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 70D4A381DB; Mon, 22 Jan 2024 23:02:57 +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=1705964577; cv=none; b=ExAZudXeSDmUAwZxSia9LFTpTXrGatdvq1khddDSwzvBc9GEAX7/SlZ9oJ3pLdMAEm+4Lx6yD+1KYP88Wy/tFIT8AHwg6l/vBw31MqWJv98XpY6Gnh8xOyqRDX+vQIetRMUQ14v3FOw0l9nAzU6ar0Jz06QPw29cYrg2gvYgSXw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705964577; c=relaxed/simple; bh=5f0TvwGjdk7WXeg6BeQeByM891O4z1o6LGJ+66Aju6g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NfROFLOPwN9lpPibZHeaVXA/+SJnbPESyh8UA3aRNlzDFvPlbjCoGLNiJOhe2d+33Kxju3vps7IVspouq0KlGWEK4OPkiHObBQ0OtKexa35rKFKwcBPF1u2vEHntOwI67xO12fDPcjymBB4aQUeJPNjs3VahCwBq6Ael/AWG2NU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lRX8TthZ; 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="lRX8TthZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C745BC43390; Mon, 22 Jan 2024 23:02:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1705964577; bh=5f0TvwGjdk7WXeg6BeQeByM891O4z1o6LGJ+66Aju6g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lRX8TthZlj3aDisktVHgkXiP6G7cCfwFBA9MwRx2XwHZpSqwSH5cDgLkmPz3218DI Iuxx5g4m6n4iVIsdilCBQdsurC1K8fKyDxouEEzrgxUvxZ/4DHhE3TQ2dpx3pUCYXy lxOl94ziInVJ6XxA9FNDjFlv11vqjPvI9XNzYzq733RlRhsxTWg58W4377ELSVP2Pt Ie3CPCjYof6TabLmFLr1bTsws8VGDgYbnj8rvmxOVajc2zqcau/sjAcBrfuWLNQAIN 2JyK31XW53Aud8EXdJptKfrPoodlDPEXn+COFCBPLrhr+NpFxlMmfC4FVot90qTF4O X/NJfKr2PhkqA== Date: Mon, 22 Jan 2024 16:02:55 -0700 From: Nathan Chancellor To: Masahiro Yamada Cc: Aiden Leong , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, ndesaulniers@google.com, nicolas@fjasle.eu, clang-built-linux , =?utf-8?B?Ru+/ve+/ve+/vW5nLXJ177+977+977+9IFPvv73vv73vv71uZw==?= Subject: Re: [PATCH v2 2/4] modpost: inform compilers that fatal() never returns Message-ID: <20240122230255.GD141255@dev-fedora.aadp> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Jan 22, 2024 at 10:29:32PM +0900, Masahiro Yamada wrote: > +CC: clang-built-linux list, Fangrui > > On Mon, Jan 22, 2024 at 1:04 PM Aiden Leong wrote: > > > > > > > The function fatal() never returns because modpost_log() calls exit(1) > > > > > when LOG_FATAL is passed. > > > > > > Inform compilers of this fact so that unreachable code flow can be > > > identified at compile time. > > > > > > Signed-off-by: Masahiro Yamada > > > Reviewed-by: Nathan Chancellor > > > --- > > > > > > Changes in v2: > > > - Use noreturn attribute together with alias > > > > > > scripts/mod/modpost.c | 3 +++ > > > scripts/mod/modpost.h | 5 ++++- > > > 2 files changed, 7 insertions(+), 1 deletion(-) > > > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > > index ca0a90158f85..c13bc9095df3 100644 > > > --- a/scripts/mod/modpost.c > > > +++ b/scripts/mod/modpost.c > > > @@ -90,6 +90,9 @@ void modpost_log(enum loglevel loglevel, const char > > *fmt, ...) > > > error_occurred = true; > > > } > > > > > > +void __attribute__((alias("modpost_log"))) > > > > Hi Masahiro, > > I cross-compile kernel on Apple Silicon MacBook Pro > > and every thing works well until this patch. > > > > My build command: > > make ARCH=arm CROSS_COMPILE=arm-none-eabi- \ > > HOSTCFLAGS="-I/opt/homebrew/opt/openssl/include" \ > > HOSTLDFLAGS="-L/opt/homebrew/opt/openssl/lib" > > > > Error message: > > scripts/mod/modpost.c:93:21: error: aliases are not supported on darwin > > > It is unfortunate. Indeed, I see this message in: > > clang/include/clang/Basic/DiagnosticSemaKinds.td > > > Is this limitation due to macOS executable (PEF), > or is it Clang-specific? Based on my admittedly brief research, this seems related to the Mach-O format. That message was added by [1] in response to [2] but the message mentioned weak aliases being supported. A further clarification was made in [3] to state that all aliases are unsupported as a result of some internal Apple bug it seems but I do see a couple of bug reports stating that may not be true [4][5] (although that does not seem relevant for this report). [1]: https://github.com/llvm/llvm-project/commit/0017c5fa92ad3b10e15fd34f3865e8e5b850a5ed [2]: https://llvm.org/bz8720 [3]: https://github.com/llvm/llvm-project/commit/4e30b96834cea5682a8e9e024dda06319825000a [4]: https://github.com/llvm/llvm-project/issues/11488 [5]: https://github.com/llvm/llvm-project/issues/71001 Cheers, Nathan