Where is eax in the pt_regs struct? Only ax is present

I am trying to use the pt_regs struct to get and set registers such as eax, but compilation errors tell me that pt_regs has no such member eax.

However, I am able to get the ax register. Can anybody tell me what is happening?

I am using 32-bit Ubuntu linux with the 3.0.0 kernel. Thank you again.