From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 54BAE2D063E; Mon, 15 Dec 2025 18:48:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765824481; cv=none; b=fOf0ODQnpFbr/y3pVkuNJmAg3p2EpXEy8pJ+2w5uSHD/0vmJgkotQJ/AjbIGBnt1pzJcdn4548RdMK6iwcZWwVUUNjtKA83CmzFsgSmkwHbOz1c0BLKJLvbgsT8PaKhEmqMQ+rf1Ok3BuIOgObXkey3wA01Rk3kEdYoPpRnND2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765824481; c=relaxed/simple; bh=iuD/WsSWcl85HIu8JbszOwwiLXHCEcfqcPAnAczZZTc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=n1D5aTmgSaz9EgWw6Zv3dKpO3qS8jz38DKC9RAllKBkmvlgrWt5e6xxNSU0bzkXPd9PvTGDPx14Fb1pNObOpVMJRA+bzjdrMwP5jN0dmHxX+t9eJa4SCALqgdSgH7myVgPIzmr+VyY9j3VCKgnprXGJoXTA/XhqQ5vzgaaS1dEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RzasYwoA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RzasYwoA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4545C4CEF5; Mon, 15 Dec 2025 18:48:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765824480; bh=iuD/WsSWcl85HIu8JbszOwwiLXHCEcfqcPAnAczZZTc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RzasYwoA/ATZKmBGK5p6VpyEauiMbVhFi/4TA9/l/mz8zBEReN/H/AdIBvf4A4/C4 hd4WLc2CdM1+oDFs+CWxlUUeYhJmPIFdp0i4udQ4ap5z9++aER/oZApaalR4/bd/Y4 1K4ydDGyhGgOYVA2fdwWP/8PbauXkEO3wu7WAM2XtZBmXOXqq8JLD6DzOwZQBl3nJ6 4awa2FoGs5wrVAuPG34u6XLfyq6r/8zdpCydVqeb8GYUdWKfuEgJkAgGWwt1Hmer/M HYdZtbmt11/bXOQfJdGbE+ahxkJvOYJUovVxubrJe5DCLcPqWBVLJ45w4H+kMK1nsG ROqJbCCdLXVZw== Date: Mon, 15 Dec 2025 18:47:59 +0000 From: Wei Liu To: "Gustavo A. R. Silva" Cc: "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH][next] hyperv: Avoid -Wflex-array-member-not-at-end warning Message-ID: <20251215184759.GA654575@liuwe-devbox-debian-v2.local> References: Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Dec 12, 2025 at 03:44:50PM +0900, Gustavo A. R. Silva wrote: > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are > getting ready to enable it, globally. > > Use the new __TRAILING_OVERLAP() helper to fix the following warning: > > include/hyperv/hvgdk_mini.h:581:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > This helper creates a union between a flexible-array member (FAM) and a > set of MEMBERS that would otherwise follow it. > > This overlays the trailing MEMBER u64 gva_list[]; onto the FAM > struct hv_tlb_flush_ex::hv_vp_set.bank_contents[], while keeping > the FAM and the start of MEMBER aligned. > > The static_assert() ensures this alignment remains, and it's > intentionally placed inmediately after the related structure --no > blank line in between. > > Signed-off-by: Gustavo A. R. Silva Gustavo, what is your build command? I would like to incorporate that into my own build tests. Thanks, Wei > --- > include/hyperv/hvgdk_mini.h | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h > index 04b18d0e37af..30fbbde81c5c 100644 > --- a/include/hyperv/hvgdk_mini.h > +++ b/include/hyperv/hvgdk_mini.h > @@ -578,9 +578,12 @@ struct hv_tlb_flush { /* HV_INPUT_FLUSH_VIRTUAL_ADDRESS_LIST */ > struct hv_tlb_flush_ex { > u64 address_space; > u64 flags; > - struct hv_vpset hv_vp_set; > - u64 gva_list[]; > + __TRAILING_OVERLAP(struct hv_vpset, hv_vp_set, bank_contents, __packed, > + u64 gva_list[]; > + ); > } __packed; > +static_assert(offsetof(struct hv_tlb_flush_ex, hv_vp_set.bank_contents) == > + offsetof(struct hv_tlb_flush_ex, gva_list)); > > struct ms_hyperv_tsc_page { /* HV_REFERENCE_TSC_PAGE */ > volatile u32 tsc_sequence; > -- > 2.43.0 >