Messages in this thread | | | Date | Wed, 14 Apr 2010 17:09:32 -0400 | From | David VomLehn <> | Subject | Re: [PATCH 1/23] Make register values available to panic notifiers |
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Martin Schwidefsky wrote: > On Mon, 12 Apr 2010 13:27:45 +0100 > Russell King <rmk@arm.linux.org.uk> wrote: > > >> On Sun, Apr 11, 2010 at 11:06:09PM -0700, David VomLehn wrote: >> >>> This patch makes panic() and die() registers available to, for example, >>> panic notifier functions. Panic notifier functions are quite useful >>> for recording crash information, but they don't get passed the register >>> values. This makes it hard to print register contents, do stack >>> backtraces, etc. The changes in this patch save the register state when >>> panic() is called and introduce a function for die() to call that allows >>> it to pass in the registers it was passed. >>> >> Can you explain why you want this? >> >> I'm wondering about the value of saving the registers; normally when a panic >> occurs, it's because of a well defined reason, and not because something >> went wrong in some CPU register; to put it another way, a panic() is a >> more controlled exception than a BUG() or a bad pointer dereference. >> > > I'm curious about the potential use case as well. So far I only wanted > to know the registers if the panic has been triggered due to an > unexpected fault with panic_on_oops=1 or in_interrupt()==1. If that > happens the die() handler prints the registers. An open coded panic is > easy to analyze, imho no need for the registers >
Good example, because helps focus the issue. In recording a subset of kernel state information from an embedded system for collection at a central point. The register values printed by die() are printed to the console, where they disappear. One of the things in this patch involves passed a pointer to those die() registers to a register panic notifier handler. So, there is a path to where panic handlers are called from die() and another one from panic() and this patch makes register values available in both cases.
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