Plan 9 and Inferno at the Google Summer of Code

Faulty Page Fault Handler

I'm still puzzled by the “hw tlb loading disabled w/o sw loading available” warning displayed by the simulator. I verified that software TLB management is enabled, and that the correct interrupt handler is invoked on a page fault. Having run out of ideas, I moved on to the next issue. The page fault handler (which eventually causes mmuput() to be called) behaves correctly the first time it's called, that is, a vacant TLB entry is used to map the page, but when the next fault occurs, mmuput() panics as it finds that the virtual page it's trying to map already exists in the TLB, which means one of two things: either the checking used in mmuput() itself is buggy, or that there's inconsistency between the hardware TLB & the STLB cached by the kernel, which is unlikely. My biggest problem now is that I can't even use print() for debugging. mmuput() is extremely sensitive to any modification I make (may be because it's running in an interrupt -- there might be some restrictions that I'm not aware of). For example, this is what I get when I modify the condition used in checking if an entry is duplicated: