Print Message Inline Assembly - c

Question

I'm trying to print a simple hello world string to the console in inline assembly. My assembly (below) works perfectly fine. I tried translating it into GAS as best as possible but putting the variables into the registers through extended assembly proved rather difficult. From what I can tell, the printmsg function doesn't actually do/print anything.
Assembly:
section .text
global _start
_start:
; Write string to stdout
mov eax, 4
mov ebx, 1
mov ecx, string
mov edx, strlen
int 0x80
; Exit
mov eax, 1
mov ebx, 0
int 0x80
section .data
string db 'Hello, World!',10
strlen equ $ - string
C:
#include <stdio.h>
#include <string.h>
void printmsg(char *msg, int len){
asm( "movl $4, %eax;"
"movl $1, %ebx;"
);
asm( "movl %1, %%ecx;"
"movl %1, %%edx;"
:
: "c" (msg), "d" (len)
);
asm("int $0x80");
}
int main(){
char *msg = "Hello, world!";
int len = strlen(msg);
printf("Len is %d\n*msg is %s\n", len, msg);
/* Print msg */
printmsg(msg, len);
/* Exit */
asm( "movl $1,%eax;"
"xorl %ebx,%ebx;"
"int $0x80"
);
}

Answer 1

Using Michael's extended assembly example:
#include <stdio.h>
#include <string.h>
void printmsg(char *string, int length){
asm( "int $0x80\n\t"
:
:"a"(4), "b"(1), "c"(string), "d"(length)
);
}
int main(){
char *string = "Hello, world!\n";
int variable = strlen(string);
/* Print msg */
printmsg(string, variable);
/* Exit */
asm( "movl $1,%eax;"
"xorl %ebx,%ebx;"
"int $0x80"
);
}