[英]Unable to print back entered text in x86 assembly
I have an Assembly program here which is supposed to print a string, allow the user the enter some text, print that exact same text again and then wait for a keypress to terminate the program, using only Win32 native functions. 我在这里有一个汇编程序,该程序应该打印一个字符串,允许用户输入一些文本,再次打印完全相同的文本,然后等待仅使用Win32本机函数的按键终止程序。
The problem is that everything seems to work, except printing the user entered string. 问题是,除了打印用户输入的字符串外,其他所有内容似乎都可以正常工作。 It just prints a blank new line. 它只是打印一个空白的新行。 Here's the code: 这是代码:
global _main
extern _GetStdHandle@4
extern _WriteFile@20
extern _ReadFile@20
extern _ExitProcess@4
section .text
_main:
mov ebp, esp
sub esp, 12
push -11
call _GetStdHandle@4
mov ebx, eax
push 0
push dword [ebp - 12]
lea ecx, [_msg_end - _msg]
push ecx
lea edx, [_msg]
push edx
push ebx
call _WriteFile@20
push -10
call _GetStdHandle@4
mov ebx, eax
push 0
lea ecx, [ebp - 8]
push ecx
push 20
lea edx, [ebp - 4]
push edx
push ebx
call _ReadFile@20
push -11
call _GetStdHandle@4
mov ebx, eax
push 0
push dword [ebp - 12]
lea ecx, [ebp - 8]
push ecx
lea edx, [ebp - 4]
push edx
push ebx
call _WriteFile@20
push -10
call _GetStdHandle@4
mov ebx, eax
push 0
lea ecx, [ebp - 8]
push ecx
push 1
lea edx, [ebp - 4]
push edx
push ebx
call _ReadFile@20
push 0
call _ExitProcess@4
_msg:
db "Hello, world!", 10
_msg_end:
EDIT - Here's the working code: 编辑 -这是工作代码:
global _main
extern _GetStdHandle@4
extern _ReadFile@20
extern _WriteFile@20
extern _ExitProcess@4
section .bss
_input_buf: resb 20
section .text
_main:
mov ebp, esp
sub esp, 8
push -10
call _GetStdHandle@4
mov ebx, eax
push 0
lea ecx, [ebp - 4]
push ecx
push 20
lea eax, [_input_buf]
push eax
push ebx
call _ReadFile@20
push -11
call _GetStdHandle@4
mov ebx, eax
push 0
lea ecx, [ebp - 8]
push ecx
mov edx, [ebp - 4]
push edx
lea eax, [_input_buf]
push eax
push ebx
call _WriteFile@20
push 0
call _ExitProcess@4
Two things: 两件事情:
You're only allocating 4 bytes - making space for two characters - as you are reading input into the last allocated dword on the stack: 在将输入读入堆栈中最后分配的dword时,您仅分配4个字节(为两个字符腾出空间):
ebp-12 [undefined]
ebp-8: [input length]
ebp-4: [input buffer]
ebp:
You're giving the length of the input string as a pointer instead of dereferencing it, making it try to output a huge number of bytes, and failing: 您将输入字符串的长度作为指针而不是取消引用,使它尝试输出大量字节,并且失败:
lea ecx, [ebp - 8]
push ecx <- address, not value
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