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

From: Wangnan (F)
Date: Thu Nov 19 2015 - 01:45:42 EST

On 2015/11/19 14:37, Ingo Molnar wrote:
* 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

Just for curiosity:

how the interrupted process continue to execute, when the PC
saved in pt_regs still pointed to 'callq' but SP and stack has
already changes? Do we fix it in kernel, or by hardware?

Thank you.

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