From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vNR9g65dPzDq60 for ; Wed, 15 Feb 2017 15:28:23 +1100 (AEDT) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1F4NdvA130870 for ; Tue, 14 Feb 2017 23:28:21 -0500 Received: from e31.co.us.ibm.com (e31.co.us.ibm.com [32.97.110.149]) by mx0a-001b2d01.pphosted.com with ESMTP id 28m9wxkcjp-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 14 Feb 2017 23:28:21 -0500 Received: from localhost by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 14 Feb 2017 21:28:20 -0700 Date: Wed, 15 Feb 2017 09:58:14 +0530 From: Ananth N Mavinakayanahalli To: "Naveen N. Rao" Cc: Masami Hiramatsu , Michael Ellerman , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON_FTRACE Reply-To: ananth@linux.vnet.ibm.com References: <1cc8a5580ae3a642fea137b7fe9c526402d4af33.1487098440.git.naveen.n.rao@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1cc8a5580ae3a642fea137b7fe9c526402d4af33.1487098440.git.naveen.n.rao@linux.vnet.ibm.com> Message-Id: <20170215042814.GA4660@in.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Feb 15, 2017 at 12:28:34AM +0530, Naveen N. Rao wrote: > Allow kprobes to be placed on ftrace _mcount() call sites. This > optimization avoids the use of a trap, by riding on ftrace > infrastructure. > > This depends on HAVE_DYNAMIC_FTRACE_WITH_REGS which depends on > MPROFILE_KERNEL, which is only currently enabled on powerpc64le with > newer toolchains. > > Based on the x86 code by Masami. > > Signed-off-by: Naveen N. Rao > --- > arch/powerpc/Kconfig | 1 + > arch/powerpc/include/asm/kprobes.h | 10 ++++ > arch/powerpc/kernel/Makefile | 3 ++ > arch/powerpc/kernel/kprobes-ftrace.c | 100 +++++++++++++++++++++++++++++++++++ > arch/powerpc/kernel/kprobes.c | 4 +- > arch/powerpc/kernel/optprobes.c | 3 ++ > 6 files changed, 120 insertions(+), 1 deletion(-) > create mode 100644 arch/powerpc/kernel/kprobes-ftrace.c You'll also need to update Documentation/features/debug/kprobes-on-ftrace/arch-support.txt > +/* Ftrace callback handler for kprobes */ > +void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > + struct ftrace_ops *ops, struct pt_regs *regs) > +{ > + struct kprobe *p; > + struct kprobe_ctlblk *kcb; > + unsigned long flags; > + > + /* Disable irq for emulating a breakpoint and avoiding preempt */ > + local_irq_save(flags); > + hard_irq_disable(); > + > + p = get_kprobe((kprobe_opcode_t *)nip); > + if (unlikely(!p) || kprobe_disabled(p)) > + goto end; > + > + kcb = get_kprobe_ctlblk(); > + if (kprobe_running()) { > + kprobes_inc_nmissed_count(p); > + } else { > + unsigned long orig_nip = regs->nip; > + /* Kprobe handler expects regs->nip = nip + 1 as breakpoint hit */ Can you clarify this? On powerpc, the regs->nip at the time of breakpoint hit points to the probed instruction, not the one after. Ananth