crypto: Add aesdec_IMC

Add a primitive for InvMixColumns.

Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

crypto/aes.c

@@ -1322,6 +1322,65 @@ void aesenc_SB_SR_AK_genrev(AESState *r, const AESState *s, const AESState *k)
     aesenc_SB_SR_AK_swap(r, s, k, true);
 }
 
+/*
+ * Perform InvMixColumns.
+ */
+static inline void
+aesdec_IMC_swap(AESState *r, const AESState *st, bool swap)
+{
+    int swap_b = swap * 0xf;
+    int swap_w = swap * 0x3;
+    bool be = HOST_BIG_ENDIAN ^ swap;
+    uint32_t t;
+
+    /* Note that AES_imc is encoded for big-endian. */
+    t = (AES_imc[st->b[swap_b ^ 0x0]][0] ^
+         AES_imc[st->b[swap_b ^ 0x1]][1] ^
+         AES_imc[st->b[swap_b ^ 0x2]][2] ^
+         AES_imc[st->b[swap_b ^ 0x3]][3]);
+    if (!be) {
+        t = bswap32(t);
+    }
+    r->w[swap_w ^ 0] = t;
+
+    t = (AES_imc[st->b[swap_b ^ 0x4]][0] ^
+         AES_imc[st->b[swap_b ^ 0x5]][1] ^
+         AES_imc[st->b[swap_b ^ 0x6]][2] ^
+         AES_imc[st->b[swap_b ^ 0x7]][3]);
+    if (!be) {
+        t = bswap32(t);
+    }
+    r->w[swap_w ^ 1] = t;
+
+    t = (AES_imc[st->b[swap_b ^ 0x8]][0] ^
+         AES_imc[st->b[swap_b ^ 0x9]][1] ^
+         AES_imc[st->b[swap_b ^ 0xA]][2] ^
+         AES_imc[st->b[swap_b ^ 0xB]][3]);
+    if (!be) {
+        t = bswap32(t);
+    }
+    r->w[swap_w ^ 2] = t;
+
+    t = (AES_imc[st->b[swap_b ^ 0xC]][0] ^
+         AES_imc[st->b[swap_b ^ 0xD]][1] ^
+         AES_imc[st->b[swap_b ^ 0xE]][2] ^
+         AES_imc[st->b[swap_b ^ 0xF]][3]);
+    if (!be) {
+        t = bswap32(t);
+    }
+    r->w[swap_w ^ 3] = t;
+}
+
+void aesdec_IMC_gen(AESState *r, const AESState *st)
+{
+    aesdec_IMC_swap(r, st, false);
+}
+
+void aesdec_IMC_genrev(AESState *r, const AESState *st)
+{
+    aesdec_IMC_swap(r, st, true);
+}
+
 /*
  * Perform InvSubBytes + InvShiftRows + AddRoundKey.
  */

host/include/generic/host/crypto/aes-round.h

@@ -15,6 +15,8 @@ void aesenc_SB_SR_AK_accel(AESState *, const AESState *,
                            const AESState *, bool)
     QEMU_ERROR("unsupported accel");
 
+void aesdec_IMC_accel(AESState *, const AESState *, bool)
+    QEMU_ERROR("unsupported accel");
 void aesdec_ISB_ISR_AK_accel(AESState *, const AESState *,
                              const AESState *, bool)
     QEMU_ERROR("unsupported accel");

include/crypto/aes-round.h

@@ -59,6 +59,24 @@ static inline void aesenc_SB_SR_AK(AESState *r, const AESState *st,
     }
 }
 
+/*
+ * Perform InvMixColumns.
+ */
+
+void aesdec_IMC_gen(AESState *ret, const AESState *st);
+void aesdec_IMC_genrev(AESState *ret, const AESState *st);
+
+static inline void aesdec_IMC(AESState *r, const AESState *st, bool be)
+{
+    if (HAVE_AES_ACCEL) {
+        aesdec_IMC_accel(r, st, be);
+    } else if (HOST_BIG_ENDIAN == be) {
+        aesdec_IMC_gen(r, st);
+    } else {
+        aesdec_IMC_genrev(r, st);
+    }
+}
+
 /*
  * Perform InvSubBytes + InvShiftRows + AddRoundKey.
  */