On Mon, Oct 3, 2022, at 3:21 PM, Ali Raza wrote: > For a UKL thread, returning to a signal handler is not done with iret or > sysret. This means we need to adjust the way the return stack frame is > handled for these threads. When constructing the signal frame, we leave > the previous frame in place because we will return to it from the signal > handler. We also leave space for pushing eflags and the return address. > UKL threads will only use the __KERNEL_DS value in the ss register and 0xC3 > in the cs register. This is unclear. Are you taking about returning from the kernel fault code *to* the signal handler or are you talking about returning *from* the user signal hander to the user code that was running when the signal happened? In any case, I don't see what this has to do with iret or sysret. Surely UKL can use a sigreturn() just like regular Linux. The part where a UKL thread has permission to return to a CPL0 context should be a separate patch. --Andy
