Re: [Crash-utility] [PATCH] do not check sp if ip points to user space

> Right, but the fact of the matter is that a backtrace cannot be > performed for a task with a nonsensical SP value, so it doesn't > make a difference whether it was in user-space or kernel-space. > So the "cannot determine starting stack pointer" error message > should still be displayed as it currently does -- and with my patch > suggestion, the registers can be dumped (if available) before > returning. > I understand. The condition to be used here is whether the backtrace can be performed or not, implied by SP values pointing at outside a variety of kernel stacks; I guess this is the definition of nonsensical SP you've mean. I think the new behaviour reasonable. By the way, I have a question that what intension do you have behind !is_kernel_text(ip)? Just to exclude the case of user text? I guess you're intending here also to exclude other possibilities.

Because sadump runs beyond the logic of kernel, register values contained in vmcore sometimes the ones in real-address mode, appearing having run in some firmware, which often happens at crash during boot time.

I'm also wondering if there's other dump mechanism that can lead to this kind of situation. For example, although I don't understand detailed behaviour of NMI, if assuming NMI immediately triggered even when running in firmware without rolling back register values saved when entering the firmware context from kernel, register values in NMI frames would be the ones in firmware and it would be concluded that the situation can happen on kdump (and others that uses NMI); but I have never seen such register values on kdump...