[CRYPTO] Add alignmask for low-level cipher implementations

The VIA Padlock device requires the input and output buffers to
be aligned on 16-byte boundaries.  This patch adds the alignmask
attribute for low-level cipher implementations to indicate their
alignment requirements.

The mid-level crypt() function will copy the input/output buffers
if they are not aligned correctly before they are passed to the
low-level implementation.

Strictly speaking, some of the software implementations require
the buffers to be aligned on 4-byte boundaries as they do 32-bit
loads.  However, it is not clear whether it is better to copy
the buffers or pay the penalty for unaligned loads/stores.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 49 insertions, 7 deletions

diff --git a/crypto/api.c b/crypto/api.c
index 394169a8577d..f55856b21992 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -168,6 +168,12 @@ int crypto_register_alg(struct crypto_alg *alg)
 {
         int ret = 0;
         struct crypto_alg *q;
+
+        if (alg->cra_alignmask & (alg->cra_alignmask + 1))
+                return -EINVAL;
+
+        if (alg->cra_alignmask > PAGE_SIZE)
+                return -EINVAL;
         
         down_write(&crypto_alg_sem);
         
diff --git a/crypto/cipher.c b/crypto/cipher.c
index 54c4a560070d..85eb12f8e564 100644
--- a/crypto/cipher.c
+++ b/crypto/cipher.c
@@ -41,8 +41,10 @@ static unsigned int crypt_slow(const struct cipher_desc *desc,
                                struct scatter_walk *in,
                                struct scatter_walk *out, unsigned int bsize)
 {
-        u8 src[bsize];
-        u8 dst[bsize];
+        unsigned int alignmask = desc->tfm->__crt_alg->cra_alignmask;
+        u8 buffer[bsize * 2 + alignmask];
+        u8 *src = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
+        u8 *dst = src + bsize;
         unsigned int n;
 
         n = scatterwalk_copychunks(src, in, bsize, 0);
@@ -59,15 +61,24 @@ static unsigned int crypt_slow(const struct cipher_desc *desc,
 static inline unsigned int crypt_fast(const struct cipher_desc *desc,
                                       struct scatter_walk *in,
                                       struct scatter_walk *out,
-                                      unsigned int nbytes)
+                                      unsigned int nbytes, u8 *tmp)
 {
         u8 *src, *dst;
 
         src = in->data;
         dst = scatterwalk_samebuf(in, out) ? src : out->data;
 
+        if (tmp) {
+                memcpy(tmp, in->data, nbytes);
+                src = tmp;
+                dst = tmp;
+        }
+
         nbytes = desc->prfn(desc, dst, src, nbytes);
 
+        if (tmp)
+                memcpy(out->data, tmp, nbytes);
+
         scatterwalk_advance(in, nbytes);
         scatterwalk_advance(out, nbytes);
 
@@ -87,6 +98,8 @@ static int crypt(const struct cipher_desc *desc,
         struct scatter_walk walk_in, walk_out;
         struct crypto_tfm *tfm = desc->tfm;
         const unsigned int bsize = crypto_tfm_alg_blocksize(tfm);
+        unsigned int alignmask = tfm->__crt_alg->cra_alignmask;
+        unsigned long buffer = 0;
 
         if (!nbytes)
                 return 0;
@@ -100,16 +113,27 @@ static int crypt(const struct cipher_desc *desc,
         scatterwalk_start(&walk_out, dst);
 
         for(;;) {
-                unsigned int n;
+                unsigned int n = nbytes;
+                u8 *tmp = NULL;
+
+                if (!scatterwalk_aligned(&walk_in, alignmask) ||
+                    !scatterwalk_aligned(&walk_out, alignmask)) {
+                        if (!buffer) {
+                                buffer = __get_free_page(GFP_ATOMIC);
+                                if (!buffer)
+                                        n = 0;
+                        }
+                        tmp = (u8 *)buffer;
+                }
 
                 scatterwalk_map(&walk_in, 0);
                 scatterwalk_map(&walk_out, 1);
 
-                n = scatterwalk_clamp(&walk_in, nbytes);
+                n = scatterwalk_clamp(&walk_in, n);
                 n = scatterwalk_clamp(&walk_out, n);
 
                 if (likely(n >= bsize))
-                        n = crypt_fast(desc, &walk_in, &walk_out, n);
+                        n = crypt_fast(desc, &walk_in, &walk_out, n, tmp);
                 else
                         n = crypt_slow(desc, &walk_in, &walk_out, bsize);
 
@@ -119,10 +143,15 @@ static int crypt(const struct cipher_desc *desc,
                 scatterwalk_done(&walk_out, 1, nbytes);
 
                 if (!nbytes)
-                        return 0;
+                        break;
 
                 crypto_yield(tfm);
         }
+
+        if (buffer)
+                free_page(buffer);
+
+        return 0;
 }
 
 static unsigned int cbc_process_encrypt(const struct cipher_desc *desc,
diff --git a/crypto/scatterwalk.h b/crypto/scatterwalk.h
index 5495bb970816..e79925c474a3 100644
--- a/crypto/scatterwalk.h
+++ b/crypto/scatterwalk.h
@@ -55,6 +55,12 @@ static inline void scatterwalk_advance(struct scatter_walk *walk,
         walk->len_this_segment -= nbytes;
 }
 
+static inline unsigned int scatterwalk_aligned(struct scatter_walk *walk,
+                                               unsigned int alignmask)
+{
+        return !(walk->offset & alignmask);
+}
+
 void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg);
 int scatterwalk_copychunks(void *buf, struct scatter_walk *walk, size_t nbytes, int out);
 void scatterwalk_map(struct scatter_walk *walk, int out);
diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index 26ce01c25745..ac9d49beecd3 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -124,6 +124,7 @@ struct crypto_alg {
         u32 cra_flags;
         unsigned int cra_blocksize;
         unsigned int cra_ctxsize;
+        unsigned int cra_alignmask;
         const char cra_name[CRYPTO_MAX_ALG_NAME];
 
         union {