nasm

问题 I'm creating custom mbr, something like mbr-lovenote and i can't create code that will copy 9th sector - (there is located original mbr) to 1st sector, i already tried take some code from mbr-lovenote and modify it, but i find out that code only load sector in memory and jump to it, but i have to copy it. I write my code, the code will be loaded from fist sector on PhysicalDrive0 , but i don't know why it doesn't works. ;---create buffer buffer db 512 ;---read sector - 9th mov ax, buffer ;ES:

问题 I have the following code in NASM: ;sleep.asm [SECTION .text] global _start _start: xor eax,eax mov ebx, 0x00016630 ;address of Sleep mov ax, 5000 ;pause for 5000ms push eax call ebx ;Sleep(ms); Where 0x00016630 is the address of Sleep function (taken from dumpbin from kernel32.dll). I would like to make executable file to run in Win 10. What I did was: nasm -f win32 sleep.asm and have sleep.obj as result. So now I have to link it. I choose link.exe Unfortunately with the following command

问题 The program needs to take in a simple string from the user and display it back. I have gotten the program to take input from the user but I can't seem to store it. Here is what I have so far: BITS 32 global _main section .data prompt db "Enter a string: ", 13, 10, '$' input resd 1 ; something I can using to store the users input. name db "Name: ******", 13, 10,'$' StudentID db "********", 13, 10, '$' InBoxID db "*************", 13, 10, '$' Assignment db "************", 13, 10, '$' version db

问题 I'm very new to assembly, before only C C++ I was trying to create a simple application that print all the prime number from 2 to given input When I run, it crashes, and that's normal. Looking at OllyDbg, the guilty piece is this: move eax, ebx idiv ecx ; !!! here It is strange because ecx is not 0 Values are EAX = 0000 0004, ECX = 0000 0002, and it says me that's an Integer_Overflow (exception C000 0095) How it's possible to have an overflow during a division? Both operands are 32bit

问题 section .data var dd 10 section .text add [var] , eax for above code nasm gives error operation size not specified, but if we reverse it add eax, [var] it doesn't gives error. why error for only first and not for second type ? 回答1: You need specify size like this: add dword [var],eax 回答2: Because the first operand is the destination operand and needs to be a register so instead just move it back : add eax, [var] mov [var], eax 来源： https://stackoverflow.com/questions/39426316/adding-value-in

问题 I know that you can create a string in nasm by writing this: mystring db 'Hello World' But if I want to move a single character, let's say e, the second character in the string to the al register. How can I do that? Should I write mov al, mystring+1 or something? And how do I make an int variable? Can I write: myint db 4 回答1: 'mystring + 1' is the address of the second byte of the string. mov al, mystring + 1 stores (the least significant byte of) that address in al. To indicate that you don

问题 Recently started learning Assembly so I'm relatively new to this. We use Linux back at school but I wanted to try coding on my PC. I'm using nasm on a Win8.1 64-bit system. Here's the code: section .text global _WinMain@16 _WinMain@16: mov edx, len mov ecx, msg mov ebx, 1 mov eax, 4 ret 16 mov eax, 1 ret 16 section .data msg db 'Hello, world!', 0xA len equ $ - msg nasm seems to be running since it responds to the commands, but it doesn't execute the program: How can I run the program? Is

问题 I am writing a bootloader in assembly (NASM instruction set), but for some reason it doesn't show any letter. [BITS 16] [ORG 0x7C00] JMP $ MOV AL, 0x65 MOV AH, 0x0E MOV BL, 0x07 MOV BH, 0x00 INT 0x10 TIMES 510 - ($ - $$) db 0 DW 0xAA55 All I see is the _ cursor. 回答1: JMP $ Jumps to itself. Removing it will let the other code run 来源： https://stackoverflow.com/questions/38085205/print-ascii-character-on-screen

问题 I need to determine the number of negative and positive numbers in an array in assembler. It seems that the assembler doesn't recognizes them as negative numbers. How can I solve this problem? I define the array this way: word_array db 3, -2, 11, -1, -2, -7, -5, -20 I have this function that counts the positive ones: count_positives: mov dx, word [word_array + 2*ecx - 2] cmp edx, 0 JL skip inc ebx skip: loopnz count_positives 回答1: Count either negative or non-negative, and subtract that from

问题 Using GDB to debug assembly programs produced by NASM/MinGW doesn't stop at breakpoints? Assembling and linking the program below produce unexpected results when debugging using GDB. nasm -g -f win32 insertion_sort_static.asm ld insertion_sort_static.obj -o test Now, when I run GDB and set a breakpoint at _exit , the program doesn't break at the specified point. Instead the program terminate. gdb test (gdb) break exit Breakpoint 1 at 0x401034 (gdb) run Starting program: C:\Users\nze\Desktop