commit fdd967ebdc53c1d3947f3fc145087579e32011ff
author Dave Rodgman <dave.rodgman@arm.com> Tue Nov 22 18:55:17 2022 +0000
committer Dave Rodgman <dave.rodgman@arm.com> Tue Nov 22 18:55:17 2022 +0000
tree 6795b9bc0cdc90d59eb8832047a924ab6d79e030
parent 8c18baf8c1ef8c2ed24981e2298d0e730eaa1e1b

Detect support for unaligned memory access

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>

library/common.h

diff --git a/library/common.h b/library/common.h
index d1af48e..bcb99f7 100644
--- a/library/common.h
+++ b/library/common.h
@@ -69,6 +69,18 @@
  */
 #define MBEDTLS_ALLOW_PRIVATE_ACCESS
 
+/** Detect architectures where unaligned memory accesses are safe and performant.
+ *
+ * This list is incomplete.
+ */
+#if defined(__i386__) || defined(__amd64__) || defined( __x86_64__) \
+    || defined(__ARM_FEATURE_UNALIGNED) \
+    || defined(__aarch64__) \
+    || defined(__ARM_ARCH_8__) || defined(__ARM_ARCH_8A__) || defined(__ARM_ARCH_8M__) \
+    || defined(__ARM_ARCH_7A__)
+#define MBEDTLS_ALLOW_UNALIGNED_ACCESS
+#endif
+
 /** Byte Reading Macros
  *
  * Given a multi-byte integer \p x, MBEDTLS_BYTE_n retrieves the n-th
@@ -404,6 +416,7 @@
  */
 static inline void mbedtls_xor( unsigned char* r, unsigned char const *a, unsigned char const *b, size_t n )
 {
+#if defined(MBEDTLS_ALLOW_UNALIGNED_ACCESS)
     uint32_t *a32 = (uint32_t*)a;
     uint32_t *b32 = (uint32_t*)b;
     uint32_t *r32 = (uint32_t*)r;
@@ -415,6 +428,12 @@
     {
         r[i] = a[i] ^ b[i];
     }
+#else
+    for ( size_t i = 0; i < n; i++ )
+    {
+        r[i] = a[i] ^ b[i];
+    }
+#endif
 }
 
 /* Fix MSVC C99 compatible issue