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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 BA621C00449 for ; Mon, 8 Oct 2018 07:22:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BB6D2087C for ; Mon, 8 Oct 2018 07:22:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="2SCc0Bxt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7BB6D2087C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1726451AbeJHOck (ORCPT ); Mon, 8 Oct 2018 10:32:40 -0400 Received: from merlin.infradead.org ([205.233.59.134]:48356 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725950AbeJHOck (ORCPT ); Mon, 8 Oct 2018 10:32:40 -0400 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=zoATZdqlafS/3eCKuhEuqAYlbGPUieQWmTRfBK1bszU=; b=2SCc0BxtxOQteT9FdVUqkHLTJ 3v9pMKjF1ywQ5UAIttruDcGJuGiQnoUb6y1dBWwBEo/nHKe84dS7mu4IKBCDZUav7FrLunqHhLqDV WAT3OLHk0mnSbauMfMb7WNF1/Fn50y1JPI/3t7Qx86JZx3Z412IqrNdQtUx9JPNu0SfeM0mfNuEub ONIEWxE+6BQ93RWKW0ajhbQJnFtQ+2jycuV1TiERvm1NpK/JMd9x0GKUJb2uJidEyL6odP/ieZRv2 Wfc1oY/y11l/U8KgNpjrnVXnM1zetDJYVQPsJ47/YC4oaw1rLQvqgZNrmTtsB0Q0d+fAwz5kXDcOO OX/EZsA+Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1g9PrK-0002Wc-Fo; Mon, 08 Oct 2018 07:21:52 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 51A5520268264; Mon, 8 Oct 2018 09:21:34 +0200 (CEST) Date: Mon, 8 Oct 2018 09:21:34 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Ingo Molnar , Andrew Morton , Thomas Gleixner , Masami Hiramatsu , Mathieu Desnoyers , Matthew Helsley , "Rafael J . Wysocki" , David Woodhouse , Paolo Bonzini , Josh Poimboeuf , Jason Baron , Jiri Kosina , ard.biesheuvel@linaro.org, Andy Lutomirski Subject: Re: [POC][RFC][PATCH 1/2] jump_function: Addition of new feature "jump_function" Message-ID: <20181008072134.GB5663@hirez.programming.kicks-ass.net> References: <20181006015110.653946300@goodmis.org> <20181006015720.634688468@goodmis.org> <20181006121211.GA5663@hirez.programming.kicks-ass.net> <20181006093905.46276505@vmware.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181006093905.46276505@vmware.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 06, 2018 at 09:39:05AM -0400, Steven Rostedt wrote: > On Sat, 6 Oct 2018 14:12:11 +0200 > Peter Zijlstra wrote: > > > On Fri, Oct 05, 2018 at 09:51:11PM -0400, Steven Rostedt wrote: > > > +#define arch_dynfunc_trampoline(name, def) \ > > > + asm volatile ( \ > > > + ".globl dynfunc_" #name "; \n\t" \ > > > + "dynfunc_" #name ": \n\t" \ > > > + "jmp " #def " \n\t" \ > > > + ".balign 8 \n \t" \ > > > + : : : "memory" ) > > > > Bah, what is it with you people and trampolines. Why can't we, just like > > jump_label, patch the call directly? > > > > The whole call+jmp thing is silly, don't do that. It just wrecks I$ and > > is slower for no real reason afaict. > > My first attempt was to do just that. But to add a label at the > call site required handling all the parameters too. See my branch: > ftrace/jump_function-v1 for how ugly it got (and it didn't work). Can't we hijack the relocation records for these functions before they get thrown out in the (final) link pass or something?