[CRYPTO] api: Add crypto_inc and crypto_xor

With the addition of more stream ciphers we need to curb the proliferation
of ad-hoc xor functions.  This patch creates a generic pair of functions,
crypto_inc and crypto_xor which does big-endian increment and exclusive or,
respectively.

For optimum performance, they both use u32 operations so alignment must be
as that of u32 even though the arguments are of type u8 *.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 47 insertions, 0 deletions

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 8383282de1dd..08eca6da1d53 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -605,6 +605,53 @@ int crypto_tfm_in_queue(struct crypto_queue *queue, struct crypto_tfm *tfm)
 }
 EXPORT_SYMBOL_GPL(crypto_tfm_in_queue);
 
+static inline void crypto_inc_byte(u8 *a, unsigned int size)
+{
+        u8 *b = (a + size);
+        u8 c;
+
+        for (; size; size--) {
+                c = *--b + 1;
+                *b = c;
+                if (c)
+                        break;
+        }
+}
+
+void crypto_inc(u8 *a, unsigned int size)
+{
+        __be32 *b = (__be32 *)(a + size);
+        u32 c;
+
+        for (; size >= 4; size -= 4) {
+                c = be32_to_cpu(*--b) + 1;
+                *b = cpu_to_be32(c);
+                if (c)
+                        return;
+        }
+
+        crypto_inc_byte(a, size);
+}
+EXPORT_SYMBOL_GPL(crypto_inc);
+
+static inline void crypto_xor_byte(u8 *a, const u8 *b, unsigned int size)
+{
+        for (; size; size--)
+                *a++ ^= *b++;
+}
+
+void crypto_xor(u8 *dst, const u8 *src, unsigned int size)
+{
+        u32 *a = (u32 *)dst;
+        u32 *b = (u32 *)src;
+
+        for (; size >= 4; size -= 4)
+                *a++ ^= *b++;
+
+        crypto_xor_byte((u8 *)a, (u8 *)b, size);
+}
+EXPORT_SYMBOL_GPL(crypto_xor);
+
 static int __init crypto_algapi_init(void)
 {
         crypto_init_proc();