On Mon, Nov 19, 2018 at 09:00:08AM -0800, Andy Lutomirski wrote: > On Mon, Nov 19, 2018 at 8:02 AM Jarkko Sakkinen > <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > > > On Mon, Nov 19, 2018 at 07:29:36AM -0800, Andy Lutomirski wrote: > > > 1. The kernel needs some way to know *when* to apply this fixup. > > > Decoding the instruction stream and doing it to all exceptions that > > > hit an ENCLU instruction seems like a poor design. > > > > I'm not sure why you would ever need to do any type of fixup as the idea > > is to just return to AEP i.e. from chosen exceptions (EPCM, #UD) the AEP > > would work the same way as for exceptions that the kernel can deal with > > except filling the exception information to registers. > > Sure, but how does the kernel know when to do that and when to send a > signal? I don't really like decoding the instruction stream to figure > it out. Hmm... why you have to decode instruction stream to find that out? Would just depend on exception type (#GP with EPCM, #UD). Or are you saying that kernel should need to SIGSEGV if there is in fact ENCLU so that there is no infinite trap loop? Sorry, I'm a bit lost here that where does this decoding requirement comes from in the first place. I understand how it is used in Sean's proposal... Anyway, this option can be probably discarded without further consideration because apparently single stepping can cause #DB SS fault if AEP handler is anything else than a single instruction. For me it seems that by ruling out options, vDSO option is what is left. I don't like it but at least it works... /Jarkko
