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c - X86-64 NASM 调用 extern c 函数

转载 作者:行者123 更新时间:2023-11-30 18:27:33 25 4
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我对汇编很陌生,但了解一点 C。我正在尝试像这样的外部函数调用

extern _printf
str db "Hello", 0
push str
call _printf

但除了scanfprintf之外,找不到任何使用外部函数的教程。如何调用 strcmp

最佳答案

这是我的回答。但它特定于 x86-64。请注意,将参数插入函数时,通常将前 6 个放入寄存器 rdirsirdxrcxr8r9。其余的被插入堆栈。此规范称为 System V ABI(请注意,Windows 使用称为“Microsoft x64 调用约定”的不同约定)。

    segment .data     ; or use .rodata for read-only data.
str1 db "Hello", 0x0
str2 db "Hellx", 0x0
fmt db "Comparison = %d", 0xa, 0x0

segment .text
global main
extern strcmp, printf
default rel ; RIP-relative addressing for [name] is what you want.

main:
; Create a stack-frame, re-aligning the stack to 16-byte alignment before calls
push rbp
mov rbp, rsp

; Prepare the arguments for strcmp.
lea rdi, [str1]
lea rsi, [str2]

; Call strcmp, return value is in rax.
call strcmp

; Prepare arguments for printf.
lea rdi, [fmt]
mov esi, eax ; int return value from strcmp -> 2nd arg for printf
xor eax, eax ; Indicate no floating point args to printf.

; Call printf
call printf

; Return 0 (EXIT_SUCCESS), and destroy the stack frame.
xor eax, eax
leave ; or just pop rbp because RSP is still pointing at the saved RBP
ret

关于c - X86-64 NASM 调用 extern c 函数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54657687/

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