Messages in this thread | | | Subject | Re: [RFC] systemtap: begin the process of using proper kernel APIs (part1: use kprobe symbol_name/offset instead of address) | From | Peter Zijlstra <> | Date | Fri, 18 Jul 2008 15:10:27 +0200 |
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On Fri, 2008-07-18 at 09:02 -0400, Frank Ch. Eigler wrote: > Peter Zijlstra <peterz@infradead.org> writes: > > > [...] > >> Right now x86 doesn't really have a good reliable unwinder that > >> works without frame pointer. I think systemtap > >> recently switched to Jan Beulich's dwarf2 unwinder. Before > >> switching to the in kernel unwinder that one would need to be > >> re-merged again. > > > > Those are two separate issues. > > > > 1) stap ought to use the kernel's infrastructure and not re-implement > > its own. > > 2) if the kernel's infrastructure doesn't meet requirements, improve > > it. > > They are related to the extent that readers may not realize some > implications of systemtap being/becoming a *kernel-resident* but not > *kernel-focused* tool. > > For example, we're about to do unwinding/stack-traces of userspace > programs. To what extent do you think the kernel unwinder (should one > reappear in git) would welcome patches that provide zero benefit to > the kernel, but only enable a peculiar (nonintrusive) sort of > unwinding we would need for complex userspace stacks?
I think sysprof (kernel/trace/trace_sysprof.c) already does user-space stack unwinding. So pushing that capability further up the chain when a second user (stap) comes along makes perfect sense.
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