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 0FBC313B280; Tue, 22 Jul 2025 08:27:05 +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=1753172826; cv=none; b=cInUyapxyoy424iHD7qa3rodzBZXYp0CBH06Wb9sWfpnarhYQ7j0rpO+zqaXXT2FlXQpzE7dS9wdhaR4synz0FFRBbnRdMtZcMRX4LUJLbaFtkL6TtRUbjZpOK0m9VCQJ6dKEsR8sr3gi8Rsj0ixlTH7/GccBUi4Do2P7MC4hQg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753172826; c=relaxed/simple; bh=yGkRA/6qnjLPhMkWmaVYag52FJSXvc8HTUW6Y3Xuzs4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KYRKMBd2RL8BmzrTn5ZGMAYqWd8awu2tWJDNN3Zyp+ilwTip8eDxdrw0ywuEelMRszYD6iX4kW3JLPIDoWH1t3wDPa/o7fykgyLCTUM4hXmJuUu4FbI1riiEtZFOjhXJM18gzuzatMjn3J1qCp4i4LaN3FW/b2VNw9xWPgjagz8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ftIKtFsS; 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="ftIKtFsS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A537C4CEF5; Tue, 22 Jul 2025 08:26:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753172825; bh=yGkRA/6qnjLPhMkWmaVYag52FJSXvc8HTUW6Y3Xuzs4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ftIKtFsS+75DjkESBKR4C/0fTfhjTO5EAQaosz6bDp0SBtC0xu6jrbFmvS+RKsdrx f4dMY3bCIrRdjzyHRTqQ2IS3DbC0aaJA20FDQXMOHNRYWFh4FtQSBKE6qcpYZfqwwn EBlY5p7lMzTdcc4tj5YJJGVzamw8NuZS2DY35/I8OtpLoIXd1OL5/ZeHJymCJvh1YO fQNqEpJ2tIsXeilrIIv/4unMX0gRI4A5tYLUiPoiE/g7dGzpTCnD1Qfrv0OCm/INtf +6BTjWwe4qdBcxVcEwQyD1qD72/jVzjC0CRHbF2sbB7CBVIvfoxl37x9XjTdsKkyQI 517UWQRiFJG/g== Date: Tue, 22 Jul 2025 11:26:46 +0300 From: Mike Rapoport To: Kees Cook Cc: Will Deacon , Arnd Bergmann , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Paolo Bonzini , Vitaly Kuznetsov , Henrique de Moraes Holschuh , Hans de Goede , Ilpo =?iso-8859-1?Q?J=E4rvinen?= , "Rafael J. Wysocki" , Len Brown , Masami Hiramatsu , Ard Biesheuvel , Michal Wilczynski , Juergen Gross , Andy Shevchenko , "Kirill A. Shutemov" , Roger Pau Monne , David Woodhouse , Usama Arif , "Guilherme G. Piccoli" , Thomas Huth , Brian Gerst , kvm@vger.kernel.org, ibm-acpi-devel@lists.sourceforge.net, platform-driver-x86@vger.kernel.org, linux-acpi@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-efi@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , "Gustavo A. R. Silva" , Christoph Hellwig , Andrey Konovalov , Andrey Ryabinin , Masahiro Yamada , Nathan Chancellor , Nicolas Schier , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v3 04/13] x86: Handle KCOV __init vs inline mismatches Message-ID: References: <20250717231756.make.423-kees@kernel.org> <20250717232519.2984886-4-kees@kernel.org> <202507181541.B8CFAC7E@keescook> Precedence: bulk X-Mailing-List: linux-kselftest@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: <202507181541.B8CFAC7E@keescook> On Fri, Jul 18, 2025 at 03:51:28PM -0700, Kees Cook wrote: > On Fri, Jul 18, 2025 at 11:36:32AM +0300, Mike Rapoport wrote: > > Hi Kees, > > > > On Thu, Jul 17, 2025 at 04:25:09PM -0700, Kees Cook wrote: > > > When KCOV is enabled all functions get instrumented, unless the > > > __no_sanitize_coverage attribute is used. To prepare for > > > __no_sanitize_coverage being applied to __init functions, we have to > > > handle differences in how GCC's inline optimizations get resolved. For > > > x86 this means forcing several functions to be inline with > > > __always_inline. > > > > > > Signed-off-by: Kees Cook > > > > ... > > > > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > > > index bb19a2534224..b96746376e17 100644 > > > --- a/include/linux/memblock.h > > > +++ b/include/linux/memblock.h > > > @@ -463,7 +463,7 @@ static inline void *memblock_alloc_raw(phys_addr_t size, > > > NUMA_NO_NODE); > > > } > > > > > > -static inline void *memblock_alloc_from(phys_addr_t size, > > > +static __always_inline void *memblock_alloc_from(phys_addr_t size, > > > phys_addr_t align, > > > phys_addr_t min_addr) > > > > I'm curious why from all memblock_alloc* wrappers this is the only one that > > needs to be __always_inline? > > Thread-merge[1], adding Will Deacon, who was kind of asking the same > question. > > Based on what I can tell, GCC has kind of fragile inlining logic, in the > sense that it can change whether or not it inlines something based on > optimizations. It looks like the kcov instrumentation being added (or in > this case, removed) from a function changes the optimization results, > and some functions marked "inline" are _not_ inlined. In that case, we end up > with __init code calling a function not marked __init, and we get the > build warnings I'm trying to eliminate. > > So, to Will's comment, yes, the problem is somewhat fragile (though > using either __always_inline or __init will deterministically solve it). > We've tripped over this before with GCC and the solution has usually > been to just use __always_inline and move on. > > For memblock_alloc*, it appears to be that the heuristic GCC uses > resulted in only memblock_alloc_from() being a problem in this case. I > can certainly mark them all as __always_inline if that is preferred. We had a few of those already converted to __always_inline, so I'm ok with continuing to fix them one at at time. Gives a feeling of job security ;-) > -- > Kees Cook -- Sincerely yours, Mike.