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 750abf211e2..477d37d83b3 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 aa2c42fdd97..0d60a44acac 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;
 }