nasm

问题 This question already has answers here : Issue storing a byte into a register x86-64 assembly (1 answer) Why can't I move directly a byte to a 64 bit register? (2 answers) Closed 2 years ago . Here is what i want to do: add rsi, word [rsi+16] I want to read the unsigned short value which is at rsi+16 adress. And i want to add this value to rsi. Here is the error i get in nasm: s2.asm:62: error: mismatch in operand sizes This is strange. Why nasm and my cpu are not able to add 16 bits to 64

问题 This question already has answers here : Issue storing a byte into a register x86-64 assembly (1 answer) Why can't I move directly a byte to a 64 bit register? (2 answers) Closed 2 years ago . Here is what i want to do: add rsi, word [rsi+16] I want to read the unsigned short value which is at rsi+16 adress. And i want to add this value to rsi. Here is the error i get in nasm: s2.asm:62: error: mismatch in operand sizes This is strange. Why nasm and my cpu are not able to add 16 bits to 64

问题 I want to call printf function from assembly language in linux. i want to know the method for for 64 bit and 32 bit assembly language programs. 1) please tell me for two cases if i want to pass a 32 bit arguement and 64 bit arguement in printf with a string. how should i do it? 2) for x86 32 bit architecture if i want to do the same thing as in point 1. please tell me the code. and let me know do i need to adjust the stack for both cases and do i just need to pass the arguements in registers?

问题 I'm working on a very basic shell where the only command currently is 'help'. If you type something wrong, you're informed that the command isnt recognized. Somewhere in the segment and stack setup I have a bug that causes the shell to spit out some nonsense after I type anything and then freeze completely. Error I get in terminal qemu: fatal: Trying to execute code outside RAM or ROM at 0xff0fe990 EAX=0000ffe0 EBX=0000ffff ECX=ff00e990 EDX=0000e000 ESI=000001a4 EDI=0000011e EBP=00000019 ESP

问题 I'm working on a very basic shell where the only command currently is 'help'. If you type something wrong, you're informed that the command isnt recognized. Somewhere in the segment and stack setup I have a bug that causes the shell to spit out some nonsense after I type anything and then freeze completely. Error I get in terminal qemu: fatal: Trying to execute code outside RAM or ROM at 0xff0fe990 EAX=0000ffe0 EBX=0000ffff ECX=ff00e990 EDX=0000e000 ESI=000001a4 EDI=0000011e EBP=00000019 ESP

问题 I am trying to execute the following with execve : /bin//nc -lnke /bin/bash -p 4444 When reading the man page for execve , I see the following requirements: int execve(const char *filename, char *const argv[], char *const envp[]); The issue I am running into is pushing arguments to argv ; I do not understand how you push an array (in assembly) for this to work properly. The assembly that I am currently using is below: global _start _start: xor eax, eax ; command push eax push 0x636e2f2f push

问题 I am trying to execute the following with execve : /bin//nc -lnke /bin/bash -p 4444 When reading the man page for execve , I see the following requirements: int execve(const char *filename, char *const argv[], char *const envp[]); The issue I am running into is pushing arguments to argv ; I do not understand how you push an array (in assembly) for this to work properly. The assembly that I am currently using is below: global _start _start: xor eax, eax ; command push eax push 0x636e2f2f push

问题 The expression is: times 512-($-$$) db 0 I know what the dollar sign means but I don't know what it means when it's double. What does the double dollar sign mean? 回答1: When all else fails, Read The Fine Manual (section 3.5 "Expressions"): NASM supports two special tokens in expressions, allowing calculations to involve the current assembly position: the $ and $$ tokens. $ evaluates to the assembly position at the beginning of the line containing the expression; so you can code an infinite

问题 How come this program is not printing out to the screen, am I missing something on the INT 80 command? section .bss section .data hello: db "Hello World",0xa ;10 is EOL section .text global _start _start: mov ecx, 0; ; int i = 0; loop: mov dl, byte [hello + ecx] ; while(data[i] != EOF) { cmp dl, 0xa ; je exit ; mov ebx, ecx ; store conetents of i (ecx) ; Print single character mov eax, 4 ; set sys_write syscall mov ecx, byte [hello + ebx] ; ... mov edx, 1 ; move one byte at a time int 0x80 ;

问题 So recently we learned about floating point operations and got a few questions as a homework. One of those is: "Write down the calling convention of single precision floats!". So i know about the xmm registers and know that on double precision the first input goes into xmm0 and so on. I looked up the topic on Google but couldn't find the answer. Would be nice if someone could help me on this question. 回答1: Every calling convention I'm familiar with handles single float the same as it does