Recent questions tagged Assembly

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assembly - Does referencing constants without a dollar sign have a distinct meaning?

I wrote: mov 60, %rax GNU as accepted it, although I should have written mov $60, %rax Is there any difference between two such calls? 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 - "C variable type sizes are machine dependent." Is it really true? signed & unsigned numbers ;

I've been told that C types are machine dependent. Today I wanted to verify it. void legacyTypes() { /* character ... 64-bit & 32-bit machine? 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 - Interrupting instruction in the middle of execution

Suppose that CPU is running an assembly instruction, say, FOO that will be executed in several clocks ( ... types of interrupts' prioritization? 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 do 8-bit and 16-bit processors access more RAM with two registers?

Something that has always confused me is how 8-bit computers access more than 256 bytes of RAM. I know that it must use ... : mov a, [x] ??? 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 - Displaying characters with DOS or BIOS

Looking through Ralph Brown's interrupt list, I discovered that there are many different ways to output text ... I choose between 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 - Does using mix of pxor and xorps affect performance?

I've come across a fast CRC computation using PCLMULQDQ implementation. I see, that guys mix pxor and xorps ... coding style, for fun? 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 .word and .equ in MIPS?

I think both do about the same: Variable declaration and initialization. Can you please elaborate? 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 - 8086 random number generator (not just using the system time)?

I am using assembly 8086emu and I need a numbers generator for 8 numbers. I tried to use this piece of ... Math.random() function in emu8086. 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 - dollar-terminated strings

In my assembly language class, our first assignment was to write a program to print out a simple dollar-terminated ... it using a google search. 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 execute a call instruction with a 64-bit absolute address?

I am trying to call a function - that should have an absolute address when compiled and linked - from machine ... ignored when MAP_FIXED is set. 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 - OsDev syscall/sysret and sysenter/sysexit instructions enabling

I am building an 32 bit OS in assembly. I have setup the IDT and I am handling program interruptus ... sysenter instructions! (No duplication) See Question&Answers more detail:os...

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

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813 views

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assembly - Creating a simple multiboot kernel loaded with grub2

I'm trying to follow the instructions here to build a simple OS kernel: http://mikeos.sourceforge.net/write-your- ... -felf32 seems to work... 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 move 128-bit immediates to XMM registers

There already is a question on this, but it was closed as "ambiguous" so I'm opening a new one - I've ... a 128-bit immediate (constant) 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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915 views

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assembly - Is it possible to use 32 bits registers/instructions in real mode?

I'm confused about a simple assembly problem when studying some simple os source code. In this website: http ... /instructions in real mode? 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 - Use ld on 64-bit platform to generate 32-bit executable

I wrote an assembly that is assemble with: $as --32 -o hello.o hello.s Then I tried to generate an executable ... from my 32-bit shared object? See Question&Answers more detail:os...

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

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851 views

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assembly - In what situation would the AVX2 gather instructions be faster than individually loading the data?

I have been investigating the use of the new gather instructions of the AVX2 instruction set. Specifically, I decided ... wants to try this out. 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 - Greater than, less than equal, greater than equal in MIPS

Given two registers $s0, $s1, how can I convert the following pseudocode into MIPS assembly language using only the slt ( ... ) { go to label3 } See Question&Answers more detail:os...

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

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999 views

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assembly - iOS ARM64 Syscalls

I am learning more about shellcode and making syscalls in arm64 on iOS devices. The device I am testing on is ... why this code was emitted. See Question&Answers more detail:os...

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

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1.0k views

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assembly - How to interpret x86 opcode map?

In looking at an x86 opcode map such as this: http://www.mlsite.net/8086/#tbl_map1 It defines mappings, for ... that) would be super helpful. See Question&Answers more detail:os...

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

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928 views

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assembly - Weird MIPS assembler behavior with jump (and link) instruction

So, we're studying MIPS architecture at school and we're implementing a MIPS32 architecture. I thought I'd ... places with the last instruction? See Question&Answers more detail:os...

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

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964 views

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assembly - GCC inline assembler, mixing register sizes (x86)

Does anyone know how I can get rid of the following assembler warning? Code is x86, 32 bit: int test (int ... allocation job up to the compiler. See Question&Answers more detail:os...

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

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776 views

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assembly - Get file size with stat syscall

I'm trying to get file size wit stat syscall with assembly (nasm): section .data encodeFile db "/home/user/file ... STAT.st_size] there is 0 too See Question&Answers more detail:os...

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

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855 views

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assembly - Are the data registers EAX, EBX, ECX and EDX interchangeable

I'm stepping into the world of Assembly Language Programming. I'm trying to understand everything found on: ... think that is Linux environment See Question&Answers more detail:os...

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

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819 views

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assembly - Which segment register is used by default?

I am studying computer architecture from the Intel Manual. The thing that I understand is that the instructions that we ... for mov eax, [edi]? See Question&Answers more detail:os...

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

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954 views

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assembly - An efficient way to do basic 128 bit integer calculations in C++?

Some years ago I needed a way to do some basic 128 bit integer math with Cuda: 128 bit integer on cuda?. ... and bit shifting in 128 bits? See Question&Answers more detail:os...

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

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745 views

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assembly - Why doesn't RFO after retirement break memory ordering?

I thought that I understood how L1D write miss is handled, but thinking carefully about it made me ... maintain correct memory ordering? See Question&Answers more detail:os...

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

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1.0k views

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assembly - Anyone knows what "mov edi,edi " does?

69A8AB13 int 3 69A8AB14 int 3 69A8AB15 mov edi,edi 69A8AB17 push ebp 69A8AB18 mov ebp,esp mov edi,edi doesn't make sense for me,what's it 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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1.2k views

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assembly - What does `dup (?)` mean in TASM?

I have this code here, but I'm unfamiliar with the syntax. STACK16_SIZE = 100h stack16 db STACK16_SIZE dup (?) I ... dup mean in TASM, exactly? See Question&Answers more detail:os...

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

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