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 0F347C4332F for ; Thu, 14 Dec 2023 20:11:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 81C618D00E4; Thu, 14 Dec 2023 15:11:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7CCA68D00C7; Thu, 14 Dec 2023 15:11:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 694978D00E4; Thu, 14 Dec 2023 15:11:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 580FC8D00C7 for ; Thu, 14 Dec 2023 15:11:47 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 27C0D1A03B8 for ; Thu, 14 Dec 2023 20:11:47 +0000 (UTC) X-FDA: 81566519454.22.0BE2155 Received: from mail-oi1-f179.google.com (mail-oi1-f179.google.com [209.85.167.179]) by imf11.hostedemail.com (Postfix) with ESMTP id 63FA940009 for ; Thu, 14 Dec 2023 20:11:45 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=EbMwlcHa; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf11.hostedemail.com: domain of pedro.falcato@gmail.com designates 209.85.167.179 as permitted sender) smtp.mailfrom=pedro.falcato@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1702584705; 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=Kfh8Dy6cQrhts0Y+UCJGg173DSLFoHSRig78lNgd6Fg=; b=CBI9AM40yajKMTl5QWSTJ3cqmfw0eDK9gXsfbcr1j9f2/KCN8ciNU8B2thQV5TzzuevbDv G8eu928CcpOjEHaujdhitZuttJiq43RmJCrZN++EB/srVdh26dtdnBHw4oJFX+vdm6quin zzi66WKlMs6L11dksREs+FVP/oBMWVY= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=EbMwlcHa; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf11.hostedemail.com: domain of pedro.falcato@gmail.com designates 209.85.167.179 as permitted sender) smtp.mailfrom=pedro.falcato@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1702584705; a=rsa-sha256; cv=none; b=7uXa75C+ZskUrRsQmtDgp24A7JGUt2NXV8k2kkqGjdD4XQdXKkRLiQ2TqKWMhD1HRlRL1X /TArrGy16p0t+fyiQyEUS0X6yEny7AERQa9tJxg3gtrH1sO8+di/pT+wjd/LEUHHBdczmv Qz59kCY0o7+gJUUR9KkQl7Sn1Jzubp8= Received: by mail-oi1-f179.google.com with SMTP id 5614622812f47-3ba0dfc9001so2247880b6e.2 for ; Thu, 14 Dec 2023 12:11:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1702584704; x=1703189504; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=Kfh8Dy6cQrhts0Y+UCJGg173DSLFoHSRig78lNgd6Fg=; b=EbMwlcHaezVksQwYol0mKG5GDnO2ONlNt+Slykp5bqdYhER1Pl+GFI05vg9B2kbrwn LhtVH8Kv7vlAyU36q3D71JvDOhU0qNFqznVn5szuMtJRop6dDsRnH5xoSS6Vsfa/Xua1 z7kYikq8Ziv3fpCJxCx/Rn/QCpjBHUnjRzltPjnHgTdqopX4pdCBxP+Gk5Cvc+KI88KS e5q+SjO90tOFfP8XgYvk11PXfnbvc7ksdxTWnpE2BwxsPa+CAh7HY3FYgWr3uorxywy9 NS1+tKfohf9Yuqyj6KGFxZaOwVyKP1k2QBdDQ451nrfXJ5NS0o6y0IYWHFRNt9Dnleip So9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702584704; x=1703189504; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Kfh8Dy6cQrhts0Y+UCJGg173DSLFoHSRig78lNgd6Fg=; b=cXLxPI+0PLX4134tFdX40yQse1sddyvVyP9itpdqjyCk78P7pLzOgHPHjoWiHCtMTc UWMoN5LTNmmWA3MZelRcbjNM9tlpFpU2mX/K83TTTVSV/PVYIG8O/fwDdm11gPKzMO8/ Guo3YvfPvNQuYx0iTDmPO0zJWDpULnODr0EMBts7TvatozmLHyLi6+FvXKblGqQWrkRm HBvwBPOnixRE2riL6G/DGVBLQGV6hG3yvNz4AupAOhDX49cLESy4+iBHofanAbnYRt0Z B4XQqyV3cZrKoxKdFfAtXM9g+CFwZXh1kaZ5qb35LP0lE2U2Utq9k8ode/CebsQoFLjc gsGg== X-Gm-Message-State: AOJu0YxZGFc3DZ9WtoC3Tsb4gtFFT8T2EXPiBf8aIvYjR+Ob0tO5Sl0c 3B0kWC0NMfcRT0jsjQLFYoMwpEVdN378dWb2wvQ= X-Google-Smtp-Source: AGHT+IE5OtfH6BmGn7Qjmv1Kb5hVv+UX/aLg+H3qizYtKhsIVRhRCc9OkzMWNCWsZ1PQBkFFBiPeRwTjP8svWjT4CCo= X-Received: by 2002:a05:6808:3849:b0:3ba:c52:7245 with SMTP id ej9-20020a056808384900b003ba0c527245mr9035807oib.95.1702584704448; Thu, 14 Dec 2023 12:11:44 -0800 (PST) MIME-Version: 1.0 References: <20231212231706.2680890-1-jeffxu@chromium.org> <20231212231706.2680890-12-jeffxu@chromium.org> In-Reply-To: From: Pedro Falcato Date: Thu, 14 Dec 2023 20:11:32 +0000 Message-ID: Subject: Re: [RFC PATCH v3 11/11] mseal:add documentation To: =?UTF-8?Q?Stephen_R=C3=B6ttger?= Cc: Linus Torvalds , Jeff Xu , jeffxu@chromium.org, akpm@linux-foundation.org, keescook@chromium.org, jannh@google.com, willy@infradead.org, gregkh@linuxfoundation.org, jorgelo@chromium.org, groeck@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, dave.hansen@intel.com, linux-hardening@vger.kernel.org, deraadt@openbsd.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 63FA940009 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: wpkg9aciaa5gcxdzko6nwxzr7bo5s6o8 X-HE-Tag: 1702584705-447165 X-HE-Meta: U2FsdGVkX19wNKmwl/9LWKO++gxl9TSW3iKIfsoAN9nmwsOWt2urNOEXNwHHDjYAs3RM+jMbgcNrvQYVXdFrJloSe3TY8dDGt3qxQ+7FdELhOz745ktXtXgI0K7rukAE5zxPV0J6kcKs0W14q49xeY90pdy9gyx5N08JAha06WQ8gqCEAO6rZQNIRLZe/r9afugq4zujCH77vXjoDG4UQKJm5MMX1bl3JyaeSu1laajL20RqLXFAB8u4I41eZ+bajVCrEuA9UeLKjRDa2v/chljbFS1EbVOk2klWPJiZ7ZZIs8Ijy5xKL4bdo0IICuNXY0qpKDs9XvVlzmhnNu6ZdJyS94D9syXFSeRls4xwhkFDv6MTaW0HvDDdYdZtayVmBjfNy1HwOIp/0H0uZWDErAoz8KQY5bFFjwl206ZhKSdYp6PfpMONN1VTiy8vbWtFs6/2STOH21VsoWgkxxh+RWqBt9fSmorkWZmvVzyMFlMahLPSnr9EYYckUJa/Skvtidtk64T4WW95zpHJiRSZDQkKn2zp9hmcW3SVzea2JZ1cGJvGb+eAXJFYO64H1jeWasvK3a/H5AN71n1Booth17PKvkqcW4JSC3gSfHKab1fFkR1YkNmVfgoqqUowmJGe5h7YT3GGzCqVMsSVCyxF5Sj1H7R/3qxJ00cI4OcPNEGRQ5scQ19+XHlQOE5gTwhcaV6l9rfYDCVbqBj4M3VL+53t1jBzS7VSZPraTBVrOPXs3SPTUzCAwp9OQIxJDD2HjMvpM+64wXeYM/1CCD2/TR2mco8q+6guj5yc7+Kw+bUAOuU1RtDuKWQemCKrviw21Mt89Vbph7Shd6yugUELa+MlENopJgyOCkpS3auTdSjedMmxCOteZGBTUdOYGj0qLs6tjoFS1It+cdFl2l0cjoPqrWks1Wf1CIhDl8E0DMfXp/V9b/lcfunSERv0PlJ9Qi4g9ScP8ubK8bB3lYR WUzW7OhN hUmTr88/SRK9sSf/Hi6UEiQS/qgCCwl5RcE2xzOGW0ftW8cVq659eoAg51pyuoO1vTtrJ/sRETwQ2wYJfBu0ayWBva6I5eM8l03NI2bH8AjifNKvYH52gW5etPofZkusYTDGWgsCaxuFCrlR8gWoJv1B42xJVKHflCD2cCu12Mh4/sTFolCtQREqM7v2qUYu7egK9wBDpDCO1OwAnUtC0WdfdzuC8dEOvwE9uMXTAC3nCUTwDgSFULWZQHygSL4rqxpCQIWT/rJ4/qvWRWjmQYNd9+kMi7W+fpxdkKwCrNGScAcZBJuNdD32lTksvah/qNdoL+QjEBBU36Mg7DIo/Xuz26LENsemkZFRNt3U01i7HYQRcXfuINfVXmhZLu7+N0J0fVDvxTMgYMzmNGuivG1/L0DLXZtOPeZCRDHx2vDTnLJ57u6Dg/W9NexjccDKh1WMOcxEWGFp/vV3rg9LONAp/vw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Dec 14, 2023 at 6:07=E2=80=AFPM Stephen R=C3=B6ttger wrote: > > On Thu, Dec 14, 2023 at 2:31=E2=80=AFAM Linus Torvalds > wrote: > > > > On Wed, 13 Dec 2023 at 16:36, Jeff Xu wrote: > > > > > > > > > > IOW, when would you *ever* say "seal this area, but MADV_DONTNEED i= s ok"? > > > > > > > The MADV_DONTNEED is OK for file-backed mapping. > > > > Right. It makes no semantic difference. So there's no point to it. > > > > My point was that you added this magic flag for "not ok for RO anon map= ping". > > > > It's such a *completely* random flag, that I go "that's just crazy > > random - make sealing _always_ disallow that case". > > > > So what I object to in this series is basically random small details > > that should just eb part of the basic act of sealing. > > > > I think sealing should just mean "you can't do any operations that > > have semantic meaning for the mapping, because it is SEALED". > > > > So I think sealing should automatically mean "can't do MADV_DONTNEED > > on anon memory", because that's basically equivalent to a munmap/remap > > operation. > > In Chrome, we have a use case to allow MADV_DONTNEED on sealed memory. I don't want to be that guy (*believe me*), but what if there was a way to attach BPF programs to mm's? Such that you could handle 'seal failures' in BPF, and thus allow for this sort of weird semantics? e.g: madvise(MADV_DONTNEED) on a sealed region fails, kernel invokes the BPF program (that chrome loaded), BPF program sees it was a MADV_DONTNEED and allows it to proceed. It requires BPF but sounds like a good compromise in order to not get an ugly API? --=20 Pedro