Re: Getting empty callchain from perf_callchain_kernel()
From: Peter Zijlstra
Date: Fri May 24 2019 - 04:56:40 EST
On Thu, May 23, 2019 at 10:24:13AM -0500, Josh Poimboeuf wrote:
> Here's the latest version which should fix it in all cases (based on
That patch suffers an inconsitency, the comment states:
'if they have "jump_table" in the name'
while the actual code implements:
'if the name starts with "jump_table"'
Other than that, I suppose that works just fine ;-)
> There's no need to put special cases in the FP unwinder when we can
> instead just fix the frame pointer usage in the JIT code.
> For ORC, I'm thinking we may be able to just require that all generated
> code (BPF and others) always use frame pointers. Then when ORC doesn't
> recognize a code address, it could try using the frame pointer as a
Yes, this seems like a sensible approach. We'd also have to audit the
ftrace and kprobe trampolines, IIRC they only do framepointer setup for
CONFIG_FRAME_POINTER currently, which should be easy to fix (after the
patches I have to fix the FP generation in the first place: