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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C7924CA9EB7 for ; Tue, 22 Oct 2019 11:28:38 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9E8AD214B2 for ; Tue, 22 Oct 2019 11:28:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="qPW9YzPd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9E8AD214B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=2309EUqNQZUpZSWmKrwP3u4C60VHH4aPMEg7r33LuYI=; b=qPW9YzPdwyh2Fz /zNrq5UDzG1T9H+9bdbjkdl1YYg0KSkqbpmVXv3T3IbiFJgHyFt4WHmkR04JwJaiKt2letY8qn5+O 7W3sY0voU+6VRC15cV4oSW5P0wRdNKvOQf3kQl5gT9UkT+EZJ2vI7n932YxFs9ax0ryuc+6TG8QpI cfGtiHp4gbexajYbCPrOEX4lkUm17UP0hjfBjMFnqWaRPKt3UwGxbFXowVShcMx1L2gM6ElMdUtRD 62gpff5RVtEokbiaqkBtHlY+EizyXzhB3WvSR0xkksgxVxV9wGQvBCXRnm3fVRvDK0+VwElDBpMsa GWcZHXUiNWJlc3g77jpQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iMsL7-0004ZB-Vu; Tue, 22 Oct 2019 11:28:37 +0000 Received: from [217.140.110.172] (helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iMsL4-0004YL-Pq for linux-arm-kernel@lists.infradead.org; Tue, 22 Oct 2019 11:28:36 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E47011007; Tue, 22 Oct 2019 04:28:23 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C6E213F718; Tue, 22 Oct 2019 04:28:21 -0700 (PDT) Date: Tue, 22 Oct 2019 12:28:11 +0100 From: Mark Rutland To: Steven Rostedt Subject: Re: [PATCH 1/8] ftrace: add ftrace_init_nop() Message-ID: <20191022112811.GA11583@lakrids.cambridge.arm.com> References: <20191021163426.9408-1-mark.rutland@arm.com> <20191021163426.9408-2-mark.rutland@arm.com> <20191021140756.613a1bac@gandalf.local.home> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191021140756.613a1bac@gandalf.local.home> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191022_042834_925257_6DF5D7DA X-CRM114-Status: GOOD ( 23.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jthierry@redhat.com, will@kernel.org, ard.biesheuvel@linaro.org, peterz@infradead.org, catalin.marinas@arm.com, deller@gmx.de, jpoimboe@redhat.com, linux-kernel@vger.kernel.org, takahiro.akashi@linaro.org, mingo@redhat.com, james.morse@arm.com, jeyu@kernel.org, amit.kachhap@arm.com, svens@stackframe.org, duwe@suse.de, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 21, 2019 at 02:07:56PM -0400, Steven Rostedt wrote: > On Mon, 21 Oct 2019 17:34:19 +0100 > Mark Rutland wrote: > > > Architectures may need to perform special initialization of ftrace > > callsites, and today they do so by special-casing ftrace_make_nop() when > > the expected branch address is MCOUNT_ADDR. In some cases (e.g. for > > patchable-function-entry), we don't have an mcount-like symbol and don't > > want a synthetic MCOUNT_ADDR, but we may need to perform some > > initialization of callsites. > > > > To make it possible to separate initialization from runtime > > modification, and to handle cases without an mcount-like symbol, this > > patch adds an optional ftrace_init_nop() function that architectures can > > implement, which does not pass a branch address. > > > > Where an architecture does not provide ftrace_init_nop(), we will fall > > back to the existing behaviour of calling ftrace_make_nop() with > > MCOUNT_ADDR. > > > > At the same time, ftrace_code_disable() is renamed to > > ftrace_code_init_disabled() to make it clearer that it is intended to > > intialize a callsite into a disabled state, and is not for disabling a > > callsite that has been runtime enabled. > > To make the name even better, let's just rename it to: > > ftrace_nop_initialization() > > I think that may be the best description for it. Perhaps ftrace_nop_initialize(), so that it's not a noun? I've made it ftrace_nop_initialization() in my branch for now. > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index f296d89be757..afd7e210e595 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -2493,15 +2493,22 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter) > > return &iter->pg->records[iter->index]; > > } > > > > +#ifndef ftrace_init_nop > > +static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > > +{ > > + return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > > +} > > +#endif > > Can you place the above in the ftrace.h header. That's where that would > belong. > > #ifndef ftrace_init_nop > struct module; > static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > { > return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > } > #endif True. I've put this immediately after ftrace_make_nop() in the header, and given it a kerneldoc comment. There's a declaration for struct module at the top of the header, so I've just relied on that That looks like: | /** | * ftrace_init_nop - initialize a nop call site | * @mod: module structure if called by module load initialization | * @rec: the mcount call site record | * | * This is a very sensitive operation and great care needs | * to be taken by the arch. The operation should carefully | * read the location, check to see if what is read is indeed | * what we expect it to be, and then on success of the compare, | * it should write to the location. | * | * The code segment at @rec->ip should be as initialized by the | * compiler | * | * Return must be: | * 0 on success | * -EFAULT on error reading the location | * -EINVAL on a failed compare of the contents | * -EPERM on error writing to the location | * Any other value will be considered a failure. | */ | #ifndef ftrace_init_nop | static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) | { | return ftrace_make_nop(mod, rec, MCOUNT_ADDR); | } | #endif Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel