Memory allocation differences between 2.4.18 and 2.5.52

[Adam Khan]

It seems that the kmalloc() function on 2.4.18 provides memory
allocation blocks on 8-byte boundaries. 2.5.52 provides memory
allocation blocks on 4-byte boundaries.

We have run into an issue with a device driver developed for 2.4.18 and
ported to 2.5.52. The driver requires buffers that are allocated on
8-byte boundaries. 
Can anyone explain why this difference in buffer boundaries exists?
Any suggestions to ensure that the buffer allocation is 8-byte bounded?
Can we write a my_kmalloc() function that would always return an 8-byte
bounded buffer. 

Thanks in advance,
Adam