From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 448622F5A1A; Mon, 12 Jan 2026 12:07:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768219657; cv=none; b=XhXcRsxZbZPM0ZiOlSbXLueXmM6JsS0OKBMudlcGu/b+qeBebvJllDTRTx1zEIZHOkF8jWgcPBfgCYLkMATXlPJpqE6MfOAYsdSUGb//vJ/HqVTMvpNiewrN8Bc0XVpf/r3lQnc7Xg7yb9LP4gdMjrVnh1sVkf2jPeO/StxNPpU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768219657; c=relaxed/simple; bh=tKJ8EDq4hyO9AfeKyEDudrJUogYLnmYlcaBZEU+u42c=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=gw8hlqn8CKWdKUxHPjqeEm4tcdq6tVv9qXsKdFpfYUDdqW7aEZ0vEq/M/Dn+kB55dwtD4AiHt5W2aIEsPE7Yf6b7JtwN0zNVEtBWzSBs9iM3Jg4dm+Ytf9xqYXvu5yVT5mhQ/sUU12hyPG2rFUVvl/gmAkSg+15CosHmGVj7Unc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=DO8Z/JkF; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="DO8Z/JkF" Received: from ehlo.thunderbird.net (c-76-133-66-138.hsd1.ca.comcast.net [76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 60CC6xQs2138474 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Mon, 12 Jan 2026 04:07:00 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 60CC6xQs2138474 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025122301; t=1768219621; bh=8w8Yf25k/xbVuxmaBEr1voG9vNuzE/WuhThoLNwL46A=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=DO8Z/JkFSYVbjS5zUCknTK30Ahxbo7bkPGf22zRu3WPf6C4Czx+Bcn/OqmfVDeF7C VRZhJXf4/8TAjD38hZaJoydL5v4mXb4E498Y2oSdRlgJrmy/nK3ACfmvrwlN+2K3Lu Up0bLALF7nXgE3rZtMkN+YqpMf45KUV0Su5e9polyNwhrFT43hsH0kiZnfMMu7w6Md reb5UXixVSnln+b4YjxYwRNih7DSBtggOo1SQBm6pcP1GYCxuIjXshYwnBQ/+zynWu 43mpZf9sMHMxk9BFKVxkvN2YaD7RQKhU73V14VtNf4YYxDsX1C4fBGkL2KV8OCl8Bq tm/8+Hc/aNwdw== Date: Mon, 12 Jan 2026 04:06:58 -0800 From: "H. Peter Anvin" To: David Laight CC: Ard Biesheuvel , linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Josh Poimboeuf , Peter Zijlstra , Kees Cook , Uros Bizjak , Brian Gerst , linux-hardening@vger.kernel.org Subject: =?US-ASCII?Q?Re=3A_=5BRFC/RFT_PATCH_04/19=5D_x86=3A_Make_the_64?= =?US-ASCII?Q?-bit_bzImage_always_physically_relocatable?= User-Agent: K-9 Mail for Android In-Reply-To: <20260112104746.6521740c@pumpkin> References: <20260108092526.28586-21-ardb@kernel.org> <20260108092526.28586-25-ardb@kernel.org> <3f2e8d7c-6029-49ef-8e31-a3eb5efb385b@zytor.com> <20260112104746.6521740c@pumpkin> Message-ID: <532BA26A-7477-4F1D-B8BD-84EABFB4F91C@zytor.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=utf-8 Content-Transfer-Encoding: quoted-printable On January 12, 2026 2:47:46 AM PST, David Laight wrote: >On Sun, 11 Jan 2026 20:01:02 -0800 >"H=2E Peter Anvin" wrote: > >> On 2026-01-08 01:25, Ard Biesheuvel wrote: >> > On x86_64, the physical placement of the kernel is independent from i= ts >> > mapping in the 'High Kernel Mapping' range=2E This means that even a >> > position dependent kernel built without boot-time relocation support = can >> > run from any suitably aligned physical address, and there is no need = to >> > make this behavior dependent on whether or not the kernel is virtuall= y >> > relocatable=2E >> >=20 >> > On i386, the situation is different, given that the physical and virt= ual >> > load offsets must be equal, and so only a relocatable kernel can be >> > loaded at a physical address that deviates from its build-time defaul= t=2E >> >=20 >> > Clarify this in Kconfig and in the code, and advertise the 64-bit >> > bzImage as loadable at any physical offset regardless of whether >> > CONFIG_RELOCATABLE is set=2E In practice, this makes little differenc= e, >> > given that it defaults to 'y' and is a prerequisite for EFI_STUB and >> > RANDOMIZE_BASE, but it will help with some future refactoring of the >> > relocation code=2E >> > =20 >>=20 >> I don't see any reason to support non-relocatable kernels anymore=2E In= fact, in >> a patchset I am working on I have already removed it=2E > >For just 64bit, or 32bit as well? >The 'bloat' for 32bit will be higher due to the lack of pc-relative >addressing=2E > > David > >>=20 >> -hpa >>=20 >>=20 > Either=2E The bloat is strictly boot time=2E