/* RomFS storage access routines * * Copyright © 2007 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * 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. */ #include <linux/fs.h> #include <linux/mtd/super.h> #include <linux/buffer_head.h> #include "internal.h" #if !defined(CONFIG_ROMFS_ON_MTD) && !defined(CONFIG_ROMFS_ON_BLOCK) #error no ROMFS backing store interface configured #endif #ifdef CONFIG_ROMFS_ON_MTD #define ROMFS_MTD_READ(sb, ...) ((sb)->s_mtd->read((sb)->s_mtd, ##__VA_ARGS__)) /* * read data from an romfs image on an MTD device */ static int romfs_mtd_read(struct super_block *sb, unsigned long pos, void *buf, size_t buflen) { size_t rlen; int ret; ret = ROMFS_MTD_READ(sb, pos, buflen, &rlen, buf); return (ret < 0 || rlen != buflen) ? -EIO : 0; } /* * determine the length of a string in a romfs image on an MTD device */ static ssize_t romfs_mtd_strnlen(struct super_block *sb, unsigned long pos, size_t maxlen) { ssize_t n = 0; size_t segment; u_char buf[16], *p; size_t len; int ret; /* scan the string up to 16 bytes at a time */ while (maxlen > 0) { segment = min_t(size_t, maxlen, 16); ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf); if (ret < 0) return ret; p = memchr(buf, 0, len); if (p) return n + (p - buf); maxlen -= len; pos += len; n += len; } return n; } /* * compare a string to one in a romfs image on MTD * - return 1 if matched, 0 if differ, -ve if error */ static int romfs_mtd_strcmp(struct super_block *sb, unsigned long pos, const char *str, size_t size) { u_char buf[17]; size_t len, segment; int ret; /* scan the string up to 16 bytes at a time, and attempt to grab the * trailing NUL whilst we're at it */ buf[0] = 0xff; while (size > 0) { segment = min_t(size_t, size + 1, 17); ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf); if (ret < 0) return ret; len--; if (memcmp(buf, str, len) != 0) return 0; buf[0] = buf[len]; size -= len; pos += len; str += len; } /* check the trailing NUL was */ if (buf[0]) return 0; return 1; } #endif /* CONFIG_ROMFS_ON_MTD */ #ifdef CONFIG_ROMFS_ON_BLOCK /* * read data from an romfs image on a block device */ static int romfs_blk_read(struct super_block *sb, unsigned long pos, void *buf, size_t buflen) { struct buffer_head *bh; unsigned long offset; size_t segment; /* copy the string up to blocksize bytes at a time */ while (buflen > 0) { offset = pos & (ROMBSIZE - 1); segment = min_t(size_t, buflen, ROMBSIZE - offset); bh = sb_bread(sb, pos >> ROMBSBITS); if (!bh) return -EIO; memcpy(buf, bh->b_data + offset, segment); brelse(bh); buf += segment; buflen -= segment; pos += segment; } return 0; } /* * determine the length of a string in romfs on a block device */ static ssize_t romfs_blk_strnlen(struct super_block *sb, unsigned long pos, size_t limit) { struct buffer_head *bh; unsigned long offset; ssize_t n = 0; size_t segment; u_char *buf, *p; /* scan the string up to blocksize bytes at a time */ while (limit > 0) { offset = pos & (ROMBSIZE - 1); segment = min_t(size_t, limit, ROMBSIZE - offset); bh = sb_bread(sb, pos >> ROMBSBITS); if (!bh) return -EIO; buf = bh->b_data + offset; p = memchr(buf, 0, segment); brelse(bh); if (p) return n + (p - buf); limit -= segment; pos += segment; n += segment; } return n; } /* * compare a string to one in a romfs image on a block device * - return 1 if matched, 0 if differ, -ve if error */ static int romfs_blk_strcmp(struct super_block *sb, unsigned long pos, const char *str, size_t size) { struct buffer_head *bh; unsigned long offset; size_t segment; bool matched, terminated = false; /* compare string up to a block at a time */ while (size > 0) { offset = pos & (ROMBSIZE - 1); segment = min_t(size_t, size, ROMBSIZE - offset); bh = sb_bread(sb, pos >> ROMBSBITS); if (!bh) return -EIO; matched = (memcmp(bh->b_data + offset, str, segment) == 0); size -= segment; pos += segment; str += segment; if (matched && size == 0 && offset + segment < ROMBSIZE) { if (!bh->b_data[offset + segment]) terminated = true; else matched = false; } brelse(bh); if (!matched) return 0; } if (!terminated) { /* the terminating NUL must be on the first byte of the next * block */ BUG_ON((pos & (ROMBSIZE - 1)) != 0); bh = sb_bread(sb, pos >> ROMBSBITS); if (!bh) return -EIO; matched = !bh->b_data[0]; brelse(bh); if (!matched) return 0; } return 1; } #endif /* CONFIG_ROMFS_ON_BLOCK */ /* * read data from the romfs image */ int romfs_dev_read(struct super_block *sb, unsigned long pos, void *buf, size_t buflen) { size_t limit; limit = romfs_maxsize(sb); if (pos >= limit) return -EIO; if (buflen > limit - pos) buflen = limit - pos; #ifdef CONFIG_ROMFS_ON_MTD if (sb->s_mtd) return romfs_mtd_read(sb, pos, buf, buflen); #endif #ifdef CONFIG_ROMFS_ON_BLOCK if (sb->s_bdev) return romfs_blk_read(sb, pos, buf, buflen); #endif return -EIO; } /* * determine the length of a string in romfs */ ssize_t romfs_dev_strnlen(struct super_block *sb, unsigned long pos, size_t maxlen) { size_t limit; limit = romfs_maxsize(sb); if (pos >= limit) return -EIO; if (maxlen > limit - pos) maxlen = limit - pos; #ifdef CONFIG_ROMFS_ON_MTD if (sb->s_mtd) return romfs_mtd_strnlen(sb, pos, limit); #endif #ifdef CONFIG_ROMFS_ON_BLOCK if (sb->s_bdev) return romfs_blk_strnlen(sb, pos, limit); #endif return -EIO; } /* * compare a string to one in romfs * - the string to be compared to, str, may not be NUL-terminated; instead the * string is of the specified size * - return 1 if matched, 0 if differ, -ve if error */ int romfs_dev_strcmp(struct super_block *sb, unsigned long pos, const char *str, size_t size) { size_t limit; limit = romfs_maxsize(sb); if (pos >= limit) return -EIO; if (size > ROMFS_MAXFN) return -ENAMETOOLONG; if (size + 1 > limit - pos) return -EIO; #ifdef CONFIG_ROMFS_ON_MTD if (sb->s_mtd) return romfs_mtd_strcmp(sb, pos, str, size); #endif #ifdef CONFIG_ROMFS_ON_BLOCK if (sb->s_bdev) return romfs_blk_strcmp(sb, pos, str, size); #endif return -EIO; }