ext4: Add support for non-native signed/unsigned htree hash algorithms

The original ext3 hash algorithms assumed that variables of type char
were signed, as God and K&R intended.  Unfortunately, this assumption
is not true on some architectures.  Userspace support for marking
filesystems with non-native signed/unsigned chars was added two years
ago, but the kernel-side support was never added (until now).

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 67 insertions, 10 deletions

diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index 556ca8eba3d..ac8f168c8ab 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -35,23 +35,71 @@ static void TEA_transform(__u32 buf[4], __u32 const in[])
 
 
 /* The old legacy hash */
-static __u32 dx_hack_hash(const char *name, int len)
+static __u32 dx_hack_hash_unsigned(const char *name, int len)
 {
-        __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+        __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+        const unsigned char *ucp = (const unsigned char *) name;
+
+        while (len--) {
+                hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
+
+                if (hash & 0x80000000)
+                        hash -= 0x7fffffff;
+                hash1 = hash0;
+                hash0 = hash;
+        }
+        return hash0 << 1;
+}
+
+static __u32 dx_hack_hash_signed(const char *name, int len)
+{
+        __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+        const signed char *scp = (const signed char *) name;
+
         while (len--) {
-                __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
+                hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
 
-                if (hash & 0x80000000) hash -= 0x7fffffff;
+                if (hash & 0x80000000)
+                        hash -= 0x7fffffff;
                 hash1 = hash0;
                 hash0 = hash;
         }
-        return (hash0 << 1);
+        return hash0 << 1;
+}
+
+static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
+{
+        __u32   pad, val;
+        int     i;
+        const signed char *scp = (const signed char *) msg;
+
+        pad = (__u32)len | ((__u32)len << 8);
+        pad |= pad << 16;
+
+        val = pad;
+        if (len > num*4)
+                len = num * 4;
+        for (i = 0; i < len; i++) {
+                if ((i % 4) == 0)
+                        val = pad;
+                val = ((int) scp[i]) + (val << 8);
+                if ((i % 4) == 3) {
+                        *buf++ = val;
+                        val = pad;
+                        num--;
+                }
+        }
+        if (--num >= 0)
+                *buf++ = val;
+        while (--num >= 0)
+                *buf++ = pad;
 }
 
-static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
+static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
 {
         __u32   pad, val;
         int     i;
+        const unsigned char *ucp = (const unsigned char *) msg;
 
         pad = (__u32)len | ((__u32)len << 8);
         pad |= pad << 16;
@@ -62,7 +110,7 @@ static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
         for (i = 0; i < len; i++) {
                 if ((i % 4) == 0)
                         val = pad;
-                val = msg[i] + (val << 8);
+                val = ((int) ucp[i]) + (val << 8);
                 if ((i % 4) == 3) {
                         *buf++ = val;
                         val = pad;
@@ -95,6 +143,8 @@ int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
         const char      *p;
         int             i;
         __u32           in[8], buf[4];
+        void            (*str2hashbuf)(const char *, int, __u32 *, int) =
+                                str2hashbuf_signed;
 
         /* Initialize the default seed for the hash checksum functions */
         buf[0] = 0x67452301;
@@ -113,13 +163,18 @@ int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
         }
 
         switch (hinfo->hash_version) {
+        case DX_HASH_LEGACY_UNSIGNED:
+                hash = dx_hack_hash_unsigned(name, len);
+                break;
         case DX_HASH_LEGACY:
-                hash = dx_hack_hash(name, len);
+                hash = dx_hack_hash_signed(name, len);
                 break;
+        case DX_HASH_HALF_MD4_UNSIGNED:
+                str2hashbuf = str2hashbuf_unsigned;
         case DX_HASH_HALF_MD4:
                 p = name;
                 while (len > 0) {
-                        str2hashbuf(p, len, in, 8);
+                        (*str2hashbuf)(p, len, in, 8);
                         half_md4_transform(buf, in);
                         len -= 32;
                         p += 32;
@@ -127,10 +182,12 @@ int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
                 minor_hash = buf[2];
                 hash = buf[1];
                 break;
+        case DX_HASH_TEA_UNSIGNED:
+                str2hashbuf = str2hashbuf_unsigned;
         case DX_HASH_TEA:
                 p = name;
                 while (len > 0) {
-                        str2hashbuf(p, len, in, 4);
+                        (*str2hashbuf)(p, len, in, 4);
                         TEA_transform(buf, in);
                         len -= 16;
                         p += 16;