Re: [PATCH v3 28/32] crypto: lib/aes - export sbox and inverse sbox

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Jun 27, 2019 at 12:26:43PM +0200, Ard Biesheuvel wrote:
> There are a few copies of the AES S-boxes floating around, so export
> the ones from the AES library so that we can reuse them in other
> modules.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  include/crypto/aes.h | 3 +++
>  lib/crypto/aes.c     | 6 ++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/include/crypto/aes.h b/include/crypto/aes.h
> index df8426fd8051..8e0f4cf948e5 100644
> --- a/include/crypto/aes.h
> +++ b/include/crypto/aes.h
> @@ -67,4 +67,7 @@ void aes_encrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in);
>   */
>  void aes_decrypt(const struct crypto_aes_ctx *ctx, u8 *out, const u8 *in);
>  
> +extern const u8 crypto_aes_sbox[];
> +extern const u8 crypto_aes_inv_sbox[];
> +
>  #endif
> diff --git a/lib/crypto/aes.c b/lib/crypto/aes.c
> index 9928b23e0a8a..467f0c35a0e0 100644
> --- a/lib/crypto/aes.c
> +++ b/lib/crypto/aes.c
> @@ -82,6 +82,12 @@ static volatile const u8 __cacheline_aligned aes_inv_sbox[] = {
>  	0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
>  };
>  
> +extern const u8 crypto_aes_sbox[] __alias(aes_sbox);
> +extern const u8 crypto_aes_inv_sbox[] __alias(aes_inv_sbox);
> +
> +EXPORT_SYMBOL(crypto_aes_sbox);
> +EXPORT_SYMBOL(crypto_aes_inv_sbox);

I got a compiler warning:

In file included from ./include/linux/linkage.h:7,
                 from ./include/linux/kernel.h:8,
                 from ./include/linux/crypto.h:16,
                 from ./include/crypto/aes.h:10,
                 from lib/crypto/aes.c:6:
lib/crypto/aes.c:88:15: warning: array ‘crypto_aes_sbox’ assumed to have one element
 EXPORT_SYMBOL(crypto_aes_sbox);
               ^~~~~~~~~~~~~~~
./include/linux/export.h:79:21: note: in definition of macro ‘___EXPORT_SYMBOL’
  extern typeof(sym) sym;      \
                     ^~~
lib/crypto/aes.c:88:1: note: in expansion of macro ‘EXPORT_SYMBOL’
 EXPORT_SYMBOL(crypto_aes_sbox);
 ^~~~~~~~~~~~~
lib/crypto/aes.c:89:15: warning: array ‘crypto_aes_inv_sbox’ assumed to have one element
 EXPORT_SYMBOL(crypto_aes_inv_sbox);
               ^~~~~~~~~~~~~~~~~~~
./include/linux/export.h:79:21: note: in definition of macro ‘___EXPORT_SYMBOL’
  extern typeof(sym) sym;      \
                     ^~~
lib/crypto/aes.c:89:1: note: in expansion of macro ‘EXPORT_SYMBOL’
 EXPORT_SYMBOL(crypto_aes_inv_sbox);
 ^~~~~~~~~~~~~