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 6B636C43458 for ; Fri, 3 Jul 2026 14:51:16 +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:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=pcleEhbC+dTWtJEQxQVfa82QuKy95U7nQIPkrIDg3l0=; b=fNRmh3CqHOjuqu x5RGhdLdNjnhNfKOHLLY+N6It3aiINH/1JrCHCdt1igOKxZhQl3QR03/w5NK1c0GhObGSMl6wIX4I 1c+zld2kVHVqyVWHDIA9YodIxoVf+lMK/dmHYT1nhRh8vU+vLcDuMy7Aa/13wAM0w2jQlfli5d8Sd 2vyNDfRy5ReriTylJHzVm/NyGiSsTJHDQF9yvrkj5dTca3LjXCJuRYKKLGLB92SQ5jfOhfVzQmSyq khnvw2JR/geUv0n1lMYVmmIGGM2QUasJWKLMl6Wj3P1jTJyBgIbD88WJoiqU0lZCwptDn85kHae2J kOXUDSfcte5u8oHMR/IA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wffEO-00000007JzK-3Oss; Fri, 03 Jul 2026 14:51:04 +0000 Received: from out-189.mta0.migadu.com ([91.218.175.189]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wffEM-00000007Jxl-0aFy for linux-riscv@lists.infradead.org; Fri, 03 Jul 2026 14:51:03 +0000 Message-ID: <8f75dc18-dd4c-4989-a76c-eec6cc513ccf@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783090246; h=from:from: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; bh=CXlZY4gPG+zU33k3H0xm4g/0VaNA0tr7HNt5303WUBg=; b=UDBNB8/0B1x3/BrOa/t8tH6XYsteLhqIKb6sFPxo+8voiJoXwSGbGVTm7m2V2fKjxbZfG5 wYXqGIpNv/UsD7//6L9xKs/IvOligQC3lhghGNicG75MZUNKdc91kSBysgQAuIKoLqiQ3k zeQenTliY3QJ+tbtFUjK7MHFfZ7WXFo= Date: Fri, 3 Jul 2026 22:50:29 +0800 MIME-Version: 1.0 Subject: Re: [PATCH] mm/mseal: fix mseal documentation for 32-bit kernels To: Pedro Falcato References: <20260703022507.187457-1-leon.hwang@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Leon Hwang In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260703_075102_340078_923321EA X-CRM114-Status: GOOD ( 28.66 ) 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: , Cc: linux-doc@vger.kernel.org, Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Gary Guo , linux-riscv@lists.infradead.org, Vlastimil Babka , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , Jonathan Corbet , Alice Ryhl , Miguel Ojeda , Albert Ou , Jann Horn , Nathan Chancellor , Shuah Khan , Lorenzo Stoakes , Andrew Morton , Alexandre Ghiti , "Liam R . Howlett" , Nicolas Schier , Randy Dunlap , Douglas Anderson , Palmer Dabbelt , Thomas Gleixner , Paul Walmsley 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 2026/7/3 17:44, Pedro Falcato wrote: > On Fri, Jul 03, 2026 at 10:25:07AM +0800, Leon Hwang wrote: >> mseal.o is built only for 64-bit kernels, so 32-bit kernels fall back >> to sys_ni_syscall() and return -ENOSYS rather than -EPERM. >> >> Document the -EINTR return from mmap_write_lock_killable(), fix the >> CONFIG_MSEAL_SYSTEM_MAPPINGS typo, and describe system mappings in >> terms of VM_SEALED_SYSMAP. >> >> Signed-off-by: Leon Hwang >> --- >> Documentation/userspace-api/mseal.rst | 18 ++++++++++-------- >> init/Kconfig | 2 +- >> mm/mseal.c | 4 ++-- >> 3 files changed, 13 insertions(+), 11 deletions(-) >> >> diff --git a/Documentation/userspace-api/mseal.rst b/Documentation/userspace-api/mseal.rst >> index ea9b11a0bd89..1f1cf206670c 100644 >> --- a/Documentation/userspace-api/mseal.rst >> +++ b/Documentation/userspace-api/mseal.rst >> @@ -50,8 +50,10 @@ mseal syscall signature >> * The start address (``addr``) is not allocated. >> * The end address (``addr`` + ``len``) is not allocated. >> * A gap (unallocated memory) between start and end address. >> - - **-EPERM**: >> - * sealing is supported only on 64-bit CPUs, 32-bit is not supported. >> + - **-EINTR**: >> + * Interrupted while waiting for the mmap write lock. >> + - **-ENOSYS**: >> + * The kernel does not implement ``mseal()``. >> >> **Note about error return**: >> - For above error cases, users can expect the given memory range is > > Honestly, this whole thing needs to be deleted. We need a proper manpage. $ man mseal No manual entry for mseal When searching "mseal manual" using Google, this doc is the first entry. So, this change is worthy. > >> @@ -62,7 +64,8 @@ mseal syscall signature >> memory range could happen. However, those cases should be rare. >> >> **Architecture support**: >> - mseal only works on 64-bit CPUs, not 32-bit CPUs. >> + mseal is built only for 64-bit kernels. 32-bit kernels return >> + ``-ENOSYS``. > > This LGTM. > >> >> **Idempotent**: >> users can call mseal multiple times. mseal on an already sealed memory >> @@ -131,20 +134,19 @@ Use cases >> - Chrome browser: protect some security sensitive data structures. >> >> - System mappings: >> - The system mappings are created by the kernel and includes vdso, vvar, >> + The system mappings are created by the kernel and include vdso, vvar, >> vvar_vclock, vectors (arm compat-mode), sigpage (arm compat-mode), uprobes. >> >> Those system mappings are readonly only or execute only, memory sealing can >> - protect them from ever changing to writable or unmmap/remapped as different >> + protect them from ever changing to writable or unmapped/remapped as different >> attributes. This is useful to mitigate memory corruption issues where a >> corrupted pointer is passed to a memory management system. > > Also LGTM. > >> >> If supported by an architecture (CONFIG_ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS), >> - the CONFIG_MSEAL_SYSTEM_MAPPINGS seals all system mappings of this >> - architecture. >> + CONFIG_MSEAL_SYSTEM_MAPPINGS seals mappings marked with VM_SEALED_SYSMAP. > > VM_SEALED_SYSMAP isn't meaningful to userspace. Got it. Will drop this change. > >> >> The following architectures currently support this feature: x86-64, arm64, >> - loongarch and s390. >> + loongarch, riscv, and s390. > > This is also useless, every 64-bit architecture will support this. Do you mean dropping this sentence, or this change? > >> >> WARNING: This feature breaks programs which rely on relocating >> or unmapping system mappings. Known broken software at the time >> diff --git a/init/Kconfig b/init/Kconfig >> index 5230d4879b1c..12bb39f637b1 100644 >> --- a/init/Kconfig >> +++ b/init/Kconfig >> @@ -2112,7 +2112,7 @@ config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS >> from a kernel perspective. >> >> After the architecture enables this, a distribution can set >> - CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature. >> + CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature. >> >> For complete descriptions of memory sealing, please see >> Documentation/userspace-api/mseal.rst >> diff --git a/mm/mseal.c b/mm/mseal.c >> index 9781647483d1..0464c7b94ab9 100644 >> --- a/mm/mseal.c >> +++ b/mm/mseal.c >> @@ -132,8 +132,8 @@ static int mseal_apply(struct mm_struct *mm, >> * addr is not a valid address (not allocated). >> * end (start + len) is not a valid address. >> * a gap (unallocated memory) between start and end. >> - * -EPERM: >> - * - In 32 bit architecture, sealing is not supported. >> + * -EINTR: >> + * interrupted while waiting for the mmap write lock. >> * Note: >> * user can call mseal(2) multiple times, adding a seal on an >> * already sealed memory is a no-action (no error). > > And this whole header needs to be deleted as well. No one's looking at > kernel code for documentation (and if they are, we did a horrendous job > at actually documenting the thing). > Just to confirm, do you mean removing the entire function comment above do_mseal()? Thanks, Leon _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv