Hi. This past week I had to fix a bug in the load/store multiple emulation code and also introduce support for all access permission checks when traversing the guest page tables, including the Domain Access Control settings used on ARM. This has gotten me through start_kernel and through the first couple of context switches between the kernel threads. I eventually end up in init() -> do_basic_setup() -> do_initcalls(), where the system crashes on a guest NULL pointer exception. Due to the linker magic with init calls, it's hard to reason about where this bug occurs. (I should say that I strongly expect it to be a bug, since I am guessing that no logic can be based on a NULL pointer fault this early in the kernel). I have sent an e-mail (forwarded below) to the linux-arm mailing list to see if I could get any advice on getting the UART serial console up at this point. Otherwise I think I am left with disassembling the guest kernel and matching the address for the NULL pointer error, and hopefully it will be somewhere meaningful and not in some general utility function. If anyone has any other input on how to proceed, it will (as always) be fantastic. Best, Christoffer ---------- Forwarded message ---------- From: Christoffer Dall <cd2436 at columbia.edu> Date: Wed, Dec 16, 2009 at 8:25 PM Subject: Early pl011 console for debugging KVM for ARM port To: linux-arm-kernel at lists.infradead.org Hi everyone. I am working on a port of KVM for arm (http://android.chazy.dk) and I am somewhat stuck. I encounter a crash somewhere in do_initcalls(), but I do not have console at this point, as my only console is the pl011 uart device. Not having the console makes it quite hard to track down the bugs (an effort I do by placing asm("swi 0xMAGIC") at various locations) for now. Does anyone know how to enable such a console earlier? I tried simply calling pl011_init() before the initcalls loop, but I eventually hit a NULL pointer exception inside list_add_tail(&kobj->entry,&kobj->kset->list); called from kobject_add(...) in lib/kobject.c. I can gather it's the kobj->kset->list.prev, which is NULL. As far as I understand, these structures should have been initialized at this point. Can anyone confirm? Any help is greatly appreciated! Thanks, Christoffer Dall
