From patchwork Fri Sep 18 01:56:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Randy Dunlap X-Patchwork-Id: 11783831 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6A67892C for ; Fri, 18 Sep 2020 01:56:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A1B720838 for ; Fri, 18 Sep 2020 01:56:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="mpZsUV3i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726267AbgIRB4x (ORCPT ); Thu, 17 Sep 2020 21:56:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726009AbgIRB4x (ORCPT ); Thu, 17 Sep 2020 21:56:53 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D95ECC06174A; Thu, 17 Sep 2020 18:56:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=2vCDwiPR2yaZdRJxWxgBGGfBruV3oiY2jDxmJ1dPfyo=; b=mpZsUV3iI6ME1iCtPwx9U99TlA 0ZfoagZAb4dVB+cyPmH41GaHhHtB+BlVvd6r36kL2xoOqwzkl8JAmZAHbF/cNqnO39UKHenqfth1T 1kwEpObXDx6XJPYQEKERAKHcvMks33r7A83lLSJrz3PZQSJbDUR4Yf4wKem+U8N0dr37MvGZGU7y0 bi1u883t8b9N03102tksoVnbhyyy7cxHTJeZmiesqs6nPT6R5jpTdZdHo45mY07Uo/V6DTQAP4uOr vuliLZd+CNneK5dprmMajckBnuiUUKz7nPWjrZr7J921cUxukwKrAo3J48YefZ2a93iUkWQZxDxf9 vzmZzIWQ==; Received: from [2601:1c0:6280:3f0::19c2] (helo=smtpauth.infradead.org) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kJ5dr-0007g2-5n; Fri, 18 Sep 2020 01:56:51 +0000 From: Randy Dunlap To: linux-kernel@vger.kernel.org Cc: Randy Dunlap , Karel Zak , Paul Gortmaker , Jens Axboe , linux-block@vger.kernel.org, Alexander Viro , Martin Mares , linux-video@atrey.karlin.mff.cuni.cz, "H. Peter Anvin" , Jonathan Corbet , linux-doc@vger.kernel.org Subject: [RFC PATCH v2 2/2] Documentation/admin-guide: blockdev/ramdisk: remove use of "rdev" Date: Thu, 17 Sep 2020 18:56:40 -0700 Message-Id: <20200918015640.8439-3-rdunlap@infradead.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200918015640.8439-1-rdunlap@infradead.org> References: <20200918015640.8439-1-rdunlap@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Remove use of "rdev" from blockdev/ramdisk.rst and update admin-guide/kernel-parameters.txt. "rdev" is considered antiquated, ancient, archaic, obsolete, deprecated {choose any or all}. "rdev" was removed from util-linux in 2010: https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=a3e40c14651fccf18e7954f081e601389baefe3f Signed-off-by: Randy Dunlap Cc: Karel Zak Cc: Paul Gortmaker Cc: Jens Axboe Cc: linux-block@vger.kernel.org Cc: Alexander Viro Cc: Martin Mares Cc: linux-video@atrey.karlin.mff.cuni.cz Cc: "H. Peter Anvin" Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org --- v2: modify Changelog date format. No email address for these: nCc: Werner Almesberger nCc: Stephen Tweedie nCc: Peter MacDonald Documentation/admin-guide/blockdev/ramdisk.rst | 70 ++++---------- Documentation/admin-guide/kernel-parameters.txt | 9 - 2 files changed, 27 insertions(+), 52 deletions(-) --- lnx-59-rc5.orig/Documentation/admin-guide/blockdev/ramdisk.rst +++ lnx-59-rc5/Documentation/admin-guide/blockdev/ramdisk.rst @@ -6,7 +6,7 @@ Using the RAM disk block device with Lin 1) Overview 2) Kernel Command Line Parameters - 3) Using "rdev -r" + 3) Using "rdev" 4) An Example of Creating a Compressed RAM Disk @@ -59,51 +59,27 @@ default is 4096 (4 MB). rd_size See ramdisk_size. -3) Using "rdev -r" ------------------- +3) Using "rdev" +--------------- -The usage of the word (two bytes) that "rdev -r" sets in the kernel image is -as follows. The low 11 bits (0 -> 10) specify an offset (in 1 k blocks) of up -to 2 MB (2^11) of where to find the RAM disk (this used to be the size). Bit -14 indicates that a RAM disk is to be loaded, and bit 15 indicates whether a -prompt/wait sequence is to be given before trying to read the RAM disk. Since -the RAM disk dynamically grows as data is being written into it, a size field -is not required. Bits 11 to 13 are not currently used and may as well be zero. -These numbers are no magical secrets, as seen below:: - - ./arch/x86/kernel/setup.c:#define RAMDISK_IMAGE_START_MASK 0x07FF - ./arch/x86/kernel/setup.c:#define RAMDISK_PROMPT_FLAG 0x8000 - ./arch/x86/kernel/setup.c:#define RAMDISK_LOAD_FLAG 0x4000 - -Consider a typical two floppy disk setup, where you will have the -kernel on disk one, and have already put a RAM disk image onto disk #2. - -Hence you want to set bits 0 to 13 as 0, meaning that your RAM disk -starts at an offset of 0 kB from the beginning of the floppy. -The command line equivalent is: "ramdisk_start=0" - -You want bit 14 as one, indicating that a RAM disk is to be loaded. -The command line equivalent is: "load_ramdisk=1" - -You want bit 15 as one, indicating that you want a prompt/keypress -sequence so that you have a chance to switch floppy disks. -The command line equivalent is: "prompt_ramdisk=1" - -Putting that together gives 2^15 + 2^14 + 0 = 49152 for an rdev word. -So to create disk one of the set, you would do:: - - /usr/src/linux# cat arch/x86/boot/zImage > /dev/fd0 - /usr/src/linux# rdev /dev/fd0 /dev/fd0 - /usr/src/linux# rdev -r /dev/fd0 49152 +"rdev" is an obsolete, deprecated, antiquated utility that could be used +to set the boot device in a Linux kernel image. -If you make a boot disk that has LILO, then for the above, you would use:: +Instead of using rdev, just place the boot device information on the +kernel command line and pass it to the kernel from the bootloader. + +You can also pass arguments to the kernel by setting FDARGS in +arch/x86/boot/Makefile and specify in initrd image by setting FDINITRD in +arch/x86/boot/Makefile. - append = "ramdisk_start=0 load_ramdisk=1 prompt_ramdisk=1" +Some of the kernel command line boot options that may apply here are:: -Since the default start = 0 and the default prompt = 1, you could use:: + ramdisk_start=N + ramdisk_size=M - append = "load_ramdisk=1" +If you make a boot disk that has LILO, then for the above, you would use:: + append = "ramdisk_start=N ramdisk_size=M" 4) An Example of Creating a Compressed RAM Disk ----------------------------------------------- @@ -151,12 +127,9 @@ f) Put the RAM disk image onto the flopp dd if=/tmp/ram_image.gz of=/dev/fd0 bs=1k seek=400 -g) Use "rdev" to set the boot device, RAM disk offset, prompt flag, etc. - For prompt_ramdisk=1, load_ramdisk=1, ramdisk_start=400, one would - have 2^15 + 2^14 + 400 = 49552:: - - rdev /dev/fd0 /dev/fd0 - rdev -r /dev/fd0 49552 +g) Make sure that you have already specified the boot information in + FDARGS and FDINITRD or that you use a bootloader to pass kernel + command line boot options to the kernel. That is it. You now have your boot/root compressed RAM disk floppy. Some users may wish to combine steps (d) and (f) by using a pipe. @@ -167,11 +140,14 @@ users may wish to combine steps (d) and Changelog: ---------- +SEPT-2020 : + + Removed usage of "rdev" + 10-22-04 : Updated to reflect changes in command line options, remove obsolete references, general cleanup. James Nelson (james4765@gmail.com) - 12-95 : Original Document --- lnx-59-rc5.orig/Documentation/admin-guide/kernel-parameters.txt +++ lnx-59-rc5/Documentation/admin-guide/kernel-parameters.txt @@ -2441,8 +2441,7 @@ memblock=debug [KNL] Enable memblock debug messages. - load_ramdisk= [RAM] List of ramdisks to load from floppy - See Documentation/admin-guide/blockdev/ramdisk.rst. + load_ramdisk= [RAM] [Deprecated] lockd.nlm_grace_period=P [NFS] Assign grace period. Format: @@ -3921,9 +3920,7 @@ Param: - step/bucket size as a power of 2 for statistical time based profiling. - prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk - before loading. - See Documentation/admin-guide/blockdev/ramdisk.rst. + prompt_ramdisk= [RAM] [Deprecated] prot_virt= [S390] enable hosting protected virtual machines isolated from the hypervisor (if hardware supports @@ -3981,6 +3978,8 @@ ramdisk_size= [RAM] Sizes of RAM disks in kilobytes See Documentation/admin-guide/blockdev/ramdisk.rst. + ramdisk_start= [RAM] RAM disk image start address + random.trust_cpu={on,off} [KNL] Enable or disable trusting the use of the CPU's random number generator (if available) to