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

[Ingo Molnar]

* 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 
post-instruction.

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

Thanks,

	Ingo
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