用户输入和输出在我的汇编代码中不起作用 [英] User input and output doesn't work in my assembly code
问题描述
下面的程序编译没有错误，但运行时它不提示任何输入，也不打印任何内容.有什么问题，我该如何解决?
我使用这些命令来组装和链接:
/usr/local/bin/nasm -f macho32 $1ld -macosx_version_min 10.9.0 -lSystem -o 运行 $filename.o -e _start -lc我的代码是:
section .data;换行字符串新行:db 0xa, 0xd长度:等于 $-NEWLINE.bss 节输入:resd 1节.text全局_start_开始:;读取字符移动 eax, 0x3移动 ebx, 0x1mov ecx, INPT移动 edx, 0x1整数 80 小时;打印字符移动 eax, 0x4移动 ebx, 0x1mov ecx, INPT移动 edx, 0x1整数 80 小时;输出后打印新行移动 eax, 0x4移动 ebx, 0x1mov ecx, NEWLINEmov edx, 长度整数 0x80;终止移动 eax, 0x1异或 ebx, ebx整数 0x80您的代码中有迹象表明您在为 OS/X(BSD) 生成代码时可能一直在使用 Linux 教程.Linux 和 OS/X 具有不同的 SYSCALL 调用约定.在 OS/X 32 位程序中，int 0x80 需要在堆栈上传递参数(EAX 中的系统调用除外).
在 OS/X 上通过 int 0x80 使用 32 位 SYSCALL 需要注意的重要事项是:
- 在堆栈上传递的参数，从右到左推送
- 在压入所有参数后，您必须在堆栈上分配额外的 4 个字节(DWORD)
- eax 寄存器中的系统调用号
- 通过中断 0x80 调用
在为 int 0x80 以相反的顺序将参数压入堆栈后，您必须在堆栈上分配额外的 4 个字节(DWORD).堆栈上该内存位置的值无关紧要.此要求是来自 旧的 UNIX 约定.
SYSCALL 号码及其参数的列表可以在 APPLE 头文件.您将需要这些SYSCALL:
<块引用>1 AUE_EXIT ALL { void exit(int rval);}3 AUE_NULL ALL { user_ssize_t read(int fd, user_addr_t cbuf, user_size_t nbyte);}4 AUE_NULL ALL { user_ssize_t write(int fd, user_addr_t cbuf, user_size_t nbyte);}我评论了一些示例代码，这些示例代码的功能与您可能试图实现的功能相似:
section .data;换行字符串新行:db 0xa, 0xd长度:等于 $-NEWLINE.bss 节输入:resd 1全局_start节.text_开始:和 esp, -16 ;确保堆栈在程序开始时对齐 16 字节;在这个例子中没有必要，因为我们不调用;符合 OS/X 32 位 ABI 的外部函数推双字 1 ;读取 1 个字符推双字输入；输入缓冲器推双字 0 ;标准输入 = FD 0移动 eax, 3 ;系统调用 sys_read子 esp, 4 ;int 0x80 需要堆栈上的额外 4 个字节整数 0x80添加 esp, 16 ;恢复堆栈推双字 1 ;打印 1 个字符推双字输入；输出缓冲区 = 我们读入字符的缓冲区推双字 1 ;标准输出 = FD 1移动 eax, 4 ;系统调用 sys_write子 esp, 4 ;int 0x80 需要堆栈上的额外 4 个字节整数 0x80添加 esp, 16 ;恢复堆栈推双字长度;要写入的字符数推送双字新行；在 NEWLINE 字符串中写入数据推双字 1 ;标准输出 = FD 1移动 eax, 4 ;系统调用 sys_write子 esp, 4 ;int 0x80 需要堆栈上的额外 4 个字节整数 0x80添加 esp, 16 ;恢复堆栈推双字 0 ;程序返回值 = 0移动 eax, 1 ;系统调用 sys_exit子 esp, 4 ;int 0x80 需要堆栈上的额外 4 个字节整数 0x80 和 esp, -16 仅在您需要将堆栈对齐到 16 字节边界作为未来堆栈操作的基线时才需要.如果您打算调用符合 OS/X 32 位 ABI 堆栈预计在函数 CALL 之前以 16 字节对齐.对于通过 int 0x80 的系统调用，这种对齐不是必需的.
您应该能够组装并链接它:
nasm -f macho32 test.asm -o test.old -macosx_version_min 10.9.0 -o test test.o -e _start -lSystem并运行它:
./testThe following program compiles without errors, but when run it doesn't prompt for any input and nothing prints. What's the problem, and how can I fix it?
I use these commands to assemble and link:
/usr/local/bin/nasm -f macho32 $1
ld -macosx_version_min 10.9.0 -lSystem -o run $filename.o -e _start -lc
My code is:
section .data
;New line string
NEWLINE: db 0xa, 0xd
LENGTH: equ $-NEWLINE
section .bss
INPT: resd 1
section .text
global _start
_start:
;Read character
mov eax, 0x3
mov ebx, 0x1
mov ecx, INPT
mov edx, 0x1
int 80h
;print character
mov eax, 0x4
mov ebx, 0x1
mov ecx, INPT
mov edx, 0x1
int 80h
;Print new line after the output
mov eax, 0x4
mov ebx, 0x1
mov ecx, NEWLINE
mov edx, LENGTH
int 0x80
;Terminate
mov eax, 0x1
xor ebx, ebx
int 0x80
There are signs in your code that you may have been using a Linux tutorial when producing code for OS/X(BSD). Linux and OS/X have differing SYSCALL calling conventions. In OS/X 32-bit programs int 0x80 requires parameters (except the syscall in EAX) to be passed on a stack.
The important things to be aware of with 32-bit SYSCALLs via int 0x80 on OS/X are:
- arguments passed on the stack, pushed right-to-left
- you must allocate an additional 4 bytes (a DWORD) on the stack after you push all the arguments
- syscall number in the eax register
- call by interrupt 0x80
After pushing arguments on the stack in reverse order for int 0x80 you must allocate an additional 4 bytes (a DWORD) on the stack. The value in that memory location on the stack doesn't matter. This requirement is an artifact from an old UNIX convention.
A list of the SYSCALL numbers and their parameters can be found in the APPLE header files. You'll need these SYSCALLs:
1 AUE_EXIT ALL { void exit(int rval); } 3 AUE_NULL ALL { user_ssize_t read(int fd, user_addr_t cbuf, user_size_t nbyte); } 4 AUE_NULL ALL { user_ssize_t write(int fd, user_addr_t cbuf, user_size_t nbyte); }
I have commented some example code that would be similar in functionality to what you may have been attempting to achieve:
section .data
;New line string
NEWLINE: db 0xa, 0xd
LENGTH: equ $-NEWLINE
section .bss
INPT: resd 1
global _start
section .text
_start:
and esp, -16 ; Make sure stack is 16 byte aligned at program start
; not necessary in this example since we don't call
; external functions that conform to the OS/X 32-bit ABI
push dword 1 ; Read 1 character
push dword INPT ; Input buffer
push dword 0 ; Standard input = FD 0
mov eax, 3 ; syscall sys_read
sub esp, 4 ; Extra 4 bytes on stack needed by int 0x80
int 0x80
add esp, 16 ; Restore stack
push dword 1 ; Print 1 character
push dword INPT ; Output buffer = buffer we read characters into
push dword 1 ; Standard output = FD 1
mov eax, 4 ; syscall sys_write
sub esp, 4 ; Extra 4 bytes on stack needed by int 0x80
int 0x80
add esp, 16 ; Restore stack
push dword LENGTH ; Number of characters to write
push dword NEWLINE ; Write the data in the NEWLINE string
push dword 1 ; Standard output = FD 1
mov eax, 4 ; syscall sys_write
sub esp, 4 ; Extra 4 bytes on stack needed by int 0x80
int 0x80
add esp, 16 ; Restore stack
push dword 0 ; Return value from program = 0
mov eax, 1 ; syscall sys_exit
sub esp, 4 ; Extra 4 bytes on stack needed by int 0x80
int 0x80
The and esp, -16 is only necessary if you need to align the stack to a 16-byte boundary as a baseline for future stack operations. If you intend to call external functions that conform to the OS/X 32-bit ABI the stack is expected to be 16-byte aligned immediately preceding a function CALL. This alignment is not necessary for system calls via int 0x80.
You should be able to assemble and link it with:
nasm -f macho32 test.asm -o test.o
ld -macosx_version_min 10.9.0 -o test test.o -e _start -lSystem
And run it with:
./test
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