instruction: 0.970
runtime: 0.018
syscall: 0.012



incorrect handling of [r32] address (long mode)

while executing in Long Mode (x86-64) instructions such as

mov eax,[r15d]

end up executing as

mov eax,[r15]

according to x86 programmer manuals the behavior of using the Address-Size override (in long mode) is supposed to ignore the high 32bits of the register. I use this fact in my operating system to reduce register usage (the high 32 bits of r15 holds other data). consequently a general protection exception occurs since the memory address isn't "canonical". this error doesn't always appear since the high 32 bits might not be zero in those conditions.