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 52C3C221FBA; Thu, 18 Dec 2025 19:42:32 +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=1766086953; cv=none; b=Km7O9IhhWehHOuU2xH7VGpmly30/eLgUw0d6i9fPfrCTJ0nC1j3NQLLILNxmobTPAkoj34Ng49Vpntu5XyT60nFbn/9ECl5MCvrsANUNpRmT3vQpArTAcdkgs73Wdnruqvfpn8oB/wueYeWrIdlFgwLGKQoCBjUg/7F2wHZEfe0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766086953; c=relaxed/simple; bh=Q+MRclBGFMwxUpU9evUqOewKe5CVGGDK/sd4p6ct9YM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gTtLN1BnW7nbW9eswhUvBww8r0jqZswRqQdETHWPwm9EGQtWohtscbsD23C6CawdxKkiZm6P39zOT07rO2WEYTK4x0OwKZAN9jWfXX9xn5zbSBQ+qEr4KgZjVuehioyaD5ob2cWoWsJQwPcDA2qHH7jkJFwnX/6JXv1aQ22w+jA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UsbFCVHr; 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="UsbFCVHr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1B24C19421; Thu, 18 Dec 2025 19:42:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766086952; bh=Q+MRclBGFMwxUpU9evUqOewKe5CVGGDK/sd4p6ct9YM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UsbFCVHr1HmajwGkQWEJB0+RiJKLmeT46tVo4pqtpZt84q0m3BusxrJAPS7zvVrq/ y/1trThpzgN7NxPKisRS7j9MtZS0o7mk4mBkzmv49QIgscAo92FoRvb81JC2n4VWEd cvSuY5uFK/YVk8i/aCYv8/7su18GSsUp/CKHMcspAfeEBjcZFXssdcN4QIrs4K5/jX IcZHC37JdHzWWnSjLrhotyafBz9byNmaufw3DcSkzIxnZmmCx/5d5Q60zd/ahpNhbV OBLLcQHuTFnvzYPJRX2/oaEN7aAp+yc3Uv+bO7iabK4oREMOgnNMRyMnxdS+5wNFas YiWeCx/lzpdNw== Date: Thu, 18 Dec 2025 19:42:31 +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: <20251218194231.GC1749918@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 Applied. I fixed a typo in the commit message ("inmediately" -> "immediately"). 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 >