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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 69E8DC47082 for ; Sat, 5 Jun 2021 11:11:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 551FD61242 for ; Sat, 5 Jun 2021 11:11:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230222AbhFELMs convert rfc822-to-8bit (ORCPT ); Sat, 5 Jun 2021 07:12:48 -0400 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:35529 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230197AbhFELMo (ORCPT ); Sat, 5 Jun 2021 07:12:44 -0400 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-476-XAGNN3y7OmmpP6l2y-Mz6Q-1; Sat, 05 Jun 2021 07:10:47 -0400 X-MC-Unique: XAGNN3y7OmmpP6l2y-Mz6Q-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9DFBF1927800; Sat, 5 Jun 2021 11:10:45 +0000 (UTC) Received: from krava.cust.in.nbox.cz (unknown [10.40.192.14]) by smtp.corp.redhat.com (Postfix) with ESMTP id EC6DA614FD; Sat, 5 Jun 2021 11:10:42 +0000 (UTC) From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "Steven Rostedt (VMware)" Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Daniel Xu , Viktor Malik Subject: [PATCH 02/19] x86/ftrace: Remove fault protection code in prepare_ftrace_return Date: Sat, 5 Jun 2021 13:10:17 +0200 Message-Id: <20210605111034.1810858-3-jolsa@kernel.org> In-Reply-To: <20210605111034.1810858-1-jolsa@kernel.org> References: <20210605111034.1810858-1-jolsa@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jolsa@kernel.org X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="US-ASCII" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org From: "Steven Rostedt (VMware)" Removing the fault protection code when writing return_hooker to stack. As Steven noted: > That protection was there from the beginning due to being "paranoid", > considering ftrace was bricking network cards. But that protection > would not have even protected against that. Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Jiri Olsa --- arch/x86/kernel/ftrace.c | 38 +++----------------------------------- 1 file changed, 3 insertions(+), 35 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 1b3ce3b4a2a2..c555624da989 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -625,12 +625,10 @@ int ftrace_disable_ftrace_graph_caller(void) * Hook the return address and push it in the stack of return addrs * in current thread info. */ -void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, +void prepare_ftrace_return(unsigned long ip, unsigned long *parent, unsigned long frame_pointer) { unsigned long return_hooker = (unsigned long)&return_to_handler; - unsigned long old; - int faulted; /* * When resuming from suspend-to-ram, this function can be indirectly @@ -650,37 +648,7 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; - /* - * Protect against fault, even if it shouldn't - * happen. This tool is too much intrusive to - * ignore such a protection. - */ - asm volatile( - "1: " _ASM_MOV " (%[parent]), %[old]\n" - "2: " _ASM_MOV " %[return_hooker], (%[parent])\n" - " movl $0, %[faulted]\n" - "3:\n" - - ".section .fixup, \"ax\"\n" - "4: movl $1, %[faulted]\n" - " jmp 3b\n" - ".previous\n" - - _ASM_EXTABLE(1b, 4b) - _ASM_EXTABLE(2b, 4b) - - : [old] "=&r" (old), [faulted] "=r" (faulted) - : [parent] "r" (parent), [return_hooker] "r" (return_hooker) - : "memory" - ); - - if (unlikely(faulted)) { - ftrace_graph_stop(); - WARN_ON(1); - return; - } - - if (function_graph_enter(old, self_addr, frame_pointer, parent)) - *parent = old; + if (!function_graph_enter(*parent, ip, frame_pointer, parent)) + *parent = return_hooker; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ -- 2.31.1