Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752910AbaJUDte (ORCPT ); Mon, 20 Oct 2014 23:49:34 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:42025 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751014AbaJUDtd (ORCPT ); Mon, 20 Oct 2014 23:49:33 -0400 Message-ID: <5445D7C5.1080006@hitachi.com> Date: Tue, 21 Oct 2014 12:49:25 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Heiko Carstens Cc: Ananth N Mavinakayanahalli , Anil S Keshavamurthy , "David S. Miller" , Ingo Molnar , Vojtech Pavlik , Jiri Kosina , Jiri Slaby , Steven Rostedt , Martin Schwidefsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] kprobes: introduce ARCH_HANDLES_KPROBES_ON_FTRACE References: <1413802794-38998-1-git-send-email-heiko.carstens@de.ibm.com> <1413802794-38998-2-git-send-email-heiko.carstens@de.ibm.com> In-Reply-To: <1413802794-38998-2-git-send-email-heiko.carstens@de.ibm.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/10/20 19:59), Heiko Carstens wrote: > Allow architectures to implement handling of kprobes on function > tracer call sites on their own, without depending on common code. > > This patch removes the kprobes check if a kprobe is being placed > on a function tracer call site and therefore gives full responsibility > of handling this correctly to the architecture. > > This patch also introduces a user space visible change: if a kprobe > is placed into the middle of an ftrace instruction the return value > is changed from -EINVAL to -EILSEQ also for architectures which do > not support KPROBES_ON_FTRACE. > However in reality this change shouldn't matter at all. Could you try to remove new kconfig by using a weak function? This could be done with below functions: In kernel/kprobes.c: int __weak arch_check_ftrace_location(struct kprobe *p) { unsigned long ftrace_addr = ftrace_location((unsigned long)p->addr); if (ftrace_addr) { ... } And in arch/s390/kernel/kprobes.c: int arch_check_ftrace_location(struct kprobe *p) { return 0; } And in include/linux/kprobes.h int arch_check_ftrace_location(struct kprobe *p); Then, we don't need to add any macros or kconfigs. Thank you, > > Signed-off-by: Heiko Carstens > --- > arch/Kconfig | 8 ++++++++ > kernel/kprobes.c | 36 +++++++++++++++++++++--------------- > 2 files changed, 29 insertions(+), 15 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 05d7a8a458d5..e1a8e0edf03f 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -85,6 +85,14 @@ config KPROBES_ON_FTRACE > passing of pt_regs to function tracing, then kprobes can > optimize on top of function tracing. > > +config ARCH_HANDLES_KPROBES_ON_FTRACE > + def_bool n > + help > + If an architecture can handle kprobes on function tracer call > + sites on own, then this option should be selected. This option > + removes the check which otherwise prevents to set kprobes on > + function tracer call sites. > + > config UPROBES > def_bool n > select PERCPU_RWSEM > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 3995f546d0f3..4b57fe9fbeb7 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1410,28 +1410,34 @@ static inline int check_kprobe_rereg(struct kprobe *p) > return ret; > } > > -static int check_kprobe_address_safe(struct kprobe *p, > - struct module **probed_mod) > +static int check_ftrace_location(struct kprobe *p) > { > - int ret = 0; > unsigned long ftrace_addr; > > - /* > - * If the address is located on a ftrace nop, set the > - * breakpoint to the following instruction. > - */ > ftrace_addr = ftrace_location((unsigned long)p->addr); > - if (ftrace_addr) { > -#ifdef CONFIG_KPROBES_ON_FTRACE > - /* Given address is not on the instruction boundary */ > - if ((unsigned long)p->addr != ftrace_addr) > - return -EILSEQ; > + if (!ftrace_addr) > + return 0; > + /* Given address is not on the instruction boundary */ > + if ((unsigned long)p->addr != ftrace_addr) > + return -EILSEQ; > + /* If an architecture handles kprobes on ftrace, we're done */ > + if (IS_ENABLED(CONFIG_ARCH_HANDLES_KPROBES_ON_FTRACE)) > + return 0; > + if (IS_ENABLED(CONFIG_KPROBES_ON_FTRACE)) { > p->flags |= KPROBE_FLAG_FTRACE; > -#else /* !CONFIG_KPROBES_ON_FTRACE */ > - return -EINVAL; > -#endif > + return 0; > } > + return -EINVAL; > +} > + > +static int check_kprobe_address_safe(struct kprobe *p, > + struct module **probed_mod) > +{ > + int ret; > > + ret = check_ftrace_location(p); > + if (ret) > + return ret; > jump_label_lock(); > preempt_disable(); > > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/