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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67490C4320E for ; Sun, 8 Aug 2021 08:41:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4544D60F0F for ; Sun, 8 Aug 2021 08:41:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231274AbhHHImL (ORCPT ); Sun, 8 Aug 2021 04:42:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45408 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231308AbhHHImL (ORCPT ); Sun, 8 Aug 2021 04:42:11 -0400 Received: from mail-wr1-x430.google.com (mail-wr1-x430.google.com [IPv6:2a00:1450:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CF5BC0613CF for ; Sun, 8 Aug 2021 01:41:52 -0700 (PDT) Received: by mail-wr1-x430.google.com with SMTP id q11so4969710wrr.9 for ; Sun, 08 Aug 2021 01:41:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=KJhEInyGZS6KjVnrdNnP2ioa0x2HrO2OblcHmifm000=; b=KTTDnKR1lARspZa72O52ipW1zEXnFHBZq6vn2xcL2+TnJBdBB6SOfJQ/h5/Cxat4m4 Ceyp3YySPPgL7QWRSfs5vZFhZ+VrezgfokR08YYyPgCSWRreuUULh9fCnjwAug2rVyzK piVrzDNvjGHSosO0rGSf5KQxK18fZW39iW/plFoy1IerhNMI8eusrR+yJzt3E4da4UXN 4iq94hzDVj1oCTK07ca5HBEQRKxBjRr9eLg2zfSIVxWxotQDzLdLlMn3h1ldx/b9Zd+C JzFMWyw6HYRerbto59r5YwFnyaeIs9iuNVx0wso9PHR9afPCzDhR6nzAjX7EUqGd38N0 vEeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=KJhEInyGZS6KjVnrdNnP2ioa0x2HrO2OblcHmifm000=; b=WsQNPdmvLMNqjIE18HYyw71lVjX/SUkl5fySMm3UadJy0JFEiuhKE6ZbmPUTrKf+4m n/UOyijuGZ25GgABWr1bstRcApOiO2CYDIhVaQDJ8lJqEeVVtrIUtBxulXBafyeDW3v4 XdwHQuxZ2bpsdO92JhEcHVFbNLfh8Gvs1jtbzEla/bb1PnPGI2flQ1DvDbCGEcfPJNvz PgzXsPclJB02QFrp6FbudQoIJBSZGSs+ggw84tol01JQDvAFn6kINLSKW8R4f2a4XTbJ ApAnmH+tIZBdjZCNwhLyX2x/6dZeKb/xP9FcSbOE3seuc75tBy3NW2v8IN6JtuZ9Wp9/ S87g== X-Gm-Message-State: AOAM531FSLRnuOWd1KtfJnMqeoDO1n+6TwSRws+FXL/xn0EFEM4csI50 rma00cOeLvmAeIMzPFhno3eyefKqXKg= X-Google-Smtp-Source: ABdhPJz4qmwjuq2LsKoOWiaJYgOSyUGdxKldOWZPZ+wf9kN3TkzC/+Hd/YgeGrrZ1w49Lzukk875Ew== X-Received: by 2002:adf:e107:: with SMTP id t7mr19055693wrz.165.1628412111257; Sun, 08 Aug 2021 01:41:51 -0700 (PDT) Received: from sqli.sqli.com ([195.53.121.100]) by smtp.googlemail.com with ESMTPSA id h12sm15592004wrm.62.2021.08.08.01.41.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Aug 2021 01:41:50 -0700 (PDT) From: Alejandro Colomar To: mtk.manpages@gmail.com Cc: Mike Rapoport , linux-man@vger.kernel.org, Alejandro Colomar Subject: [PATCH 08/23] man2: new page describing memfd_secret() system call Date: Sun, 8 Aug 2021 10:41:18 +0200 Message-Id: <20210808084133.734274-9-alx.manpages@gmail.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210808084133.734274-1-alx.manpages@gmail.com> References: <20210808084133.734274-1-alx.manpages@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org From: Mike Rapoport Signed-off-by: Mike Rapoport Signed-off-by: Alejandro Colomar --- man2/memfd_secret.2 | 146 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 146 insertions(+) create mode 100644 man2/memfd_secret.2 diff --git a/man2/memfd_secret.2 b/man2/memfd_secret.2 new file mode 100644 index 000000000..466aa4236 --- /dev/null +++ b/man2/memfd_secret.2 @@ -0,0 +1,146 @@ +.\" Copyright (c) 2021, IBM Corporation. +.\" Written by Mike Rapoport +.\" +.\" Based on memfd_create(2) man page +.\" Copyright (C) 2014 Michael Kerrisk +.\" and Copyright (C) 2014 David Herrmann +.\" +.\" %%%LICENSE_START(GPLv2+) +.\" +.\" This program is free software; you can redistribute it and/or modify +.\" it under the terms of the GNU General Public License as published by +.\" the Free Software Foundation; either version 2 of the License, or +.\" (at your option) any later version. +.\" +.\" This program is distributed in the hope that it will be useful, +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +.\" GNU General Public License for more details. +.\" +.\" You should have received a copy of the GNU General Public +.\" License along with this manual; if not, see +.\" . +.\" %%%LICENSE_END +.\" +.TH MEMFD_SECRET 2 2020-08-02 Linux "Linux Programmer's Manual" +.SH NAME +memfd_secret \- create an anonymous file to access secret memory regions +.SH SYNOPSIS +.nf +.PP +.BR "#include " " /* Definition of " SYS_* " constants */" +.B #include +.PP +.BI "int syscall(SYS_memfd_secret, unsigned int " flags ); +.fi +.PP +.IR Note : +glibc provides no wrapper for +.BR memfd_secret (), +necessitating the use of +.BR syscall (2). +.SH DESCRIPTION +.BR memfd_secret () +creates an anonymous file and returns a file descriptor that refers to it. +The file provides a way to create and access memory regions +with stronger protection than usual RAM-based files and +anonymous memory mappings. +Once all references to the file are dropped, it is automatically released. +The initial size of the file is set to 0. +Following the call, the file size should be set using +.BR ftruncate (2). +.PP +The memory areas backing the file created with +.BR memfd_create(2) +are visible only to the contexts that have access to the file descriptor. +These areas are removed from the kernel page tables +and only the page tables of the processes holding the file descriptor +map the corresponding physical memory. +.PP +The following values may be bitwise ORed in +.I flags +to control the behavior of +.BR memfd_secret (2): +.TP +.B FD_CLOEXEC +Set the close-on-exec flag on the new file descriptor. +See the description of the +.B O_CLOEXEC +flag in +.BR open (2) +for reasons why this may be useful. +.PP +As its return value, +.BR memfd_secret () +returns a new file descriptor that can be used to refer to an anonymous file. +This file descriptor is opened for both reading and writing +.RB ( O_RDWR ) +and +.B O_LARGEFILE +is set for the file descriptor. +.PP +With respect to +.BR fork (2) +and +.BR execve (2), +the usual semantics apply for the file descriptor created by +.BR memfd_secret (). +A copy of the file descriptor is inherited by the child produced by +.BR fork (2) +and refers to the same file. +The file descriptor is preserved across +.BR execve (2), +unless the close-on-exec flag has been set. +.PP +The memory regions backed with +.BR memfd_secret () +are locked in the same way as +.BR mlock (2), +however the implementation will not try to +populate the whole range during the +.BR mmap (2) +call. +The amount of memory allowed for memory mappings +of the file descriptor obeys the same rules as +.BR mlock (2) +and cannot exceed +.BR RLIMIT_MEMLOCK . +.SH RETURN VALUE +On success, +.BR memfd_secret () +returns a new file descriptor. +On error, \-1 is returned and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EINVAL +.I flags +included unknown bits. +.TP +.B EMFILE +The per-process limit on the number of open file descriptors has been reached. +.TP +.B EMFILE +The system-wide limit on the total number of open files has been reached. +.TP +.B ENOMEM +There was insufficient memory to create a new anonymous file. +.TP +.B ENOSYS +.BR memfd_secret () +is not implemented on this architecture. +.SH VERSIONS +The +.BR memfd_secret (2) +system call first appeared in Linux 5.14. +.SH CONFORMING TO +The +.BR memfd_secret (2) +system call is Linux-specific. +.SH SEE ALSO +.BR fcntl (2), +.BR ftruncate (2), +.BR mlock (2), +.BR mmap (2), +.BR setrlimit (2) -- 2.32.0