> but once you take the address of your misaligned int field

Gotta work with the structure directly by taking the address of the packed structure itself.

  struct uu64 {
      u64 value;
  } __attribute__((packed));

  struct uu64 unaligned;
  struct uu64 *address = &unaligned;

  address->value; // this works

  u64 *broken = &address->value; // this doesn't

Mercifully, both gcc and clang emit address-of-packed-member warnings if it's done. So the packed structures are effectively turning silently broken nonsense code into sensible warnings. Major win.