1 files changed, 287 insertions, 0 deletions
diff --git a/fs/romfs/storage.c b/fs/romfs/storage.c
new file mode 100644
index 000000000..b57b3ffcb
--- /dev/null
+++ b/fs/romfs/storage.c
@@ -0,0 +1,287 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* RomFS storage access routines
+ *
+ * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#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, ...) 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 || buflen > limit - pos)
+		return -EIO;
+
+#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, maxlen);
+#endif
+#ifdef CONFIG_ROMFS_ON_BLOCK
+	if (sb->s_bdev)
+		return romfs_blk_strnlen(sb, pos, maxlen);
+#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;
+}