CODEWITHSUNDEEP
cassemblyx86-64fasm
IAbstract
IAbstract

Reputation: 19881

How to pass args from assembly to C function?

Using FASM, x86_64, Linux (Mint)
Passing args to C function

int arg_test(int argc, char *argv[]) {
    //  output number of args
    printf("arg count: %d\n", argc);
    printf("%s", *argv);

    return TRUE;
}

The assembly executable

public main

section     '.text'
extrn       arg_test

main:
    mov         rdi, 2          ; 1st parameter (number of args)
    mov         rsi, .arg1      ; [0] 2nd parameter
    mov         rdx, 0          ; [1] 3rd parameter (null)
    xor         rax, rax
    call    arg_test

    mov         eax, syscall_exit
    xor         edi, edi
    syscall

section     '.data'
    .arg1:  db      "arg1",         0

...The output

arg count: 2
Segmentation fault (core dumped)

What am I missing about passing args to the C function? How can I properly iterate the arguments?

Upvotes: 0

Views: 95

Answers (0)

Related Questions