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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83CE1CCFA13 for ; Thu, 26 Sep 2024 09:18:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BAEB26B00A0; Thu, 26 Sep 2024 05:18:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B5F046B00A2; Thu, 26 Sep 2024 05:18:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9D8536B00A3; Thu, 26 Sep 2024 05:18:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 813B26B00A0 for ; Thu, 26 Sep 2024 05:18:29 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E1FE91C7165 for ; Thu, 26 Sep 2024 09:18:28 +0000 (UTC) X-FDA: 82606338696.16.D11E0DA Received: from mout.gmx.net (mout.gmx.net [212.227.15.19]) by imf19.hostedemail.com (Postfix) with ESMTP id C78041A0011 for ; Thu, 26 Sep 2024 09:18:25 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=gmx.de header.s=s31663417 header.b=eLqErHt5; spf=pass (imf19.hostedemail.com: domain of deller@gmx.de designates 212.227.15.19 as permitted sender) smtp.mailfrom=deller@gmx.de; dmarc=pass (policy=quarantine) header.from=gmx.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1727342145; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=hp1g5yHqQ+Hi3UUQ0ip+nhr2opua2JZiyoX1o8S6xJ0=; b=K0LUbH66DXekPKyFtfSlHWOk6ayE8ybxMksdyzXCVVoFxnC9pbEGTQOWgTqb9LSCl0vpeY 0C3ahJENChE5lgBv4Abn5kmSiEZEOSuImUbL/Iq+04SnKuKBZbw1ht79gwlM1QXnYNrr2v r9B/ZXBYifWU6p1gb7eEQBmIjRDO0pM= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=gmx.de header.s=s31663417 header.b=eLqErHt5; spf=pass (imf19.hostedemail.com: domain of deller@gmx.de designates 212.227.15.19 as permitted sender) smtp.mailfrom=deller@gmx.de; dmarc=pass (policy=quarantine) header.from=gmx.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1727342145; a=rsa-sha256; cv=none; b=QoATOjfyRvmC5kxUPj2cbWU2Vai5urRzX3XdBX6n23eAJM5ZcE8tvF7NkOWCeEJwkD6Iw7 KvZYWoivvYAc/ryn6QFPwxKLnweItuKHKGy3vbEE1+ahBb38T6lbr9Y80h/tr8YhY5cdko 9mzueDetkFE1rc5qYmFX7aw0NBXb/z0= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.de; s=s31663417; t=1727342299; x=1727947099; i=deller@gmx.de; bh=hp1g5yHqQ+Hi3UUQ0ip+nhr2opua2JZiyoX1o8S6xJ0=; h=X-UI-Sender-Class:Message-ID:Date:MIME-Version:Subject:To:Cc: References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding:cc:content-transfer-encoding: content-type:date:from:message-id:mime-version:reply-to:subject: to; b=eLqErHt5Ba6qZEoQ+y8GVgeZp906IERMrpf8ljYAgm9BiO6PBERPFKYXEC5NHKEZ afJ/YrIxfOguW2XSuvSGzpV2izAI+B7h/d0689tMA32PeUnGr0bvXPbl2jfXYNNW9 Q19EJrmwUZ2exUv870dM1IX4bJjcGPJxage5Fcy5Vjp0j5wV0EbS3OnjODPhci/2h uSbLEQMXmZA++cPr2XrBt2M3Rlq8ptRO0Q4lM0UKloQ2n1HZQKSuQQon3hWMTf7O0 2HCn13s/EYSYJ+OOw/cMdFW9HMAD+U4nSukB8Ny5wO1HTUw+KIP6z0BYElfX3JYwc /23dGiJv4IV6Nd+q0w== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from [10.8.0.6] ([78.94.87.245]) by mail.gmx.net (mrgmx005 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MC30Z-1slkQh2YiD-00HUUz; Thu, 26 Sep 2024 11:18:18 +0200 Message-ID: <079aea54-a3ab-413e-aa4f-0dce06c8e142@gmx.de> Date: Thu, 26 Sep 2024 11:18:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/5] [RFC] mm: Remove MAP_UNINITIALIZED support To: Arnd Bergmann , linux-mm@kvack.org Cc: Arnd Bergmann , "Jason A. Donenfeld" , Alexander Viro , Alexandre Torgue , Andreas Larsson , Andrew Morton , Ard Biesheuvel , Christian Brauner , Christoph Hellwig , Christophe Leroy , Damien Le Moal , David Hildenbrand , Greg Ungerer , Kees Cook , "Liam R . Howlett" , Lorenzo Stoakes , Matt Turner , Max Filippov , Michael Ellerman , Michal Hocko , Nicholas Piggin , Richard Henderson , Thomas Bogendoerfer , Vladimir Murzin , Vlastimil Babka , linux-stm32@st-md-mailman.stormreply.com, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org References: <20240925210615.2572360-1-arnd@kernel.org> <20240925210615.2572360-6-arnd@kernel.org> Content-Language: en-US From: Helge Deller Autocrypt: addr=deller@gmx.de; keydata= xsFNBF3Ia3MBEAD3nmWzMgQByYAWnb9cNqspnkb2GLVKzhoH2QD4eRpyDLA/3smlClbeKkWT HLnjgkbPFDmcmCz5V0Wv1mKYRClAHPCIBIJgyICqqUZo2qGmKstUx3pFAiztlXBANpRECgwJ r+8w6mkccOM9GhoPU0vMaD/UVJcJQzvrxVHO8EHS36aUkjKd6cOpdVbCt3qx8cEhCmaFEO6u CL+k5AZQoABbFQEBocZE1/lSYzaHkcHrjn4cQjc3CffXnUVYwlo8EYOtAHgMDC39s9a7S90L 69l6G73lYBD/Br5lnDPlG6dKfGFZZpQ1h8/x+Qz366Ojfq9MuuRJg7ZQpe6foiOtqwKym/zV dVvSdOOc5sHSpfwu5+BVAAyBd6hw4NddlAQUjHSRs3zJ9OfrEx2d3mIfXZ7+pMhZ7qX0Axlq Lq+B5cfLpzkPAgKn11tfXFxP+hcPHIts0bnDz4EEp+HraW+oRCH2m57Y9zhcJTOJaLw4YpTY GRUlF076vZ2Hz/xMEvIJddRGId7UXZgH9a32NDf+BUjWEZvFt1wFSW1r7zb7oGCwZMy2LI/G aHQv/N0NeFMd28z+deyxd0k1CGefHJuJcOJDVtcE1rGQ43aDhWSpXvXKDj42vFD2We6uIo9D 1VNre2+uAxFzqqf026H6cH8hin9Vnx7p3uq3Dka/Y/qmRFnKVQARAQABzRxIZWxnZSBEZWxs ZXIgPGRlbGxlckBnbXguZGU+wsGRBBMBCAA7AhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheA FiEERUSCKCzZENvvPSX4Pl89BKeiRgMFAl3J1zsCGQEACgkQPl89BKeiRgNK7xAAg6kJTPje uBm9PJTUxXaoaLJFXbYdSPfXhqX/BI9Xi2VzhwC2nSmizdFbeobQBTtRIz5LPhjk95t11q0s uP5htzNISPpwxiYZGKrNnXfcPlziI2bUtlz4ke34cLK6MIl1kbS0/kJBxhiXyvyTWk2JmkMi REjR84lCMAoJd1OM9XGFOg94BT5aLlEKFcld9qj7B4UFpma8RbRUpUWdo0omAEgrnhaKJwV8 qt0ULaF/kyP5qbI8iA2PAvIjq73dA4LNKdMFPG7Rw8yITQ1Vi0DlDgDT2RLvKxEQC0o3C6O4 iQq7qamsThLK0JSDRdLDnq6Phv+Yahd7sDMYuk3gIdoyczRkXzncWAYq7XTWl7nZYBVXG1D8 gkdclsnHzEKpTQIzn/rGyZshsjL4pxVUIpw/vdfx8oNRLKj7iduf11g2kFP71e9v2PP94ik3 Xi9oszP+fP770J0B8QM8w745BrcQm41SsILjArK+5mMHrYhM4ZFN7aipK3UXDNs3vjN+t0zi qErzlrxXtsX4J6nqjs/mF9frVkpv7OTAzj7pjFHv0Bu8pRm4AyW6Y5/H6jOup6nkJdP/AFDu 5ImdlA0jhr3iLk9s9WnjBUHyMYu+HD7qR3yhX6uWxg2oB2FWVMRLXbPEt2hRGq09rVQS7DBy dbZgPwou7pD8MTfQhGmDJFKm2jvOwU0EXchrcwEQAOsDQjdtPeaRt8EP2pc8tG+g9eiiX9Sh rX87SLSeKF6uHpEJ3VbhafIU6A7hy7RcIJnQz0hEUdXjH774B8YD3JKnAtfAyuIU2/rOGa/v UN4BY6U6TVIOv9piVQByBthGQh4YHhePSKtPzK9Pv/6rd8H3IWnJK/dXiUDQllkedrENXrZp eLUjhyp94ooo9XqRl44YqlsrSUh+BzW7wqwfmu26UjmAzIZYVCPCq5IjD96QrhLf6naY6En3 ++tqCAWPkqKvWfRdXPOz4GK08uhcBp3jZHTVkcbo5qahVpv8Y8mzOvSIAxnIjb+cklVxjyY9 dVlrhfKiK5L+zA2fWUreVBqLs1SjfHm5OGuQ2qqzVcMYJGH/uisJn22VXB1c48yYyGv2HUN5 lC1JHQUV9734I5cczA2Gfo27nTHy3zANj4hy+s/q1adzvn7hMokU7OehwKrNXafFfwWVK3OG 1dSjWtgIv5KJi1XZk5TV6JlPZSqj4D8pUwIx3KSp0cD7xTEZATRfc47Yc+cyKcXG034tNEAc xZNTR1kMi9njdxc1wzM9T6pspTtA0vuD3ee94Dg+nDrH1As24uwfFLguiILPzpl0kLaPYYgB wumlL2nGcB6RVRRFMiAS5uOTEk+sJ/tRiQwO3K8vmaECaNJRfJC7weH+jww1Dzo0f1TP6rUa fTBRABEBAAHCwXYEGAEIACAWIQRFRIIoLNkQ2+89Jfg+Xz0Ep6JGAwUCXchrcwIbDAAKCRA+ Xz0Ep6JGAxtdEAC54NQMBwjUNqBNCMsh6WrwQwbg9tkJw718QHPw43gKFSxFIYzdBzD/YMPH l+2fFiefvmI4uNDjlyCITGSM+T6b8cA7YAKvZhzJyJSS7pRzsIKGjhk7zADL1+PJei9p9idy RbmFKo0dAL+ac0t/EZULHGPuIiavWLgwYLVoUEBwz86ZtEtVmDmEsj8ryWw75ZIarNDhV74s BdM2ffUJk3+vWe25BPcJiaZkTuFt+xt2CdbvpZv3IPrEkp9GAKof2hHdFCRKMtgxBo8Kao6p Ws/Vv68FusAi94ySuZT3fp1xGWWf5+1jX4ylC//w0Rj85QihTpA2MylORUNFvH0MRJx4mlFk XN6G+5jIIJhG46LUucQ28+VyEDNcGL3tarnkw8ngEhAbnvMJ2RTx8vGh7PssKaGzAUmNNZiG MB4mPKqvDZ02j1wp7vthQcOEg08z1+XHXb8ZZKST7yTVa5P89JymGE8CBGdQaAXnqYK3/yWf FwRDcGV6nxanxZGKEkSHHOm8jHwvQWvPP73pvuPBEPtKGLzbgd7OOcGZWtq2hNC6cRtsRdDx 4TAGMCz4j238m+2mdbdhRh3iBnWT5yPFfnv/2IjFAk+sdix1Mrr+LIDF++kiekeq0yUpDdc4 ExBy2xf6dd+tuFFBp3/VDN4U0UfG4QJ2fg19zE5Z8dS4jGIbLg== In-Reply-To: <20240925210615.2572360-6-arnd@kernel.org> Content-Type: text/plain; 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MAP_HUGE_SHIFT/MAP_HUGE_MASK were > added in 2012 for architectures supporting hugepages, which at the time > did not overlap with the ones supporting NOMMU. > > Adding the macro under an #ifdef was obviously a mistake, which > Christoph Hellwig tried to address by making it unconditionally defined > to 0x4000000 as part of the series to support RISC-V NOMMU kernels. At > this point linux/mman.h contained two conflicting definitions for bit 26= , > though the two are still mutually exclusive at runtime in all supported > configurations. > > According to the commit 854e9ed09ded ("mm: support madvise(MADV_FREE)") > description, it was previously used internally by facebook, which > would have resulted in MAP_HUGE_1MB turning into MAP_HUGE_2MB > with MAP_UNINITIALIZED enabled, and every other page size implying > MAP_UNINITIALIZED. I assume there are no remaining out of tree users > on MMU-enabled kernels today. > > I do not see any sensible way to redefine the macros for the ABI in > a way avoids breaking something. The only ideas so far are: > > - do nothing, try to document the bug, hope for the best > > - remove the kernel implementation and redefine MAP_UNINITIALIZED to > zero in the header to silently turn it off for everyone. There are > few NOMMU users left, and the ones that do use NOMMU usually turn > off MMAP_ALLOW_UNINITIALIZED, as it still has the potential to cause > bugs and even security issues on systems with a memory protection > unit. > > - remove both the implementation and the macro to force a build > failure for anyone trying to use the feature. This way we can > see who complains and whether we need to put it back in some > form or change the userspace sources to no longer pass the flag. > > Implement the third option here for the sake of discussion. Usually I'd vote for option #2, which means remove the kernel implementati= on and redefine MAP_UNINITIALIZED to zero in the header. A few years back this turned out to be the "most compatible" solution. But today, and specifically regarding MAP_UNINITIALIZED, I think we should= get rid of it now. This flag is useless and build issues will force people to drop it. Helge