GCC inline assembly read value from array

While learning gcc inline assembly I was playing a bit with memory access. I'm trying to read a value from an array using a value from a different array as index. Both arrays are initialized to something.

Initialization:

uint8_t* index = (uint8_t*)malloc(256);
memset(index, 33, 256);

uint8_t* data = (uint8_t*)malloc(256);
memset(data, 44, 256);

Array access:

unsigned char read(void *index,void *data) {
        unsigned char value;

        asm __volatile__ (
        "  movzb (%1), %%edx\n"
        "  movzb (%2, %%edx), %%eax\n"
        : "=r" (value)
        : "c" (index), "c" (data)
        : "%eax", "%edx");

        return value;
    }

This is how I use the function:

unsigned char value = read(index, data);

Now I would expect it to return 44. But it actually returns me some random value. Am I reading from uninitialzed memory? Also I'm not sure how to tell the compiler that it should assign the value from eax to the variable value.