From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3F1CC4724C for ; Thu, 7 May 2020 10:00:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84D7B21841 for ; Thu, 7 May 2020 10:00:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588845619; bh=Ko6k8yqP06qLO+fR2BdBxjRgEa8MZZiOx9Hf589ZMx4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Edq66qG/EqMDiwcMcbFIbGcJ150xeU467T7W1VfWppWmRKrbwTZwvp+KrkeGuYfzQ a9AO4WiaNoVPJ1/t4MFUdbd6KCXevQ0skijtxOL7FQ2Y8r0DW1YXTr5ocGa7MLeP56 mjXfjelxRMK4lYNvP0rYZtaFb5VMEWyg9dc77OoQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726751AbgEGKAS (ORCPT ); Thu, 7 May 2020 06:00:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:38698 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726565AbgEGKAD (ORCPT ); Thu, 7 May 2020 06:00:03 -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 D52452083B; Thu, 7 May 2020 09:59:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588845602; bh=Ko6k8yqP06qLO+fR2BdBxjRgEa8MZZiOx9Hf589ZMx4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0ifHte+WaaOnrGKB6g/CwIZIOBFQBXXFFT84SIJ8kY0txiPpt2IIUCifUpkoUF3y9 0kcoYGHkYa1qEHYieX41XlxUs/JBtZ0QgtVizzIAAnldahFdPdDLN4MnpD9I1mf9Eq wapM4oPFqcr8q0T0y9+6Fla6bSX7CGEWul+fViso= 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 1/3] x86/kprobes: Support nested kprobes Date: Thu, 7 May 2020 18:59:55 +0900 Message-Id: <158884559505.12656.1357851132314046716.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 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Make kprobes to accept 1-level nesting instead of missing it. 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. This is useful if user wants to trace/debug the code which can be invoked from another kprobe handlers. 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 int3 handler # echo stacktrace > events/kprobes/p_ring_buffer_lock_reserve_0/trigger # echo 1 > events/kprobes/enable # cat trace ... cat-161 [000] d..1 46602.280111: p_vfs_read_0: (vfs_read+0x0/0x150) cat-161 [000] d..2 46602.280222: p_ring_buffer_lock_reserve_0: (ring_buffer_lock_reserve+0x0/0x400) cat-161 [000] d..2 46602.280247: => kprobe_trace_func => kprobe_dispatcher => aggr_pre_handler => kprobe_int3_handler => do_int3 => int3 => ring_buffer_lock_reserve => trace_event_buffer_lock_reserve => kprobe_trace_func => kprobe_dispatcher => aggr_pre_handler => kprobe_int3_handler => do_int3 => int3 => vfs_read => kernel_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 This shows int3 is nested. Signed-off-by: Masami Hiramatsu --- 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 +++-- 5 files changed, 92 insertions(+), 67 deletions(-) diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h index 073eb7ad2f56..60ca23aeece8 100644 --- a/arch/x86/include/asm/kprobes.h +++ b/arch/x86/include/asm/kprobes.h @@ -83,6 +83,8 @@ static inline int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) return optinsn->size; } +#define KPROBE_NEST_MAX 2 + struct prev_kprobe { struct kprobe *kp; unsigned long status; @@ -95,7 +97,8 @@ struct kprobe_ctlblk { unsigned long kprobe_status; unsigned long kprobe_old_flags; unsigned long kprobe_saved_flags; - struct prev_kprobe prev_kprobe; + struct prev_kprobe prev[KPROBE_NEST_MAX]; + int nested; }; extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr); diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h index 7d3a2e2daf01..490e871df36e 100644 --- a/arch/x86/kernel/kprobes/common.h +++ b/arch/x86/kernel/kprobes/common.h @@ -91,11 +91,46 @@ extern int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn); extern void synthesize_reljump(void *dest, void *from, void *to); extern void synthesize_relcall(void *dest, void *from, void *to); +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; + kcb->prev[i].old_flags = kcb->kprobe_old_flags; + kcb->prev[i].saved_flags = kcb->kprobe_saved_flags; +} + +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; + kcb->kprobe_old_flags = kcb->prev[i].old_flags; + kcb->kprobe_saved_flags = kcb->prev[i].saved_flags; +} + +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_OPTPROBES -extern int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter); +extern int setup_detour_execution(struct kprobe *p, struct pt_regs *regs); extern unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr); #else /* !CONFIG_OPTPROBES */ -static inline int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter) +static inline int setup_detour_execution(struct kprobe *p, struct pt_regs *regs) { return 0; } diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 4d7022a740ab..998524b73d4d 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -520,24 +520,6 @@ void arch_remove_kprobe(struct kprobe *p) } } -static nokprobe_inline void -save_previous_kprobe(struct kprobe_ctlblk *kcb) -{ - kcb->prev_kprobe.kp = kprobe_running(); - kcb->prev_kprobe.status = kcb->kprobe_status; - kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags; - kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags; -} - -static nokprobe_inline void -restore_previous_kprobe(struct kprobe_ctlblk *kcb) -{ - __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); - kcb->kprobe_status = kcb->prev_kprobe.status; - kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags; - kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags; -} - static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) @@ -581,26 +563,34 @@ void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) } NOKPROBE_SYMBOL(arch_prepare_kretprobe); -static void setup_singlestep(struct kprobe *p, struct pt_regs *regs, - struct kprobe_ctlblk *kcb, int reenter) +static nokprobe_inline +int setup_booster_execution(struct kprobe *p, struct pt_regs *regs) { - if (setup_detour_execution(p, regs, reenter)) - return; - #if !defined(CONFIG_PREEMPTION) if (p->ainsn.boostable && !p->post_handler) { /* Boost up -- we can execute copied instructions directly */ + regs->ip = (unsigned long)p->ainsn.insn; + return 1; + } +#endif + return 0; +} + +static void setup_singlestep(struct kprobe *p, struct pt_regs *regs, + struct kprobe_ctlblk *kcb, int reenter) +{ + if (setup_detour_execution(p, regs) || + setup_booster_execution(p, regs)) { if (!reenter) - reset_current_kprobe(); + pop_current_kprobe(kcb); /* * Reentering boosted probe doesn't reset current_kprobe, * nor set current_kprobe, because it doesn't use single * stepping. */ - regs->ip = (unsigned long)p->ainsn.insn; return; } -#endif + if (reenter) { save_previous_kprobe(kcb); set_current_kprobe(p, regs, kcb); @@ -630,6 +620,11 @@ static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs, switch (kcb->kprobe_status) { case KPROBE_HIT_SSDONE: case KPROBE_HIT_ACTIVE: + if (kcb->nested < KPROBE_NEST_MAX - 1) { + save_previous_kprobe(kcb); + return 0; + } + fallthrough; case KPROBE_HIT_SS: kprobes_inc_nmissed_count(p); setup_singlestep(p, regs, kcb, 1); @@ -678,26 +673,24 @@ int kprobe_int3_handler(struct pt_regs *regs) p = get_kprobe(addr); if (p) { - if (kprobe_running()) { - if (reenter_kprobe(p, regs, kcb)) - return 1; - } else { - set_current_kprobe(p, regs, kcb); - kcb->kprobe_status = KPROBE_HIT_ACTIVE; - - /* - * If we have no pre-handler or it returned 0, we - * continue with normal processing. If we have a - * pre-handler and it returned non-zero, that means - * user handler setup registers to exit to another - * instruction, we must skip the single stepping. - */ - if (!p->pre_handler || !p->pre_handler(p, regs)) - setup_singlestep(p, regs, kcb, 0); - else - reset_current_kprobe(); + if (kprobe_running() && reenter_kprobe(p, regs, kcb)) return 1; - } + + set_current_kprobe(p, regs, kcb); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + + /* + * If we have no pre-handler or it returned 0, we + * continue with normal processing. If we have a + * pre-handler and it returned non-zero, that means + * user handler setup registers to exit to another + * instruction, we must skip the single stepping. + */ + if (!p->pre_handler || !p->pre_handler(p, regs)) + setup_singlestep(p, regs, kcb, 0); + else + pop_current_kprobe(kcb); + return 1; } else if (*addr != INT3_INSN_OPCODE) { /* * The breakpoint instruction was removed right @@ -994,13 +987,7 @@ int kprobe_debug_handler(struct pt_regs *regs) cur->post_handler(cur, regs, 0); } - /* Restore back the original saved kprobes variables and continue. */ - if (kcb->kprobe_status == KPROBE_REENTER) { - restore_previous_kprobe(kcb); - goto out; - } - reset_current_kprobe(); -out: + pop_current_kprobe(kcb); /* * if somebody else is singlestepping across a probe point, flags * will have TF set, in which case, continue the remaining processing @@ -1043,10 +1030,7 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) */ regs->flags |= kcb->kprobe_old_flags; - if (kcb->kprobe_status == KPROBE_REENTER) - restore_previous_kprobe(kcb); - else - reset_current_kprobe(); + pop_current_kprobe(kcb); } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE || kcb->kprobe_status == KPROBE_HIT_SSDONE) { /* diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c index 681a4b36e9bb..b695c2e118f8 100644 --- a/arch/x86/kernel/kprobes/ftrace.c +++ b/arch/x86/kernel/kprobes/ftrace.c @@ -25,13 +25,15 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, return; kcb = get_kprobe_ctlblk(); - if (kprobe_running()) { + if (!kprobe_can_nest()) { kprobes_inc_nmissed_count(p); } else { unsigned long orig_ip = regs->ip; /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ regs->ip = ip + sizeof(kprobe_opcode_t); + if (kprobe_running()) + save_previous_kprobe(kcb); __this_cpu_write(current_kprobe, p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (!p->pre_handler || !p->pre_handler(p, regs)) { @@ -50,7 +52,7 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, * If pre_handler returns !0, it changes regs->ip. We have to * skip emulating post_handler. */ - __this_cpu_write(current_kprobe, NULL); + pop_current_kprobe(kcb); } } NOKPROBE_SYMBOL(kprobe_ftrace_handler); diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index ea13f6888284..ec7cfd4906e3 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -168,15 +168,16 @@ STACK_FRAME_NON_STANDARD(optprobe_template_func); static void optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) { + struct kprobe_ctlblk *kcb; /* This is possible if op is under delayed unoptimizing */ if (kprobe_disabled(&op->kp)) return; preempt_disable(); - if (kprobe_running()) { + kcb = get_kprobe_ctlblk(); + if (!kprobe_can_nest(kcb)) { kprobes_inc_nmissed_count(&op->kp); } else { - struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); /* Save skipped registers */ regs->cs = __KERNEL_CS; #ifdef CONFIG_X86_32 @@ -186,10 +187,12 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) regs->ip = (unsigned long)op->kp.addr + INT3_INSN_SIZE; regs->orig_ax = ~0UL; + 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); } preempt_enable(); } @@ -500,7 +503,7 @@ extern void arch_unoptimize_kprobes(struct list_head *oplist, } } -int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter) +int setup_detour_execution(struct kprobe *p, struct pt_regs *regs) { struct optimized_kprobe *op; @@ -509,8 +512,6 @@ int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter) op = container_of(p, struct optimized_kprobe, kp); /* Detour through copied instructions */ regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; - if (!reenter) - reset_current_kprobe(); return 1; } return 0;