Recent questions tagged x86

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x86 - How to install ia32-libs in Ubuntu 14.04 LTS (Trusty Tahr)

I installed Ubuntu 14.04 (Trusty Tahr) yesterday. Everything seems OK. But when I tried to compile some C code, ... How can I fix this problem? See Question&Answers more detail:os...

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

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x86 - Get size of assembly instructions

I need to read instructions one-by-one from a small code segment in memory and I have to find out the size ... I read is opcode or information? See Question&Answers more detail:os...

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

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x86 - What was the original reason for the design of AT&T assembly syntax?

When using assembly instructions on x86 or amd64, programmer can use "Intel" (i.e. nasm compiler) or "AT&T" ... the creators of the processor? See Question&Answers more detail:os...

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

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x86 - What does "DS:[40207A]" mean in assembly?

0040103A CALL DWORD PTR DS:[40207A] USER32.MessageBoxA What does DS: mean? See Question&Answers more detail:os...

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

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x86 - about assembly CF(Carry) and OF(Overflow) flag

It's known that CF indicates unsigned carry out and OF indicates signed overflow. So how does an assembly ... flags be used interchangeably? See Question&Answers more detail:os...

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

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x86 - Fastest way to compute absolute value using SSE

I am aware of 3 methods, but as far as I know, only the first 2 are generally used: Mask off the ... right? Thoughts and opinions are welcome. See Question&Answers more detail:os...

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

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x86 - Assembly Language - How to do Modulo?

Is there something like a modulo operator or instruction in x86 assembly? See Question&Answers more detail:os...

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

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x86 - How do I enable SSE for my freestanding bootable code?

(This question was originally about the CVTSI2SD instruction and the fact that I thought it didn't work on ... restoring them when necessary. See Question&Answers more detail:os...

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

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x86 - double condition checking in assembly

i'm beginning assembly, i'm using nasm for assembling the code, i'm trying to process a string residing in ... 100) do something thanks alot ! See Question&Answers more detail:os...

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

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x86 64 - Address canonical form and pointer arithmetic

On AMD64 compliant architectures, addresses need to be in canonical form before being dereferenced. From the Intel manual, ... by the 47th bit? See Question&Answers more detail:os...

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

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x86 - Why can't you set the instruction pointer directly?

The Wikipedia article about x86 assembly says that "the IP register cannot be accessed by the programmer ... are the technical restrictions? See Question&Answers more detail:os...

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

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x86 - Assembly - JG/JNLE/JL/JNGE after CMP

I don't understand the JG/JNLE/JL/JNGE instructions, which come after CMP. for example, If I have: CMP al,dl jg ... would jump to label1, and when we wouldn't. Question&Answers:os...

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

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x86 - What does "int 0x80" mean in assembly code?

Can someone explain what the following assembly code does? int 0x80 Question&Answers:os...

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

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x86 64 - Why can't kernel code use a Red Zone

It is highly recommended when creating a 64-bit kernel (for x86_64 platform), to instruct the compiler not to use the ... if it is enabled. But why is that? Question&Answers:os...

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

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x86 assembler: floating point compare

As part of a compiler project I have to write GNU assembler code for x86 to compare floating point values. I have ... pop only one value or does it pop both? Question&Answers:os...

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

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x86 - What is stack frame in assembly?

What is the structure of a stack frame and how is it used while calling functions in assembly? Question&Answers:os...

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

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x86 - What exactly happens when a skylake CPU mispredicts a branch?

I'm trying to understand in detail what happens to instructions in the various stages of the skylake CPU pipeline ... , but found no clarity on these points. Question&Answers:os...

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

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x86 - Difference between JA and JG in assembly

Can you please tell me the difference between JUMP IF ABOVE AND JUMP IF GREATER in Assembly language? when do i ... of them? do they give me different results? Question&Answers:os...

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

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x86 - 8086 assembly on DOSBox: Bug with idiv instruction?

I was helping a friend of mine debug his program, and we narrowed it down to an issue which occurs ... infinitum. Does anyone have any explanation for this? Question&Answers:os...

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

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x86 64 - Mach-O 64-bit format does not support 32-bit absolute addresses. NASM Accessing Array

Running this code off my Mac computer, using command: nasm -f macho64 -o max.a maximum.asm This is the ... bit format does not support 32-bit absolute addresses Question&Answers:os...

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

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x86 - Why is there not a register that contains the higher bytes of EAX?

%AX = (%AH + %AL) So why not %EAX = (%SOME_REGISTER + %AX) for some register %SOME_REGISTER? Question&Answers:os...

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

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x86 - How do you use gcc to generate assembly code in Intel syntax?

The gcc -S option will generate assembly code in AT&T syntax, is there a way to generate files in Intel syntax? Or is there a way to convert between the two? Question&Answers:os...

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

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x86 - What does cltq do in assembly?

0x0000000000400553 <main+59>: mov -0x4(%rbp),%eax 0x0000000000400556 <main+62>: cltq 0x0000000000400558 <main+64>: shl ... <main+88>: jne 0x400530 <main+24> Question&Answers:os...

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

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x86 16 - Assembly 8086 | Sum of an array, printing multi-digit numbers

I've written a pretty simple code in asm x8086 and I'm facing an error. If anyone could help me with a brief ... --- exit: mov ax, 4c00h int 21h END start Question&Answers:os...

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

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x86 - Assembly, printing ascii number

I have a problem with my assembly code. I want to print number stored in register cx, but when i tried to ... PROCEDURE JMP ASC2 ;ELSE REPEAT EXTT: RET P4 ENDP Question&Answers:os...

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

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x86 - What if there is no return statement in a CALLed block of code in assembly programs

What happens if i say 'call ' instead of jump? Since there is no return statement written, does control just pass over ... : cmp %eax, $1 call one mov $10, %eax Question&Answers:os...

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

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x86 - is there an inverse instruction to the movemask instruction in intel avx2?

The movemask instruction(s) take an __m256i and return an int32 where each bit (either the first 4, ... or little loops that implement this operation. Question&Answers:os...

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

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x86 - Globally Invisible load instructions

Can some of the load instructions be never globally visible due to store load forwarding ? To put it another ... from the L1D should make it globally invisible. Question&Answers:os...

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

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