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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 7CF62C5CFE7 for ; Wed, 11 Jul 2018 19:34:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18A41213A2 for ; Wed, 11 Jul 2018 19:34:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18A41213A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=efficios.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388243AbeGKTka convert rfc822-to-8bit (ORCPT ); Wed, 11 Jul 2018 15:40:30 -0400 Received: from mail-io0-f195.google.com ([209.85.223.195]:36201 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726783AbeGKTka (ORCPT ); Wed, 11 Jul 2018 15:40:30 -0400 Received: by mail-io0-f195.google.com with SMTP id k3-v6so25348865iog.3 for ; Wed, 11 Jul 2018 12:34:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=z6lBAhaj7J8zlV4W9OGnReI0JD6aheHLFyTFvVy1k0A=; b=CdknEz6qKMJQozMGdCKhoW+gDBpGnKgG4zvcs6lSmXVjjBlfkyD7fWglLwiQIlpbgM ccOlZgcmsovxqmJjAw0oxa8Ijfd3Lw0lOLYpCL93OU5aV0GNqeQM4Ll+s4wmLq6mo8pu f2dAHso878Bc85kRdzDPfvEy3VOOaeoYkG8fctgctuvmdfPhTn6B57gh8R5BC36L+ZHI 0tcMM+os+L3jPUGBAwZLy5hm5/0/z6oTCKEdJwJr6FaGw3Q+QWu679jayjZj5kxQ5IZ+ 95gjojyzuXhcHeuhRE3grlbdN2LmStXnxHrCcoLYbMvjoRyDV2bJ6ocCDzwr1mgvagLb aVuQ== X-Gm-Message-State: AOUpUlETLWdF/vXDdBzSXa6/PwTZBplmLB1LrhZGD2soJrbXAcnbIiq2 kMgbs5IqI1+RLIm2hP2fmokB4FjthuiToBkr0jld8Mv1 X-Google-Smtp-Source: AAOMgpdSXWuUN1Wy8g1MNzM9ajkqPFMehCEkiZpMmTNSka8Bwd+IJy6cGMTb/k50MKY6NF/5TiAoKczBwhN1+GLmJ7A= X-Received: by 2002:a6b:b711:: with SMTP id h17-v6mr455584iof.521.1531337682442; Wed, 11 Jul 2018 12:34:42 -0700 (PDT) MIME-Version: 1.0 References: <1500044315-9508-1-git-send-email-francis.deslauriers@efficios.com> <1500044315-9508-3-git-send-email-francis.deslauriers@efficios.com> <20170714142900.1c91949c@gandalf.local.home> <20180316112517.66bdd85a@gandalf.local.home> <229385456.11580.1521217739037.JavaMail.zimbra@efficios.com> <20180316124134.30fa47d5@gandalf.local.home> <20180316124840.3e83bbec@gandalf.local.home> <1577244734.11604.1521222781948.JavaMail.zimbra@efficios.com> <20180317091334.55f1fc325c26deaa4d4a4d19@kernel.org> <20180317102211.a648f26ae0d5a53d95c63022@kernel.org> <20180703183048.1eeeef4a@gandalf.local.home> In-Reply-To: <20180703183048.1eeeef4a@gandalf.local.home> From: Francis Deslauriers Date: Wed, 11 Jul 2018 15:34:30 -0400 Message-ID: Subject: Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist_func to kprobe blacklist To: Steven Rostedt Cc: Mathieu Desnoyers , Masami Hiramatsu , Peter Zijlstra , linux-kernel , torvalds@linux-foundation.org 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 Hi Steven, I tested it and it prevents the kernel crash I am witnessing. As for the side-effect that Masami mentioned regarding not being able to probe function inside the trace_kprobe.c file, I suggest we move the target function in its own separate compile unit so it can be compiled with the ftrace cflags. See patch below. Thanks Francis >From d5a3645bd0046f28275d6b60207958f2751c1f47 Mon Sep 17 00:00:00 2001 From: Francis Deslauriers Date: Wed, 11 Jul 2018 12:34:22 -0400 Subject: [PATCH] selftest/ftrace: Move kprobe selftest function to separate compile unit Move selftest function to its own compile unit so it can be compiled with the ftrace cflags (CC_FLAGS_FTRACE) allowing it to be probed during the ftrace startup tests. Signed-off-by: Francis Deslauriers --- kernel/trace/Makefile | 5 +++++ kernel/trace/trace_kprobe.c | 12 +----------- kernel/trace/trace_kprobe_selftest.c | 10 ++++++++++ kernel/trace/trace_kprobe_selftest.h | 7 +++++++ 4 files changed, 23 insertions(+), 11 deletions(-) create mode 100644 kernel/trace/trace_kprobe_selftest.c create mode 100644 kernel/trace/trace_kprobe_selftest.h diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index e2538c7..e38771e 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -13,6 +13,11 @@ obj-y += trace_selftest_dynamic.o endif endif +ifdef CONFIG_FTRACE_STARTUP_TEST +CFLAGS_trace_kprobe_selftest.o = $(CC_FLAGS_FTRACE) +obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe_selftest.o +endif + # If unlikely tracing is enabled, do not trace these files ifdef CONFIG_TRACING_BRANCHES KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 952dc2a..3fe966f 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -24,6 +24,7 @@ #include #include "trace_probe.h" +#include "trace_kprobe_selftest.h" #define KPROBE_EVENT_SYSTEM "kprobes" #define KRETPROBE_MAXACTIVE_MAX 4096 @@ -1560,17 +1561,6 @@ fs_initcall(init_kprobe_trace); #ifdef CONFIG_FTRACE_STARTUP_TEST -/* - * The "__used" keeps gcc from removing the function symbol - * from the kallsyms table. 'noinline' makes sure that there - * isn't an inlined version used by the test method below - */ -static __used __init noinline int -kprobe_trace_selftest_target(int a1, int a2, int a3, int a4, int a5, int a6) -{ - return a1 + a2 + a3 + a4 + a5 + a6; -} - static __init struct trace_event_file * find_trace_probe_file(struct trace_kprobe *tk, struct trace_array *tr) { diff --git a/kernel/trace/trace_kprobe_selftest.c b/kernel/trace/trace_kprobe_selftest.c new file mode 100644 index 0000000..a3d2090 --- /dev/null +++ b/kernel/trace/trace_kprobe_selftest.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Function used during the kprobe self test. This function is in a seperate + * compile unit so it can be compile with CC_FLAGS_FTRACE to ensure that it + * can be probed by the selftests. + */ +int kprobe_trace_selftest_target(int a1, int a2, int a3, int a4, int a5, int a6) +{ + return a1 + a2 + a3 + a4 + a5 + a6; +} diff --git a/kernel/trace/trace_kprobe_selftest.h b/kernel/trace/trace_kprobe_selftest.h new file mode 100644 index 0000000..9243d4e --- /dev/null +++ b/kernel/trace/trace_kprobe_selftest.h @@ -0,0 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Function used during the kprobe self test. This function is in a seperate + * compile unit so it can be compile with CC_FLAGS_FTRACE to ensure that it + * can be probed by the selftests. + */ +int kprobe_trace_selftest_target(int a1, int a2, int a3, int a4, int a5, int a6); -- 2.7.4 Le mar. 3 juill. 2018, à 18 h 31, Steven Rostedt a écrit : > > Mathieu and Francis, > > Looking back, this thread never got further. Would Masami's patch work > for you? > > -- Steve > > > On Sat, 17 Mar 2018 10:22:11 +0900 > Masami Hiramatsu wrote: > > > On Sat, 17 Mar 2018 09:13:34 +0900 > > Masami Hiramatsu wrote: > > > > > On Fri, 16 Mar 2018 13:53:01 -0400 (EDT) > > > Mathieu Desnoyers wrote: > > > > > > > ----- On Mar 16, 2018, at 12:48 PM, rostedt rostedt@goodmis.org wrote: > > > > > > > > > On Fri, 16 Mar 2018 12:41:34 -0400 > > > > > Steven Rostedt wrote: > > > > > > > > > >> Yes, kprobes are dangerous. I'm not saying it shouldn't be fixed, I'm > > > > >> saying that I don't have time to fix it now, but would be happy to > > > > >> accept patches if someone else does so. > > > > > > > > > > And looking at what I replied before for the original patch. It would > > > > > probably be a good idea to blacklist directories. Like we do with > > > > > function tracing. We probably should black list both kernel/tracing and > > > > > kernel/events from being probed. > > > > > > > > > > Did this come up at plumbers? You were there too, I don't remember > > > > > discussing it there. > > > > > > > > I don't remember this coming up last Plumbers nor KS neither, given > > > > that we were focused on other topics. > > > > > > > > Would the general approach you envision be based on emitting all code > > > > generated by compilation of all objects under kernel/tracing and > > > > kernel/events into a specific "nokprobes" text section of the kernel ? > > > > Perhaps we could create a specific linker scripts for those directories, > > > > or do you have in mind a neater way to do this ? > > > > > > .kprobes.text section still exists. As I pointed in previous mail, I don't > > > think we have to put all those code into that section. But if you want, > > > it is acceptable to have a kconfig which push most of those ftrace related > > > code into .kprobes.text section. > > > > Or, we can check it by ftrace_location_range() as below patch. > > > > Note that as a side-effect, we can not trace functions in trace_kprobe.c > > anymore, and this means it is hard to me to make a testcase of kprobe events. > > It was the easiest (and maintainable) way to make test cases... sigh. > > > > ----- > > tracing: kprobes: Prohibit probing on notrace function > > > > From: Masami Hiramatsu > > > > Prohibit kprobe-events probing on notrace function. > > Since probing on the notrace function can cause recursive > > event call. In most case those are just skipped, but > > in some case it falls into infinit recursive call. > > > > Signed-off-by: Masami Hiramatsu > > --- > > kernel/trace/trace_kprobe.c | 23 +++++++++++++++++++++++ > > 1 file changed, 23 insertions(+) > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index 5ce9b8cf7be3..7404b012e51a 100644 > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -487,6 +487,23 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) > > return ret; > > } > > > > +#ifdef CONFIG_KPROBES_ON_FTRACE > > +static bool within_notrace_func(struct trace_kprobe *tk) > > +{ > > + unsigned long offset, size, addr; > > + > > + addr = kallsyms_lookup_name(trace_kprobe_symbol(tk)); > > + addr += trace_kprobe_offset(tk); > > + > > + if (!kallsyms_lookup_size_offset(addr, &size, &offset)) > > + return true; /* Out of range. */ > > + > > + return !ftrace_location_range(addr - offset, addr - offset + size); > > +} > > +#else > > +#define within_notrace_func(tk) (false) > > +#endif > > + > > /* Internal register function - just handle k*probes and flags */ > > static int __register_trace_kprobe(struct trace_kprobe *tk) > > { > > @@ -495,6 +512,12 @@ static int __register_trace_kprobe(struct trace_kprobe *tk) > > if (trace_probe_is_registered(&tk->tp)) > > return -EINVAL; > > > > + if (within_notrace_func(tk)) { > > + pr_warn("Could not probe notrace function %s\n", > > + trace_kprobe_symbol(tk)); > > + return -EINVAL; > > + } > > + > > for (i = 0; i < tk->tp.nr_args; i++) > > traceprobe_update_arg(&tk->tp.args[i]); > > > > > -- Francis Deslauriers Software developer EfficiOS inc.