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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4435C433EF for ; Tue, 25 Jan 2022 14:37:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230384AbiAYOhC (ORCPT ); Tue, 25 Jan 2022 09:37:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1388297AbiAYOdL (ORCPT ); Tue, 25 Jan 2022 09:33:11 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 259A1C06175F; Tue, 25 Jan 2022 06:32:01 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id EB0C0B8180A; Tue, 25 Jan 2022 14:31:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3D2DC340E0; Tue, 25 Jan 2022 14:31:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643121118; bh=TjiX/pJ3jr1qZrQo1Hb5I+RhGqJRpdiNcaSW38hFvnM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=e1hvj+wKBMDc9NHJ/xRYFOPWv5n/MtaAM3F4UlC2BsUaiRgMLLxmsB902n4OgqXu3 zp1HhY5+TwltC9oFSD/J3iIMa6+Q2mdF0eVNvr+tW+6Lcktjr+m2H+4zoGY/PkIfoz Ab4TV2TWjYDvWJyhlL0frwnaJKQ+ENBZGnEYcqlW+O2tQU3H/b7rRjSdYPIrAKJCf1 LSNIEQ229hJjpl/I1dbUNGpg+uTvbbz3QNdvlwmwBdbKWPNfScWnRr/AUCmagRbRJU edsg8f3i5R1Sk/nCutJrdIEgJe0Z4b5YAwVsCP65mtpuR2IPmumAsPMxSnTPAxyKC6 6UH8vt6C+SJzg== Date: Tue, 25 Jan 2022 23:31:54 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: Kees Cook , Stephen Rothwell , "Steven Rostedt (VMware)" , Linux Kernel Mailing List , Linux Next Mailing List Subject: Re: linux-next: build failure after merge of the kspp tree Message-Id: <20220125233154.dac280ed36944c0c2fe6f3ac@kernel.org> In-Reply-To: <20220125222732.98ce2e445726e773f40e122e@kernel.org> References: <20220125145006.677e3709@canb.auug.org.au> <202201242230.C54A6BCDFE@keescook> <20220125222732.98ce2e445726e773f40e122e@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org On Tue, 25 Jan 2022 22:27:32 +0900 Masami Hiramatsu wrote: > > /* > > * struct trace_event_data_offsets_ { > > * u32 ; > > * u32 ; > > * [...] > > * }; > > * > > * The __dynamic_array() macro will create each u32 , this is > > * to keep the offset of each array from the beginning of the event. > > * The size of an array is also encoded, in the higher 16 bits of > > * . > > */ > > > > So, I think -Warray-bounds is refusing to see the destination as > > anything except a u32, but being accessed at 4 (sizeof(u32)) + 8 > > (address && 0xffff) (?) > > Ah, I got it. Yes, that's right. __data_loc() will access the data > from the __entry, but the __rel_loc() points the same address from > the encoded field ("__rel_loc_foo" in this case) itself. > This is introduced for the user application event, which doesn't > know the actual __entry size because the __entry includes some > kernel internal defined fields. > > > But if this is true, I would imagine there would be plenty of other > > warnings? I'm currently stumped. > > That is because __rel_loc is used only in the sample code in the kernel > for testing. Other use-cases comes from user-space. > Hmm, can we skip this boundary check for this example? If the -Warray-bounds determines the destination array size from the type of given pointer, we can just change the macro as below; #define __get_rel_dynamic_array(field) ((void *)__entry + \ offsetof(typeof(*__entry), __rel_loc_##field) + \ sizeof(__entry->__rel_loc_##field) + \ (__entry->__rel_loc_##field & 0xffff)) This must works same as __get_dynamic_array() macro. Could you try this patch? >From 2982ba01367ec1f746a4f128512436e5325a7f9d Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Tue, 25 Jan 2022 23:19:30 +0900 Subject: [PATCH] tracing: Avoid -Warray-bounds warning for __rel_loc macro Since -Warray-bounds checks the destination size from the type of given pointer, __assign_rel_str() macro gets warned because it passes the pointer to the 'u32' field instead of 'trace_event_raw_*' data structure. Pass the data address calculated from the 'trace_event_raw_*' instead of 'u32' __rel_loc field. Signed-off-by: Masami Hiramatsu Reported-by: Stephen Rothwell Cc: Kees Cook --- include/trace/trace_events.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h index 8c6f7c433518..65d927e059d3 100644 --- a/include/trace/trace_events.h +++ b/include/trace/trace_events.h @@ -318,9 +318,10 @@ TRACE_MAKE_SYSTEM_STR(); #define __get_str(field) ((char *)__get_dynamic_array(field)) #undef __get_rel_dynamic_array -#define __get_rel_dynamic_array(field) \ - ((void *)(&__entry->__rel_loc_##field) + \ - sizeof(__entry->__rel_loc_##field) + \ +#define __get_rel_dynamic_array(field) \ + ((void *)__entry + \ + offsetof(typeof(*__entry), __rel_loc_##field) + \ + sizeof(__entry->__rel_loc_##field) + \ (__entry->__rel_loc_##field & 0xffff)) #undef __get_rel_dynamic_array_len -- 2.25.1 -- Masami Hiramatsu