assembly

问题 I am currently working on an assembly program, but I need to make the program wait every once in a while. So, I have been using int 15h/ah = 86h, but for some reason DosBox is giving me a hard time, and the program either gets confused with pixels (wierd colors) or in the worse case; crash. Can someone please help me? 回答1: I had this issue as well. Based on the answer at Problems with BIOS delay function (INT 15h / AH = 86h), I was able to get it working by making sure to set AL to zero

问题 So we have like this safes challenge in assembly, you need to create safes and keys that will break them and end the infinite loop. Here's an example for a safe: loopy: mov ax, [1900] cmp ax,1234 jne loopy and a key: loopy2: mov ax, 1234 mov [1900],ax jmp loopy2 So I have a safe and a key, and I don't understand why it doesn't work: here's my safe: org 100h mySafe: mov dx,5 mov ax, [5768h] mov bx,7 mov word [180h],2 mul word [180h] mov [180h],bx push ax dec bx mov cx,dx mov ax,dx loopy1: add

问题 I'm trying to change this line 0041DE91 | 8B 46 64 | mov eax,dword ptr ds:[esi+64] 0041DE94 | 83 C4 0C | add esp,C 0041DE97 | 83 F8 01 | cmp eax,1 to 0041DE91 | mov eax, 10 But the instruction which was 3 bytes occupies 5 bytes and spills into the two addresses below it: 0041DE91 | B8 0A 00 00 00 | mov eax,10 0041DE96 | 0C 83 | or al,83 0041DE98 | F8 | clc Is it possible to do this in a debugger to a pre-compiled program? 回答1: In 32-bit code (where there's no red-zone to clobber) you can move

问题 I have main function in C that runs code in assembly. I just want to make simple sum: main.c #include <stdio.h> extern int addByAssembly(int first_number, int second_number); int main (int argc, char **argv) { int sum=0; sum = addByAssembly(5,4); printf ("%d\n",sum); return 0; } addByAssembly.s .data SYSREAD = 0 SYSWRITE = 1 SYSEXIT = 60 STDOUT = 1 STDIN = 0 EXIT_SUCCESS = 0 .text #.global main #main: #call write #movq $SYSEXIT, %rax #movq $EXIT_SUCCESS, %rdi #syscall #******** .globl

问题 i have a problem. I making simple OS kernel with this tutorial: http://wiki.osdev.org/Bare_Bones#Linking_the_Kernel but,if i want to link files boot.o and kernel.o, gcc compiler returns this error: boot.o: In function `start': boot.asm:(.text+0x6): undefined reference to `kernel_main' collect2.exe: error: ld returned 1 exit status. sources of files: boot.asm ; Declare constants used for creating a multiboot header. MBALIGN equ 1<<0 ; align loaded modules on page boundaries MEMINFO equ 1<<1 ;

问题 i have a problem. I making simple OS kernel with this tutorial: http://wiki.osdev.org/Bare_Bones#Linking_the_Kernel but,if i want to link files boot.o and kernel.o, gcc compiler returns this error: boot.o: In function `start': boot.asm:(.text+0x6): undefined reference to `kernel_main' collect2.exe: error: ld returned 1 exit status. sources of files: boot.asm ; Declare constants used for creating a multiboot header. MBALIGN equ 1<<0 ; align loaded modules on page boundaries MEMINFO equ 1<<1 ;

问题 I'm trying to understand the workings of the D flag in the code segment descriptor when used in the x86-64 code. It's set in the D/B bit 22 of the code segment descriptor as shown on this diagram: The Intel documentation (from section 3.4.5 Segment Descriptors) states the following: D/B (default operation size/default stack pointer size and/or upper bound) flag Performs different functions depending on whether the segment descriptor is an executable code segment, an expand-down data segment,

问题 i have been following a YouTube tutorial on how to make an operating system, as well as experimenting with writing assembly code my self. I use NASM to turn my assembly files into executable binaries, and use qemu to run them. -=-=-=-=-= boot.asm [org 0x7c00] mov [BOOT_DISK], dl mov bp, 0x7c00 mov sp, bp mov bx, tst call pst call readisk %include 'print.asm' %include 'diskread.asm' jmp $ times 510-($-$$) db 0 db 0x55, 0xaa -=-=-=-=-= diskread.asm PROGRAM_SPAVE equ 0x7e00 readisk: mov bx,

问题 i have been following a YouTube tutorial on how to make an operating system, as well as experimenting with writing assembly code my self. I use NASM to turn my assembly files into executable binaries, and use qemu to run them. -=-=-=-=-= boot.asm [org 0x7c00] mov [BOOT_DISK], dl mov bp, 0x7c00 mov sp, bp mov bx, tst call pst call readisk %include 'print.asm' %include 'diskread.asm' jmp $ times 510-($-$$) db 0 db 0x55, 0xaa -=-=-=-=-= diskread.asm PROGRAM_SPAVE equ 0x7e00 readisk: mov bx,

问题 i understand what the other calls are doing but when i get line 36, i don't get what's happening? my 3 parameters are rsi = 5, rdx = 6, rcx = 7 On line 26 my %rax = 25 then on line 30 my rsi changes from 5 to 37 can you explain why this happens? and what is 0x40272e 0x0000000000401212 <+0>: sub $0x8,%rsp # subtract 8 from rsp 0x0000000000401216 <+4>: lea -0x1(%rdx),%rax # rax = -1 + rdx 0x000000000040121a <+8>: cmp $0xf,%rax # rax ?? 0xf '-1' 'SI' 0x000000000040121e <+12>: ja 0x40124f <phase