On Wed, May 07, 2008 at 04:49:53PM -0700, David VomLehn wrote: > This patch contains the kernel stack backtrace code we've been running for > about a year on our MIPS-based settop box. It is considerably larger than > the existing backtrace implementation and so is configurable in the Kernel > Hacking section. It also requires that KALLSYMS be enabled. In return, I > think it offers some advantages over the existing backtrace code: > > o It will backtrace over nested interrupts and exceptions, allowing > detailed analysis of was going on when it was invoked. > o It handles a number of corner cases involving instructions in branch > delay slots. > o It is very careful to use __get_user when fetching stack data and > instructions, meaning that it will fail gracefully even in the presence of > stack corruption. > o It identifies whether the $sp register or another register is being used > as the frame pointer. Assuming people are happy with this submission, there > is a small subsequent patch I'll submit that dumps the frame pointer value > as part of the backtrace. > o It segregates the backtrace code into a subdirectory of arch/mips/kernel > rather than cluttering up traps.c or the kernel directory. > > The main reason I am submitting this as a request for comments rather than > as a normal patch is that, though I wrote it with 64-bit systems in mind, I > don't have access to a 64-bit system on which to test it. I am happy to > merge any 64-bit-specific changes. For 32-bit systems, I'll claim it's > ready to go. > > The other reason is that this is an RFC is that it is such a large, single > chunk of code that there are certainly lots of comments that people will > have. I'm not naive enough to think it's really ready without more review. > > [Note: for anyone who was at the MIPS backtrace session at the CELF > Conference, this is the code I was talking about.] I wasn't even aware of the session. > Signed-off-by: David VomLehn <dvomlehn@xxxxxxxxx> > +#ifndef numberof > +#define numberof(a) (sizeof(a) / sizeof((a) [0])) > +#endif I really just glanced over the patch. I think I like the promise of more accurate backtraces because frequently one (1) backtrace is all information which there ever will be available for debugging. o Use ARRAY_SIZE() from <linux/kernel.h> instead of numberof. o Please run the patch through scripts/checkpatch.pl and fix the resulting errors. o Your patch got linewrapped by your mail client. Ralf
