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Date: Wed, 22 May 2019 12:45:17 -0500 From: Josh Poimboeuf <jpoimboe@...hat.com> To: Alexei Starovoitov <ast@...com> Cc: Peter Zijlstra <peterz@...radead.org>, Kairui Song <kasong@...hat.com>, Song Liu <songliubraving@...com>, lkml <linux-kernel@...r.kernel.org>, Kernel Team <Kernel-team@...com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, "bpf@...r.kernel.org" <bpf@...r.kernel.org> Subject: Re: Getting empty callchain from perf_callchain_kernel() On Wed, May 22, 2019 at 02:49:07PM +0000, Alexei Starovoitov wrote: > The one that is broken is prog_tests/stacktrace_map.c > There we attach bpf to standard tracepoint where > kernel suppose to collect pt_regs before calling into bpf. > And that's what bpf_get_stackid_tp() is doing. > It passes pt_regs (that was collected before any bpf) > into bpf_get_stackid() which calls get_perf_callchain(). > Same thing with kprobes, uprobes. Is it trying to unwind through ___bpf_prog_run()? If so, that would at least explain why ORC isn't working. Objtool currently ignores that function because it can't follow the jump table. -- Josh
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