From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752398AbeEQAA3 (ORCPT ); Wed, 16 May 2018 20:00:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:59608 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752146AbeEQAA2 (ORCPT ); Wed, 16 May 2018 20:00:28 -0400 From: Masami Hiramatsu To: Thomas Gleixner , Ingo Molnar Cc: x86@kernel.org, Masami Hiramatsu , Ingo Molnar , "H . Peter Anvin" , linux-kernel@vger.kernel.org, Ananth N Mavinakayanahalli , Andrew Morton , Steven Rostedt , Laura Abbott , Josef Bacik , Alexei Starovoitov , Ravi Bangoria Subject: [PATCH -tip v3 7/7] x86: kprobes: Do not disable preempt on int3 path Date: Thu, 17 May 2018 09:00:03 +0900 Message-Id: <152651520340.25583.15074431112097053694.stgit@devbox> X-Mailer: git-send-email 2.13.6 In-Reply-To: <152651499561.25583.14488389770693278906.stgit@devbox> References: <152651499561.25583.14488389770693278906.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 Since int3 and debug exception(for singlestep) are run with IRQ disabled and while running single stepping we drop IF from regs->flags, that path must not be preemptible. So we can remove the preempt disable/enable calls from that path. Signed-off-by: Masami Hiramatsu Suggested-by: Ingo Molnar --- Changes in v3: - Split user-side changes to another patch Changes in v2: - Include user-side changes. --- Documentation/kprobes.txt | 11 +++++------ arch/x86/kernel/kprobes/core.c | 18 ++++-------------- arch/x86/kernel/kprobes/opt.c | 1 - 3 files changed, 9 insertions(+), 21 deletions(-) diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index 907a3017c0f2..3e9e99ea751b 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -566,12 +566,11 @@ the same handler) may run concurrently on different CPUs. Kprobes does not use mutexes or allocate memory except during registration and unregistration. -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). In any case, -your handler should not yield the CPU (e.g., by attempting to acquire -a semaphore). +Probe handlers are run with preemption disabled or interrupt disabled, +which depends on the architecture and optimization state. (e.g., +kretprobe handlers and optimized kprobe handlers run without interrupt +disabled on x86/x86-64). In any case, your handler should not yield +the CPU (e.g., by attempting to acquire a semaphore, or waiting I/O). Since a return probe is implemented by replacing the return address with the trampoline's address, stack backtraces and calls diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 215a28bdd9df..a2896ff47ebc 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -596,7 +596,6 @@ static void setup_singlestep(struct kprobe *p, struct pt_regs *regs, * stepping. */ regs->ip = (unsigned long)p->ainsn.insn; - preempt_enable_no_resched(); return; } #endif @@ -669,12 +668,10 @@ int kprobe_int3_handler(struct pt_regs *regs) addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t)); /* - * We don't want to be preempted for the entire - * duration of kprobe processing. We conditionally - * re-enable preemption at the end of this function, - * and also in reenter_kprobe() and setup_singlestep(). + * We don't want to be preempted for the entire duration of kprobe + * processing. Since int3 and debug trap disables irqs and we clear + * IF while singlestepping, it must be no preemptible. */ - preempt_disable(); kcb = get_kprobe_ctlblk(); p = get_kprobe(addr); @@ -695,10 +692,8 @@ int kprobe_int3_handler(struct pt_regs *regs) */ if (!p->pre_handler || !p->pre_handler(p, regs)) setup_singlestep(p, regs, kcb, 0); - else { + else reset_current_kprobe(); - preempt_enable_no_resched(); - } return 1; } } else if (*addr != BREAKPOINT_INSTRUCTION) { @@ -712,11 +707,9 @@ int kprobe_int3_handler(struct pt_regs *regs) * the original instruction. */ regs->ip = (unsigned long)addr; - preempt_enable_no_resched(); return 1; } /* else: not a kprobe fault; let the kernel handle it */ - preempt_enable_no_resched(); return 0; } NOKPROBE_SYMBOL(kprobe_int3_handler); @@ -967,8 +960,6 @@ int kprobe_debug_handler(struct pt_regs *regs) } reset_current_kprobe(); out: - preempt_enable_no_resched(); - /* * if somebody else is singlestepping across a probe point, flags * will have TF set, in which case, continue the remaining processing @@ -1015,7 +1006,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) restore_previous_kprobe(kcb); else reset_current_kprobe(); - preempt_enable_no_resched(); } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE || kcb->kprobe_status == KPROBE_HIT_SSDONE) { /* diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index 203d398802a3..eaf02f2e7300 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -491,7 +491,6 @@ int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter) regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; if (!reenter) reset_current_kprobe(); - preempt_enable_no_resched(); return 1; } return 0;