From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751578AbdISKC4 (ORCPT ); Tue, 19 Sep 2017 06:02:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:52926 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750948AbdISKCz (ORCPT ); Tue, 19 Sep 2017 06:02:55 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F4DA21D29 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org From: Masami Hiramatsu To: Ingo Molnar , mingo@redhat.com Cc: x86@kernel.org, Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, Peter Zijlstra , Ananth N Mavinakayanahalli , Thomas Gleixner , "H . Peter Anvin" , "Paul E . McKenney" , Alexei Starovoitov , Alexei Starovoitov Subject: [PATCH -tip v3 6/7] kprobes/x86: Remove disable_irq from ftrace-based/optimized kprobe Date: Tue, 19 Sep 2017 19:02:20 +0900 Message-Id: <150581534039.32348.11331736206004264553.stgit@devbox> X-Mailer: git-send-email 2.13.5 In-Reply-To: <150581509713.32348.1905525476438163954.stgit@devbox> References: <150581509713.32348.1905525476438163954.stgit@devbox> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Actually kprobes doesn't need to disable irq if it is called from ftrace/jump trampoline code because Documentation/kprobes.txt says ----- Probe handlers are run with preemption disabled. Depending on the architecture and optimization state, handlers may also run with interrupts disabled (e.g., kretprobe handlers and optimized kprobe handlers run without interrupt disabled on x86/x86-64). ----- So let's remove irq disabling from those handlers. Signed-off-by: Masami Hiramatsu --- arch/x86/kernel/kprobes/ftrace.c | 9 ++------- arch/x86/kernel/kprobes/opt.c | 4 ---- 2 files changed, 2 insertions(+), 11 deletions(-) diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c index bcfee4f69b0e..8dc0161cec8f 100644 --- a/arch/x86/kernel/kprobes/ftrace.c +++ b/arch/x86/kernel/kprobes/ftrace.c @@ -61,14 +61,11 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, { struct kprobe *p; struct kprobe_ctlblk *kcb; - unsigned long flags; - - /* Disable irq for emulating a breakpoint and avoiding preempt */ - local_irq_save(flags); + /* Preempt is disabled by ftrace */ p = get_kprobe((kprobe_opcode_t *)ip); if (unlikely(!p) || kprobe_disabled(p)) - goto end; + return; kcb = get_kprobe_ctlblk(); if (kprobe_running()) { @@ -91,8 +88,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, * resets current kprobe, and keep preempt count +1. */ } -end: - local_irq_restore(flags); } NOKPROBE_SYMBOL(kprobe_ftrace_handler); diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index 36e4f61c3eec..511aad1990a0 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -154,13 +154,10 @@ STACK_FRAME_NON_STANDARD(optprobe_template_func); static void optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) { - unsigned long flags; - /* This is possible if op is under delayed unoptimizing */ if (kprobe_disabled(&op->kp)) return; - local_irq_save(flags); preempt_disable(); if (kprobe_running()) { kprobes_inc_nmissed_count(&op->kp); @@ -182,7 +179,6 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) __this_cpu_write(current_kprobe, NULL); } preempt_enable_no_resched(); - local_irq_restore(flags); } NOKPROBE_SYMBOL(optimized_callback);