From:   Gabriel Krisman Bertazi <krisman@collabora.com>
To:     tytso@mit.edu
Cc:     linux-ext4@vger.kernel.org, Olaf Weber <olaf@sgi.com>,
        Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Subject: [PATCH v7 02/10] unicode: Introduce code for UTF-8 normalization
Date:   Sat, 13 Apr 2019 15:25:25 -0400
Message-Id: <20190413192533.2549-3-krisman@collabora.com>
In-Reply-To: <20190413192533.2549-1-krisman@collabora.com>
References: <20190413192533.2549-1-krisman@collabora.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-ext4-owner@vger.kernel.org
Precedence: bulk

From: Olaf Weber <olaf@sgi.com>

Supporting functions for UTF-8 normalization are in utf8norm.c with the
header utf8norm.h. Two normalization forms are supported: nfdi and
nfdicf.

  nfdi:
   - Apply unicode normalization form NFD.
   - Remove any Default_Ignorable_Code_Point.

  nfdicf:
   - Apply unicode normalization form NFD.
   - Remove any Default_Ignorable_Code_Point.
   - Apply a full casefold (C + F).

For the purposes of the code, a string is valid UTF-8 if:

 - The values encoded are 0x1..0x10FFFF.
 - The surrogate codepoints 0xD800..0xDFFFF are not encoded.
 - The shortest possible encoding is used for all values.

The supporting functions work on null-terminated strings (utf8 prefix)
and on length-limited strings (utf8n prefix).

From the original SGI patch and for conformity with coding standards,
the utf8data_t typedef was dropped, since it was just masking the struct
keyword.  On other occasions, namely utf8leaf_t and utf8trie_t, I
decided to keep it, since they are simple pointers to memory buffers,
and using uchars here wouldn't provide any more meaningful information.

From the original submission, we also converted from the compatibility
form to canonical.

Changes since v6:
  - Fix potential null dereference (0day)

Changes since v4:
  - Convert to canonical decomposition form.

Changes since RFC v1:
  - utf8_version_is_supported receives maj, min and rev as separate
  arguments. (Olaf Weber)

Signed-off-by: Olaf Weber <olaf@sgi.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
  [Rebase to Mainline]
  [Fix up checkpatch.pl warnings]
  [Drop typedefs]
  [move out of libxfs]
  [Convert from NFKD to NFD]
---
 fs/unicode/Makefile    |   2 +
 fs/unicode/utf8-norm.c | 642 +++++++++++++++++++++++++++++++++++++++++
 fs/unicode/utf8n.h     | 112 +++++++
 3 files changed, 756 insertions(+)
 create mode 100644 fs/unicode/utf8-norm.c
 create mode 100644 fs/unicode/utf8n.h

diff --git a/fs/unicode/Makefile b/fs/unicode/Makefile
index 764f8e5da4bb..16d43d180416 100644
--- a/fs/unicode/Makefile
+++ b/fs/unicode/Makefile
@@ -1,5 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
+obj-$(CONFIG_UNICODE) += utf8-norm.o
+
 # This rule is not invoked during the kernel compilation.  It is used to
 # regenerate the utf8data.h header file.
 utf8data.h.new: *.txt $(objdir)/scripts/mkutf8data
diff --git a/fs/unicode/utf8-norm.c b/fs/unicode/utf8-norm.c
new file mode 100644
index 000000000000..aa2980f26527
--- /dev/null
+++ b/fs/unicode/utf8-norm.c
@@ -0,0 +1,642 @@
+/*
+ * Copyright (c) 2014 SGI.
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include "utf8n.h"
+
+struct utf8data {
+	unsigned int maxage;
+	unsigned int offset;
+};
+
+#define __INCLUDED_FROM_UTF8NORM_C__
+#include "utf8data.h"
+#undef __INCLUDED_FROM_UTF8NORM_C__
+
+int utf8version_is_supported(u8 maj, u8 min, u8 rev)
+{
+	int i = ARRAY_SIZE(utf8agetab) - 1;
+	unsigned int sb_utf8version = UNICODE_AGE(maj, min, rev);
+
+	while (i >= 0 && utf8agetab[i] != 0) {
+		if (sb_utf8version == utf8agetab[i])
+			return 1;
+		i--;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(utf8version_is_supported);
+
+/*
+ * UTF-8 valid ranges.
+ *
+ * The UTF-8 encoding spreads the bits of a 32bit word over several
+ * bytes. This table gives the ranges that can be held and how they'd
+ * be represented.
+ *
+ * 0x00000000 0x0000007F: 0xxxxxxx
+ * 0x00000000 0x000007FF: 110xxxxx 10xxxxxx
+ * 0x00000000 0x0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
+ * 0x00000000 0x001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+ * 0x00000000 0x03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
+ * 0x00000000 0x7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
+ *
+ * There is an additional requirement on UTF-8, in that only the
+ * shortest representation of a 32bit value is to be used.  A decoder
+ * must not decode sequences that do not satisfy this requirement.
+ * Thus the allowed ranges have a lower bound.
+ *
+ * 0x00000000 0x0000007F: 0xxxxxxx
+ * 0x00000080 0x000007FF: 110xxxxx 10xxxxxx
+ * 0x00000800 0x0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
+ * 0x00010000 0x001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+ * 0x00200000 0x03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
+ * 0x04000000 0x7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
+ *
+ * Actual unicode characters are limited to the range 0x0 - 0x10FFFF,
+ * 17 planes of 65536 values.  This limits the sequences actually seen
+ * even more, to just the following.
+ *
+ *          0 -     0x7F: 0                   - 0x7F
+ *       0x80 -    0x7FF: 0xC2 0x80           - 0xDF 0xBF
+ *      0x800 -   0xFFFF: 0xE0 0xA0 0x80      - 0xEF 0xBF 0xBF
+ *    0x10000 - 0x10FFFF: 0xF0 0x90 0x80 0x80 - 0xF4 0x8F 0xBF 0xBF
+ *
+ * Within those ranges the surrogates 0xD800 - 0xDFFF are not allowed.
+ *
+ * Note that the longest sequence seen with valid usage is 4 bytes,
+ * the same a single UTF-32 character.  This makes the UTF-8
+ * representation of Unicode strictly smaller than UTF-32.
+ *
+ * The shortest sequence requirement was introduced by:
+ *    Corrigendum #1: UTF-8 Shortest Form
+ * It can be found here:
+ *    http://www.unicode.org/versions/corrigendum1.html
+ *
+ */
+
+/*
+ * Return the number of bytes used by the current UTF-8 sequence.
+ * Assumes the input points to the first byte of a valid UTF-8
+ * sequence.
+ */
+static inline int utf8clen(const char *s)
+{
+	unsigned char c = *s;
+
+	return 1 + (c >= 0xC0) + (c >= 0xE0) + (c >= 0xF0);
+}
+
+/*
+ * utf8trie_t
+ *
+ * A compact binary tree, used to decode UTF-8 characters.
+ *
+ * Internal nodes are one byte for the node itself, and up to three
+ * bytes for an offset into the tree.  The first byte contains the
+ * following information:
+ *  NEXTBYTE  - flag        - advance to next byte if set
+ *  BITNUM    - 3 bit field - the bit number to tested
+ *  OFFLEN    - 2 bit field - number of bytes in the offset
+ * if offlen == 0 (non-branching node)
+ *  RIGHTPATH - 1 bit field - set if the following node is for the
+ *                            right-hand path (tested bit is set)
+ *  TRIENODE  - 1 bit field - set if the following node is an internal
+ *                            node, otherwise it is a leaf node
+ * if offlen != 0 (branching node)
+ *  LEFTNODE  - 1 bit field - set if the left-hand node is internal
+ *  RIGHTNODE - 1 bit field - set if the right-hand node is internal
+ *
+ * Due to the way utf8 works, there cannot be branching nodes with
+ * NEXTBYTE set, and moreover those nodes always have a righthand
+ * descendant.
+ */
+typedef const unsigned char utf8trie_t;
+#define BITNUM		0x07
+#define NEXTBYTE	0x08
+#define OFFLEN		0x30
+#define OFFLEN_SHIFT	4
+#define RIGHTPATH	0x40
+#define TRIENODE	0x80
+#define RIGHTNODE	0x40
+#define LEFTNODE	0x80
+
+/*
+ * utf8leaf_t
+ *
+ * The leaves of the trie are embedded in the trie, and so the same
+ * underlying datatype: unsigned char.
+ *
+ * leaf[0]: The unicode version, stored as a generation number that is
+ *          an index into utf8agetab[].  With this we can filter code
+ *          points based on the unicode version in which they were
+ *          defined.  The CCC of a non-defined code point is 0.
+ * leaf[1]: Canonical Combining Class. During normalization, we need
+ *          to do a stable sort into ascending order of all characters
+ *          with a non-zero CCC that occur between two characters with
+ *          a CCC of 0, or at the begin or end of a string.
+ *          The unicode standard guarantees that all CCC values are
+ *          between 0 and 254 inclusive, which leaves 255 available as
+ *          a special value.
+ *          Code points with CCC 0 are known as stoppers.
+ * leaf[2]: Decomposition. If leaf[1] == 255, then leaf[2] is the
+ *          start of a NUL-terminated string that is the decomposition
+ *          of the character.
+ *          The CCC of a decomposable character is the same as the CCC
+ *          of the first character of its decomposition.
+ *          Some characters decompose as the empty string: these are
+ *          characters with the Default_Ignorable_Code_Point property.
+ *          These do affect normalization, as they all have CCC 0.
+ *
+ * The decompositions in the trie have been fully expanded.
+ *
+ * Casefolding, if applicable, is also done using decompositions.
+ *
+ * The trie is constructed in such a way that leaves exist for all
+ * UTF-8 sequences that match the criteria from the "UTF-8 valid
+ * ranges" comment above, and only for those sequences.  Therefore a
+ * lookup in the trie can be used to validate the UTF-8 input.
+ */
+typedef const unsigned char utf8leaf_t;
+
+#define LEAF_GEN(LEAF)	((LEAF)[0])
+#define LEAF_CCC(LEAF)	((LEAF)[1])
+#define LEAF_STR(LEAF)	((const char *)((LEAF) + 2))
+
+#define MINCCC		(0)
+#define MAXCCC		(254)
+#define STOPPER		(0)
+#define	DECOMPOSE	(255)
+
+/*
+ * Use trie to scan s, touching at most len bytes.
+ * Returns the leaf if one exists, NULL otherwise.
+ *
+ * A non-NULL return guarantees that the UTF-8 sequence starting at s
+ * is well-formed and corresponds to a known unicode code point.  The
+ * shorthand for this will be "is valid UTF-8 unicode".
+ */
+static utf8leaf_t *utf8nlookup(const struct utf8data *data, const char *s,
+			       size_t len)
+{
+	utf8trie_t	*trie = NULL;
+	int		offlen;
+	int		offset;
+	int		mask;
+	int		node;
+
+	if (!data)
+		return NULL;
+	if (len == 0)
+		return NULL;
+
+	trie = utf8data + data->offset;
+	node = 1;
+	while (node) {
+		offlen = (*trie & OFFLEN) >> OFFLEN_SHIFT;
+		if (*trie & NEXTBYTE) {
+			if (--len == 0)
+				return NULL;
+			s++;
+		}
+		mask = 1 << (*trie & BITNUM);
+		if (*s & mask) {
+			/* Right leg */
+			if (offlen) {
+				/* Right node at offset of trie */
+				node = (*trie & RIGHTNODE);
+				offset = trie[offlen];
+				while (--offlen) {
+					offset <<= 8;
+					offset |= trie[offlen];
+				}
+				trie += offset;
+			} else if (*trie & RIGHTPATH) {
+				/* Right node after this node */
+				node = (*trie & TRIENODE);
+				trie++;
+			} else {
+				/* No right node. */
+				node = 0;
+				trie = NULL;
+			}
+		} else {
+			/* Left leg */
+			if (offlen) {
+				/* Left node after this node. */
+				node = (*trie & LEFTNODE);
+				trie += offlen + 1;
+			} else if (*trie & RIGHTPATH) {
+				/* No left node. */
+				node = 0;
+				trie = NULL;
+			} else {
+				/* Left node after this node */
+				node = (*trie & TRIENODE);
+				trie++;
+			}
+		}
+	}
+	return trie;
+}
+
+/*
+ * Use trie to scan s.
+ * Returns the leaf if one exists, NULL otherwise.
+ *
+ * Forwards to utf8nlookup().
+ */
+static utf8leaf_t *utf8lookup(const struct utf8data *data, const char *s)
+{
+	return utf8nlookup(data, s, (size_t)-1);
+}
+
+/*
+ * Maximum age of any character in s.
+ * Return -1 if s is not valid UTF-8 unicode.
+ * Return 0 if only non-assigned code points are used.
+ */
+int utf8agemax(const struct utf8data *data, const char *s)
+{
+	utf8leaf_t	*leaf;
+	int		age = 0;
+	int		leaf_age;
+
+	if (!data)
+		return -1;
+	while (*s) {
+		leaf = utf8lookup(data, s);
+		if (!leaf)
+			return -1;
+
+		leaf_age = utf8agetab[LEAF_GEN(leaf)];
+		if (leaf_age <= data->maxage && leaf_age > age)
+			age = leaf_age;
+		s += utf8clen(s);
+	}
+	return age;
+}
+EXPORT_SYMBOL(utf8agemax);
+
+/*
+ * Minimum age of any character in s.
+ * Return -1 if s is not valid UTF-8 unicode.
+ * Return 0 if non-assigned code points are used.
+ */
+int utf8agemin(const struct utf8data *data, const char *s)
+{
+	utf8leaf_t	*leaf;
+	int		age;
+	int		leaf_age;
+
+	if (!data)
+		return -1;
+	age = data->maxage;
+	while (*s) {
+		leaf = utf8lookup(data, s);
+		if (!leaf)
+			return -1;
+		leaf_age = utf8agetab[LEAF_GEN(leaf)];
+		if (leaf_age <= data->maxage && leaf_age < age)
+			age = leaf_age;
+		s += utf8clen(s);
+	}
+	return age;
+}
+EXPORT_SYMBOL(utf8agemin);
+
+/*
+ * Maximum age of any character in s, touch at most len bytes.
+ * Return -1 if s is not valid UTF-8 unicode.
+ */
+int utf8nagemax(const struct utf8data *data, const char *s, size_t len)
+{
+	utf8leaf_t	*leaf;
+	int		age = 0;
+	int		leaf_age;
+
+	if (!data)
+		return -1;
+	while (len && *s) {
+		leaf = utf8nlookup(data, s, len);
+		if (!leaf)
+			return -1;
+		leaf_age = utf8agetab[LEAF_GEN(leaf)];
+		if (leaf_age <= data->maxage && leaf_age > age)
+			age = leaf_age;
+		len -= utf8clen(s);
+		s += utf8clen(s);
+	}
+	return age;
+}
+EXPORT_SYMBOL(utf8nagemax);
+
+/*
+ * Maximum age of any character in s, touch at most len bytes.
+ * Return -1 if s is not valid UTF-8 unicode.
+ */
+int utf8nagemin(const struct utf8data *data, const char *s, size_t len)
+{
+	utf8leaf_t	*leaf;
+	int		leaf_age;
+	int		age;
+
+	if (!data)
+		return -1;
+	age = data->maxage;
+	while (len && *s) {
+		leaf = utf8nlookup(data, s, len);
+		if (!leaf)
+			return -1;
+		leaf_age = utf8agetab[LEAF_GEN(leaf)];
+		if (leaf_age <= data->maxage && leaf_age < age)
+			age = leaf_age;
+		len -= utf8clen(s);
+		s += utf8clen(s);
+	}
+	return age;
+}
+EXPORT_SYMBOL(utf8nagemin);
+
+/*
+ * Length of the normalization of s.
+ * Return -1 if s is not valid UTF-8 unicode.
+ *
+ * A string of Default_Ignorable_Code_Point has length 0.
+ */
+ssize_t utf8len(const struct utf8data *data, const char *s)
+{
+	utf8leaf_t	*leaf;
+	size_t		ret = 0;
+
+	if (!data)
+		return -1;
+	while (*s) {
+		leaf = utf8lookup(data, s);
+		if (!leaf)
+			return -1;
+		if (utf8agetab[LEAF_GEN(leaf)] > data->maxage)
+			ret += utf8clen(s);
+		else if (LEAF_CCC(leaf) == DECOMPOSE)
+			ret += strlen(LEAF_STR(leaf));
+		else
+			ret += utf8clen(s);
+		s += utf8clen(s);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(utf8len);
+
+/*
+ * Length of the normalization of s, touch at most len bytes.
+ * Return -1 if s is not valid UTF-8 unicode.
+ */
+ssize_t utf8nlen(const struct utf8data *data, const char *s, size_t len)
+{
+	utf8leaf_t	*leaf;
+	size_t		ret = 0;
+
+	if (!data)
+		return -1;
+	while (len && *s) {
+		leaf = utf8nlookup(data, s, len);
+		if (!leaf)
+			return -1;
+		if (utf8agetab[LEAF_GEN(leaf)] > data->maxage)
+			ret += utf8clen(s);
+		else if (LEAF_CCC(leaf) == DECOMPOSE)
+			ret += strlen(LEAF_STR(leaf));
+		else
+			ret += utf8clen(s);
+		len -= utf8clen(s);
+		s += utf8clen(s);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(utf8nlen);
+
+/*
+ * Set up an utf8cursor for use by utf8byte().
+ *
+ *   u8c    : pointer to cursor.
+ *   data   : const struct utf8data to use for normalization.
+ *   s      : string.
+ *   len    : length of s.
+ *
+ * Returns -1 on error, 0 on success.
+ */
+int utf8ncursor(struct utf8cursor *u8c, const struct utf8data *data,
+		const char *s, size_t len)
+{
+	if (!data)
+		return -1;
+	if (!s)
+		return -1;
+	u8c->data = data;
+	u8c->s = s;
+	u8c->p = NULL;
+	u8c->ss = NULL;
+	u8c->sp = NULL;
+	u8c->len = len;
+	u8c->slen = 0;
+	u8c->ccc = STOPPER;
+	u8c->nccc = STOPPER;
+	/* Check we didn't clobber the maximum length. */
+	if (u8c->len != len)
+		return -1;
+	/* The first byte of s may not be an utf8 continuation. */
+	if (len > 0 && (*s & 0xC0) == 0x80)
+		return -1;
+	return 0;
+}
+EXPORT_SYMBOL(utf8ncursor);
+
+/*
+ * Set up an utf8cursor for use by utf8byte().
+ *
+ *   u8c    : pointer to cursor.
+ *   data   : const struct utf8data to use for normalization.
+ *   s      : NUL-terminated string.
+ *
+ * Returns -1 on error, 0 on success.
+ */
+int utf8cursor(struct utf8cursor *u8c, const struct utf8data *data,
+	       const char *s)
+{
+	return utf8ncursor(u8c, data, s, (unsigned int)-1);
+}
+EXPORT_SYMBOL(utf8cursor);
+
+/*
+ * Get one byte from the normalized form of the string described by u8c.
+ *
+ * Returns the byte cast to an unsigned char on succes, and -1 on failure.
+ *
+ * The cursor keeps track of the location in the string in u8c->s.
+ * When a character is decomposed, the current location is stored in
+ * u8c->p, and u8c->s is set to the start of the decomposition. Note
+ * that bytes from a decomposition do not count against u8c->len.
+ *
+ * Characters are emitted if they match the current CCC in u8c->ccc.
+ * Hitting end-of-string while u8c->ccc == STOPPER means we're done,
+ * and the function returns 0 in that case.
+ *
+ * Sorting by CCC is done by repeatedly scanning the string.  The
+ * values of u8c->s and u8c->p are stored in u8c->ss and u8c->sp at
+ * the start of the scan.  The first pass finds the lowest CCC to be
+ * emitted and stores it in u8c->nccc, the second pass emits the
+ * characters with this CCC and finds the next lowest CCC. This limits
+ * the number of passes to 1 + the number of different CCCs in the
+ * sequence being scanned.
+ *
+ * Therefore:
+ *  u8c->p  != NULL -> a decomposition is being scanned.
+ *  u8c->ss != NULL -> this is a repeating scan.
+ *  u8c->ccc == -1   -> this is the first scan of a repeating scan.
+ */
+int utf8byte(struct utf8cursor *u8c)
+{
+	utf8leaf_t *leaf;
+	int ccc;
+
+	for (;;) {
+		/* Check for the end of a decomposed character. */
+		if (u8c->p && *u8c->s == '\0') {
+			u8c->s = u8c->p;
+			u8c->p = NULL;
+		}
+
+		/* Check for end-of-string. */
+		if (!u8c->p && (u8c->len == 0 || *u8c->s == '\0')) {
+			/* There is no next byte. */
+			if (u8c->ccc == STOPPER)
+				return 0;
+			/* End-of-string during a scan counts as a stopper. */
+			ccc = STOPPER;
+			goto ccc_mismatch;
+		} else if ((*u8c->s & 0xC0) == 0x80) {
+			/* This is a continuation of the current character. */
+			if (!u8c->p)
+				u8c->len--;
+			return (unsigned char)*u8c->s++;
+		}
+
+		/* Look up the data for the current character. */
+		if (u8c->p)
+			leaf = utf8lookup(u8c->data, u8c->s);
+		else
+			leaf = utf8nlookup(u8c->data, u8c->s, u8c->len);
+
+		/* No leaf found implies that the input is a binary blob. */
+		if (!leaf)
+			return -1;
+
+		ccc = LEAF_CCC(leaf);
+		/* Characters that are too new have CCC 0. */
+		if (utf8agetab[LEAF_GEN(leaf)] > u8c->data->maxage) {
+			ccc = STOPPER;
+		} else if (ccc == DECOMPOSE) {
+			u8c->len -= utf8clen(u8c->s);
+			u8c->p = u8c->s + utf8clen(u8c->s);
+			u8c->s = LEAF_STR(leaf);
+			/* Empty decomposition implies CCC 0. */
+			if (*u8c->s == '\0') {
+				if (u8c->ccc == STOPPER)
+					continue;
+				ccc = STOPPER;
+				goto ccc_mismatch;
+			}
+			leaf = utf8lookup(u8c->data, u8c->s);
+		}
+
+		/*
+		 * If this is not a stopper, then see if it updates
+		 * the next canonical class to be emitted.
+		 */
+		if (ccc != STOPPER && u8c->ccc < ccc && ccc < u8c->nccc)
+			u8c->nccc = ccc;
+
+		/*
+		 * Return the current byte if this is the current
+		 * combining class.
+		 */
+		if (ccc == u8c->ccc) {
+			if (!u8c->p)
+				u8c->len--;
+			return (unsigned char)*u8c->s++;
+		}
+
+		/* Current combining class mismatch. */
+ccc_mismatch:
+		if (u8c->nccc == STOPPER) {
+			/*
+			 * Scan forward for the first canonical class
+			 * to be emitted.  Save the position from
+			 * which to restart.
+			 */
+			u8c->ccc = MINCCC - 1;
+			u8c->nccc = ccc;
+			u8c->sp = u8c->p;
+			u8c->ss = u8c->s;
+			u8c->slen = u8c->len;
+			if (!u8c->p)
+				u8c->len -= utf8clen(u8c->s);
+			u8c->s += utf8clen(u8c->s);
+		} else if (ccc != STOPPER) {
+			/* Not a stopper, and not the ccc we're emitting. */
+			if (!u8c->p)
+				u8c->len -= utf8clen(u8c->s);
+			u8c->s += utf8clen(u8c->s);
+		} else if (u8c->nccc != MAXCCC + 1) {
+			/* At a stopper, restart for next ccc. */
+			u8c->ccc = u8c->nccc;
+			u8c->nccc = MAXCCC + 1;
+			u8c->s = u8c->ss;
+			u8c->p = u8c->sp;
+			u8c->len = u8c->slen;
+		} else {
+			/* All done, proceed from here. */
+			u8c->ccc = STOPPER;
+			u8c->nccc = STOPPER;
+			u8c->sp = NULL;
+			u8c->ss = NULL;
+			u8c->slen = 0;
+		}
+	}
+}
+EXPORT_SYMBOL(utf8byte);
+
+const struct utf8data *utf8nfdi(unsigned int maxage)
+{
+	int i = ARRAY_SIZE(utf8nfdidata) - 1;
+
+	while (maxage < utf8nfdidata[i].maxage)
+		i--;
+	if (maxage > utf8nfdidata[i].maxage)
+		return NULL;
+	return &utf8nfdidata[i];
+}
+EXPORT_SYMBOL(utf8nfdi);
+
+const struct utf8data *utf8nfdicf(unsigned int maxage)
+{
+	int i = ARRAY_SIZE(utf8nfdicfdata) - 1;
+
+	while (maxage < utf8nfdicfdata[i].maxage)
+		i--;
+	if (maxage > utf8nfdicfdata[i].maxage)
+		return NULL;
+	return &utf8nfdicfdata[i];
+}
+EXPORT_SYMBOL(utf8nfdicf);
diff --git a/fs/unicode/utf8n.h b/fs/unicode/utf8n.h
new file mode 100644
index 000000000000..696e52124296
--- /dev/null
+++ b/fs/unicode/utf8n.h
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2014 SGI.
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef UTF8NORM_H
+#define UTF8NORM_H
+
+#include <linux/types.h>
+#include <linux/export.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+/* Encoding a unicode version number as a single unsigned int. */
+#define UNICODE_MAJ_SHIFT		(16)
+#define UNICODE_MIN_SHIFT		(8)
+
+#define UNICODE_AGE(MAJ, MIN, REV)			\
+	(((unsigned int)(MAJ) << UNICODE_MAJ_SHIFT) |	\
+	 ((unsigned int)(MIN) << UNICODE_MIN_SHIFT) |	\
+	 ((unsigned int)(REV)))
+
+/* Highest unicode version supported by the data tables. */
+extern int utf8version_is_supported(u8 maj, u8 min, u8 rev);
+
+/*
+ * Look for the correct const struct utf8data for a unicode version.
+ * Returns NULL if the version requested is too new.
+ *
+ * Two normalization forms are supported: nfdi and nfdicf.
+ *
+ * nfdi:
+ *  - Apply unicode normalization form NFD.
+ *  - Remove any Default_Ignorable_Code_Point.
+ *
+ * nfdicf:
+ *  - Apply unicode normalization form NFD.
+ *  - Remove any Default_Ignorable_Code_Point.
+ *  - Apply a full casefold (C + F).
+ */
+extern const struct utf8data *utf8nfdi(unsigned int maxage);
+extern const struct utf8data *utf8nfdicf(unsigned int maxage);
+
+/*
+ * Determine the maximum age of any unicode character in the string.
+ * Returns 0 if only unassigned code points are present.
+ * Returns -1 if the input is not valid UTF-8.
+ */
+extern int utf8agemax(const struct utf8data *data, const char *s);
+extern int utf8nagemax(const struct utf8data *data, const char *s, size_t len);
+
+/*
+ * Determine the minimum age of any unicode character in the string.
+ * Returns 0 if any unassigned code points are present.
+ * Returns -1 if the input is not valid UTF-8.
+ */
+extern int utf8agemin(const struct utf8data *data, const char *s);
+extern int utf8nagemin(const struct utf8data *data, const char *s, size_t len);
+
+/*
+ * Determine the length of the normalized from of the string,
+ * excluding any terminating NULL byte.
+ * Returns 0 if only ignorable code points are present.
+ * Returns -1 if the input is not valid UTF-8.
+ */
+extern ssize_t utf8len(const struct utf8data *data, const char *s);
+extern ssize_t utf8nlen(const struct utf8data *data, const char *s, size_t len);
+
+/*
+ * Cursor structure used by the normalizer.
+ */
+struct utf8cursor {
+	const struct utf8data	*data;
+	const char	*s;
+	const char	*p;
+	const char	*ss;
+	const char	*sp;
+	unsigned int	len;
+	unsigned int	slen;
+	short int	ccc;
+	short int	nccc;
+};
+
+/*
+ * Initialize a utf8cursor to normalize a string.
+ * Returns 0 on success.
+ * Returns -1 on failure.
+ */
+extern int utf8cursor(struct utf8cursor *u8c, const struct utf8data *data,
+		      const char *s);
+extern int utf8ncursor(struct utf8cursor *u8c, const struct utf8data *data,
+		       const char *s, size_t len);
+
+/*
+ * Get the next byte in the normalization.
+ * Returns a value > 0 && < 256 on success.
+ * Returns 0 when the end of the normalization is reached.
+ * Returns -1 if the string being normalized is not valid UTF-8.
+ */
+extern int utf8byte(struct utf8cursor *u8c);
+
+#endif /* UTF8NORM_H */
-- 
2.20.1