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Re: [RFC] systemtap: begin the process of using proper kernel APIs (part1: use kprobe symbol_name/offset instead of address)
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: Peter Zijlstra <peterz at infradead dot org>
- Cc: Andi Kleen <andi at firstfloor dot org>, James Bottomley <James dot Bottomley at HansenPartnership dot com>, linux-kernel <linux-kernel at vger dot kernel dot org>, systemtap at sourceware dot org, jbeulich at novell dot com
- Date: Fri, 18 Jul 2008 09:02:19 -0400
- Subject: Re: [RFC] systemtap: begin the process of using proper kernel APIs (part1: use kprobe symbol_name/offset instead of address)
- References: <1216146802.3312.95.camel@localhost.localdomain> <87ej5rsgk4.fsf@basil.nowhere.org> <1216373009.5232.130.camel@twins>
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?
- FChE