I need help with my code (Segmentation Fault) C inline Assembly?

Can someone tell me whats wrong with my code please I need to reverse a string that i must input but the reversal is supposed to happen in Assambley. It compiles and everything but i get a segmentation fault here is the code:


#include <stdio.h>
#include <string.h>

static inline char * reverse(char *destination, const char *source, int length);

int main(int argc, char **argv) {
char *reverse_string;
//char *original_string;
//old_str="Hello, World!";
char original_string[BUFSIZ];
char *p;
if (fgets(original_string,sizeof(original_s… stdin)!=NULL)
if((p=strchr(original_string,'\n'))!=NUL…
*p='\0';

reverse(reverse_string, original_string, sizeof(original_string));
printf("Original String:\t %s\n", original_string);
printf("Reversed String:\t %s\n", reverse_string);
return 0;
}

char * reverse(char *destination, const char *source, int length) {
int d0, d1, d2, d3, d4, d5, d6;
__asm__ (
"add %%ebx, %%esi\n\t" /*Move to end of string*/
"std\n\t" /*Decrement esi after load*/
"lodsb\n\t" /*Load esi into al*/
"sub $1, %%ebx\n\t"
"mov %%al, %%cl\n\t" /*mov contents of al to cl*/
"1:\tstd\n\t" /*Begin loop, decrement esi after load*/
"lodsb\n\t" /*Load esi into al*/
"cld\n\t" /*Clear flg*/
"stosb\n\t" /*Store al in edi*/
"sub $1, %%ebx\n\t" /*subtract 1 from strlenght counter*/
"cmp $0, %%ebx\n\t" /*Compare ebx to 0*/
"jne 1b\n\t"
"mov $0, %%edi\n\t" /*Add null terminating char to new str*/
: "=&S"(d0), "=&D"(d1), "=&a"(d2), "=&b" (d3) /*output*/
/*** &S --> ESI, &D --> EDI, &a --> eax ***/
: "0" (source), "1" (destination), "3" (length) /*input*/
: "memory"); /*clobber registers*/
return destination;
}