Need to figure out the meaning of following inline assembly code

Question

static int func_name (const uint8_t * address)
{
    int result;
    asm ("movl $1f, %0; movzbl %1, %0; 1:"
   : "=&a" (result) : "m" (*address));

    return result;
}

I have gone through inline assembly references over internet. But i am unable to figure out what this code is doing, eg. what is $1f ? And what does "m" means? Isn't the normal inline convention to use "=r" and "r" ?

Answer 1

$1f is the address of the 1 label. The f specifies to look for the first label named 1 in the forward direction. "m" is an input operand that is in memory. "=&a" is an output operand that uses the eax register. a specifies the register to use, = makes it an output operand, and & guarantees that other operands will not share the same register.

Here, %0 will be replaced with the first operand (the eax register) and %1 by the second operand (The address pointed to by address).

All these and more are explained in the GCC documentation on Inline assembly and asm contraints.