From patchwork Wed Aug 10 06:59:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Artem Savkov X-Patchwork-Id: 12940279 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1399DC3F6B0 for ; Wed, 10 Aug 2022 06:59:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231238AbiHJG7N (ORCPT ); Wed, 10 Aug 2022 02:59:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229636AbiHJG7M (ORCPT ); Wed, 10 Aug 2022 02:59:12 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1D51E72EC0 for ; Tue, 9 Aug 2022 23:59:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1660114749; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=zls4Cl4FNP8DuIoFTM3V5sZep3mW2y+G5cy1prlx7I0=; b=Oa+Xq19lT8oMUDSVJ9ZylSYA3k0GtX7EFTn/OrjnHZg/AS+AGJr4ao1fWP2B5PYaTieoTK b8AQaf5IihXzPKfvkZdik3wRESQFRm+Ss+ARc1siNo9urJD+E8hDjoJOIWlC+chr4Pl+Od QKg55GshPPF1hENCciFM09ZQLdae+3U= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-412-gkP8E-dwMIC2KGuJo0mo-w-1; Wed, 10 Aug 2022 02:59:08 -0400 X-MC-Unique: gkP8E-dwMIC2KGuJo0mo-w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 269F43821C0B; Wed, 10 Aug 2022 06:59:08 +0000 (UTC) Received: from shodan.usersys.redhat.com (unknown [10.43.17.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D6DE618EB5; Wed, 10 Aug 2022 06:59:07 +0000 (UTC) Received: by shodan.usersys.redhat.com (Postfix, from userid 1000) id CBA131C02A9; Wed, 10 Aug 2022 08:59:06 +0200 (CEST) From: Artem Savkov To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrea Arcangeli , Daniel Vacek , Jiri Olsa , Song Liu , Daniel Xu , Kumar Kartikeya Dwivedi , Artem Savkov Subject: [PATCH bpf-next v5 0/3] destructive bpf_kfuncs Date: Wed, 10 Aug 2022 08:59:02 +0200 Message-Id: <20220810065905.475418-1-asavkov@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net eBPF is often used for kernel debugging, and one of the widely used and powerful debugging techniques is post-mortem debugging with a full memory dump. Triggering a panic at exactly the right moment allows the user to get such a dump and thus a better view at the system's state. Right now the only way to do this in BPF is to signal userspace to trigger kexec/panic. This is suboptimal as going through userspace requires context changes and adds significant delays taking system further away from "the right moment". On a single-cpu system the situation is even worse because BPF program won't even be able to block the thread of interest. This patchset tries to solve this problem by allowing properly marked tracing bpf programs to call crash_kexec() kernel function. The only requirement for now to run programs calling crash_kexec() or other destructive kfuncs is CAP_SYS_BOOT capability. When signature checking for bpf programs is available it is possible that stricter rules will be applied to programs utilizing destructive kfuncs. Changes in v5: - documentation numbering fixed - no more warning on failed kfunc registration Changes in v4: - added description for KF_DESTRUCTIVE flag to documentation Changes in v3: - moved kfunc set registration to kernel/bpf/helpers.c Changes in v2: - BPF_PROG_LOAD flag dropped as it doesn't fully achieve it's aim of preventing accidental execution of destructive bpf programs - selftest moved to the end of patchset - switched to kfunc destructive flag instead of a separate set Changes from RFC: - sysctl knob dropped - using crash_kexec() instead of panic() - using kfuncs instead of adding a new helper Artem Savkov (3): bpf: add destructive kfunc flag bpf: export crash_kexec() as destructive kfunc selftests/bpf: add destructive kfunc test Documentation/bpf/kfuncs.rst | 9 +++++ include/linux/btf.h | 3 +- kernel/bpf/helpers.c | 18 ++++++++++ kernel/bpf/verifier.c | 5 +++ net/bpf/test_run.c | 5 +++ .../selftests/bpf/prog_tests/kfunc_call.c | 36 +++++++++++++++++++ .../bpf/progs/kfunc_call_destructive.c | 14 ++++++++ 7 files changed, 89 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_destructive.c