unicode: implement higher level API for string handling

This patch integrates the utf8n patches with some higher level API to
perform UTF-8 string comparison, normalization and casefolding
operations.  Implemented is a variation of NFD, and casefold is
performed by doing full casefold on top of NFD.  These algorithms are
based on the core implemented by Olaf Weber from SGI.
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/unicode/Makefile

 # SPDX-License-Identifier: GPL-2.0
 
-obj-$(CONFIG_UNICODE) += utf8-norm.o
+obj-$(CONFIG_UNICODE) += unicode.o
+
+unicode-y := utf8-norm.o utf8-core.o
 
 # This rule is not invoked during the kernel compilation.  It is used to
 # regenerate the utf8data.h header file.

fs/unicode/utf8-core.c

+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/parser.h>
+#include <linux/errno.h>
+#include <linux/unicode.h>
+
+#include "utf8n.h"
+
+int utf8_validate(const struct unicode_map *um, const struct qstr *str)
+{
+	const struct utf8data *data = utf8nfdi(um->version);
+
+	if (utf8nlen(data, str->name, str->len) < 0)
+		return -1;
+	return 0;
+}
+EXPORT_SYMBOL(utf8_validate);
+
+int utf8_strncmp(const struct unicode_map *um,
+		 const struct qstr *s1, const struct qstr *s2)
+{
+	const struct utf8data *data = utf8nfdi(um->version);
+	struct utf8cursor cur1, cur2;
+	int c1, c2;
+
+	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
+		return -EINVAL;
+
+	if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
+		return -EINVAL;
+
+	do {
+		c1 = utf8byte(&cur1);
+		c2 = utf8byte(&cur2);
+
+		if (c1 < 0 || c2 < 0)
+			return -EINVAL;
+		if (c1 != c2)
+			return 1;
+	} while (c1);
+
+	return 0;
+}
+EXPORT_SYMBOL(utf8_strncmp);
+
+int utf8_strncasecmp(const struct unicode_map *um,
+		     const struct qstr *s1, const struct qstr *s2)
+{
+	const struct utf8data *data = utf8nfdicf(um->version);
+	struct utf8cursor cur1, cur2;
+	int c1, c2;
+
+	if (utf8ncursor(&cur1, data, s1->name, s1->len) < 0)
+		return -EINVAL;
+
+	if (utf8ncursor(&cur2, data, s2->name, s2->len) < 0)
+		return -EINVAL;
+
+	do {
+		c1 = utf8byte(&cur1);
+		c2 = utf8byte(&cur2);
+
+		if (c1 < 0 || c2 < 0)
+			return -EINVAL;
+		if (c1 != c2)
+			return 1;
+	} while (c1);
+
+	return 0;
+}
+EXPORT_SYMBOL(utf8_strncasecmp);
+
+int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
+		  unsigned char *dest, size_t dlen)
+{
+	const struct utf8data *data = utf8nfdicf(um->version);
+	struct utf8cursor cur;
+	size_t nlen = 0;
+
+	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
+		return -EINVAL;
+
+	for (nlen = 0; nlen < dlen; nlen++) {
+		int c = utf8byte(&cur);
+
+		dest[nlen] = c;
+		if (!c)
+			return nlen;
+		if (c == -1)
+			break;
+	}
+	return -EINVAL;
+}
+
+EXPORT_SYMBOL(utf8_casefold);
+
+int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
+		   unsigned char *dest, size_t dlen)
+{
+	const struct utf8data *data = utf8nfdi(um->version);
+	struct utf8cursor cur;
+	ssize_t nlen = 0;
+
+	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
+		return -EINVAL;
+
+	for (nlen = 0; nlen < dlen; nlen++) {
+		int c = utf8byte(&cur);
+
+		dest[nlen] = c;
+		if (!c)
+			return nlen;
+		if (c == -1)
+			break;
+	}
+	return -EINVAL;
+}
+
+EXPORT_SYMBOL(utf8_normalize);
+
+static int utf8_parse_version(const char *version, unsigned int *maj,
+			      unsigned int *min, unsigned int *rev)
+{
+	substring_t args[3];
+	char version_string[12];
+	const struct match_token token[] = {
+		{1, "%d.%d.%d"},
+		{0, NULL}
+	};
+
+	strncpy(version_string, version, sizeof(version_string));
+
+	if (match_token(version_string, token, args) != 1)
+		return -EINVAL;
+
+	if (match_int(&args[0], maj) || match_int(&args[1], min) ||
+	    match_int(&args[2], rev))
+		return -EINVAL;
+
+	return 0;
+}
+
+struct unicode_map *utf8_load(const char *version)
+{
+	struct unicode_map *um = NULL;
+	int unicode_version;
+
+	if (version) {
+		unsigned int maj, min, rev;
+
+		if (utf8_parse_version(version, &maj, &min, &rev) < 0)
+			return ERR_PTR(-EINVAL);
+
+		if (!utf8version_is_supported(maj, min, rev))
+			return ERR_PTR(-EINVAL);
+
+		unicode_version = UNICODE_AGE(maj, min, rev);
+	} else {
+		unicode_version = utf8version_latest();
+		printk(KERN_WARNING"UTF-8 version not specified. "
+		       "Assuming latest supported version (%d.%d.%d).",
+		       (unicode_version >> 16) & 0xff,
+		       (unicode_version >> 8) & 0xff,
+		       (unicode_version & 0xff));
+	}
+
+	um = kzalloc(sizeof(struct unicode_map), GFP_KERNEL);
+	if (!um)
+		return ERR_PTR(-ENOMEM);
+
+	um->charset = "UTF-8";
+	um->version = unicode_version;
+
+	return um;
+}
+EXPORT_SYMBOL(utf8_load);
+
+void utf8_unload(struct unicode_map *um)
+{
+	kfree(um);
+}
+EXPORT_SYMBOL(utf8_unload);
+
+MODULE_LICENSE("GPL v2");

fs/unicode/utf8-norm.c

@@ -38,6 +38,12 @@ int utf8version_is_supported(u8 maj, u8 min, u8 rev)
 }
 EXPORT_SYMBOL(utf8version_is_supported);
 
+int utf8version_latest(void)
+{
+	return utf8vers;
+}
+EXPORT_SYMBOL(utf8version_latest);
+
 /*
  * UTF-8 valid ranges.
  *

fs/unicode/utf8n.h

@@ -32,6 +32,7 @@
 
 /* Highest unicode version supported by the data tables. */
 extern int utf8version_is_supported(u8 maj, u8 min, u8 rev);
+extern int utf8version_latest(void);
 
 /*
  * Look for the correct const struct utf8data for a unicode version.

include/linux/unicode.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_UNICODE_H
+#define _LINUX_UNICODE_H
+
+#include <linux/init.h>
+#include <linux/dcache.h>
+
+struct unicode_map {
+	const char *charset;
+	int version;
+};
+
+int utf8_validate(const struct unicode_map *um, const struct qstr *str);
+
+int utf8_strncmp(const struct unicode_map *um,
+		 const struct qstr *s1, const struct qstr *s2);
+
+int utf8_strncasecmp(const struct unicode_map *um,
+		 const struct qstr *s1, const struct qstr *s2);
+
+int utf8_normalize(const struct unicode_map *um, const struct qstr *str,
+		   unsigned char *dest, size_t dlen);
+
+int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
+		  unsigned char *dest, size_t dlen);
+
+struct unicode_map *utf8_load(const char *version);
+void utf8_unload(struct unicode_map *um);
+
+#endif /* _LINUX_UNICODE_H */