From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4803E4D2EC3; Tue, 15 Sep 2026 11:36:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789472167; cv=none; b=kAswy1JAT/UnrrNLBVprN3EdwcojInfe7HhwYmPRCT+BxVXpp6yfCrCvj0iNcYpmUObwYAaiEA7O2BK9OFOryJeiHN2uxs0BKFnhCFgFSX1h3EKefFvLXrOzBTgTOzGy5ahbfNm1uZ7s7hjLGs/yzXf4wAGHQI4SqCx5OKn98tY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789472167; c=relaxed/simple; bh=f6k58a+kyyJlKOysXGIm7+YVKxFPsWG0XnA963ZSmGs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P5wzn5BD/7W+UjIy7MF7NOm2JoIT8KFUT15vDVCMQ9KpsVDlXMyL9SH+mtnM6krC13Q23M7xcDkDMYu7S/m8vQA6lrd+1wpcQHA08t5v0IfrwEIKaoMGJ7RafOY4ChZ74aUOM37/Fs7nW1DLxXJKtdHHk1/ibMGBok33VoNa2pg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GYZsbVig; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GYZsbVig" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A1D91F00893; Tue, 15 Sep 2026 11:35:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789472164; bh=4BVB43/k5lHtsFkUgtZDywdRjbEBMWb9Mg6O6YdeHrM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=GYZsbVigjxwfzphIbqofaPFJmaKXOkEJuH9NfOFwlWENp60vpodSbVNNMVPrnsCGh mKkYFPjcJBJCWstEr5ZbUWw1p8gupBALyutxo/nsXoXJJVjfsUUEDeTeRzg9vNDFKw QyLxl+67I5PApcQALeqp8arjqQrJPg8lKGehuzOG7XGzc750cxvm391kPGZaHUEXVh rRpJvi2VXfCOPb4wIvdWYnRC2MlJNBFBn7hGBAKR93OKepAk7efnXRPGiZufX/FUGN bMk95QWIuEMEbgWtoC+OwCCABis9Vc8v3v1aLMq5PD8Vs1rzrsq653sDeKOiCR8bmb RSzE6TAD8kDPw== Date: Tue, 15 Sep 2026 12:35:53 +0100 From: "Lorenzo Stoakes (ARM)" To: Arnd Bergmann Cc: Linus Torvalds , Kees Cook , Nathan Chancellor , Nicolas Schier , Nick Desaulniers , Bill Wendling , Justin Stitt , Masahiro Yamada , Alexey Gladkov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Ilias Apalodimas , Josh Poimboeuf , Peter Zijlstra , Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?B?QmrDtnJu?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , Onur =?utf-8?B?w5Z6a2Fu?= , Jonathan Corbet , Randy Dunlap , "Gustavo A. R. Silva" , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-riscv@lists.infradead.org, Linux-Arch , linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, Jens Axboe , linux-hardening@vger.kernel.org Subject: Re: [PATCH v2 00/21] kbuild: significantly speed up kernel builds Message-ID: References: <20260914-build-speedup-v2-0-39817ec5db23@kernel.org> <202609140833.88C0E16E50@keescook> <7646eb0c-7c4a-4ec2-9562-66a74c4d9858@app.fastmail.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <7646eb0c-7c4a-4ec2-9562-66a74c4d9858@app.fastmail.com> On Tue, Sep 15, 2026 at 10:53:51AM +0200, Arnd Bergmann wrote: > On Mon, Sep 14, 2026, at 17:53, Linus Torvalds wrote: > > On Mon, 14 Sept 2026 at 08:41, Kees Cook wrote: > >> > >> One area I think might solved via an LLM is the 3-pass kallsyms stuff. > >> If we could get a deterministic kallsyms build in 1 pass, that would be > >> very nice. A lot of people have tried, but it has eluded upstreaming. > > > > Even the three-pass one hasn't apparently always been entirely > > deterministic. We've had random reports over the years of it failing > > in some circumstances. > > This tends to break whenever a linker (rather than the compiler) starts > creating a new type of symbols that show up in pass 2. > > > Maybe we've fixed it all, or maybe the failures just go imperceptibly > > rare. Regardless, it has definitely been fragile. > > The rate seems to be once every few years, looking at the list > of exceptions added to scripts/kallsyms.c (now scripts/mksysmap): > > efe6e3068067 ("kallsyms: fix nonconverging kallsyms table with lld") > 516d980f8541 ("scripts/kallsyms: skip ppc compiler stub *.long_branch.* / *.plt_branch.*") > b9b74be163a2 ("ARM: 8555/1: kallsyms: ignore ARM mode switching veneers") > > I'm sure there are other instances on architectures that get less > build coverage. Yeah, it's stuff like this that makes it more sensible in general to use existing tooling where that makes sense, e.g. also the .mod.S stuff. Though I also think dropping some of these arches would be a good idea ;) *ahem*. In any case, I think the bigger picture ideas like a single pass kallsyms is stuff for the future. The way I see it: grab the really low-hanging fruit (this series), then the medium-hanging fruit, and only then enter the pits of hell to fight the satanic hordes which clasp on to what remains. > > Arnd -- Cheers, Lorenzo