On Mon, Jan 05, 2015 at 08:13:49AM -0800, Andy Lutomirski wrote: > > Just wondering how bad it would be to fill out the actual pt_regs that > > was previously partially initialized? > > Bad, for at least two reasons. > > One is that we don't actually know which regs are initialized. bx, > bp, r12 etc are particularly bad in this regard, due to the FORK_LIKE > mechanism and similar optimizations.
Right, but you need to deal with that anyhow. > The other is that the uninitialized part of task_pt_regs can be used > for something else entirely. If we have a syscall instruction > immediately followed by a regular interrupt, then the interrupt's > hardware frame will overlap task_pt_regs. (I'm not going to claim > that this design is sensible, but it is what it is. IIRC Denys > Vlasenko had some patches to partially clean this up.) Ah, urgh. Yes painful that. > It would be possible to rework the code to avoid an extra pt_regs > copy, but I don't see an obvious way to do it cleanly. Yeah, we'll see how this works, I was just curious on the exact need for the copy, but if as you say, the original structure might not even exist properly (even though we have a pointer to it) that's bad (TM). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
