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=-4.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 52CECC433DF for ; Fri, 26 Jun 2020 11:43:12 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id A5F352082E for ; Fri, 26 Jun 2020 11:43:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="HW7pMPoh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A5F352082E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19175-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 1354 invoked by uid 550); 26 Jun 2020 11:43:04 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 1334 invoked from network); 26 Jun 2020 11:43:04 -0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=dY6UukHlcZ+e82YPYVTQRIm6jOfXAELNJfA0ddnH3+0=; b=HW7pMPohMNzcNWBrOKQR8629sZ nWVaNWWPYIkUbTocP1X7DaVMrLJyG+42HOb3gYa31ahAN0A9SDdMsxfvrhpa2NhQm82vYxw9YspeO 1M5y3dWrFnrmgzCjiVs8YhefAkoxs/xTmpxvoQ3Nbpz8Q+In7EI/KlCNxjmjP5rgTbfm6eBTBeF76 vizq1+U5H2tltHhneBCOdiW/U+nLYPmp4Zav8pPi8++UvCfn9aFu2mm4se8UZowRKHXBhSuBX1exq mHY2ns73zDMjIkR2nTGxS88dg/TS6tMHFLQutMWIVA9O+RXcOX0QKMAQPFwX25yccxW0i76etxb+g WXnTya+A==; Date: Fri, 26 Jun 2020 13:42:26 +0200 From: Peter Zijlstra To: Sami Tolvanen Cc: Steven Rostedt , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org, Josh Poimboeuf , mhelsley@vmware.com Subject: Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool Message-ID: <20200626114226.GH4817@hirez.programming.kicks-ass.net> References: <20200624203200.78870-1-samitolvanen@google.com> <20200624203200.78870-5-samitolvanen@google.com> <20200624212737.GV4817@hirez.programming.kicks-ass.net> <20200624214530.GA120457@google.com> <20200625074530.GW4817@hirez.programming.kicks-ass.net> <20200625161503.GB173089@google.com> <20200625200235.GQ4781@hirez.programming.kicks-ass.net> <20200625224042.GA169781@google.com> <20200626112931.GF4817@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200626112931.GF4817@hirez.programming.kicks-ass.net> On Fri, Jun 26, 2020 at 01:29:31PM +0200, Peter Zijlstra wrote: > On Thu, Jun 25, 2020 at 03:40:42PM -0700, Sami Tolvanen wrote: > > Anyway, since objtool is run before recordmcount, I just left this unchanged > > for testing and ignored the recordmcount warnings about __mcount_loc already > > existing. Something is a bit off still though, I see this at boot: > > > > ------------[ ftrace bug ]------------ > > ftrace failed to modify > > [] __tracepoint_iter_initcall_level+0x0/0x40 > > actual: 0f:1f:44:00:00 > > Initializing ftrace call sites > > ftrace record flags: 0 > > (0) > > expected tramp: ffffffff81056500 > > ------------[ cut here ]------------ > > > > Otherwise, this looks pretty good. > > Ha! it is trying to convert the "CALL __fentry__" into a NOP and not > finding the CALL -- because objtool already made it a NOP... > > Weird, I thought recordmcount would also write NOPs, it certainly has > code for that. I suppose we can use CC_USING_NOP_MCOUNT to avoid those, > but I'd rather Steve explain this before I wreck things further. Something like so would ignore whatever text is there and rewrite it with ideal_nop. --- diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index c84d28e90a58..98a6a93d7615 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -109,9 +109,11 @@ static int __ref ftrace_modify_code_direct(unsigned long ip, const char *old_code, const char *new_code) { - int ret = ftrace_verify_code(ip, old_code); - if (ret) - return ret; + if (old_code) { + int ret = ftrace_verify_code(ip, old_code); + if (ret) + return ret; + } /* replace the text with the new text */ if (ftrace_poke_late) @@ -124,9 +126,8 @@ ftrace_modify_code_direct(unsigned long ip, const char *old_code, int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned long ip = rec->ip; - const char *new, *old; + const char *new; - old = ftrace_call_replace(ip, addr); new = ftrace_nop_replace(); /* @@ -138,7 +139,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long ad * just modify the code directly. */ if (addr == MCOUNT_ADDR) - return ftrace_modify_code_direct(ip, old, new); + return ftrace_modify_code_direct(ip, NULL, new); /* * x86 overrides ftrace_replace_code -- this function will never be used