On 09/05/2014 06:58 PM, beh...@converseincode.com wrote:
> From: Vinícius Tinti <viniciusti...@gmail.com>
>
> Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99
> compliant equivalent. This is the original VLAIS struct.
>
> struct {
> struct shash_desc shash;
> char ctx[crypto_shash_descsize(tfm)];
> } desc;
>
> This patch instead allocates the appropriate amount of memory using an char
> array.
>
> The new code can be compiled with both gcc and clang.
>
> struct shash_desc contains a flexible array member member ctx declared with
> CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning
> of the array declared after struct shash_desc with long long.
>
> No trailing padding is required because it is not a struct type that can
> be used in an array.
>
> The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long
> as would be the case for a struct containing a member with
> CRYPTO_MINALIGN_ATTR.
We copied this from one of the other crypto api users, and I'm sure
cooking up all these patches was not a great way to your afternoon.
But, can I talk you into making a helper macro of some kind for this and
putting it into the crypto api headers? Honestly this setup seems
really error prone.
-chris
>
> Signed-off-by: Jan-Simon Möller <dl...@gmx.de>
> Signed-off-by: Behan Webster <beh...@converseincode.com>
> Signed-off-by: Vinícius Tinti <viniciusti...@gmail.com>
> Signed-off-by: Mark Charlebois <charl...@gmail.com>
> ---
> fs/btrfs/hash.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
> index 85889aa..a62743f 100644
> --- a/fs/btrfs/hash.c
> +++ b/fs/btrfs/hash.c
> @@ -33,18 +33,18 @@ void btrfs_hash_exit(void)
>
> u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length)
> {
> - struct {
> - struct shash_desc shash;
> - char ctx[crypto_shash_descsize(tfm)];
> - } desc;
> + char desc[sizeof(struct shash_desc) +
> + crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR;
> + struct shash_desc *shash = (struct shash_desc *)desc;
> + u32 *ctx = (u32 *)shash_desc_ctx(shash);
> int err;
>
> - desc.shash.tfm = tfm;
> - desc.shash.flags = 0;
> - *(u32 *)desc.ctx = crc;
> + shash->tfm = tfm;
> + shash->flags = 0;
> + *ctx = crc;
>
> - err = crypto_shash_update(&desc.shash, address, length);
> + err = crypto_shash_update(shash, address, length);
> BUG_ON(err);
>
> - return *(u32 *)desc.ctx;
> + return *ctx;
> }
>
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