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 11E78281520; Tue, 4 Mar 2025 17:08:00 +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=1741108081; cv=none; b=JJ0M0wqEOF+kf/+sj4fpTOrhsflWm/YpTd7VatKcEhWwtpCswN7t9qsoN0pUtDMOIr8mNznv57zZYZpars+HLxcl6XyFleM/PK8AxIWmGSjgRGFSXuAFRxevjbSBMy3wpXjos5g/bNyAng4x9vdccLJWzj/+7pJjY3HaWt44lj0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741108081; c=relaxed/simple; bh=ExQy865opXw6DJMm2Zy8thSEQ2//ZajmzZjhLDdgip8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lNIF2diNE7S7lAZrKhXy2KLBn8+z/VbnN5MS7mW/1cOSm+tt6Q0jblth+YsJpnDOQ7HVZUOLmHUfbzK9iPae6w27UXIVqt+dGG78zB/NQhfrlHuQxr0+wxvwPYwa/p+gaAzi0lBPnIFTqorIbS1YgWS2I0O4cWeY9cBRVm35UWQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U/S/n5mc; 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="U/S/n5mc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74E9FC4CEE7; Tue, 4 Mar 2025 17:08:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741108080; bh=ExQy865opXw6DJMm2Zy8thSEQ2//ZajmzZjhLDdgip8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=U/S/n5mcWu/UBrYJ+TCBDohmSpkaKpp3W/oYgHiI/KuhAbI9KA2kv7BZLyzpMCfOt 5Wq8oedYv0QjWahN3qmeV3zxSsUGOq2uOUp/yflUURVb/OTCKj8hW7Vxnp8gBESsjC pc2HyY1m7X1gZDrLSonteoxRMWPrg7RwvOkKcEJgi/fTEGOMeFqPe+AKHrnuCe2evj 4+CGuNjEonQLrRuMQXHebM9/xLHR0V2qQ/ZRWoWxw6hWG9Q2EvGTPOkbjYC976JGta kmU7BYLOeu+jvgOx9uHuREM5azgdxWj5CcwgpT/+IY6xkW5/rRoQOEqIASs706Ky6i CHiKZp8kuCXww== Date: Tue, 4 Mar 2025 09:07:57 -0800 From: Kees Cook To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Masahiro Yamada , Nicolas Schier , llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, David Gow , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] kbuild: clang: Support building UM with SUBARCH=i386 Message-ID: <202503040842.1177A1F15B@keescook> References: <20250303215240.work.379-kees@kernel.org> <05a25510-ab44-4eb1-a878-71e84c8aff0d@t-8ch.de> <20250304102536.GB2529736@ax162> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Mar 04, 2025 at 03:51:19PM +0100, Thomas Weißschuh wrote: > On 2025-03-04 11:25:36+0100, Nathan Chancellor wrote: > > On Mon, Mar 03, 2025 at 11:29:58PM +0100, Thomas Weißschuh wrote: > > > On 2025-03-03 13:52:41-0800, Kees Cook wrote: > > > > > > This is also what exists in tools/testing/selftests/lib.mk. > > > Minus the missing CONFIG_FORTIFY_SOURCE on clang x86_32 > > > and a failure of overflow.DEFINE_FLEX_test (clang 19.1.7). > > > > Does Kees's other patch resolve the second issue? It'll obviously fix > > the first :P > > > > https://lore.kernel.org/20250303214929.work.499-kees@kernel.org/ > > No, it doesn't. > > Running tests with: > $ .kunit/linux kunit.filter_glob=overflow.DEFINE_FLEX_test kunit.enable=1 mem=1G console=tty kunit_shutdown=halt > [15:48:30] =================== overflow (1 subtest) =================== > [15:48:30] # DEFINE_FLEX_test: EXPECTATION FAILED at lib/overflow_kunit.c:1200 > [15:48:30] Expected __builtin_dynamic_object_size(two_but_zero, 0) == expected_raw_size, but > [15:48:30] __builtin_dynamic_object_size(two_but_zero, 0) == 12 (0xc) > [15:48:30] expected_raw_size == 8 (0x8) > [15:48:30] [FAILED] DEFINE_FLEX_test > [15:48:30] # module: overflow_kunit > [15:48:30] ==================== [FAILED] overflow ===================== > [15:48:30] ============================================================ > [15:48:30] Testing complete. Ran 1 tests: failed: 1 > [15:48:31] Elapsed time: 43.985s total, 0.001s configuring, 43.818s building, 0.133s running > > If I force CONFIG_CC_HAS_COUNTED_BY=n then the test succeeds. > Clang 19.1.7 from the Arch Linux repos. I wasn't seeing with Clang 20 from git: ClangBuiltLinux clang version 20.0.0git (git@github.com:llvm/llvm-project.git 72901fe19eb1e55d0ee1c380ab7a9f57d2f187c5) But I do see the error with ToT Clang: ClangBuiltLinux clang version 21.0.0git (git@github.com:llvm/llvm-project.git eee3db5421040cfc3eae6e92ed714650a6f741fa) Clang 17.1: (does not support counted_by) # DEFINE_FLEX_test: missing counted_by # DEFINE_FLEX_test: sizeof(two_but_zero): 8 # DEFINE_FLEX_test: __struct_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero->array): 4 Clang 19.1.1: (actually is _does_ support counted_by, but Linux disables it) # DEFINE_FLEX_test: missing counted_by # DEFINE_FLEX_test: sizeof(two_but_zero): 8 # DEFINE_FLEX_test: __struct_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero->array): 4 GCC 13.3: # DEFINE_FLEX_test: missing counted_by # DEFINE_FLEX_test: sizeof(two_but_zero): 8 # DEFINE_FLEX_test: __struct_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero->array): 4 Clang 21 (ToT): # DEFINE_FLEX_test: has counted_by # DEFINE_FLEX_test: sizeof(two_but_zero): 8 # DEFINE_FLEX_test: __struct_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero->array): 0 GCC 15 (ToT): # DEFINE_FLEX_test: has counted_by # DEFINE_FLEX_test: sizeof(two_but_zero): 8 # DEFINE_FLEX_test: __struct_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero): 12 # DEFINE_FLEX_test: __member_size(two_but_zero->array): 0 It seems like the on-stack sizes with __bdos all agree now, regardless of the used compiler features. It is only the array size calculation that now gets masked by counted_by. (i.e. the stack size is overridden by the zero "count" for the array elements.) I'll send a fix for the test... -- Kees Cook