On Wed, Jun 10, 2009 at 09:26:40PM -0400, Robin Getz wrote: > I would be interested in Paul and Russell - how have you solved this issue? > (Or do your kernel's never crash? :)
We haven't any dedicated solution to reading out the crash messages. What we do have is a very basic platform specific serial IO implementation which we call "low level debug" - it just provides a number of functions (eg, printascii). These functions are callable from assembly or C, and can work whether the MMU is enabled or not. People can enable the low level debug build option and patch into kernel/printk.c to hook it up (or place printascii etc where-ever they choose.) It has the advantage that it is entirely synchronous from every context. Yes, it requires a little bit of effort on the part of the developer to hook it up - so far no one has complained about the process of hooking this facility up in their kernel. You can use this to debug SMP bringup, but you risk having each CPU stomping on each other's messages - so it's in no way perfect. The other way I've seen people read out crash messages is using a debugger to dump the kernel's log buffer directly. That seems to work as well as any other method, and has the advantage that it doesn't require any kernel modifications. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
