Recent questions tagged Assembly

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assembly - Can constant non-invariant tsc change frequency across cpu states?

I used to benchmark Linux System Calls with rdtsc to get the counter difference before and after the system call. ... , but not invariant tsc. 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 - When using the MOV mnemonic to load/copy a string to a memory register in MASM, are the characters stored in reverse order?

I want to know if using the MOV instruction to copy a string into a register causes the string to be stored in ... set the zero flag, right? 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 - addressing array elements in nasm

I'm very new to assembly and NASM and there is a code: SECTION .data array db 89, 10, 67, 1, 4, ... mess instead of the array elements value. 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 is POPCNT implemented in hardware?

According to http://www.agner.org/optimize/instruction_tables.pdf, the POPCNT instruction (which returns the ... efficiently in hardware? 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 - Debugging bootloader with gdb in qemu

There seems to be a problem with the Freedos bootloader. (It appears that the bootcode can't find the kernel in ... you want to try yourself.] 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 - The prefetch instruction

It appears the general logic for prefetch usage is that prefetch can be added, provided the code is busy in ... instruction should be used ? 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 constant after fixup?

For some reason, when I try to compile this bit of code, the compiler says syscall.s:72:invalid constant ( ... what caused the error though. 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 - When are GAS ELF the directives .type, .thumb, .size and .section needed?

I'm working on an assembly program for an ARM Cortex-M3 based microcontroller (Thumb 2 instruction set), using ... me, with more knowledge. 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 - Do any languages / compilers utilize the x86 ENTER instruction with a nonzero nesting level?

Those familiar with x86 assembly programming are very used to the typical function prologue / epilogue: push ebp ... ENTER: Create Stack Frame 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 create or manipulate GPU assembler?

Does any one have experience in creating/manipulating GPU machine code, possibly at run-time? I am ... related information is welcome. 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 - Performance of x86 rep instructions on modern (pipelined/superscalar) processors

I've been writing in x86 assembly lately (for fun) and was wondering whether or not rep prefixed string ... not important to the manufacturers? 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 difference between unconditional branch and unconditional jump (instructions in MIPS)?

You may look into Wikipedia or short summary for students. Everybody says that there are two instructions for the ... . But nobody tells why? 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 - MIPS: relevant use for a stack pointer ($sp) and the stack

Currently I'm studying for my computer organization midterm, and I'm trying to fully understand the stack ... some useful code examples? 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 - Homoiconic and "unrestricted" self modifying code + Is lisp really self modifying?

I will be forward in admiting that my knowledge of Lisp is extremely minimal. However I am extremely interested in ... Haha, scary thought :P]) 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 .S files?

I've seen .S files in various projects such as in the Linux Kernel, FreeBSD kernel, or in some other projects. ... we have .c files instead ? 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 meaning of align an the start of a section?

What is the meaning of align an the start of a section? For example: align 4 a: dw 0 How does it save memory access? 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 SP (stack) and LR in ARM?

I am reading definitions over and over again and I still not getting what are SP and LR in ARM? I understand PC ... not getting what SP is for. 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's the difference between a word and byte?

I've done some research. A byte is 8 bits and a word is the smallest unit that can be addressed on memory. ... but what would that make a word? 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 - Getting the error: "Instruction references undefined symbol ... main" in QTSpim

I'm trying to compute (a * c) - (b / d), and so far my assembly code is: .data A: .word 5 B: ... 0x0c000000 jal 0x0000000 [main] ;188: jal main" 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 explanation of this x86 Hello World using 32-bit int 0x80 Linux system calls from _start?

section .text global _start ;must be declared for using gcc _start: ;tell linker entry point mov edx, len ; ... basic working of this 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 - x86_64 Cannot add 64 bit value to rax, "operand mismatch on 'add'"

I am trying to assemble some 64-bit code and the assembling fails on the line: addq $0xffffff7fc0005000, %rax with ... target of `x86_64-elf'. 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 characterize a workload by obtaining the instruction type breakdown?

I want to obtain the percentage of memory read-write instructions in a test program, preferably dynamically. Apart from ... if it supports WSL. 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 - db usage in nasm, try to store and print string

I was trying to store a few strings in my assembly, and use WriteString to print out on the screen. However, I ... run on ubuntu 12.04 32bit. 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 difference between the encodings for the call instruction in x86 asm?

For reference: an HTML extract of Intel's documentation for the call instruction. I am aware that section 3.1.1.3 ... ? FF 15 90 98 76 70 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 access the carry flag while adding two 64 bit numbers using asm in C

Yeah thanks that works. @PeterCordes. Also __int128 works. But one more thing as you said using the intrinsics of ... it by modifying this 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 - Why is default operand size 32 bits in 64 mode?

I am reading Intel doc, vol. 1 and There is a chapter of 3.6.1 Operand Size and Address Size in 64 ... ). Do I understand it correctly? 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 increment a letter in string in lc3?

I am writing an LC3 program that increments each letter of a three-letter word stored in memory following the program. ... out how to do 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 - ASM language pointer to an array

my project I'm supposed to create a program that fills an array with an x number of fibbonacci numbers. In ... ExitProcess,0 main endp end main See Question&Answers more detail:os...

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

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