我对汇编很陌生,但懂一点 C。我正在玩外部函数调用,比如
extern _printf
str db "Hello", 0
push str
call _printf
但除了scanf
和printf
外,找不到任何使用extern 函数的教程。如何调用 strcmp
?
最佳答案
这是我的答案。虽然它特定于 x86-64。请注意,将参数推送到函数时,通常将前 6 个放入寄存器 rdi
、rsi
、rdx
、rcx
、r8
和 r9
。其余的被插入堆栈。此规范称为 System V ABI(请注意,Windows 使用不同的约定,称为“Microsoft x64 调用约定”)。
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/56240743/