NLS: update handling of Unicode

This patch (as1239) updates the kernel's treatment of Unicode.  The
character-set conversion routines are well behind the current state of
the Unicode specification: They don't recognize the existence of code
points beyond plane 0 or of surrogate pairs in the UTF-16 encoding.

The old wchar_t 16-bit type is retained because it's still used in
lots of places.  This shouldn't cause any new problems; if a
conversion now results in an invalid 16-bit code then before it must
have yielded an undefined code.

Difficult-to-read names like "utf_mbstowcs" are replaced with more
transparent names like "utf8s_to_utf16s" and the ordering of the
parameters is rationalized (buffer lengths come immediate after the
pointers they refer to, and the inputs precede the outputs).
Fortunately the low-level conversion routines are used in only a few
places; the interfaces to the higher-level uni2char and char2uni
methods have been left unchanged.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 116 insertions, 61 deletions

diff --git a/fs/nls/nls_base.c b/fs/nls/nls_base.c
index 750abf2..477d37d 100644
--- a/fs/nls/nls_base.c
+++ b/fs/nls/nls_base.c
@@ -15,6 +15,7 @@
 #include <linux/errno.h>
 #include <linux/kmod.h>
 #include <linux/spinlock.h>
+#include <asm/byteorder.h>
 
 static struct nls_table default_table;
 static struct nls_table *tables = &default_table;
@@ -43,10 +44,17 @@ static const struct utf8_table utf8_table[] =
     {0,						       /* end of table    */}
 };
 
-int
-utf8_mbtowc(wchar_t *p, const __u8 *s, int n)
+#define UNICODE_MAX	0x0010ffff
+#define PLANE_SIZE	0x00010000
+
+#define SURROGATE_MASK	0xfffff800
+#define SURROGATE_PAIR	0x0000d800
+#define SURROGATE_LOW	0x00000400
+#define SURROGATE_BITS	0x000003ff
+
+int utf8_to_utf32(const u8 *s, int len, unicode_t *pu)
 {
-	long l;
+	unsigned long l;
 	int c0, c, nc;
 	const struct utf8_table *t;
   
@@ -57,12 +65,13 @@ utf8_mbtowc(wchar_t *p, const __u8 *s, int n)
 		nc++;
 		if ((c0 & t->cmask) == t->cval) {
 			l &= t->lmask;
-			if (l < t->lval)
+			if (l < t->lval || l > UNICODE_MAX ||
+					(l & SURROGATE_MASK) == SURROGATE_PAIR)
 				return -1;
-			*p = l;
+			*pu = (unicode_t) l;
 			return nc;
 		}
-		if (n <= nc)
+		if (len <= nc)
 			return -1;
 		s++;
 		c = (*s ^ 0x80) & 0xFF;
@@ -72,76 +81,119 @@ utf8_mbtowc(wchar_t *p, const __u8 *s, int n)
 	}
 	return -1;
 }
+EXPORT_SYMBOL(utf8_to_utf32);
 
-int
-utf8_mbstowcs(wchar_t *pwcs, const __u8 *s, int n)
+int utf32_to_utf8(unicode_t u, u8 *s, int maxlen)
 {
-	__u16 *op;
-	const __u8 *ip;
-	int size;
-
-	op = pwcs;
-	ip = s;
-	while (*ip && n > 0) {
-		if (*ip & 0x80) {
-			size = utf8_mbtowc(op, ip, n);
-			if (size == -1) {
-				/* Ignore character and move on */
-				ip++;
-				n--;
-			} else {
-				op++;
-				ip += size;
-				n -= size;
-			}
-		} else {
-			*op++ = *ip++;
-			n--;
-		}
-	}
-	return (op - pwcs);
-}
-
-int
-utf8_wctomb(__u8 *s, wchar_t wc, int maxlen)
-{
-	long l;
+	unsigned long l;
 	int c, nc;
 	const struct utf8_table *t;
-  
+
 	if (!s)
 		return 0;
-  
-	l = wc;
+
+	l = u;
+	if (l > UNICODE_MAX || (l & SURROGATE_MASK) == SURROGATE_PAIR)
+		return -1;
+
 	nc = 0;
 	for (t = utf8_table; t->cmask && maxlen; t++, maxlen--) {
 		nc++;
 		if (l <= t->lmask) {
 			c = t->shift;
-			*s = t->cval | (l >> c);
+			*s = (u8) (t->cval | (l >> c));
 			while (c > 0) {
 				c -= 6;
 				s++;
-				*s = 0x80 | ((l >> c) & 0x3F);
+				*s = (u8) (0x80 | ((l >> c) & 0x3F));
 			}
 			return nc;
 		}
 	}
 	return -1;
 }
+EXPORT_SYMBOL(utf32_to_utf8);
 
-int
-utf8_wcstombs(__u8 *s, const wchar_t *pwcs, int maxlen)
+int utf8s_to_utf16s(const u8 *s, int len, wchar_t *pwcs)
 {
-	const __u16 *ip;
-	__u8 *op;
+	u16 *op;
 	int size;
+	unicode_t u;
+
+	op = pwcs;
+	while (*s && len > 0) {
+		if (*s & 0x80) {
+			size = utf8_to_utf32(s, len, &u);
+			if (size < 0) {
+				/* Ignore character and move on */
+				size = 1;
+			} else if (u >= PLANE_SIZE) {
+				u -= PLANE_SIZE;
+				*op++ = (wchar_t) (SURROGATE_PAIR |
+						((u >> 10) & SURROGATE_BITS));
+				*op++ = (wchar_t) (SURROGATE_PAIR |
+						SURROGATE_LOW |
+						(u & SURROGATE_BITS));
+			} else {
+				*op++ = (wchar_t) u;
+			}
+			s += size;
+			len -= size;
+		} else {
+			*op++ = *s++;
+			len--;
+		}
+	}
+	return op - pwcs;
+}
+EXPORT_SYMBOL(utf8s_to_utf16s);
+
+static inline unsigned long get_utf16(unsigned c, enum utf16_endian endian)
+{
+	switch (endian) {
+	default:
+		return c;
+	case UTF16_LITTLE_ENDIAN:
+		return __le16_to_cpu(c);
+	case UTF16_BIG_ENDIAN:
+		return __be16_to_cpu(c);
+	}
+}
+
+int utf16s_to_utf8s(const wchar_t *pwcs, int len, enum utf16_endian endian,
+		u8 *s, int maxlen)
+{
+	u8 *op;
+	int size;
+	unsigned long u, v;
 
 	op = s;
-	ip = pwcs;
-	while (*ip && maxlen > 0) {
-		if (*ip > 0x7f) {
-			size = utf8_wctomb(op, *ip, maxlen);
+	while (len > 0 && maxlen > 0) {
+		u = get_utf16(*pwcs, endian);
+		if (!u)
+			break;
+		pwcs++;
+		len--;
+		if (u > 0x7f) {
+			if ((u & SURROGATE_MASK) == SURROGATE_PAIR) {
+				if (u & SURROGATE_LOW) {
+					/* Ignore character and move on */
+					continue;
+				}
+				if (len <= 0)
+					break;
+				v = get_utf16(*pwcs, endian);
+				if ((v & SURROGATE_MASK) != SURROGATE_PAIR ||
+						!(v & SURROGATE_LOW)) {
+					/* Ignore character and move on */
+					continue;
+				}
+				u = PLANE_SIZE + ((u & SURROGATE_BITS) << 10)
+						+ (v & SURROGATE_BITS);
+				pwcs++;
+				len--;
+			}
+			size = utf32_to_utf8(u, op, maxlen);
 			if (size == -1) {
 				/* Ignore character and move on */
 			} else {
@@ -149,13 +201,13 @@ utf8_wcstombs(__u8 *s, const wchar_t *pwcs, int maxlen)
 				maxlen -= size;
 			}
 		} else {
-			*op++ = (__u8) *ip;
+			*op++ = (u8) u;
 			maxlen--;
 		}
-		ip++;
 	}
-	return (op - s);
+	return op - s;
 }
+EXPORT_SYMBOL(utf16s_to_utf8s);
 
 int register_nls(struct nls_table * nls)
 {
@@ -467,9 +519,5 @@ EXPORT_SYMBOL(unregister_nls);
 EXPORT_SYMBOL(unload_nls);
 EXPORT_SYMBOL(load_nls);
 EXPORT_SYMBOL(load_nls_default);
-EXPORT_SYMBOL(utf8_mbtowc);
-EXPORT_SYMBOL(utf8_mbstowcs);
-EXPORT_SYMBOL(utf8_wctomb);
-EXPORT_SYMBOL(utf8_wcstombs);
 
 MODULE_LICENSE("Dual BSD/GPL");
diff --git a/fs/nls/nls_utf8.c b/fs/nls/nls_utf8.c
index aa2c42f..0d60a44 100644
--- a/fs/nls/nls_utf8.c
+++ b/fs/nls/nls_utf8.c
@@ -15,7 +15,11 @@ static int uni2char(wchar_t uni, unsigned char *out, int boundlen)
 {
 	int n;
 
-	if ( (n = utf8_wctomb(out, uni, boundlen)) == -1) {
+	if (boundlen <= 0)
+		return -ENAMETOOLONG;
+
+	n = utf32_to_utf8(uni, out, boundlen);
+	if (n < 0) {
 		*out = '?';
 		return -EINVAL;
 	}
@@ -25,11 +29,14 @@ static int uni2char(wchar_t uni, unsigned char *out, int boundlen)
 static int char2uni(const unsigned char *rawstring, int boundlen, wchar_t *uni)
 {
 	int n;
+	unicode_t u;
 
-	if ( (n = utf8_mbtowc(uni, rawstring, boundlen)) == -1) {
+	n = utf8_to_utf32(rawstring, boundlen, &u);
+	if (n < 0 || u > MAX_WCHAR_T) {
 		*uni = 0x003f;	/* ? */
-		n = -EINVAL;
+		return -EINVAL;
 	}
+	*uni = (wchar_t) u;
 	return n;
 }