On Tue, Dec 30, 2014 at 08:03:27PM +0100, Peter Zijlstra wrote: > On Thu, Dec 25, 2014 at 07:48:28AM -0800, Andy Lutomirski wrote: > > On a quick look, there are plenty of other bugs in there besides just > > the stack pointer issue. The ABI check that uses TIF_IA32 in the perf > > core is completely wrong. TIF_IA32 may be equal to the actual > > userspace bitness by luck, but, if so, that's more or less just luck. > > And there's a user_mode test that should be user_mode_vm. > > > > Also, it's not just sp that's wrong. There are various places that > > you can interrupt in which many of the registers have confusing > > locations. You could try using the cfi unwind data, but that's > > unlikely to work for regs like cs and ss, and, during context switch, > > this has very little chance of working. > > > > What's the point of this feature? Honestly, my suggestion would be to > > delete it instead of trying to fix it. It's also not clear to me that > > there aren't serious security problems here -- it's entirely possible > > for sensitive *kernel* values to and up in task_pt_regs at certain > > times, and if you run during context switch and there's no code to > > suppress this dump during context switch, then you could be showing > > regs that belong to the wrong task. > > Of course the people who actually wrote the code are not on CC :/ > > There's two users of this iirc; > > 1) the dwarf stack unwinder thingy, which basically dumps the userspace > regs and the top of userspace stack on 'event'.
looks like this solves the issue I was trying to fix long time ago: http://marc.info/?l=linux-kernel&m=134934717011451&w=2 this seems a lot simpler ;-) I'll test.. jirka -- 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/
