kern/misc: Implement faster grub_memcpy() for aligned buffers

When both "dest" and "src" are aligned, copying the data in grub_addr_t
sized chunks is more efficient than a byte-by-byte copy.

Also tweak __aeabi_memcpy(), __aeabi_memcpy4(), and __aeabi_memcpy8(),
since grub_memcpy() is not inline anymore.

Optimization for unaligned buffers was omitted to maintain code
simplicity and readability. The current chunk-copy optimization
for aligned buffers already provides a noticeable performance
improvement (*) for Argon2 keyslot decryption.

  (*) On my system, for a LUKS2 keyslot configured with a 1 GB Argon2
      memory requirement, this patch reduces the decryption time from
      22 seconds to 12 seconds.

Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/kern/compiler-rt.c

@@ -24,7 +24,7 @@
 void * GRUB_BUILTIN_ATTR
 memcpy (void *dest, const void *src, grub_size_t n)
 {
-	return grub_memmove (dest, src, n);
+	return grub_memcpy (dest, src, n);
 }
 void * GRUB_BUILTIN_ATTR
 memmove (void *dest, const void *src, grub_size_t n)
@@ -372,11 +372,11 @@ grub_int32_t
 __aeabi_idiv (grub_int32_t a, grub_int32_t b)
   __attribute__ ((alias ("__divsi3")));
 void *__aeabi_memcpy (void *dest, const void *src, grub_size_t n)
-  __attribute__ ((alias ("grub_memcpy")));
+  __attribute__ ((alias ("memcpy")));
 void *__aeabi_memcpy4 (void *dest, const void *src, grub_size_t n)
-  __attribute__ ((alias ("grub_memcpy")));
+  __attribute__ ((alias ("memcpy")));
 void *__aeabi_memcpy8 (void *dest, const void *src, grub_size_t n)
-  __attribute__ ((alias ("grub_memcpy")));
+  __attribute__ ((alias ("memcpy")));
 void *__aeabi_memset (void *s, int c, grub_size_t n)
   __attribute__ ((alias ("memset")));