On Tue, Nov 06, 2018 at 09:47:52AM -0700, Keith Busch wrote: > On Tue, Nov 06, 2018 at 04:34:08PM +0000, Lorenzo Pieralisi wrote: > > The question is whether we really need to dynamically patch the kernel > > with ftrace to achieve what that patch does. > > > > Furthermore, it would also be good to report what bugs we are actually > > fixing, from what you are writing falling back to the current method if > > !DYNAMIC_FTRACE_WITH_REGS is broken in many ways and I would start with > > fixing the current behaviour with something that does not depend on arch > > features that may not even be implemented. > > There are two problems with the current method: > > 1. It may dereference pci_dev after it was freed > 2. The pci_dev's children inherit its fake pci_bus's ops on > enumeration > > Both result in kernel panic. That's my point, current test module is not robust, I wanted to ask if there is a way to fix it that does not depend on arch features, because if there is a dependency that is not met we are still not fixing the current code, using it as a fallback can still create issues. > The dynamic kernel patch just seemed like a cool way to inject errors > without messing with the driver's structures. But if there's a more > elegant way to do it, I'm all for it. If you have a simple reproducer for the bugs I am happy to help you test it (I can also apply arm64 DYNAMIC_FTRACE_WITH_REGS patches and test that new code path if that's the final direction we are taking). Thanks, Lorenzo
