linux - 带有用户输出的 NASM 代码，然后输入到参数中。 (代码错误)

Question

我在使用以下代码实现用户输出和参数时遇到问题。

一个 BASH 示例，我想在 NASM 中实现一个类似的示例函数。

read -p "Enter the group you would like to create: " newgroup
groupadd $newgroup

The reason why I am creating this code is to show a comparison of different languages, used within Linux, This is one part of my research project. So i know, this can be done in other languages e.g. Python BASH and C etc. Before anyone asks.

我相信我在正确的地方，这是下面的代码。

;---------------------------NSAM----------------------
section .data                  ; initialized data, can be var's
userg:      db "Type in the user group to add:  ",10,0  ; 1st string, 10 is used to drop down a line. 0 is used to end the line.
userg_L:    equ $-userg ; string length, automatically updates how long the string is, so you don't have to type 10 etc. every time its changed 
respns:     db "groupadded: ",10,0          ; 2nd string, 10 is used to drop down a line. 0 is used to end the line.
respns_L    equ $-respns ; 2nd string length, automatically updates how long the string is, so you don't have to type 10 etc. every time its changed 
command:         db      '/bin/groupadd', 0h    ; command to execute.
arg1:            db      userg, 0h ; Shows all users on the system.
argu:            dd      command
                 dd      arg1               ; arguments passed to the command line.
                 dd      0h                 ; struct.
enviro:          dd      0h                 ; no arguments are need for the environment variables.

;========================================================
section .bss                           ; uninitialised data, also can be var's
userg_V resb    255            ; reserves 255 bytes of data.

;========================================================

section .text               ; Asm core code. any of the sections can be in any order.
global _start:          ; Makes _start the global function

_start:                 ; Makes _start the global function
mov     eax, 0x04       ; store the system call code = 4 e.g. = kernel function (sys_write)
mov     ebx, 0x01       ; 1 is the code to where to write the Asm out to. 1= The terminal
mov     ecx, userg      ; contains the label of the string.
mov     edx, userg_L    ; this is the length of the string.
int     80h             ; calls the Linux kernel

mov     eax, 0x03       ; 3 is the code to read user input. e.g. kernel function (sys_read)
mov     ebx, 0x00       ; This is the error code memory block.
mov     ecx, userg_V        ; reserves 255 bytes of data name of string.
mov     edx, 255        ; reserves 255 bytes of data.
int     80h             ; calls the Linux kernel.

mov     eax, 0x04       ; store the system call code = 4 e.g. = kernel function (sys_write)
mov     ebx, 0x01       ; 1 is the code to where to write the Asm out to. 1= The terminal
mov     ecx, respns     ; calls the var
mov     edx, respns_L       ; calls the userg var length 
int     80h         ; calls the Linux kernel.

mov     eax, 0x04       ; store the system call code = 4 e.g. = kernel function (sys_write)
mov     ebx, 0x01       ; 1 is the code to where to write the Asm out to. 1= The terminal
mov     ecx, userg_V        ; reserves 255 bytes of data name of string.
mov     edx, 255        ; reserves 255 bytes of data.
int     80h         ; calls the Linux kernel.

mov     edx, enviro         ; Environment variables
    mov     ecx, argu           ; Arguments to pass to the command line
    mov     ebx, command        ; address to execute
    mov     eax, 11             ; SYS_EXECVE kernel opcode (11)
    int     80h
call    exit            ; Calls the exit function.


;---------------------------------ASM exit code below!-------------------------------------------
exit:
mov     eax, 0x01       ; [EAX] is 1 this is the exit code! e.g. = kernel function (sys_exit)
mov     ebx, 0x00       ; This is the error code memory block.
int     80h         ; calls the Linux kernel.

错误是:

ld -s -o myasm myasm.o
myasm.o: In function `arg1':
myasm.asm:(.data+0x3e): relocation truncated to fit: R_386_8 against `.data'

此错误已使用 dd 修复，但不会将用户组添加到系统。

下面的代码可以显示所有用户，但不会将用户输入作为参数。这是工作命令代码的示例，但没有用户输入。那么如何使用命令行代码实现用户输入。

command:         db      '/bin/cat', 0h    ; command to execute.
arg1:            db      '/etc/passwd', 0h ; Shows all users on the system.

Answer 1

这是固定版本。请注意，groupadd 可能不在 /bin 中，如果 exec 失败，您应该打印一条错误消息。

;---------------------------NASM----------------------
section .data                  ; initialized data, can be var's
userg:      db "Type in the user group to add:  ",10  ; 1st string, 10 is used to drop down a line.
userg_L:    equ $-userg ; string length, automatically updates how long the string is, so you don't have to type 10 etc. every time its changed
respns:     db "groupadded: ",10          ; 2nd string, 10 is used to drop down a line. 0 is used to end the line.
respns_L    equ $-respns ; 2nd string length, automatically updates how long the string is, so you don't have to type 10 etc. every time its changed
command:         db      '/bin/groupadd', 0h    ; command to execute.
argu:            dd      command
                 dd      userg_V               ; arguments passed to the command line.
                 dd      0h                 ; struct.
enviro:          dd      0h                 ; no arguments are need for the environment variables.

;========================================================
section .bss                           ; uninitialised data, also can be var's
userg_V resb    255            ; reserves 255 bytes of data.

;========================================================

section .text               ; Asm core code. any of the sections can be in any order.
global _start:          ; Makes _start the global function

_start:                 ; Makes _start the global function
mov     eax, 0x04       ; store the system call code = 4 e.g. = kernel function (sys_write)
mov     ebx, 0x01       ; 1 is the code to where to write the Asm out to. 1= The terminal
mov     ecx, userg      ; contains the label of the string.
mov     edx, userg_L    ; this is the length of the string.
int     80h             ; calls the Linux kernel

mov     eax, 0x03       ; 3 is the code to read user input. e.g. kernel function (sys_read)
mov     ebx, 0x00       ; This is the error code memory block.
mov     ecx, userg_V        ; reserves 255 bytes of data name of string.
mov     edx, 255        ; reserves 255 bytes of data.
int     80h             ; calls the Linux kernel.
push    eax             ; save length of input

mov     eax, 0x04       ; store the system call code = 4 e.g. = kernel function (sys_write)
mov     ebx, 0x01       ; 1 is the code to where to write the Asm out to. 1= The terminal
mov     ecx, respns     ; calls the var
mov     edx, respns_L       ; calls the userg var length
int     80h         ; calls the Linux kernel.

mov     eax, 0x04       ; store the system call code = 4 e.g. = kernel function (sys_write)
mov     ebx, 0x01       ; 1 is the code to where to write the Asm out to. 1= The terminal
mov     ecx, userg_V    ; the input text
mov     edx, [esp]      ; the length of the input text
int     80h         ; calls the Linux kernel.

pop     eax             ; get back input length
mov     [eax + userg_V - 1], byte 0 ; chop off trailing newline
mov     edx, enviro         ; Environment variables
    mov     ecx, argu           ; Arguments to pass to the command line
    mov     ebx, command        ; address to execute
    mov     eax, 11             ; SYS_EXECVE kernel opcode (11)
    int     80h

;---------------------------------ASM exit code below!-------------------------------------------
exit:
mov     eax, 0x01       ; [EAX] is 1 this is the exit code! e.g. = kernel function (sys_exit)
mov     ebx, 0x00       ; This is the error code memory block.
int     80h         ; calls the Linux kernel.