Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling taken at 'callq' instruction

From: Ingo Molnar
Date: Thu Nov 19 2015 - 01:37:33 EST

* Wangnan (F) <wangnan0@xxxxxxxxxx> wrote:

> >perf cmdline is
> >
> ># ./pref record -g -F 9 --call-graph dwarf ./test_dwarf_unwind
> >
> >Use default events, precise_ip == 2 so uses PEBS.
> >
> Testetd 'cycles', 'cycles:p' and 'cycles:pp'. Only 'cycles:pp' captures
> sample at callq. So maybe a PEBS problem?

Well, that's how our PEBS sampling works: we roll back the instruction pointer to
point at the instruction generating the sample. The state itself is

So dwarf unwind has to take this into account. Should the kernel pass in the
original (uncorrected) RIP as well, perhaps?


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