Recent questions tagged assembly

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assembly - Error: Runtime exception ... store address not aligned on word boundary

I am trying to print binary digits of any integer input and store them in the array starting at the ... aligned on word boundary 0x100100ab 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 labels and dd declarations work in NASM? What's the C equivalent?

I'm trying to understand what'd be the C equivalent of some nasm idioms like these ones: %define CONSTANT1 1 ... empty, what does that mean? 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 Multiplication with 3: IMUL vs SHL + ADD

I developed a program in x86-64 assembly which needs to iterate many times through the same operation: IMUL rdx ... stick with the IMUL command? 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 - GDB - Address of breakpoint

I scripted a simply assembly code, and now i'm trying to debug it using gdb. In gdb i typed : (gdb) ... program is still not loaded in RAM) 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 can I store an unknown number of inputs in different addresses in LMC (little-man-computer)?

I want to create a code that ask the user to input a number n, then ask for n inputs and store them all in ... DAT 001 N DAT 000 NBS DAT 000 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 best way to remember the x86-64 System V arg register order?

I often forget the registers that I need to use for each argument in a syscall, and everytime I forget I ... google this question every 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 - Multiplication with constant - imul or shl-add-combination

This question is about how we multiply an integer with a constant. So let's look at a simple function ... Primarily interested in Intel Haswell. 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 - Which is faster, imm64 or m64 for x86-64?

After testing about 10 billion times, if imm64 is 0.1 nanoseconds faster than m64 for AMD64, The m64 seems to ... imm64 turned out to be faster. 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 - Assembler use of segment register

Recently I was writing assembly and the program I wrote ran without any problems under DOSBox. Now I need to port ... PC says it runs MSDOS 6 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 - Confused by [ebp-0xc] instead of [ebp-4] in Art of Exploitation example

I am reading the book Hacking: The Art of Exploitation, 2nd Edition and in the simple C program #include <stdio. ... ret End of assembler dump. 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 - CMP in x86 with parentheses and address

I have the following line in x86 Assembly language that I don't know what it does... cmp %eax, ... clarification would be much appreciated! 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 do x86 FP compares set CF like unsigned integers, instead of using signed conditions?

The following documentation is provided in the Intel Instruction Reference for the COMISD instruction: Compares the double- ... a bit strange. 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 many whole numbers in IEEE 754

I am trying to figure out how many different whole numbers exist in the ieee 754. The number I got was 1778384895 ... . Thanks a lot in advance. 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 instructions to set parity, overflow, & sign flags

We have the STC instruction to set the carry flag. Do we have similar instructions for parity, overflow, sign ... seems these don't exist! 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 - Loading an xmm from GP regs

Let's say you have values in rax and rdx you want to load into an xmm register. One way would be: movq xmm0 ... though! Is there a better way? 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 - Error: operand size mismatch for `movq'

I'm trying to compile the following assembly... movq $0x3534373536383235, 0x000000000055638f8 movq $0x55638f8, %rdi retq The first ... ~~~~~~~~~ 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 the bios know what type of BPB is present?

If I want my bootloader to boot from a usb stick, I have to include a BPB. The usb stick is running in ... bios know where to update what 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 - Local labels in GNU assembler; gdb printing backtrace as though labels are functions

Two pieces of example code; first some C++ code calling into assembly: /* test1.cc */ #include <stdio.h> ... me in the right direction, please? 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 - Sign or Zero Extension of address in 64bit mode for MOV moffs32?

Let's have an instruction MOV EAX,[0xFFFFFFFF] encoded in 64bit mode as 67A1FFFFFFFF (effective address-size is ... or B) 00000000FFFFFFFF ? 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 - Is Zero Register 'zr' in aarch64 essentially ground?

Recently started messing with AArch64 assembly and I noticed that it has an assigned register strictly for zero ... in different outcomes? See Question&Answers more detail:os...

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

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753 views

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assembly - Why does Clang do this optimization trick only from Sandy Bridge onward?

I noticed that Clang does an interesting division optimization trick for the following snippet int64_t s2(int64_t a, int64_t ... or ICC 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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881 views

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assembly - What is the "EU" in x86 architecture? (calculates effective address?)

I read somewhere that effective addresses (as in the LEA instruction) in x86 instructions are calculated by the " ... by searching the web. 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 a system executes a part of the file that is zero-padded?

I've seen in some posts/videos/files that they are zero-padded to look bigger than they are, or match "same ... 's the instruction set for 0x0? 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 use bits in a byte to set dwords in ymm register without AVX2? (Inverse of vmovmskps)

What I'm trying to achieve is based on each bit in a byte, set to all ones in each dword in a ... sandy bridge compatible so no avx2. 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 - Reason to use the carry bit and the overflow bit

I am taking an Introduction to Embedded Systems Class. As I was reading, I encountered an interesting question on ... on this issue please? 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 know if a register is a "general purpose register"?

I am trying to understand what criteria a register must have to be called a "general purpose register". I ... is a special purpose register? See Question&Answers more detail:os...

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

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792 views

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assembly - Interrupts, Instruction Pointer, and Instruction Queue in 8086

Suppose an external interrupt request is made to 8086. Processor will handle the interrupt after completing the ... advance from the 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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784 views

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assembly - weird behaviour of code (corrupted draw) when using own keyboard interrupt `int 09h` handler

I'm working on an assignment for the univesity, we need to create a simple breakout/arkanoid clone, it is going ... int 21h Thanks for reading! See Question&Answers more detail:os...

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

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