From owner-freebsd-hackers@freebsd.org Fri Mar 20 19:39:47 2020 Return-Path: Delivered-To: freebsd-hackers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 389DD270EA8; Fri, 20 Mar 2020 19:39:47 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "gate2.funkthat.com", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 48kYy90DHPz3H1K; Fri, 20 Mar 2020 19:39:44 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.15.2/8.15.2) with ESMTPS id 02KJdglQ065246 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 20 Mar 2020 12:39:42 -0700 (PDT) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.15.2/8.15.2/Submit) id 02KJdgtV065245; Fri, 20 Mar 2020 12:39:42 -0700 (PDT) (envelope-from jmg) Date: Fri, 20 Mar 2020 12:39:42 -0700 From: John-Mark Gurney To: Arpan Palit Cc: freebsd-hackers@freebsd.org, freebsd-questions@freebsd.org, freebsd-drivers@freebsd.org Subject: Re: How to access a user space file from kernel space in FreeBSD. Message-ID: <20200320193942.GL4213@funkthat.com> Mail-Followup-To: Arpan Palit , freebsd-hackers@freebsd.org, freebsd-questions@freebsd.org, freebsd-drivers@freebsd.org References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 11.3-STABLE amd64 X-PGP-Fingerprint: D87A 235F FB71 1F3F 55B7 ED9B D5FF 5A51 C0AC 3D65 X-Files: The truth is out there X-URL: https://www.funkthat.com/ X-Resume: https://www.funkthat.com/~jmg/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.6.1 (2016-04-27) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (gold.funkthat.com [127.0.0.1]); Fri, 20 Mar 2020 12:39:42 -0700 (PDT) X-Rspamd-Queue-Id: 48kYy90DHPz3H1K X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=none (mx1.freebsd.org: domain of jmg@gold.funkthat.com has no SPF policy when checking 208.87.223.18) smtp.mailfrom=jmg@gold.funkthat.com X-Spamd-Result: default: False [0.49 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.59)[-0.594,0]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; TO_DN_SOME(0.00)[]; IP_SCORE(-0.42)[ip: (-1.09), ipnet: 208.87.216.0/21(-0.54), asn: 32354(-0.44), country: US(-0.05)]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[funkthat.com]; AUTH_NA(1.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_SPAM_LONG(0.30)[0.305,0]; R_SPF_NA(0.00)[]; FORGED_SENDER(0.30)[jmg@funkthat.com,jmg@gold.funkthat.com]; FREEMAIL_TO(0.00)[gmail.com]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:32354, ipnet:208.87.216.0/21, country:US]; FROM_NEQ_ENVFROM(0.00)[jmg@funkthat.com,jmg@gold.funkthat.com]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 Mar 2020 19:39:47 -0000 Arpan Palit wrote this message on Fri, Mar 20, 2020 at 20:10 +0530: > Hi all, > > I am working on (kernel)driver ioctl implementation for file read/write, > where I need to know what are API's which can expose to read,write and > close user space file from kernel space. In general I need to know the > answer for the below questions. > > i). How to open a user space file from driver(kernel space) ? > ii). How to create a new user space file from driver(kernel space) ? > iii). How to get file parameters like size of the file ? > iv). How to read/write the files from the driver(kernel space) ? The core dumping routines do something similar, so you can look at that code: https://svnweb.freebsd.org/base/head/sys/kern/kern_sig.c?annotate=358856 Are you trying to open/write a file on behalf of a process? or just need to access the file system from your driver? If you're just needing this to load firmware for a device, you should look at the firmware(9) infrastructure that already exists: https://www.freebsd.org/cgi/man.cgi?query=firmware&manpath=FreeBSD+12.1-RELEASE+and+Ports -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."