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=-5.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS autolearn=unavailable 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 B948BC43387 for ; Wed, 16 Jan 2019 09:57:53 +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 8755A20859 for ; Wed, 16 Jan 2019 09:57:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="lSPMVHLQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8755A20859 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:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yHGZJ7gLccISkGUpVigMSq3rOEo8enc0DH4h3vCHmno=; b=lSPMVHLQAWflCZ T6c3ZrDeAVdOsrIEmB7unfNeSfMPfw124QPUIpUJK/kOGVwGxYQ69IX4FYuoey+vjkh9QCM9NijB3 Cspv8m1YhVYy3n7Uz0VEK2N0Y0wsMjOz8nJT6/e2A1QXm8hgxgPb5BE1MPmujofz8T9j4kliFk6Hk 9wXTIjkG5193k7MVz5LTybE4sC25wvVccKuj3h0NWTKgijZkAL5H5hkhwrZk4DsckTw0gCUyVgzEW bjnyES77feJL4VYW464xj1HZFH2Q4V2Vds6Z879gbOMkiQ9lYtH0S5sxhXWP3jbCecjb6smx9qriz hxmXmAh89MbJTnOfpvsg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gjhxE-0004Br-HG; Wed, 16 Jan 2019 09:57:48 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gjhxB-0004BO-U8 for linux-arm-kernel@lists.infradead.org; Wed, 16 Jan 2019 09:57:47 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6AB6280D; Wed, 16 Jan 2019 01:57:43 -0800 (PST) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 311893F70D; Wed, 16 Jan 2019 01:57:41 -0800 (PST) Subject: Re: [PATCH v6] arm64: implement ftrace with regs To: Torsten Duwe , Will Deacon , Catalin Marinas , Steven Rostedt , Josh Poimboeuf , Ingo Molnar , Mark Rutland , Ard Biesheuvel , Arnd Bergmann , AKASHI Takahiro , Amit Daniel Kachhap References: <20190104141053.360F768D93@newverein.lst.de> From: Julien Thierry Message-ID: <8eb70db4-92a2-95a2-075c-f26690aab3ed@arm.com> Date: Wed, 16 Jan 2019 09:57:39 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190104141053.360F768D93@newverein.lst.de> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190116_015745_981655_90FBDF67 X-CRM114-Status: GOOD ( 29.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, 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 Hi Torsten, On 04/01/2019 14:10, Torsten Duwe wrote: > Use -fpatchable-function-entry (gcc8) to add 2 NOPs at the beginning > of each function. Replace the first NOP thus generated with a quick LR > saver (move it to scratch reg x9), so the 2nd replacement insn, the call > to ftrace, does not clobber the value. Ftrace will then generate the > standard stack frames. > > Note that patchable-function-entry in GCC disables IPA-RA, which means > ABI register calling conventions are obeyed *and* scratch registers > such as x9 are available. > > Introduce and handle an ftrace_regs_trampoline for module PLTs, right > after ftrace_trampoline, and double the size of this special section. > > Signed-off-by: Torsten Duwe > I wanted to test this patch (and try to benchmark having the "mov x9, x30" always present in function prelude vs having two nops), but I cannot get this patch to apply (despite having a version including both commits below). Could you provide a git branch from which I could try to rebase the patch? (Or a new version of the series) > --- > > This patch applies on 4.20 with the additional changes > bdb85cd1d20669dfae813555dddb745ad09323ba > (arm64/module: switch to ADRP/ADD sequences for PLT entries) > and > 7dc48bf96aa0fc8aa5b38cc3e5c36ac03171e680 > (arm64: ftrace: always pass instrumented pc in x0) > along with their respective series, or alternatively on Linus' master, > which already has these. > > changes since v5: > > * fix mentioned pc in x0 to hold the start address of the call site, > not the return address or the branch address. > This resolves the problem found by Amit. > > --- > arch/arm64/Kconfig | 2 > arch/arm64/Makefile | 4 + > arch/arm64/include/asm/assembler.h | 1 > arch/arm64/include/asm/ftrace.h | 13 +++ > arch/arm64/include/asm/module.h | 3 > arch/arm64/kernel/Makefile | 6 - > arch/arm64/kernel/entry-ftrace.S | 131 ++++++++++++++++++++++++++++++++++ > arch/arm64/kernel/ftrace.c | 125 ++++++++++++++++++++++++-------- > arch/arm64/kernel/module-plts.c | 3 > arch/arm64/kernel/module.c | 2 > drivers/firmware/efi/libstub/Makefile | 3 > include/asm-generic/vmlinux.lds.h | 1 > include/linux/compiler_types.h | 4 + > 13 files changed, 262 insertions(+), 36 deletions(-) [...] > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S [...] > @@ -122,6 +124,7 @@ skip_ftrace_call: // } > ENDPROC(_mcount) > > #else /* CONFIG_DYNAMIC_FTRACE */ > +#ifndef CONFIG_DYNAMIC_FTRACE_WITH_REGS > /* > * _mcount() is used to build the kernel with -pg option, but all the branch > * instructions to _mcount() are replaced to NOP initially at kernel start up, > @@ -159,6 +162,124 @@ GLOBAL(ftrace_graph_call) // ftrace_gra > > mcount_exit > ENDPROC(ftrace_caller) > +#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > + > +/* > + * Since no -pg or similar compiler flag is used, there should really be > + * no reference to _mcount; so do not define one. Only some value for > + * MCOUNT_ADDR is needed for comparison. Let it point here to have some > + * sort of magic value that can be recognised when debugging. > + */ > +GLOBAL(_mcount) > + ret /* make it differ from regs caller */ There's something I can't figure out. Since there are no callers to _mcount, how does the ftrace core builds up its record of patchable functions? I don't understand fully the core ftrace code but I've got the impression that without this record of struct dyn_ftrace, ftrace cannot patch in calls to tracers in the future. Am I missing something? Thanks, -- Julien Thierry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel