From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A8168C83F1A for ; Mon, 21 Jul 2025 20:55:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Bs3KopQZ7vQ04IJmy3gNz7BkAKG2eqs4hRuS78QDIMQ=; b=XbhQyD3gaTYIPd FxfXNYUeS0Tf6kLTwLsLRF1YZtEdWNmaBNrloYIQViKcrVPL9OigJuR/OsxNJTBaARTm3D+u8MD9g 16y8Kq2VB6MS7JwMoffXS/33Kdv+vTWBkvy3UOtDhBjxkqzDEM778QXxMrGdYdIIIv1nFKGBEOHqc KUlI1cEYMR9Hlg1i6AEd+2mduv+4ySnw5QVikI1ST4JrBYpgzbJs3VrA/yyDzIfpvCQdJuIw2EBJr s0JitVOQm3tj+RANISnyZhjiSKOWXi5W7Rx6brhf0Yfzrz0UsReSlnQRiyOA5PcrTA6mUSBHzDIyX jY7guhOTobzksHJXI74A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1udxY1-00000000g9p-0hIR; Mon, 21 Jul 2025 20:55:45 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1udxSN-00000000fWq-2Bdd; Mon, 21 Jul 2025 20:49:56 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id A6BBA5C4B8E; Mon, 21 Jul 2025 20:49:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 464E6C4CEF4; Mon, 21 Jul 2025 20:49:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753130994; bh=RGpMFousrm9JXr2aga1XoiQZq81gXpkDZQCrU7p8kG4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=USwBlGGycUbYKwRlz8H1PUciShFkTuZXfVpLM5MtEpyQ2A97ZmBOIYa0cGOwBplAM P/UloDehuLPGSIqgqNRVeLye3ZQJwvjrIvND/8XbCEE/heb6TuWjlHXRTmnHic7i+/ ufyzJfA+Tj1dnxW4WNlS2ijwfnLETqFwratBaRXG4lRw2vboY071pv4Rgj4gG0uneL vJADYIT6M2Sug0BnFp+wdbmKStgy/2g++iMRLOa45PAedgg8EJByYxkT5u6rz9xzId 7//OhF3fMircm2SYJfkHca/mWkXbMTQEr5KB9GUZB1xfjt2aV3YLzdWsmNabD0jVLY gzg6qfQMQz07w== Date: Mon, 21 Jul 2025 13:49:53 -0700 From: Kees Cook To: Will Deacon Cc: Ard Biesheuvel , Mike Rapoport , 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 , 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: <202507211349.D93679FB25@keescook> References: <20250717231756.make.423-kees@kernel.org> <20250717232519.2984886-4-kees@kernel.org> <202507181541.B8CFAC7E@keescook> <202507211311.8DAC4C7@keescook> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <202507211311.8DAC4C7@keescook> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250721_134955_644444_54B7FB11 X-CRM114-Status: GOOD ( 40.46 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, Jul 21, 2025 at 01:14:36PM -0700, Kees Cook wrote: > On Mon, Jul 21, 2025 at 01:47:55PM +0100, Will Deacon wrote: > > On Sun, Jul 20, 2025 at 04:10:01PM +1000, Ard Biesheuvel wrote: > > > On Sat, 19 Jul 2025 at 08:51, Kees Cook wrote: > > > > On Fri, Jul 18, 2025 at 11:36:32AM +0300, Mike Rapoport wrote: > > > > > 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. > > > > Got it, thanks for the explanation! > > > > > > 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. > > > > > > > > > > Given that 'inline' is already a macro in the kernel, could we just > > > add __attribute__((__always_inline__)) to it when KCOV is enabled? > > > > That sounds like a more robust approach and, by the sounds of it, we > > could predicate it on GCC too. That would also provide a neat place for > > a comment describing the problem. > > > > Kees, would that work for you? > > That seems like an extremely large hammer for this problem, IMO. It > feels like it could cause new strange corner cases. I'd much prefer the > small fixes I've currently got since it keeps it focused. KCOV is > already enabled for "allmodconfig", so any new instances would be found > very quickly, etc. (And GCC's fragility in this regard has already been > exposed to these cases -- it's just that I changed one of the > combinations of __init vs inline vs instrumentation. > > I could give it a try, if you really prefer the big hammer approach... I gave it a try -- it fails spectacularly. ;) Let's stick to my small fixes instead? -- Kees Cook _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv