From patchwork Wed Aug 16 17:35:32 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 110272 Delivered-To: patch@linaro.org Received: by 10.140.95.78 with SMTP id h72csp1085341qge; Wed, 16 Aug 2017 10:37:32 -0700 (PDT) X-Received: by 10.84.218.65 with SMTP id f1mr2705258plm.295.1502905052656; Wed, 16 Aug 2017 10:37:32 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1502905052; cv=none; d=google.com; s=arc-20160816; b=EJpIw+yz4UbEHuX5NKeiSMcF21SCwoc4Kve6CECYUGa0vrltJiWPfwsXytNKeCsuaQ OaF08Zjqx8HKZTaR5YfWZyOmBb8kltNVTtrGwRlphETm969fuBA+cl9kyXRpzemhrtHC l1Qs6lpdo1wFW0Mp401ke6JtbkCbnIJsp9FbPtl8dHWEUEVvPr/14nSCR8Mo6Kq32ouB efQcGLR2ORak5zfn5OoTHwvavq6WErcXlUIE8gDup7jt44jdsj+GeE1zd9+hjSXL5+C5 n3SkfP45OIj+M8pShwNE5tCZx8UpiZquEpJN/A0IWGu2hcjYiXD74z9IhSKJGEfIYqvm M6Iw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=10E1z0nE5oDaUKfVC/AmJlFLCdog/DHIl38OHLNqHJ4=; b=Oqf5MrUnFIRi6xbKyEtunehHeHL96BBUZeg53yDKhvw9Fd/ofyoMwXfndwQID2DS2L lCokS8XseStoOayo88/WO8ymFDD6pPP5tfYZZ0tGQiWGgBNj0UImbJ4gMD1frfsN45s3 afnzaxQUIw+mKRb80FUd+lmmqjsxGQB9bcY08XnhxkqNC3HQ4IKRVpUmAHV/ML4uVnhG htCf8y31oPD9VZKQKBsy0Q4fLlz+NadNZarHGJp5ih7xnulD2l4vYvH2mgqpZExZVmQQ wjzFBKzU6nNt/3OxYFuuL2MWgeHnv3aOuQyE56ndcZVykKcX4ntBENc+e8ImAzqyiu6Y MYOg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=Zh9QrKX6; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id n23si786791pfi.632.2017.08.16.10.37.31; Wed, 16 Aug 2017 10:37:32 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=Zh9QrKX6; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752779AbdHPRha (ORCPT + 26 others); Wed, 16 Aug 2017 13:37:30 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:55466 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751844AbdHPRf6 (ORCPT ); Wed, 16 Aug 2017 13:35:58 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 54E60AD79E; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=sasl; bh=BHur xDVhGuWWG0YbrCvyi3o3XR0=; b=Zh9QrKX6ScPzewp3vRAzbF3yuZvqAVl5cShW n15PRTNIS/Zff5m0lqwVRXpXet0RHRdN8zxcWFrc3t/KyJGieWHTN2A1lYFDbQFl fL1/+BdZgkYe0VEWuD/A7iOp1tRvEkaPjyMN+r8CTdmA6FXRUsi6gN8SLmOYl3sr 5N6aiSI= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 3F6A7AD79C; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) Received: from yoda.home (unknown [70.80.200.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id 9E105AD797; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 059962DA0522; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) From: Nicolas Pitre To: Alexander Viro Cc: linux-fsdevel@vger.kernel.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt Subject: [PATCH v2 1/5] cramfs: direct memory access support Date: Wed, 16 Aug 2017 13:35:32 -0400 Message-Id: <20170816173536.1879-2-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170816173536.1879-1-nicolas.pitre@linaro.org> References: <20170816173536.1879-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 5C3C34FA-82A9-11E7-95C8-FE4B1A68708C-78420484!pb-smtp1.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Small embedded systems typically execute the kernel code in place (XIP) directly from flash to save on precious RAM usage. This adds the ability to consume filesystem data directly from flash to the cramfs filesystem as well. Cramfs is particularly well suited to this feature as it is very simple and its RAM usage is already very low, and with this feature it is possible to use it with no block device support and even lower RAM usage. This patch was inspired by a similar patch from Shane Nay dated 17 years ago that used to be very popular in embedded circles but never made it into mainline. This is a cleaned-up implementation that uses far fewer memory address at run time when both methods are configured in. In the context of small IoT deployments, this functionality has become relevant and useful again. To distinguish between both access types, the cramfs_physmem filesystem type must be specified when using a memory accessible cramfs image, and the physaddr argument must provide the actual filesystem image's physical memory location. Signed-off-by: Nicolas Pitre --- fs/cramfs/Kconfig | 30 ++++++- fs/cramfs/inode.c | 264 +++++++++++++++++++++++++++++++++++++++++++----------- 2 files changed, 242 insertions(+), 52 deletions(-) -- 2.9.5 diff --git a/fs/cramfs/Kconfig b/fs/cramfs/Kconfig index 11b29d491b..5eed4ad2d5 100644 --- a/fs/cramfs/Kconfig +++ b/fs/cramfs/Kconfig @@ -1,6 +1,5 @@ config CRAMFS tristate "Compressed ROM file system support (cramfs) (OBSOLETE)" - depends on BLOCK select ZLIB_INFLATE help Saying Y here includes support for CramFs (Compressed ROM File @@ -20,3 +19,32 @@ config CRAMFS in terms of performance and features. If unsure, say N. + +config CRAMFS_BLOCKDEV + bool "Support CramFs image over a regular block device" if EXPERT + depends on CRAMFS && BLOCK + default y + help + This option allows the CramFs driver to load data from a regular + block device such a disk partition or a ramdisk. + +config CRAMFS_PHYSMEM + bool "Support CramFs image directly mapped in physical memory" + depends on CRAMFS + default y if !CRAMFS_BLOCKDEV + help + This option allows the CramFs driver to load data directly from + a linear adressed memory range (usually non volatile memory + like flash) instead of going through the block device layer. + This saves some memory since no intermediate buffering is + necessary. + + The filesystem type for this feature is "cramfs_physmem". + The location of the CramFs image in memory is board + dependent. Therefore, if you say Y, you must know the proper + physical address where to store the CramFs image and specify + it using the physaddr=0x******** mount option (for example: + "mount -t cramfs_physmem -o physaddr=0x100000 none /mnt"). + + If unsure, say N. + diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c index 7919967488..393eb27ef4 100644 --- a/fs/cramfs/inode.c +++ b/fs/cramfs/inode.c @@ -24,6 +24,7 @@ #include #include #include +#include #include "internal.h" @@ -36,6 +37,8 @@ struct cramfs_sb_info { unsigned long blocks; unsigned long files; unsigned long flags; + void *linear_virt_addr; + phys_addr_t linear_phys_addr; }; static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb) @@ -140,6 +143,9 @@ static struct inode *get_cramfs_inode(struct super_block *sb, * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to * worry about end-of-buffer issues even when decompressing a full * page cache. + * + * Note: This is all optimized away at compile time when + * CONFIG_CRAMFS_BLOCKDEV=n. */ #define READ_BUFFERS (2) /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */ @@ -160,10 +166,10 @@ static struct super_block *buffer_dev[READ_BUFFERS]; static int next_buffer; /* - * Returns a pointer to a buffer containing at least LEN bytes of - * filesystem starting at byte offset OFFSET into the filesystem. + * Populate our block cache and return a pointer from it. */ -static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) +static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset, + unsigned int len) { struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping; struct page *pages[BLKS_PER_BUF]; @@ -239,7 +245,39 @@ static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned i return read_buffers[buffer] + offset; } -static void cramfs_kill_sb(struct super_block *sb) +/* + * Return a pointer to the linearly addressed cramfs image in memory. + */ +static void *cramfs_direct_read(struct super_block *sb, unsigned int offset, + unsigned int len) +{ + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); + + if (!len) + return NULL; + if (len > sbi->size || offset > sbi->size - len) + return page_address(ZERO_PAGE(0)); + return sbi->linear_virt_addr + offset; +} + +/* + * Returns a pointer to a buffer containing at least LEN bytes of + * filesystem starting at byte offset OFFSET into the filesystem. + */ +static void *cramfs_read(struct super_block *sb, unsigned int offset, + unsigned int len) +{ + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); + + if (IS_ENABLED(CONFIG_CRAMFS_PHYSMEM) && sbi->linear_virt_addr) + return cramfs_direct_read(sb, offset, len); + else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV)) + return cramfs_blkdev_read(sb, offset, len); + else + return NULL; +} + +static void cramfs_blkdev_kill_sb(struct super_block *sb) { struct cramfs_sb_info *sbi = CRAMFS_SB(sb); @@ -247,6 +285,16 @@ static void cramfs_kill_sb(struct super_block *sb) kfree(sbi); } +static void cramfs_physmem_kill_sb(struct super_block *sb) +{ + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); + + if (sbi->linear_virt_addr) + memunmap(sbi->linear_virt_addr); + kill_anon_super(sb); + kfree(sbi); +} + static int cramfs_remount(struct super_block *sb, int *flags, char *data) { sync_filesystem(sb); @@ -254,34 +302,24 @@ static int cramfs_remount(struct super_block *sb, int *flags, char *data) return 0; } -static int cramfs_fill_super(struct super_block *sb, void *data, int silent) +static int cramfs_read_super(struct super_block *sb, + struct cramfs_super *super, int silent) { - int i; - struct cramfs_super super; + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); unsigned long root_offset; - struct cramfs_sb_info *sbi; - struct inode *root; - - sb->s_flags |= MS_RDONLY; - - sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); - if (!sbi) - return -ENOMEM; - sb->s_fs_info = sbi; - /* Invalidate the read buffers on mount: think disk change.. */ - mutex_lock(&read_mutex); - for (i = 0; i < READ_BUFFERS; i++) - buffer_blocknr[i] = -1; + /* We don't know the real size yet */ + sbi->size = PAGE_SIZE; /* Read the first block and get the superblock from it */ - memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); + mutex_lock(&read_mutex); + memcpy(super, cramfs_read(sb, 0, sizeof(*super)), sizeof(*super)); mutex_unlock(&read_mutex); /* Do sanity checks on the superblock */ - if (super.magic != CRAMFS_MAGIC) { + if (super->magic != CRAMFS_MAGIC) { /* check for wrong endianness */ - if (super.magic == CRAMFS_MAGIC_WEND) { + if (super->magic == CRAMFS_MAGIC_WEND) { if (!silent) pr_err("wrong endianness\n"); return -EINVAL; @@ -289,10 +327,10 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent) /* check at 512 byte offset */ mutex_lock(&read_mutex); - memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); + memcpy(super, cramfs_read(sb, 512, sizeof(*super)), sizeof(*super)); mutex_unlock(&read_mutex); - if (super.magic != CRAMFS_MAGIC) { - if (super.magic == CRAMFS_MAGIC_WEND && !silent) + if (super->magic != CRAMFS_MAGIC) { + if (super->magic == CRAMFS_MAGIC_WEND && !silent) pr_err("wrong endianness\n"); else if (!silent) pr_err("wrong magic\n"); @@ -301,34 +339,34 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent) } /* get feature flags first */ - if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { + if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) { pr_err("unsupported filesystem features\n"); return -EINVAL; } /* Check that the root inode is in a sane state */ - if (!S_ISDIR(super.root.mode)) { + if (!S_ISDIR(super->root.mode)) { pr_err("root is not a directory\n"); return -EINVAL; } /* correct strange, hard-coded permissions of mkcramfs */ - super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH); + super->root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH); - root_offset = super.root.offset << 2; - if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { - sbi->size = super.size; - sbi->blocks = super.fsid.blocks; - sbi->files = super.fsid.files; + root_offset = super->root.offset << 2; + if (super->flags & CRAMFS_FLAG_FSID_VERSION_2) { + sbi->size = super->size; + sbi->blocks = super->fsid.blocks; + sbi->files = super->fsid.files; } else { sbi->size = 1<<28; sbi->blocks = 0; sbi->files = 0; } - sbi->magic = super.magic; - sbi->flags = super.flags; + sbi->magic = super->magic; + sbi->flags = super->flags; if (root_offset == 0) pr_info("empty filesystem"); - else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && + else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && ((root_offset != sizeof(struct cramfs_super)) && (root_offset != 512 + sizeof(struct cramfs_super)))) { @@ -336,9 +374,18 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent) return -EINVAL; } + return 0; +} + +static int cramfs_finalize_super(struct super_block *sb, + struct cramfs_inode *cramfs_root) +{ + struct inode *root; + /* Set it all up.. */ + sb->s_flags |= MS_RDONLY; sb->s_op = &cramfs_ops; - root = get_cramfs_inode(sb, &super.root, 0); + root = get_cramfs_inode(sb, cramfs_root, 0); if (IS_ERR(root)) return PTR_ERR(root); sb->s_root = d_make_root(root); @@ -347,6 +394,92 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent) return 0; } +static int cramfs_blkdev_fill_super(struct super_block *sb, void *data, int silent) +{ + struct cramfs_sb_info *sbi; + struct cramfs_super super; + int i, err; + + sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); + if (!sbi) + return -ENOMEM; + sb->s_fs_info = sbi; + + /* Invalidate the read buffers on mount: think disk change.. */ + for (i = 0; i < READ_BUFFERS; i++) + buffer_blocknr[i] = -1; + + err = cramfs_read_super(sb, &super, silent); + if (err) + return err; + return cramfs_finalize_super(sb, &super.root); +} + +static int cramfs_physmem_fill_super(struct super_block *sb, void *data, int silent) +{ + struct cramfs_sb_info *sbi; + struct cramfs_super super; + char *p; + int err; + + sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); + if (!sbi) + return -ENOMEM; + sb->s_fs_info = sbi; + + /* + * The physical location of the cramfs image is specified as + * a mount parameter. This parameter is mandatory for obvious + * reasons. Some validation is made on the phys address but this + * is not exhaustive and we count on the fact that someone using + * this feature is supposed to know what he/she's doing. + */ + if (!data || !(p = strstr((char *)data, "physaddr="))) { + pr_err("unknown physical address for linear cramfs image\n"); + return -EINVAL; + } + sbi->linear_phys_addr = memparse(p + 9, NULL); + if (!sbi->linear_phys_addr) { + pr_err("bad value for cramfs image physical address\n"); + return -EINVAL; + } + if (sbi->linear_phys_addr & (PAGE_SIZE-1)) { + pr_err("physical address %pap for linear cramfs isn't aligned to a page boundary\n", + &sbi->linear_phys_addr); + return -EINVAL; + } + + /* + * Map only one page for now. Will remap it when fs size is known. + * Although we'll only read from it, we want the CPU cache to + * kick in for the higher throughput it provides, hence MEMREMAP_WB. + */ + pr_info("checking physical address %pap for linear cramfs image\n", &sbi->linear_phys_addr); + sbi->linear_virt_addr = memremap(sbi->linear_phys_addr, PAGE_SIZE, + MEMREMAP_WB); + if (!sbi->linear_virt_addr) { + pr_err("ioremap of the linear cramfs image failed\n"); + return -ENOMEM; + } + + err = cramfs_read_super(sb, &super, silent); + if (err) + return err; + + /* Remap the whole filesystem now */ + pr_info("linear cramfs image appears to be %lu KB in size\n", + sbi->size/1024); + memunmap(sbi->linear_virt_addr); + sbi->linear_virt_addr = memremap(sbi->linear_phys_addr, sbi->size, + MEMREMAP_WB); + if (!sbi->linear_virt_addr) { + pr_err("ioremap of the linear cramfs image failed\n"); + return -ENOMEM; + } + + return cramfs_finalize_super(sb, &super.root); +} + static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf) { struct super_block *sb = dentry->d_sb; @@ -573,38 +706,67 @@ static const struct super_operations cramfs_ops = { .statfs = cramfs_statfs, }; -static struct dentry *cramfs_mount(struct file_system_type *fs_type, - int flags, const char *dev_name, void *data) +static struct dentry *cramfs_blkdev_mount(struct file_system_type *fs_type, + int flags, const char *dev_name, void *data) +{ + return mount_bdev(fs_type, flags, dev_name, data, cramfs_blkdev_fill_super); +} + +static struct dentry *cramfs_physmem_mount(struct file_system_type *fs_type, + int flags, const char *dev_name, void *data) { - return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super); + return mount_nodev(fs_type, flags, data, cramfs_physmem_fill_super); } static struct file_system_type cramfs_fs_type = { .owner = THIS_MODULE, .name = "cramfs", - .mount = cramfs_mount, - .kill_sb = cramfs_kill_sb, + .mount = cramfs_blkdev_mount, + .kill_sb = cramfs_blkdev_kill_sb, .fs_flags = FS_REQUIRES_DEV, }; + +static struct file_system_type cramfs_physmem_fs_type = { + .owner = THIS_MODULE, + .name = "cramfs_physmem", + .mount = cramfs_physmem_mount, + .kill_sb = cramfs_physmem_kill_sb, +}; + +#ifdef CONFIG_CRAMFS_BLOCKDEV MODULE_ALIAS_FS("cramfs"); +#endif +#ifdef CONFIG_CRAMFS_PHYSMEM +MODULE_ALIAS_FS("cramfs_physmem"); +#endif static int __init init_cramfs_fs(void) { int rv; - rv = cramfs_uncompress_init(); - if (rv < 0) - return rv; - rv = register_filesystem(&cramfs_fs_type); - if (rv < 0) - cramfs_uncompress_exit(); - return rv; + if ((rv = cramfs_uncompress_init()) < 0) + goto err0; + if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && + (rv = register_filesystem(&cramfs_fs_type)) < 0) + goto err1; + if (IS_ENABLED(CONFIG_CRAMFS_PHYSMEM) && + (rv = register_filesystem(&cramfs_physmem_fs_type)) < 0) + goto err2; + return 0; + +err2: if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV)) + unregister_filesystem(&cramfs_fs_type); +err1: cramfs_uncompress_exit(); +err0: return rv; } static void __exit exit_cramfs_fs(void) { cramfs_uncompress_exit(); - unregister_filesystem(&cramfs_fs_type); + if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV)) + unregister_filesystem(&cramfs_fs_type); + if (IS_ENABLED(CONFIG_CRAMFS_PHYSMEM)) + unregister_filesystem(&cramfs_physmem_fs_type); } module_init(init_cramfs_fs) From patchwork Wed Aug 16 17:35:33 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 110270 Delivered-To: patch@linaro.org Received: by 10.140.95.78 with SMTP id h72csp1083950qge; Wed, 16 Aug 2017 10:36:11 -0700 (PDT) X-Received: by 10.84.229.78 with SMTP id d14mr2694533pln.470.1502904971106; Wed, 16 Aug 2017 10:36:11 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1502904971; cv=none; d=google.com; s=arc-20160816; b=JBOJUdmNFQvZ2Io6jE83hd8RXHzDqBRM6g/g/rIFd5ndsGOKPZxjOdXEweA6lYlg0m NSEC+VAN1Cgb5BLYF0j1GFF2dczf4o2pqw2pl3lsNkhjOrFZP+C8pHfFZYaB114E42Zs fMlw9T5l7T0EDsnbb5RZWQ3y6U+YcVPz3JsRb4oPf1FpBEFL/3SvjzeU+jq/il4Y0HKb +HTjriNxPZ3W3Ij7tqRXdgzcpAbYl2O5OUVRA6hUSCVIvmU2UBjRpencoW+0aLdhro/s SEA7+yOjNhbynQN3FnAfRKVR3rvtfYpl9J5RHA5w+8B4zmucaQNmoFg6oBYKsuLyuKM1 shOg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; 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Wed, 16 Aug 2017 13:35:57 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=sasl; bh=FRW4 h7LOGDi0rkk6CzRZnQnfVq4=; b=J+FSJHxTz9+bVarkO8RZJg6ljWmuw1MTtQNi jyhknqXvVjTMQU9PCwI8JBSdvH+CCQoKVWpNVPCRHApfwOpvB4TLwRjw8UB6SK5L 3N6SpweJdf5gL5v/SJ3YHF61kz5rq/38rzSWc9YMzMUwpEVSkqu8SQY2S9wNaG2H d5hsJsQ= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 57F57A2AB6; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) Received: from yoda.home (unknown [70.80.200.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id C25E3A2AB3; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 1DA592DA055A; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) From: Nicolas Pitre To: Alexander Viro Cc: linux-fsdevel@vger.kernel.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt Subject: [PATCH v2 2/5] cramfs: make cramfs_physmem usable as root fs Date: Wed, 16 Aug 2017 13:35:33 -0400 Message-Id: <20170816173536.1879-3-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170816173536.1879-1-nicolas.pitre@linaro.org> References: <20170816173536.1879-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 5C532F3E-82A9-11E7-84BE-9D2B0D78B957-78420484!pb-smtp2.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Nicolas Pitre --- init/do_mounts.c | 8 ++++++++ 1 file changed, 8 insertions(+) -- 2.9.5 diff --git a/init/do_mounts.c b/init/do_mounts.c index c2de5104aa..43b5817f60 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -556,6 +556,14 @@ void __init prepare_namespace(void) ssleep(root_delay); } + if (IS_ENABLED(CONFIG_CRAMFS_PHYSMEM) && root_fs_names && + !strcmp(root_fs_names, "cramfs_physmem")) { + int err = do_mount_root("cramfs", "cramfs_physmem", + root_mountflags, root_mount_data); + if (!err) + goto out; + } + /* * wait for the known devices to complete their probing * From patchwork Wed Aug 16 17:35:34 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 110269 Delivered-To: patch@linaro.org Received: by 10.140.95.78 with SMTP id h72csp1083819qge; Wed, 16 Aug 2017 10:36:04 -0700 (PDT) X-Received: by 10.99.120.68 with SMTP id t65mr2464251pgc.104.1502904964486; Wed, 16 Aug 2017 10:36:04 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1502904964; cv=none; d=google.com; s=arc-20160816; b=GiypabaEVZuJcfxnui3Cayc99s9zqVgyR+wEExwKF5ZeRcauVVJX0toGfsxr0IjmYt RVj8pPNLE3ngH/ZG3+gU/wZCurwmL/e9aUxESsLLKIRpOtiqUoz79kQTTe7GPt+jERXP PVepPv3KvTlgA5ongHxI8jt2xl1dBkb0qgh44ka4BLd7o4u5OfGtgpgSRSIiWotNedXW NO/sp4rz1pvV3lXkkdnTKLCRBPMJwDk1P1tEmDKxkYOa1PsGkdGPYcYibJaMmfRJtnlq Xe+PGE7VlkjprQ+gxXk9ualdrXGTRrp51upAAfx8/YNliGbddGUmKyH9szxtlCBSqHc0 Hw8A== ARC-Message-Signature: i=1; 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[209.132.180.67]) by mx.google.com with ESMTP id n71si808323pfj.107.2017.08.16.10.36.04; Wed, 16 Aug 2017 10:36:04 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=UDD/uC4k; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752465AbdHPRgC (ORCPT + 26 others); Wed, 16 Aug 2017 13:36:02 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:64363 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751841AbdHPRf6 (ORCPT ); Wed, 16 Aug 2017 13:35:58 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 804C4AD7A1; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=sasl; bh=uRTu uyDY9YiIQ6Bo7Wu2XK7xfec=; b=UDD/uC4kEX/Z7+Wb1k+bRxuXCOSbKhMrvdmj RLfu7VBt3sdZju0YbgU5TllKlEqhhevAvMqCoyO1PLDhVvPiaf/ZeQXy35p2CHKW HMmeuupc+tEYffJ/9a/1q6OQrYl8I2BV3bGDpwwSAWU/GrB9o/avwyqe5QgSIeH6 KhESgx0= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 6AC54AD7A0; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) Received: from yoda.home (unknown [70.80.200.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id D5E70AD799; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 358442DA0679; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) From: Nicolas Pitre To: Alexander Viro Cc: linux-fsdevel@vger.kernel.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt Subject: [PATCH v2 3/5] cramfs: implement uncompressed and arbitrary data block positioning Date: Wed, 16 Aug 2017 13:35:34 -0400 Message-Id: <20170816173536.1879-4-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170816173536.1879-1-nicolas.pitre@linaro.org> References: <20170816173536.1879-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 5C5F61B4-82A9-11E7-A21F-FE4B1A68708C-78420484!pb-smtp1.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Two new capabilities are introduced here: - The ability to store some blocks uncompressed. - The ability to locate blocks anywhere. Those capabilities can be used independently, but the combination opens the possibility for execute-in-place (XIP) of program text segments that must remain uncompressed, and in the MMU case, must have a specific alignment. It is even possible to still have the writable data segments from the same file compressed as they have to be copied into RAM anyway. This is achieved by giving special meanings to some unused block pointer bits while remaining compatible with legacy cramfs images. Signed-off-by: Nicolas Pitre --- fs/cramfs/README | 31 ++++++++++++++- fs/cramfs/inode.c | 87 +++++++++++++++++++++++++++++++++--------- include/uapi/linux/cramfs_fs.h | 20 +++++++++- 3 files changed, 118 insertions(+), 20 deletions(-) -- 2.9.5 diff --git a/fs/cramfs/README b/fs/cramfs/README index 9d4e7ea311..d71b27e0ff 100644 --- a/fs/cramfs/README +++ b/fs/cramfs/README @@ -49,17 +49,46 @@ same as the start of the (i+1)'th if there is one). The first immediately follows the last for the file. s are each 32 bits long. +When the CRAMFS_FLAG_EXT_BLOCK_POINTERS capability bit is set, each +'s top bits may contain special flags as follows: + +CRAMFS_BLK_FLAG_UNCOMPRESSED (bit 31): + The block data is not compressed and should be copied verbatim. + +CRAMFS_BLK_FLAG_DIRECT_PTR (bit 30): + The stores the actual block start offset and not + its end, shifted right by 2 bits. The block must therefore be + aligned to a 4-byte boundary. The block size is either blksize + if CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified, otherwise + the compressed data length is included in the first 2 bytes of + the block data. This is used to allow discontiguous data layout + and specific data block alignments e.g. for XIP applications. + + The order of 's is a depth-first descent of the directory tree, i.e. the same order as `find -size +0 \( -type f -o -type l \) -print'. : The i'th is the output of zlib's compress function -applied to the i'th blksize-sized chunk of the input data. +applied to the i'th blksize-sized chunk of the input data if the +corresponding CRAMFS_BLK_FLAG_UNCOMPRESSED bit is not set, +otherwise it is the input data directly. (For the last of the file, the input may of course be smaller.) Each may be a different size. (See above.) + s are merely byte-aligned, not generally u32-aligned. +When CRAMFS_BLK_FLAG_DIRECT_PTR is specified then the corresponding + may be located anywhere and not necessarily contiguous with +the previous/next blocks. In that case it is minimally u32-aligned. +If CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified then the size is always +blksize except for the last block which is limited by the file length. +If CRAMFS_BLK_FLAG_DIRECT_PTR is set and CRAMFS_BLK_FLAG_UNCOMPRESSED +is not set then the first 2 bytes of the block contains the size of the +remaining block data as this cannot be determined from the placement of +logically adjacent blocks. + Holes ----- diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c index 393eb27ef4..b825ae162c 100644 --- a/fs/cramfs/inode.c +++ b/fs/cramfs/inode.c @@ -636,33 +636,84 @@ static int cramfs_readpage(struct file *file, struct page *page) if (page->index < maxblock) { struct super_block *sb = inode->i_sb; u32 blkptr_offset = OFFSET(inode) + page->index*4; - u32 start_offset, compr_len; + u32 block_ptr, block_start, block_len; + bool uncompressed, direct; - start_offset = OFFSET(inode) + maxblock*4; mutex_lock(&read_mutex); - if (page->index) - start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, - 4); - compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - - start_offset); - mutex_unlock(&read_mutex); + block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4); + uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED); + direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR); + block_ptr &= ~CRAMFS_BLK_FLAGS; + + if (direct) { + /* + * The block pointer is an absolute start pointer, + * shifted by 2 bits. The size is included in the + * first 2 bytes of the data block when compressed, + * or PAGE_SIZE otherwise. + */ + block_start = block_ptr << 2; + if (uncompressed) { + block_len = PAGE_SIZE; + /* if last block: cap to file length */ + if (page->index == maxblock - 1) + block_len = offset_in_page(inode->i_size); + } else { + block_len = *(u16 *) + cramfs_read(sb, block_start, 2); + block_start += 2; + } + } else { + /* + * The block pointer indicates one past the end of + * the current block (start of next block). If this + * is the first block then it starts where the block + * pointer table ends, otherwise its start comes + * from the previous block's pointer. + */ + block_start = OFFSET(inode) + maxblock*4; + if (page->index) + block_start = *(u32 *) + cramfs_read(sb, blkptr_offset-4, 4); + /* Beware... previous ptr might be a direct ptr */ + if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) { + /* See comments on earlier code. */ + u32 prev_start = block_start; + block_start = prev_start & ~CRAMFS_BLK_FLAGS; + block_start <<= 2; + if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) { + block_start += PAGE_SIZE; + } else { + block_len = *(u16 *) + cramfs_read(sb, block_start, 2); + block_start += 2 + block_len; + } + } + block_start &= ~CRAMFS_BLK_FLAGS; + block_len = block_ptr - block_start; + } - if (compr_len == 0) + if (block_len == 0) ; /* hole */ - else if (unlikely(compr_len > (PAGE_SIZE << 1))) { - pr_err("bad compressed blocksize %u\n", - compr_len); + else if (unlikely(block_len > 2*PAGE_SIZE || + (uncompressed && block_len > PAGE_SIZE))) { + mutex_unlock(&read_mutex); + pr_err("bad data blocksize %u\n", block_len); goto err; + } else if (uncompressed) { + memcpy(pgdata, + cramfs_read(sb, block_start, block_len), + block_len); + bytes_filled = block_len; } else { - mutex_lock(&read_mutex); bytes_filled = cramfs_uncompress_block(pgdata, PAGE_SIZE, - cramfs_read(sb, start_offset, compr_len), - compr_len); - mutex_unlock(&read_mutex); - if (unlikely(bytes_filled < 0)) - goto err; + cramfs_read(sb, block_start, block_len), + block_len); } + mutex_unlock(&read_mutex); + if (unlikely(bytes_filled < 0)) + goto err; } memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled); diff --git a/include/uapi/linux/cramfs_fs.h b/include/uapi/linux/cramfs_fs.h index e4611a9b92..ed250aa372 100644 --- a/include/uapi/linux/cramfs_fs.h +++ b/include/uapi/linux/cramfs_fs.h @@ -73,6 +73,7 @@ struct cramfs_super { #define CRAMFS_FLAG_HOLES 0x00000100 /* support for holes */ #define CRAMFS_FLAG_WRONG_SIGNATURE 0x00000200 /* reserved */ #define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400 /* shifted root fs */ +#define CRAMFS_FLAG_EXT_BLOCK_POINTERS 0x00000800 /* block pointer extensions */ /* * Valid values in super.flags. Currently we refuse to mount @@ -82,7 +83,24 @@ struct cramfs_super { #define CRAMFS_SUPPORTED_FLAGS ( 0x000000ff \ | CRAMFS_FLAG_HOLES \ | CRAMFS_FLAG_WRONG_SIGNATURE \ - | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET ) + | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET \ + | CRAMFS_FLAG_EXT_BLOCK_POINTERS ) +/* + * Block pointer flags + * + * The maximum block offset that needs to be represented is roughly: + * + * (1 << CRAMFS_OFFSET_WIDTH) * 4 + + * (1 << CRAMFS_SIZE_WIDTH) / PAGE_SIZE * (4 + PAGE_SIZE) + * = 0x11004000 + * + * That leaves room for 3 flag bits in the block pointer table. + */ +#define CRAMFS_BLK_FLAG_UNCOMPRESSED (1 << 31) +#define CRAMFS_BLK_FLAG_DIRECT_PTR (1 << 30) + +#define CRAMFS_BLK_FLAGS ( CRAMFS_BLK_FLAG_UNCOMPRESSED \ + | CRAMFS_BLK_FLAG_DIRECT_PTR ) #endif /* _UAPI__CRAMFS_H */ From patchwork Wed Aug 16 17:35:35 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 110273 Delivered-To: patch@linaro.org Received: by 10.140.95.78 with SMTP id h72csp1085579qge; Wed, 16 Aug 2017 10:37:44 -0700 (PDT) X-Received: by 10.84.137.1 with SMTP id 1mr2683541plm.75.1502905064703; Wed, 16 Aug 2017 10:37:44 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1502905064; cv=none; d=google.com; s=arc-20160816; b=TIgpJ58nZc3iQ/4NDfPa79ynZHBYRVPx6jqu+2Bav5VJCDKj8y0WMGF9llLlViJ7u2 REgH2jintAppu+DePEKkUMJvm4XB7sviIn16hJ+Rcz5Qq5HYCbT1BSKvLssiqYkMLqof uo91JLb+N9TnZMtNrZm9TiQQXfdOBSsiKP7fn344vkGQQcIjKBnXbZQ8N3S2Fb+/vFN0 rgiwcSZQPg8EpEzbTaCpdz28RPOE7SM8UjcjLIzlrA8vFV45NKSJeOVRpHEZBZlMe1OR sYzWlRFVxuBZRIEix2D9e/jILGvdnrM0beBiHdb//+PhMKtbx+DtLKYO4dDmRYmTRYas evHg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=Iql8Y4ILbp1SDgXEy9ha3Jt8Z1+UZKf9ZQ3a7ycUX8k=; b=VdtawEXH0u1QKXPllLy89jRAwg5yMLe1ti+oBwvAeR64plaRKJ/eYu2d2IpUJAV6tL u+U6tFIqES/DA0Znn/Q0wLI2djQO3IY9cuuiDH8O291yhC2/UvvFUEhz3ynnL+tZMj0k jAMaa+WPeqO+gIEVdbuOxOchB6ZUcdA3AABbNSpfrg2wiI0DApx61fn+l6UnLLpZrVrB WsvWRD0lDUpSuQkXnMVElpIVwe4GNzAaXCKWWRpj9h7WT7Kt0er3lBCIDBfxMhm3ahOj Q0z1Dpg4xDAEJcu65E/YJGplskiZkTac7vmhF9rzF4QWgQscFosleYEvw8/8pHXql7no AAvg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=tsLpqyXO; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id n23si786791pfi.632.2017.08.16.10.37.44; Wed, 16 Aug 2017 10:37:44 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=tsLpqyXO; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752758AbdHPRh2 (ORCPT + 26 others); Wed, 16 Aug 2017 13:37:28 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:65117 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751888AbdHPRf6 (ORCPT ); Wed, 16 Aug 2017 13:35:58 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id A1034AD7A3; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=sasl; bh=Eyav aIpcQm6DbPwyHsKWLQzcEY8=; b=tsLpqyXOjwT7+wx6BCLW7kgyQsD/2wHcQShw 3K6dZ6SgIzLS5a8VbNphc6FvscPFlbmoDV9g1xOMOFiKm/sz1hamAfitT5UdxqZl o5NJ0I8/k2xo9UBqAEJPl/oM3/g1dG9TUItRqjDBqjJnRlD/N5nC+1QQEGSC9G71 Z5PdeVE= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 87F88AD7A2; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) Received: from yoda.home (unknown [70.80.200.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id EDFE9AD79A; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 5629D2DA0698; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) From: Nicolas Pitre To: Alexander Viro Cc: linux-fsdevel@vger.kernel.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt Subject: [PATCH v2 4/5] cramfs: add mmap support Date: Wed, 16 Aug 2017 13:35:35 -0400 Message-Id: <20170816173536.1879-5-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170816173536.1879-1-nicolas.pitre@linaro.org> References: <20170816173536.1879-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 5C6E537C-82A9-11E7-80EC-FE4B1A68708C-78420484!pb-smtp1.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When cramfs_physmem is used then we have the opportunity to map files directly from ROM, directly into user space, saving on RAM usage. This gives us Execute-In-Place (XIP) support. For a file to be mmap()-able, the map area has to correspond to a range of uncompressed and contiguous blocks, and in the MMU case it also has to be page aligned. A version of mkcramfs with appropriate support is necessary to create such a filesystem image. In the MMU case it may happen for a vma structure to extend beyond the actual file size. This is notably the case in binfmt_elf.c:elf_map(). Or the file's last block is shared with other files and cannot be mapped as is. Rather than refusing to mmap it, we do a partial map and set up a special vm_ops fault handler that splits the vma in two: the direct mapping vma and the memory-backed vma populated by the readpage method. In the non-MMU case it is the get_unmapped_area method that is responsible for providing the address where the actual data can be found. No mapping is necessary of course. Signed-off-by: Nicolas Pitre --- fs/cramfs/inode.c | 270 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 270 insertions(+) -- 2.9.5 Signed-off-by: Nicolas Pitre Tested-by: Chris Brandt diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c index b825ae162c..e3884c607b 100644 --- a/fs/cramfs/inode.c +++ b/fs/cramfs/inode.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -49,6 +50,7 @@ static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb) static const struct super_operations cramfs_ops; static const struct inode_operations cramfs_dir_inode_operations; static const struct file_operations cramfs_directory_operations; +static const struct file_operations cramfs_physmem_fops; static const struct address_space_operations cramfs_aops; static DEFINE_MUTEX(read_mutex); @@ -96,6 +98,10 @@ static struct inode *get_cramfs_inode(struct super_block *sb, case S_IFREG: inode->i_fop = &generic_ro_fops; inode->i_data.a_ops = &cramfs_aops; + if (IS_ENABLED(CONFIG_CRAMFS_PHYSMEM) && + CRAMFS_SB(sb)->flags & CRAMFS_FLAG_EXT_BLOCK_POINTERS && + CRAMFS_SB(sb)->linear_phys_addr) + inode->i_fop = &cramfs_physmem_fops; break; case S_IFDIR: inode->i_op = &cramfs_dir_inode_operations; @@ -277,6 +283,270 @@ static void *cramfs_read(struct super_block *sb, unsigned int offset, return NULL; } +/* + * For a mapping to be possible, we need a range of uncompressed and + * contiguous blocks. Return the offset for the first block and number of + * valid blocks for which that is true, or zero otherwise. + */ +static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages) +{ + struct super_block *sb = inode->i_sb; + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); + int i; + u32 *blockptrs, blockaddr; + + /* + * We can dereference memory directly here as this code may be + * reached only when there is a direct filesystem image mapping + * available in memory. + */ + blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode) + pgoff*4); + blockaddr = blockptrs[0] & ~CRAMFS_BLK_FLAGS; + i = 0; + do { + u32 expect = blockaddr + i * (PAGE_SIZE >> 2); + expect |= CRAMFS_BLK_FLAG_DIRECT_PTR|CRAMFS_BLK_FLAG_UNCOMPRESSED; + if (blockptrs[i] != expect) { + pr_debug("range: block %d/%d got %#x expects %#x\n", + pgoff+i, pgoff+*pages-1, blockptrs[i], expect); + if (i == 0) + return 0; + break; + } + } while (++i < *pages); + + *pages = i; + + /* stored "direct" block ptrs are shifted down by 2 bits */ + return blockaddr << 2; +} + +/* + * It is possible for cramfs_physmem_mmap() to partially populate the mapping + * causing page faults in the unmapped area. When that happens, we need to + * split the vma so that the unmapped area gets its own vma that can be backed + * with actual memory pages and loaded normally. This is necessary because + * remap_pfn_range() overwrites vma->vm_pgoff with the pfn and filemap_fault() + * no longer works with it. Furthermore this makes /proc/x/maps right. + * Q: is there a way to do split vma at mmap() time? + */ +static const struct vm_operations_struct cramfs_vmasplit_ops; +static int cramfs_vmasplit_fault(struct vm_fault *vmf) +{ + struct mm_struct *mm = vmf->vma->vm_mm; + struct vm_area_struct *vma, *new_vma; + unsigned long split_val, split_addr; + unsigned int split_pgoff, split_page; + int ret; + + /* Retrieve the vma split address and validate it */ + vma = vmf->vma; + split_val = (unsigned long)vma->vm_private_data; + split_pgoff = split_val & 0xffff; + split_page = split_val >> 16; + split_addr = vma->vm_start + split_page * PAGE_SIZE; + pr_debug("fault: addr=%#lx vma=%#lx-%#lx split=%#lx\n", + vmf->address, vma->vm_start, vma->vm_end, split_addr); + if (!split_val || split_addr >= vma->vm_end || vmf->address < split_addr) + return VM_FAULT_SIGSEGV; + + /* We have some vma surgery to do and need the write lock. */ + up_read(&mm->mmap_sem); + if (down_write_killable(&mm->mmap_sem)) + return VM_FAULT_RETRY; + + /* Make sure the vma didn't change between the locks */ + vma = find_vma(mm, vmf->address); + if (vma->vm_ops != &cramfs_vmasplit_ops) { + /* + * Someone else raced with us and could have handled the fault. + * Let it go back to user space and fault again if necessary. + */ + downgrade_write(&mm->mmap_sem); + return VM_FAULT_NOPAGE; + } + + /* Split the vma between the directly mapped area and the rest */ + ret = split_vma(mm, vma, split_addr, 0); + if (ret) { + downgrade_write(&mm->mmap_sem); + return VM_FAULT_OOM; + } + + /* The direct vma should no longer ever fault */ + vma->vm_ops = NULL; + + /* Retrieve the new vma covering the unmapped area */ + new_vma = find_vma(mm, split_addr); + BUG_ON(new_vma == vma); + if (!new_vma) { + downgrade_write(&mm->mmap_sem); + return VM_FAULT_SIGSEGV; + } + + /* + * Readjust the new vma with the actual file based pgoff and + * process the fault normally on it. + */ + new_vma->vm_pgoff = split_pgoff; + new_vma->vm_ops = &generic_file_vm_ops; + vmf->vma = new_vma; + vmf->pgoff = split_pgoff; + vmf->pgoff += (vmf->address - new_vma->vm_start) >> PAGE_SHIFT; + downgrade_write(&mm->mmap_sem); + return filemap_fault(vmf); +} + +static const struct vm_operations_struct cramfs_vmasplit_ops = { + .fault = cramfs_vmasplit_fault, +}; + +static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct inode *inode = file_inode(file); + struct super_block *sb = inode->i_sb; + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); + unsigned int pages, vma_pages, max_pages, offset; + unsigned long address; + char *fail_reason; + int ret; + + if (!IS_ENABLED(CONFIG_MMU)) + return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS; + + if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) + return -EINVAL; + + /* Could COW work here? */ + fail_reason = "vma is writable"; + if (vma->vm_flags & VM_WRITE) + goto fail; + + vma_pages = (vma->vm_end - vma->vm_start + PAGE_SIZE - 1) >> PAGE_SHIFT; + max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; + fail_reason = "beyond file limit"; + if (vma->vm_pgoff >= max_pages) + goto fail; + pages = vma_pages; + if (pages > max_pages - vma->vm_pgoff) + pages = max_pages - vma->vm_pgoff; + + offset = cramfs_get_block_range(inode, vma->vm_pgoff, &pages); + fail_reason = "unsuitable block layout"; + if (!offset) + goto fail; + address = sbi->linear_phys_addr + offset; + fail_reason = "data is not page aligned"; + if (!PAGE_ALIGNED(address)) + goto fail; + + /* Don't map the last page if it contains some other data */ + if (unlikely(vma->vm_pgoff + pages == max_pages)) { + unsigned int partial = offset_in_page(inode->i_size); + if (partial) { + char *data = sbi->linear_virt_addr + offset; + data += (max_pages - 1) * PAGE_SIZE + partial; + while ((unsigned long)data & 7) + if (*data++ != 0) + goto nonzero; + while (offset_in_page(data)) { + if (*(u64 *)data != 0) { + nonzero: + pr_debug("mmap: %s: last page is shared\n", + file_dentry(file)->d_name.name); + pages--; + break; + } + data += 8; + } + } + } + + if (pages) { + /* + * If we can't map it all, page faults will occur if the + * unmapped area is accessed. Let's handle them to split the + * vma and let the normal paging machinery take care of the + * rest through cramfs_readpage(). Because remap_pfn_range() + * repurposes vma->vm_pgoff, we have to save it somewhere. + * Let's use vma->vm_private_data to hold both the pgoff and the actual address split point. + * Maximum file size is 16MB so we can pack both together. + */ + if (pages != vma_pages) { + unsigned int split_pgoff = vma->vm_pgoff + pages; + unsigned long split_val = split_pgoff + (pages << 16); + vma->vm_private_data = (void *)split_val; + vma->vm_ops = &cramfs_vmasplit_ops; + /* to keep remap_pfn_range() happy */ + vma->vm_end = vma->vm_start + pages * PAGE_SIZE; + } + + ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT, + pages * PAGE_SIZE, vma->vm_page_prot); + /* restore vm_end in case we cheated it above */ + vma->vm_end = vma->vm_start + vma_pages * PAGE_SIZE; + if (ret) + return ret; + + pr_debug("mapped %s at 0x%08lx (%u/%u pages) to vma 0x%08lx, " + "page_prot 0x%llx\n", file_dentry(file)->d_name.name, + address, pages, vma_pages, vma->vm_start, + (unsigned long long)pgprot_val(vma->vm_page_prot)); + return 0; + } + fail_reason = "no suitable block remaining"; + +fail: + pr_debug("%s: direct mmap failed: %s\n", + file_dentry(file)->d_name.name, fail_reason); + + /* We failed to do a direct map, but normal paging will do it */ + vma->vm_ops = &generic_file_vm_ops; + return 0; +} + +#ifndef CONFIG_MMU + +static unsigned long cramfs_physmem_get_unmapped_area(struct file *file, + unsigned long addr, unsigned long len, + unsigned long pgoff, unsigned long flags) +{ + struct inode *inode = file_inode(file); + struct super_block *sb = inode->i_sb; + struct cramfs_sb_info *sbi = CRAMFS_SB(sb); + unsigned int pages, block_pages, max_pages, offset; + + pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; + max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (pgoff >= max_pages || pages > max_pages - pgoff) + return -EINVAL; + block_pages = pages; + offset = cramfs_get_block_range(inode, pgoff, &block_pages); + if (!offset || block_pages != pages) + return -ENOSYS; + addr = sbi->linear_phys_addr + offset; + pr_debug("get_unmapped for %s ofs %#lx siz %lu at 0x%08lx\n", + file_dentry(file)->d_name.name, pgoff*PAGE_SIZE, len, addr); + return addr; +} + +static unsigned cramfs_physmem_mmap_capabilities(struct file *file) +{ + return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT | NOMMU_MAP_READ | NOMMU_MAP_EXEC; +} +#endif + +static const struct file_operations cramfs_physmem_fops = { + .llseek = generic_file_llseek, + .read_iter = generic_file_read_iter, + .splice_read = generic_file_splice_read, + .mmap = cramfs_physmem_mmap, +#ifndef CONFIG_MMU + .get_unmapped_area = cramfs_physmem_get_unmapped_area, + .mmap_capabilities = cramfs_physmem_mmap_capabilities, +#endif +}; + static void cramfs_blkdev_kill_sb(struct super_block *sb) { struct cramfs_sb_info *sbi = CRAMFS_SB(sb); From patchwork Wed Aug 16 17:35:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 110274 Delivered-To: patch@linaro.org Received: by 10.140.95.78 with SMTP id h72csp1085925qge; Wed, 16 Aug 2017 10:38:03 -0700 (PDT) X-Received: by 10.99.103.6 with SMTP id b6mr2341499pgc.336.1502905083041; Wed, 16 Aug 2017 10:38:03 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1502905083; cv=none; d=google.com; s=arc-20160816; b=XKwFOGaGdo3M86RCQR/Xdrpf65prZi7t5ZHqDuAKbeVMZGKRdWb1aAlOKPuOeUKoh5 h62R0fJPf7nEZmd9A6qi6opYiA571ejqwhI+HroZ5LLpZIvRp/leCRdgQU/CWdm2yvG6 4Py1QKKr9rwH2lOKRYy5m+zn1T9N2ddD2Gf0OcEDsGMzAzQKMvZOEn6IEwarsLr7LdCl vGMvnjKu0DbGdDZLLF6yFdQEQ7LVXAJV3/+BB3e9RGP0L39sompYShMIQT2XA0Elak3G Nz9xhMFD/q37RznoW2bXREbLCbDNitEknwhB7bjR1dQUr/J8PerX7p1W5RBkqUw4JGE2 gcoA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=ZT9BZ33tFqIYjFLRrdSZfqH1UPZn/v0BzJz/JnRTPDE=; b=uh8bWnNdxWdTRM+85dftxiPePQG0dG+Fts1UG4rz7LsFO0Wm6DTDE59UA9NIaeOYIH u3s6MK7Tcmjn5ZcSfPAp4vmWfsUEpQg8MKfWLtOrfCkhkt5T0dGqTg78F91jlH0Qc2Zv XVp3yOnFDR86ct4pc4teRgHSuipa7z5T/eikF6VCHBFvxEFksoQPyr7szZQK8wSraMdu F/P0x/545F2+Ope1DqJJcdoG9GB4nhWWG7ZIhr0zh/pqA/nOpC8DC9nLISzTJMPvAW8+ Vpcav/DYqqDZVznIf8lvh9arUeJsyen99BjOzlOBG4IC75LMkMq124tdwpFEgFJD2Mvj XMIA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=Unk37GC2; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id p63si818382pfg.45.2017.08.16.10.38.02; Wed, 16 Aug 2017 10:38:03 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=Unk37GC2; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752715AbdHPRh1 (ORCPT + 26 others); Wed, 16 Aug 2017 13:37:27 -0400 Received: from pb-smtp2.pobox.com ([64.147.108.71]:61574 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751893AbdHPRf6 (ORCPT ); Wed, 16 Aug 2017 13:35:58 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 3834AA2AC0; Wed, 16 Aug 2017 13:35:58 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=sasl; bh=4LNM 4N67dUtw4Wle/S32Hi7oT/Q=; b=Unk37GC2WY2jivFyQIg8dDtmDTghlhZ/eyYg tIOq9roNv6qzdAxp49b3rsOLfdG1yTtQfyUnUZmjKLOo29Cq6KVoovijHhCBJbB+ ILVliU8Z1Xzq0w4V9xI7n7kk54OZRjOyr5yYc9WHG/m+ltmtN4m2X3LnRysNb792 yl0Byf4= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 2E90CA2ABE; Wed, 16 Aug 2017 13:35:58 -0400 (EDT) Received: from yoda.home (unknown [70.80.200.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id 9B03FA2AB9; Wed, 16 Aug 2017 13:35:57 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 71C762DA06DA; Wed, 16 Aug 2017 13:35:56 -0400 (EDT) From: Nicolas Pitre To: Alexander Viro Cc: linux-fsdevel@vger.kernel.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt Subject: [PATCH v2 5/5] cramfs: rehabilitate it Date: Wed, 16 Aug 2017 13:35:36 -0400 Message-Id: <20170816173536.1879-6-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20170816173536.1879-1-nicolas.pitre@linaro.org> References: <20170816173536.1879-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 5CD30402-82A9-11E7-A932-9D2B0D78B957-78420484!pb-smtp2.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Update documentation, pointer to latest tools, appoint myself as maintainer. Given it's been unloved for so long, I don't expect anyone will protest. Signed-off-by: Nicolas Pitre --- Documentation/filesystems/cramfs.txt | 42 ++++++++++++++++++++++++++++++++++++ MAINTAINERS | 4 ++-- fs/cramfs/Kconfig | 9 +++++--- 3 files changed, 50 insertions(+), 5 deletions(-) -- 2.9.5 diff --git a/Documentation/filesystems/cramfs.txt b/Documentation/filesystems/cramfs.txt index 4006298f67..8875d306bc 100644 --- a/Documentation/filesystems/cramfs.txt +++ b/Documentation/filesystems/cramfs.txt @@ -45,6 +45,48 @@ you can just change the #define in mkcramfs.c, so long as you don't mind the filesystem becoming unreadable to future kernels. +Memory Mapped cramfs image +-------------------------- + +The CRAMFS_PHYSMEM Kconfig option adds support for loading data directly +from a physical linear memory range (usually non volatile memory like Flash) +to cramfs instead of going through the block device layer. This saves some +memory since no intermediate buffering is necessary to hold the data before +decompressing. + +And when data blocks are kept uncompressed and properly aligned, they will +automatically be mapped directly into user space whenever possible providing +eXecute-In-Place (XIP) from ROM of read-only segments. Data segments mapped +read-write (hence they have to be copied to RAM) may still be compressed in +the cramfs image in the same file along with non compressed read-only +segments. Both MMU and no-MMU systems are supported. This is particularly +handy for tiny embedded systems with very tight memory constraints. + +The filesystem type for this feature is "cramfs_physmem" to distinguish it +from the block device (or MTD) based access. The location of the cramfs +image in memory is system dependent. You must know the proper physical +address where the cramfs image is located and specify it using the +physaddr=0x******** mount option (for example, if the physical address +of the cramfs image is 0x80100000, the following command would mount it +on /mnt: + +$ mount -t cramfs_physmem -o physaddr=0x80100000 none /mnt + +To boot such an image as the root filesystem, the following kernel +commandline parameters must be provided: + + "rootfstype=cramfs_physmem rootflags=physaddr=0x80100000" + + +Tools +----- + +A version of mkcramfs that can take advantage of the latest capabilities +described above can be found here: + +https://github.com/npitre/cramfs-tools + + For /usr/share/magic -------------------- diff --git a/MAINTAINERS b/MAINTAINERS index 44cb004c76..12f8155cfe 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3612,8 +3612,8 @@ F: drivers/cpuidle/* F: include/linux/cpuidle.h CRAMFS FILESYSTEM -W: http://sourceforge.net/projects/cramfs/ -S: Orphan / Obsolete +M: Nicolas Pitre +S: Maintained F: Documentation/filesystems/cramfs.txt F: fs/cramfs/ diff --git a/fs/cramfs/Kconfig b/fs/cramfs/Kconfig index 5eed4ad2d5..8ed27e41bd 100644 --- a/fs/cramfs/Kconfig +++ b/fs/cramfs/Kconfig @@ -1,5 +1,5 @@ config CRAMFS - tristate "Compressed ROM file system support (cramfs) (OBSOLETE)" + tristate "Compressed ROM file system support (cramfs)" select ZLIB_INFLATE help Saying Y here includes support for CramFs (Compressed ROM File @@ -15,8 +15,11 @@ config CRAMFS cramfs. Note that the root file system (the one containing the directory /) cannot be compiled as a module. - This filesystem is obsoleted by SquashFS, which is much better - in terms of performance and features. + This filesystem is limited in capabilities and performance on + purpose to remain small and low on RAM usage. It is most suitable + for small embedded systems. For a more capable compressed filesystem + you should look at SquashFS which is much better in terms of + performance and features. If unsure, say N.