linux-kernel - Re: Getting empty callchain from perf_callchain

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190522174517.pbdopvookggen3d7@treble>
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