From patchwork Thu May 7 10:00:19 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: 1285061 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@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=netdev-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=CW65V7gg; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49Hpqg46m9z9sSG for ; Thu, 7 May 2020 20:00:31 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726897AbgEGKA3 (ORCPT ); Thu, 7 May 2020 06:00:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:39100 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726809AbgEGKA1 (ORCPT ); Thu, 7 May 2020 06:00:27 -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 0989820643; Thu, 7 May 2020 10:00:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588845626; bh=Ak9464TnSkt1bqf6+8XjJiNocFWET02Yub6VNAXctoo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CW65V7ggoIGopbDpQ8tsdKdGqqWkz1ox6XgnKmxvfOcz8Vil0huCY8bkIaLAPYIKL xVoeSSV0KpK3/TvQCZBfvbXrn67gcDNCp1GxrGrAUsGCqG7zNwYGdjhBvA+N7RmAbl dVQr33+mvgt3KLCGAyJsf225TENw3D7b7LxERJIw= 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 3/3] arm: kprobes: Support nested kprobes Date: Thu, 7 May 2020 19:00:19 +0900 Message-Id: <158884561947.12656.7341370827605258688.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <158884558272.12656.7654266361809594662.stgit@devnote2> References: <158884558272.12656.7654266361809594662.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Make kprobes to accept 1-level nesting instead of missing it on arm. 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, that will be missed. 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 0 > /proc/sys/debug/kprobes-optimization # to check trap handler # echo stacktrace > events/kprobes/p_ring_buffer_lock_reserve_0/trigger # echo 1 > events/kprobes/enable # cat trace ... sh-94 [000] d... 124.945302: p_vfs_read_0: (vfs_read+0x0/0x120) sh-94 [000] d... 125.041822: p_ring_buffer_lock_reserve_0: (ring_buffer_lock_reserve+0x0/0x57c) sh-94 [000] d... 125.042102: => kprobe_dispatcher => aggr_pre_handler => kprobe_handler => kprobe_trap_handler => do_undefinstr => __und_svc_finish => ring_buffer_lock_reserve => kprobe_trace_func => kprobe_dispatcher => aggr_pre_handler => kprobe_handler => kprobe_trap_handler => do_undefinstr => __und_svc_finish => vfs_read => sys_read => ret_fast_syscall The trap handler is nested correctly. Signed-off-by: Masami Hiramatsu --- 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 ++- 4 files changed, 76 insertions(+), 44 deletions(-) diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h index 213607a1f45c..553f719bbfd5 100644 --- a/arch/arm/include/asm/kprobes.h +++ b/arch/arm/include/asm/kprobes.h @@ -32,10 +32,13 @@ struct prev_kprobe { unsigned int status; }; +#define KPROBE_NEST_MAX 2 + /* per-cpu kprobe control block */ struct kprobe_ctlblk { unsigned int kprobe_status; - struct prev_kprobe prev_kprobe; + struct prev_kprobe prev[KPROBE_NEST_MAX]; + int nested; }; void arch_remove_kprobe(struct kprobe *); diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c index 90b5bc723c83..2fe7373c3f77 100644 --- a/arch/arm/probes/kprobes/core.c +++ b/arch/arm/probes/kprobes/core.c @@ -187,18 +187,6 @@ void __kprobes arch_remove_kprobe(struct kprobe *p) } } -static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) -{ - kcb->prev_kprobe.kp = kprobe_running(); - kcb->prev_kprobe.status = kcb->kprobe_status; -} - -static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) -{ - __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); - kcb->kprobe_status = kcb->prev_kprobe.status; -} - static void __kprobes set_current_kprobe(struct kprobe *p) { __this_cpu_write(current_kprobe, p); @@ -224,6 +212,40 @@ singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) p->ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); } +static nokprobe_inline int reenter_kprobe(struct kprobe *p, + struct pt_regs *regs, + struct kprobe_ctlblk *kcb) +{ + /* Kprobe is pending, so we're recursing. */ + switch (kcb->kprobe_status) { + case KPROBE_HIT_ACTIVE: + case KPROBE_HIT_SSDONE: + if (kcb->nested < KPROBE_NEST_MAX - 1) { + save_previous_kprobe(kcb); + return 0; + } + fallthrough; + case KPROBE_HIT_SS: + /* A pre- or post-handler probe got us here. */ + kprobes_inc_nmissed_count(p); + save_previous_kprobe(kcb); + set_current_kprobe(p); + kcb->kprobe_status = KPROBE_REENTER; + singlestep(p, regs, kcb); + restore_previous_kprobe(kcb); + break; + case KPROBE_REENTER: + /* A nested probe was hit in FIQ, it is a BUG */ + pr_warn("Unrecoverable kprobe detected.\n"); + dump_kprobe(p); + fallthrough; + default: + /* impossible cases */ + BUG(); + } + return 1; +} + /* * Called with IRQs disabled. IRQs must remain disabled from that point * all the way until processing this kprobe is complete. The current @@ -262,30 +284,9 @@ void __kprobes kprobe_handler(struct pt_regs *regs) * In this case, we can skip recursing check too. */ singlestep_skip(p, regs); - } else if (cur) { - /* Kprobe is pending, so we're recursing. */ - switch (kcb->kprobe_status) { - case KPROBE_HIT_ACTIVE: - case KPROBE_HIT_SSDONE: - case KPROBE_HIT_SS: - /* A pre- or post-handler probe got us here. */ - kprobes_inc_nmissed_count(p); - save_previous_kprobe(kcb); - set_current_kprobe(p); - kcb->kprobe_status = KPROBE_REENTER; - singlestep(p, regs, kcb); - restore_previous_kprobe(kcb); - break; - case KPROBE_REENTER: - /* A nested probe was hit in FIQ, it is a BUG */ - pr_warn("Unrecoverable kprobe detected.\n"); - dump_kprobe(p); - /* fall through */ - default: - /* impossible cases */ - BUG(); - } } else { + if (cur && reenter_kprobe(p, regs, kcb)) + return; /* Probe hit and conditional execution check ok. */ set_current_kprobe(p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; @@ -305,7 +306,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs) p->post_handler(p, regs, 0); } } - reset_current_kprobe(); + pop_current_kprobe(kcb); } } else { /* @@ -342,11 +343,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) * normal page fault. */ regs->ARM_pc = (long)cur->addr; - if (kcb->kprobe_status == KPROBE_REENTER) { - restore_previous_kprobe(kcb); - } else { - reset_current_kprobe(); - } + pop_current_kprobe(kcb); break; case KPROBE_HIT_ACTIVE: diff --git a/arch/arm/probes/kprobes/core.h b/arch/arm/probes/kprobes/core.h index c3db468650ce..aaff1e0f2153 100644 --- a/arch/arm/probes/kprobes/core.h +++ b/arch/arm/probes/kprobes/core.h @@ -34,6 +34,36 @@ typedef enum probes_insn (kprobe_decode_insn_t)(probes_opcode_t, const union decode_action *, const struct decode_checker *[]); + +static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb) +{ + int i = kcb->nested++; + + kcb->prev[i].kp = kprobe_running(); + kcb->prev[i].status = kcb->kprobe_status; +} + +static nokprobe_inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb) +{ + int i = --kcb->nested; + + __this_cpu_write(current_kprobe, kcb->prev[i].kp); + kcb->kprobe_status = kcb->prev[i].status; +} + +static nokprobe_inline void pop_current_kprobe(struct kprobe_ctlblk *kcb) +{ + if (kcb->nested) + restore_previous_kprobe(kcb); + else + reset_current_kprobe(); +} + +static nokprobe_inline bool kprobe_can_nest(struct kprobe_ctlblk *kcb) +{ + return !kprobe_running() || (kcb->nested < KPROBE_NEST_MAX - 1); +} + #ifdef CONFIG_THUMB2_KERNEL extern const union decode_action kprobes_t32_actions[]; diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c index 7a449df0b359..cb4cb13bff88 100644 --- a/arch/arm/probes/kprobes/opt-arm.c +++ b/arch/arm/probes/kprobes/opt-arm.c @@ -161,13 +161,15 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) local_irq_save(flags); kcb = get_kprobe_ctlblk(); - if (kprobe_running()) { + if (!kprobe_can_nest(kcb)) { kprobes_inc_nmissed_count(&op->kp); } else { + if (kprobe_running()) + save_previous_kprobe(kcb); __this_cpu_write(current_kprobe, &op->kp); kcb->kprobe_status = KPROBE_HIT_ACTIVE; opt_pre_handler(&op->kp, regs); - __this_cpu_write(current_kprobe, NULL); + pop_current_kprobe(kcb); } /*