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=-6.9 required=3.0 tests=BAYES_00,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 61153C4741F for ; Mon, 9 Nov 2020 11:10:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03D7A2080C for ; Mon, 9 Nov 2020 11:10:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="oDJEAMEx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729478AbgKILKz (ORCPT ); Mon, 9 Nov 2020 06:10:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729255AbgKILKx (ORCPT ); Mon, 9 Nov 2020 06:10:53 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51BB5C0613CF for ; Mon, 9 Nov 2020 03:10:53 -0800 (PST) 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=FNTdaPloac3xAnTI3p38yxyfUBIIpHPtkdnpaIX+cPA=; b=oDJEAMExmpWeOpjVtmn7qfM3Cf eNJJdyC4UrGgnk+p7Psn1qMR9x8GAroA3efUiawmjJpfXBrFrnEPLLoAfOMaHI+7gnu6tj1FCQhY7 wUhyFnP9maId/VRwXIM3BpGc6uuqSU2WaeGsvFIPot1skmQ5UoaGjSQGU3l3OHDwRKq3Twwt7Lm2B RKx/KTByEwrUGQu9VzSE1HEqHvltfbungFWRBmiIzJvMN3Dd/yumtWPh4J2gNlw1cGxz4ybo1UP7n 8zSKNlWbQefoEQOeVe4VtPIo0K/J0dLkaaXZ3atKTShCZSTwQfcNeQkHX7cAVtwzrrLW3AQSfr2hU zg8xoc7g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kc54P-0005I6-Bj; Mon, 09 Nov 2020 11:10:45 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BB326304D58; Mon, 9 Nov 2020 12:10:43 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4B2CD2B09AD02; Mon, 9 Nov 2020 12:10:43 +0100 (CET) Date: Mon, 9 Nov 2020 12:10:43 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Miroslav Benes , Thomas Gleixner , Masami Hiramatsu Subject: Re: [PATCH 2/3 v4] ftrace/x86: Allow for arguments to be passed in to ftrace_regs by default Message-ID: <20201109111043.GD2594@hirez.programming.kicks-ass.net> References: <20201106214234.618790276@goodmis.org> <20201106214403.328699055@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106214403.328699055@goodmis.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 06, 2020 at 04:42:36PM -0500, Steven Rostedt wrote: > +static __always_inline struct pt_regs * > +arch_ftrace_get_regs(struct ftrace_regs *fregs) > +{ > + /* Only when FL_SAVE_REGS is set, cs will be non zero */ > + if (!fregs->regs.cs) > + return NULL; > + return &fregs->regs; > +} > +#endif > + > #endif /* CONFIG_DYNAMIC_FTRACE */ > #endif /* __ASSEMBLY__ */ > #endif /* CONFIG_FUNCTION_TRACER */ > diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S > index ac3d5f22fe64..60e3b64f5ea6 100644 > --- a/arch/x86/kernel/ftrace_64.S > +++ b/arch/x86/kernel/ftrace_64.S > @@ -140,12 +140,19 @@ SYM_FUNC_START(ftrace_caller) > /* save_mcount_regs fills in first two parameters */ > save_mcount_regs > > + /* Stack - skipping return address of ftrace_caller */ > + leaq MCOUNT_REG_SIZE+8(%rsp), %rcx > + movq %rcx, RSP(%rsp) > + > SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) > /* Load the ftrace_ops into the 3rd parameter */ > movq function_trace_op(%rip), %rdx > > - /* regs go into 4th parameter (but make it NULL) */ > - movq $0, %rcx > + /* regs go into 4th parameter */ > + leaq (%rsp), %rcx > + > + /* Only ops with REGS flag set should have CS register set */ > + movq $0, CS(%rsp) > > SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) > call ftrace_stub You now seem to be relying on save_mcount_regs() resulting in a cleared CS, however, AFAICT CS is uninitialized stack garbage.