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[209.132.180.67]) by mx.google.com with ESMTP id l62si907543pfa.56.2017.08.11.12.31.44; Fri, 11 Aug 2017 12:31:45 -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=WlSeqeW3; 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 S1753842AbdHKTbm (ORCPT + 25 others); Fri, 11 Aug 2017 15:31:42 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:60235 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753821AbdHKTbj (ORCPT ); Fri, 11 Aug 2017 15:31:39 -0400 X-Greylist: delayed 516 seconds by postgrey-1.27 at vger.kernel.org; Fri, 11 Aug 2017 15:31:38 EDT Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 9CF2DAE1F3; Fri, 11 Aug 2017 15:23:01 -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=DzuM hcjKpeO64sAi186SeOtt4D8=; b=WlSeqeW3WrmeF+WC6Eil1HU8C7iSaMDUMDmG auTX6oSHRp/HbYpbrCgpwL5ZIJGeEebAAtnyrFydObGsXoYMqE+YSGBQ6zyDeJeW JEbfEk+67IA7ZV3IPUkaTjw++U0AZF9nGztD1AsgcRCoGkGHiKK7FV6wMig0Thjn 6NYPY8g= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 94163AE1F2; Fri, 11 Aug 2017 15:23:01 -0400 (EDT) Received: from yoda.home (unknown [96.23.157.65]) (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 76EB2AE1ED; Fri, 11 Aug 2017 15:23:00 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id AC7772DA0695; Fri, 11 Aug 2017 15:22:59 -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 4/5] cramfs: add mmap support Date: Fri, 11 Aug 2017 15:22:51 -0400 Message-Id: <20170811192252.19062-5-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.4 In-Reply-To: <20170811192252.19062-1-nicolas.pitre@linaro.org> References: <20170811192252.19062-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 7D15BD6E-7ECA-11E7-B26A-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. Signed-off-by: Nicolas Pitre --- fs/cramfs/inode.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) -- 2.9.4 diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c index b825ae162c..5aedbd224e 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 +283,149 @@ 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 if that + * verifies, 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; + pr_debug("range: block %d/%d got %#x expects %#x\n", + pgoff+i, pgoff+pages-1, blockptrs[i], expect); + if (blockptrs[i] != expect) + return 0; + } while (++i < pages); + + /* stored "direct" block ptrs are shifted down by 2 bits */ + return blockaddr << 2; +} + +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, max_pages, offset; + unsigned long length, 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; + + vma->vm_ops = &generic_file_vm_ops; + if (vma->vm_flags & VM_WRITE) + return 0; + + length = vma->vm_end - vma->vm_start; + pages = (length + PAGE_SIZE - 1) >> PAGE_SHIFT; + max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (vma->vm_pgoff >= max_pages || pages > max_pages - vma->vm_pgoff) + return -EINVAL; + + 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 a partial 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 += (pages - 1) * PAGE_SIZE + partial; + fail_reason = "last partial page is shared"; + while ((unsigned long)data & 7) + if (*data++ != 0) + goto fail; + while (offset_in_page(data)) { + if (*(u64 *)data != 0) + goto fail; + data += 8; + } + } + } + + ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT, + length, vma->vm_page_prot); + if (ret) + return ret; + pr_debug("mapped %s at 0x%08lx, length %lu to vma 0x%08lx, " + "page_prot 0x%llx\n", file_dentry(file)->d_name.name, + address, length, vma->vm_start, + (unsigned long long)pgprot_val(vma->vm_page_prot)); + return 0; + +fail: + pr_debug("%s: direct mmap failed: %s\n", + file_dentry(file)->d_name.name, fail_reason); + 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, 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; + offset = cramfs_get_block_range(inode, pgoff, pages); + if (!offset) + 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);