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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, 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 B7D6DC43441 for ; Mon, 26 Nov 2018 16:02:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 557FD20645 for ; Mon, 26 Nov 2018 16:02:39 +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="dZBp+NIU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 557FD20645 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 S1726654AbeK0C5J (ORCPT ); Mon, 26 Nov 2018 21:57:09 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:57616 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726255AbeK0C5J (ORCPT ); Mon, 26 Nov 2018 21:57:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=VsTCm5zE3RpQJBZbC8onKGQcf6Oja50LKgsJ8cRfa9s=; b=dZBp+NIUabKA7+eVREo8mbGie YZXDDkAM1OLsO1qAjFuNocVVa1l/ZMwtxkplQo/veN3oucqB+igBpLrLuxcTH2nFKNAT7butgNutn vVV4db7HiKga9WvXF7VRQPQDRVckWbqk+6MaAuir5AfUG7krYaFYMnU0iJNCQeBiRbv6Zs4g1AshR oRCbcFtgJny2BR7rHoQLEsLFqTJDbqEYlaRGFAuBd41+WwtFbzwuvlwtqMsMr8fLqDQGEebgRL6qU V7Rwpb0pby4Til8m4wUgvkGwB/WKSuviN1vKwXoSWNptVEReuieYWkpxoxSy7jVTbK6PlBqeRcmaV V9gSOdFqw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gRJL0-0006LU-M8; Mon, 26 Nov 2018 16:02:18 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 12CFC2029F87F; Mon, 26 Nov 2018 17:02:17 +0100 (CET) Date: Mon, 26 Nov 2018 17:02:17 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Ard Biesheuvel , Andy Lutomirski , Steven Rostedt , Ingo Molnar , Thomas Gleixner , Linus Torvalds , Masami Hiramatsu , Jason Baron , Jiri Kosina , David Laight , Borislav Petkov , Julia Cartwright , Jessica Yu , "H. Peter Anvin" Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64 Message-ID: <20181126160217.GR2113@hirez.programming.kicks-ass.net> References: <62188c62f6dda49ca2e20629ee8e5a62a6c0b500.1543200841.git.jpoimboe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <62188c62f6dda49ca2e20629ee8e5a62a6c0b500.1543200841.git.jpoimboe@redhat.com> 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 Mon, Nov 26, 2018 at 07:55:00AM -0600, Josh Poimboeuf wrote: > diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c > index 8026d176f25c..d3869295b88d 100644 > --- a/arch/x86/kernel/static_call.c > +++ b/arch/x86/kernel/static_call.c > @@ -9,13 +9,21 @@ > > void static_call_bp_handler(void); > void *bp_handler_dest; > +void *bp_handler_continue; > > asm(".pushsection .text, \"ax\" \n" > ".globl static_call_bp_handler \n" > ".type static_call_bp_handler, @function \n" > "static_call_bp_handler: \n" > - "ANNOTATE_RETPOLINE_SAFE \n" > +#ifdef CONFIG_HAVE_STATIC_CALL_INLINE > + ANNOTATE_RETPOLINE_SAFE > + "call *bp_handler_dest \n" > + ANNOTATE_RETPOLINE_SAFE > + "jmp *bp_handler_continue \n" > +#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */ > + ANNOTATE_RETPOLINE_SAFE > "jmp *bp_handler_dest \n" > +#endif > ".popsection \n"); > > void arch_static_call_transform(void *site, void *tramp, void *func) > @@ -25,7 +33,10 @@ void arch_static_call_transform(void *site, void *tramp, void *func) > unsigned char insn_opcode; > unsigned char opcodes[CALL_INSN_SIZE]; > > - insn = (unsigned long)tramp; > + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE)) > + insn = (unsigned long)site; > + else > + insn = (unsigned long)tramp; > > mutex_lock(&text_mutex); > > @@ -41,8 +52,10 @@ void arch_static_call_transform(void *site, void *tramp, void *func) > opcodes[0] = insn_opcode; > memcpy(&opcodes[1], &dest_relative, CALL_INSN_SIZE - 1); > > - /* Set up the variable for the breakpoint handler: */ > + /* Set up the variables for the breakpoint handler: */ > bp_handler_dest = func; > + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE)) > + bp_handler_continue = (void *)(insn + CALL_INSN_SIZE); > > /* Patch the call site: */ > text_poke_bp((void *)insn, opcodes, CALL_INSN_SIZE, OK, so this is where that static_call_bp_handler comes from; you need that CALL to frob the stack. But I still think it is broken; consider: CPU0 CPU1 bp_handler = ponies; text_poke_bp(, &static_call_bp_handler) text_poke(&int3); on_each_cpu(sync) ... text_poke(/* all but first bytes */) on_each_cpu(sync) ... pt_regs->ip = &static_call_bp_handler // VCPU takes a nap... text_poke(/* first byte */) on_each_cpu(sync) ... // VCPU sleeps more bp_handler = unicorn; CALL unicorn *whoops* Now, granted, that is all rather 'unlikely', but that never stopped Murphy.