From patchwork Thu May 7 09:59:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 1285055 Return-Path: X-Original-To: incoming-bpf@patchwork.ozlabs.org Delivered-To: patchwork-incoming-bpf@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=bpf-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=default header.b=1aUldhiQ; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49Hppw20dtz9sP7 for ; Thu, 7 May 2020 19:59:52 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726222AbgEGJ7v (ORCPT ); Thu, 7 May 2020 05:59:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:38312 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725893AbgEGJ7u (ORCPT ); Thu, 7 May 2020 05:59:50 -0400 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9027C20643; Thu, 7 May 2020 09:59:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588845589; bh=1dH5G1leAYENAhuCpe5L02sl2FX0JniYY4i2b+iiscs=; h=From:To:Cc:Subject:Date:From; b=1aUldhiQbHoUUq98QeyZox9aJSM7fUex2qh2uKAqXjx1zIHigKYWqndTApyZ8Q6h+ kmOaWmRVk1MiImGIY8H0404e2ryIMSTusCdfZi2zrrVtdCKI+4inXLc8iYKXrGtO// UKpQuhTXij4WrjkTmPbAG530abAmO1w29UVHXsHQ= From: Masami Hiramatsu To: LKML Cc: Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo , Eelco Chaudron , Yonghong Song , bpf , "David S . Miller" , Network Development , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Andrii Nakryiko , Catalin Marinas , Will Deacon , Wang Nan , Russell King , linux-arm-kernel@lists.infradead.org Subject: [RFC PATCH 0/3] kprobes: Support nested kprobes Date: Thu, 7 May 2020 18:59:42 +0900 Message-Id: <158884558272.12656.7654266361809594662.stgit@devnote2> X-Mailer: git-send-email 2.20.1 User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Hi, Here is a series to add nested-kprobes support to x86, arm64 and arm (which I can test). These make kprobes to accept 1-level nesting instead of incrementing missed count. Any kprobes hits in kprobes pre/post handler context can be nested at once. If the other kprobes hits in the nested pre/post handler context or in the single-stepping context, that will be still missed. The nest level is actually easily extended, but too many nest level can lead the overflow of the kernel stack (for each nest, the stack will be consumed by saving registers, handling kprobes and pre/post handlers.) Thus, at this moment it allows only one level nest. This feature allows BPF or ftrace user to put a kprobe on BPF jited code or ftrace internal code running in the kprobe context for debugging. We can test this feature on the kernel with CONFIG_KPROBE_EVENTS_ON_NOTRACE=y as below. # cd /sys/kernel/debug/tracing # echo p ring_buffer_lock_reserve > kprobe_events # echo p vfs_read >> kprobe_events # echo stacktrace > events/kprobes/p_ring_buffer_lock_reserve_0/trigger # echo 1 > events/kprobes/enable # cat trace ... cat-151 [000] ...1 48.669190: p_vfs_read_0: (vfs_read+0x0/0x160) cat-151 [000] ...2 48.669276: p_ring_buffer_lock_reserve_0: (ring_buffer_lock_reserve+0x0/0x400) cat-151 [000] ...2 48.669288: => kprobe_dispatcher => opt_pre_handler => optimized_callback => 0xffffffffa0002331 => ring_buffer_lock_reserve => kprobe_trace_func => kprobe_dispatcher => opt_pre_handler => optimized_callback => 0xffffffffa00023b0 => vfs_read => load_elf_phdrs => load_elf_binary => search_binary_handler.part.0 => __do_execve_file.isra.0 => __x64_sys_execve => do_syscall_64 => entry_SYSCALL_64_after_hwframe To check unoptimized code, disable optprobe and dump the log. # echo 0 > /proc/sys/debug/kprobes-optimization # echo > trace # cat trace cat-153 [000] d..1 140.581433: p_vfs_read_0: (vfs_read+0x0/0x160) cat-153 [000] d..2 140.581780: p_ring_buffer_lock_reserve_0: (ring_buffer_lock_reserve+0x0/0x400) cat-153 [000] d..2 140.581811: => kprobe_dispatcher => aggr_pre_handler => kprobe_int3_handler => do_int3 => int3 => ring_buffer_lock_reserve => kprobe_trace_func => kprobe_dispatcher => aggr_pre_handler => kprobe_int3_handler => do_int3 => int3 => vfs_read => load_elf_phdrs => load_elf_binary => search_binary_handler.part.0 => __do_execve_file.isra.0 => __x64_sys_execve => do_syscall_64 => entry_SYSCALL_64_after_hwframe So we can see the kprobe can be nested. Thank you, --- Masami Hiramatsu (3): x86/kprobes: Support nested kprobes arm64: kprobes: Support nested kprobes arm: kprobes: Support nested kprobes arch/arm/include/asm/kprobes.h | 5 ++ arch/arm/probes/kprobes/core.c | 79 ++++++++++++++---------------- arch/arm/probes/kprobes/core.h | 30 +++++++++++ arch/arm/probes/kprobes/opt-arm.c | 6 ++ arch/arm64/include/asm/kprobes.h | 5 ++ arch/arm64/kernel/probes/kprobes.c | 75 ++++++++++++++++------------ arch/x86/include/asm/kprobes.h | 5 ++ arch/x86/kernel/kprobes/common.h | 39 ++++++++++++++- arch/x86/kernel/kprobes/core.c | 96 +++++++++++++++--------------------- arch/x86/kernel/kprobes/ftrace.c | 6 ++ arch/x86/kernel/kprobes/opt.c | 13 +++-- 11 files changed, 214 insertions(+), 145 deletions(-) -- Masami Hiramatsu (Linaro)