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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 775B3C43387 for ; Sun, 13 Jan 2019 15:42:07 +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 42A0A20842 for ; Sun, 13 Jan 2019 15:42:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="P5RUPrKg"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=agner.ch header.i=@agner.ch header.b="lyJwjnJa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 42A0A20842 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=agner.ch 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:Message-ID:References:In-Reply-To: Subject:To:From:Date:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1p3RrU89r0vLofPEhdHpn0iwrzNz1m3kmNWlA3QIesw=; b=P5RUPrKgtWBWIw Qb1buKysbWfVxfdA6ShivH3T1K77f7mbu09Sh517FJIDuIaSn5GuPuk8nRgexwIy60wjxZRxW/p/P 5TIwoDKJbZSs6kUx9tnSYeZ+5E10nLi4jtL/MwQJJV+QmUFImWJTlblaNXUkcv2PbAbR2ZAVpAh1a RkU6YlS4uaAdoCtVyaIKzcj+9zpt9jNFVzbT8iXLhcl2HSbbfRj5O6okEE+jkCYVwLmlsnkOb7o/R W4ah/l+aSjdeP2Wa+uhcIlvr2TJ414cx9+MIW6ZFiQe0woSdSV3gmpYYGFftjGng4bShzGRZKcIdM AoAaMyxJikkDPvtbRT4g==; 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 1gihtj-0007UZ-VT; Sun, 13 Jan 2019 15:42:03 +0000 Received: from mail.kmu-office.ch ([2a02:418:6a02::a2]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gihtf-0007TA-Dc for linux-arm-kernel@lists.infradead.org; Sun, 13 Jan 2019 15:42:01 +0000 Received: from webmail.kmu-office.ch (unknown [IPv6:2a02:418:6a02::a3]) by mail.kmu-office.ch (Postfix) with ESMTPSA id 0543B5C24F2; Sun, 13 Jan 2019 16:41:54 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=agner.ch; s=dkim; t=1547394114; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=whId9VZUnwaqxuqa4KlUIdkBQryPsOBB/uh+zXCwGk4=; b=lyJwjnJa2J/3QCxmW/d/gOHvcb5Tlwf3FQ5Ty+HeMGPFbysyuqOl/gpW7OjPx1gd9rRSC0 QB3YgEsWwVaVPAhPjhyV039gLGj+NivIKYAwbh9mnn8/R+g9pgqjT7eQBXi3WmXqYiObqT WsjWz71QAi+eWJ8P99hUMA2U5iUKFKM= MIME-Version: 1.0 Date: Sun, 13 Jan 2019 16:41:52 +0100 From: Stefan Agner To: Jeremy Fertic Subject: Re: ARM: config issue with ftrace function graph tracer In-Reply-To: <20190112010139.GA5288@r2700x.localdomain> References: <20190112010139.GA5288@r2700x.localdomain> Message-ID: X-Sender: stefan@agner.ch User-Agent: Roundcube Webmail/1.3.7 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190113_074200_343623_BE4E0047 X-CRM114-Status: GOOD ( 20.04 ) 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: linux-arm-kernel@lists.infradead.org, rostedt@goodmis.org, Russell King , Arnd Bergmann , linux-kernel@vger.kernel.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, On 12.01.2019 02:01, Jeremy Fertic wrote: > I'm having a problem with the ftrace function graph tracer on a 32 bit arm > board (orangepi pc). A bisect points to the following commit: > > f9b58e8c7d03 ("ARM: 8800/1: use choice for kernel unwinders") > > Before this commit, if I use sunxi_defconfig and then menuconfig to enable > FTRACE and FUNCTION_TRACER then the function graph tracer works. With this > commit, and as of v5.0-rc1, doing the same as above results in a broken > function graph tracer and often an oops as well. The commit introduces a > choice group and it looks like it should default to UNWINDER_FRAME_POINTER > if FUNCTION_GRAPH_TRACER is enabled. FUNCTION_GRAPH_TRACER is enabled by > default when I enable FUNCTION_TRACER but this has no effect on the choice. > The choice always defaults to the other option which is UNWINDER_ARM. If I > manually choose UNWINDER_FRAME_POINTER then the function graph tracer works > fine. The default selection is there, but this is made at "make sunxi_defconfig" time. At this point FUNCTION_GRAPH_TRACER is not enabled, hence Kconfig uses UNWIDER_ARM. However, when enabling the FUNCTION_GRAPH_TRACER Kconfig will _not_ reconsider and switch enable UNWINDER_FRAME_POINTER. Before that commit, when enabling FUNCTION_GRAPH_TRACER, we simply also enabled FRAME_POINTER... I guess we need to make sure that FUNCTION_GRAPH_TRACER depends on the UNWINDER_FRAME_POINTER choice. There is already a similar dependency with THUMB2_KERNEL. We can cleanup that dependency since UNWINDER_FRAME_POINTER already depends on !THUMB2_KERNEL. diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 664e918e2624..a2ac65a8b2cc 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -69,7 +69,7 @@ config ARM select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU select HAVE_EXIT_THREAD select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL - select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL + select HAVE_FUNCTION_GRAPH_TRACER if UNWINDER_FRAME_POINTER select HAVE_FUNCTION_TRACER if !XIP_KERNEL select HAVE_GCC_PLUGINS select HAVE_GENERIC_DMA_COHERENT diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index 6d6e0330930b..8341649fa71d 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -47,8 +47,8 @@ config DEBUG_WX choice prompt "Choose kernel unwinder" - default UNWINDER_ARM if AEABI && !FUNCTION_GRAPH_TRACER - default UNWINDER_FRAME_POINTER if !AEABI || FUNCTION_GRAPH_TRACER + default UNWINDER_ARM if AEABI + default UNWINDER_FRAME_POINTER if !AEABI help This determines which method will be used for unwinding kernel stack traces for panics, oopses, bugs, warnings, perf, /proc//stack, > > Any idea why the default behaviour has changed? The rational is stated in the commit message, the main reason was to disallow UNWINDER_FRAME_POINTER in case Clang is used (since Clang does not create the expected function prologue). The choice also aligns with how unwinders are selected on x86. -- Stefan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel