 64-bit address into other register than rax

On x64, loading from a 64-bit absolute address (that is, dereferencing a 64-bit immediate) can be done by movabs ... movabs. What am I missing? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Calculating padding length with GAS AT&T directives for a boot sector?

So I want to add padding in the bootsector. Let's say, there is currently just an endless loop in there: ... is stable enough for AT&T syntax. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Does each PUSH instruction push a multiple of 8 bytes on x64?

On x64, does each PUSH instruction push a multiple of 8 bytes? If not, how much does it push? Also ... does each function parameter consume? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - What's the size of a QWORD on a 64-bit machine?

I'm currently looking to find an answer to the above question. So far I found people saying, that the word ... and enlighten me on this topic. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Z80 ASM BNF structure... am I on the right track?

I'm trying to learn BNF and attempting to assemble some Z80 ASM code. Since I'm new to both fields, my ... am going wrong would be excellent. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - What does the MOVZBL instruction do in IA-32 AT&T syntax?

What exactly does this instruction do? movzbl 0x01(%eax,%ecx), %eax See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - what does "mov offset(%rip), %rax" do?

Does rax get offset plus the address of this instruction, or the next? From a microcode point of view it ... answer was the next instruction. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - What does NOPL do in x86 system?

what is the function of NOPL in x86 machine? It feels like it doesn't do anything, but why is it always in the assembly code? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - How to: pow(real, real) in x86

I'm looking for the implementation of pow(real, real) in x86 Assembly. Also I'd like to understand how the algorithm works. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Why GCC compiled C program needs .eh_frame section?

Test is on 32 bit x86 Linux with gcc 4.6.3 When using gcc to compile a C program and using readelf to ... inside ELF compiled from C program? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - why we can't move a 64-bit immediate value to memory?

First I am a little bit confused with the differences between movq and movabsq, my text book says: The ... designed to make things harder? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - CS:APP example uses idivq with two operands?

I am reading about x86-64 (and assembly in general) through the book "computer systems a programmer's ... compiling a short C function. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - What registers must be preserved by an x86 function?

I'm writing a function in x86 assembly that should be callable from c code, and I'm wondering which registers ... whatever pleases me in them? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Getting an label address to a register on ARM?

How do I write an instruction which will have the address a label is referencing put into a register? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - Binary Bomb - Phase 4

I am having a very difficult time tracing the assembly code for the following binary bomb (An assignment from ... ret End of assembler dump. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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assembly - How to push a 64bit int in NASM?

I'm trying to push a 64bit integer but when assembling NASM seems to want to see it as a DWORD not a ... CALL RAX pop RAX POPFQ RETN See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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