On 08/05/2010 08:53 PM, der Mouse wrote:
You said this was on a 4k/60. I don't recall whether that has any macrocoded instructions the way the uV2 does; if so, I think they usually end up executing emulation code inside system space in user mode, and if that's what's happening here then this could incidate a bug in the macrocode or it could indicate that the macrocode emulation detected a problem and faulted deliberately.
It sounds very likely that an emulated instruction is the problem. The kernel pages containing the emulate code are mapped RO for user, and the emulate code will switch back to the User process after a trap and execute the emulate code as the user. -- ragge