nasm

问题 when $ nasm -f elf64 -o thisfile.o thisfile.asm it says the line of jmp and popfd "instruction not supported in 64-bit mode" this is the whole code: SELECTOR_KERNEL_CS equ 8 extern cstart extern gdt_ptr [SECTION .bss] StackSpace resb 2 * 1024 StackTop: [section .text] global _start _start: mov esp, StackTop sgdt [gdt_ptr] call cstart lgdt [gdt_ptr] ;lidt [idt_ptr] jmp SELECTOR_KERNEL_CS:csinit csinit: push 0 popfd ; Pop top of stack into EFLAGS hlt 回答1: Since you're in 64-bit mode, you'll

问题 How do I handle errors in NASM assembly? For example I have this code to read user Input: mov eax,3 mov ebx,0 mov ecx,Buffer mov edx,BUFFERLENGTH int 80H If for some reason this system call cannot be executed, I'd like to have the program jump to a label that prints "An error has occured" or something like that. How do I do that? Also, is it possible to get the name of the exception or error code? Thanks 回答1: After the kernel call, EAX is going to have two possibilites; Number of characters

问题 I want to break at a local label in NASM assembly code using GDB. Issuing the following command yields the output: (gdb) break *start.label1 + 217 Attempt to extract a component of a value that is not a structure. Here my code goes something like this: global _start _start: ... .label1: ... How can I break at local .label1 ? 回答1: Disassemble the function where your local label is called, select the address and add a break as you normally would with the address, not the label name. You can

问题 How to tell NASM (or LD) to process labels in a way that will make the segment position-independent? The segment is going to be moved from one file to another and I want it to work properly on any position in any file. Here is the code that illustrates my problem: section .text ... message: db 'hello world!',0x00 ... mov rax,SYSCALL_WRITE mov rdi,STDOUT mov rsi,message mov rdx,13 syscall In the orginal executable it prints "Hello world!", but when the segment is moved to another elf, it

问题 I'm going through the Intel processor documentation and writing some basic assembly code at the same time. I have both nasm and as (GAS) on my server and I understand the basic differences of both assemblers. In the long run: Focusing on which of these syntax is a better idea? What are the advantages and disadvantages of these syntax? Which one is more widely used and understood? I would also appreciate any preferences you could share with me. 回答1: Focusing on which of these syntax is a

问题 I was trying to make a basic printf example in x86-64 assembly code for OSX, here's my first version: section .data msg db 'hello', 0Ah section .text extern _printf global _main _main: sub rsp, 8 mov rdi, msg mov rax, 0 call _printf add rsp, 8 ret So this code is moving the absolute address of msg into rdi for the first argument to _printf , and gcc then complains about the lack of position-independent code. The binary still works though: → nasm -f macho64 new.asm && gcc -m64 -o new new.o &&

问题 Hi I'm trying to write some assembly code that uses printf to print a given string. I am declaring my strings before use in the .data section and a test example looks as follows: extern printf extern fflush LINUX equ 80H ; interupt number for entering Linux kernel EXIT equ 60 ; Linux system call 1 i.e. exit () section .data outputstringfmt: db "%s", 0 sentence0: db "Hello\nWorld\n", 0 segment .text global main main: mov r8, sentence0 push r8 call print_sentence add rsp, 8 call os_return print

问题 I've already done a part of my OS in Assembly, but now I want to build a own bootloader for it too instead of using GRUB. When I was developing my test OS in Assembly I remember that I boot it like this: org 0x7c00 bits 16 ; OS Kernel Here times 510 - ($-$$) db 0 dw 0xAA55 This I've already know. Now I want to use this and execute the "real" OS that will be a *.bin file written to the 2nd sector of the floppy. Then I want to know somethings How can I do a bootloader in Assembly to execute

问题 I have a 32 Bit number and want to count know how many bits are 1. I'm thinking of this pseudocode: mov eax, [number] while(eax != 0) { div eax, 2 if(edx == 1) { ecx++; } shr eax, 1 } Is there a more efficient way? I'm using NASM on a x86 processor. (I'm just beginning with assembler, so please do not tell me to use code from extern libraries, because I do not even know how to include them ;) ) (I just found How to count the number of set bits in a 32-bit integer? which also contains my

问题 IDM says the memory op uses SS segment if EBP is used as base register. As a result, [ebp + esi] and [esi + ebp] references SS and DS segments, respectively. See NASM's doc: 3.3 Effective Address. In the above same section, NASM mentioned how to generate shorter machine code by replacing [eax*2] with [eax+eax] . However, NASM also generates [ebp + ebp] for [ebp*2] (i.e. no base register). I suspect [ebp+ebp] references SS segment, and [ebp*2] references DS segment. I asked NASM this question.