Re: [PATCH v7 2/2] crypto: s5p-sss: Add HASH support for Exynos

[Vladimir Zapolskiy]

Hi Kamil,

thank you for updates, I have just a few more comments.

On 10/17/2017 02:28 PM, Kamil Konieczny wrote:
> Add support for MD5, SHA1, SHA256 hash algorithms for Exynos HW.
> It uses the crypto framework asynchronous hash api.
> It is based on omap-sham.c driver.
> S5P has some HW differencies and is not implemented.
> 
> Modifications in s5p-sss:
> 
> - Add hash supporting structures and functions.
> 
> - Modify irq handler to handle both aes and hash signals.
> 
> - Resize resource end in probe if EXYNOS_HASH is enabled in
>   Kconfig.
> 
> - Add new copyright line and new author.
> 
> - Tested on Odroid-U3 with Exynos 4412 CPU, kernel 4.13-rc6
>   with crypto run-time self test testmgr
>   and with tcrypt module with: modprobe tcrypt sec=1 mode=N
>   where N=402, 403, 404 (MD5, SHA1, SHA256).
> 
> Modifications in drivers/crypto/Kconfig:
> 
> - Add new CRYPTO_DEV_EXYNOS_HASH, depend on !EXYNOS_RNG
>   and CRYPTO_DEV_S5P
> 
> - Select sw algorithms MD5, SHA1 and SHA256 in EXYNOS_HASH
>   as they are nedded for fallback.

Typo, s/nedded/needed/

[snip]

>  
>  #include <linux/clk.h>
>  #include <linux/crypto.h>
> +#include <linux/delay.h>

I can not find which interfaces from linux/delay.h are needed.
I suppose it should not be added.

[snip]

> -static struct s5p_aes_dev *s5p_dev;
> +/**
> + * struct s5p_hash_reqctx - HASH request context
> + * @dev:	Associated device

dev or dd?

> + * @op_update:	Current request operation (OP_UPDATE or OP_FINAL)
> + * @digcnt:	Number of bytes processed by HW (without buffer[] ones)
> + * @digest:	Digest message or IV for partial result
> + * @nregs:	Number of HW registers for digest or IV read/write
> + * @engine:	Bits for selecting type of HASH in SSS block
> + * @sg:		sg for DMA transfer
> + * @sg_len:	Length of sg for DMA transfer
> + * @sgl[]:	sg for joining buffer and req->src scatterlist
> + * @skip:	Skip offset in req->src for current op
> + * @total:	Total number of bytes for current request
> + * @finup:	Keep state for finup or final.
> + * @error:	Keep track of error.
> + * @bufcnt:	Number of bytes holded in buffer[]
> + * @buffer[]:	For byte(s) from end of req->src in UPDATE op
> + */
> +struct s5p_hash_reqctx {
> +	struct s5p_aes_dev	*dd;
> +	bool			op_update;
> +
> +	u64			digcnt;
> +	u8			digest[SHA256_DIGEST_SIZE];
> +
> +	unsigned int		nregs; /* digest_size / sizeof(reg) */
> +	u32			engine;
> +
> +	struct scatterlist	*sg;
> +	unsigned int		sg_len;
> +	struct scatterlist	sgl[2];
> +	unsigned int		skip;
> +	unsigned int		total;
> +	bool			finup;
> +	bool			error;
> +
> +	u32			bufcnt;
> +	u8			buffer[0];
> +};

[snip]

> +
> +/**
> + * s5p_hash_shash_digest() - calculate shash digest
> + * @tfm:	crypto transformation
> + * @flags:	tfm flags
> + * @data:	input data
> + * @len:	length of data
> + * @out:	output buffer
> + */
> +static int s5p_hash_shash_digest(struct crypto_shash *tfm, u32 flags,
> +				 const u8 *data, unsigned int len, u8 *out)
> +{
> +	SHASH_DESC_ON_STACK(shash, tfm);

Just for information, this line produces a spatch warning:

  drivers/crypto/s5p-sss.c:1534:9: warning: Variable length array is used.

I think it can be ignored.

> +
> +	shash->tfm = tfm;
> +	shash->flags = flags & ~CRYPTO_TFM_REQ_MAY_SLEEP;
> +
> +	return crypto_shash_digest(shash, data, len, out);
> +}
> +

[snip]

> +/**
> + * s5p_hash_final() - close up hash and calculate digest
> + * @req:	AHASH request
> + *
> + * Note: in final req->src do not have any data, and req->nbytes can be
> + * non-zero.
> + *
> + * If there were no input data processed yet and the buffered hash data is
> + * less than BUFLEN (64) then calculate the final hash immediately by using
> + * SW algorithm fallback.
> + *
> + * Otherwise enqueues the current AHASH request with OP_FINAL operation op
> + * and finalize hash message in HW. Note that if digcnt!=0 then there were
> + * previous update op, so there are always some buffered bytes in ctx->buffer,
> + * which means that ctx->bufcnt!=0
> + *
> + * Returns:
> + * 0 if the request has been processed immediately,
> + * -EINPROGRESS if the operation has been queued for later execution or is set
> + *		to processing by HW,
> + * -EBUSY if queue is full and request should be resubmitted later, other
> + *		negative values on error.

Do you want to add -EINVAL into the list also?

> + */
> +static int s5p_hash_final(struct ahash_request *req)
> +{
> +	struct s5p_hash_reqctx *ctx = ahash_request_ctx(req);
> +
> +	ctx->finup = true;
> +	if (ctx->error)
> +		return -EINVAL; /* uncompleted hash is not needed */
> +
> +	if (!ctx->digcnt && ctx->bufcnt < BUFLEN)
> +		return s5p_hash_final_shash(req);
> +
> +	return s5p_hash_enqueue(req, false); /* HASH_OP_FINAL */
> +}
> +

[snip]

> +/**
> + * s5p_hash_finup() - process last req->src and calculate digest
> + * @req:	AHASH request containing the last update data
> + *
> + * Return values: see s5p_hash_final above.
> + */
> +static int s5p_hash_finup(struct ahash_request *req)
> +{
> +	struct s5p_hash_reqctx *ctx = ahash_request_ctx(req);
> +	int err1, err2;
> +
> +	ctx->finup = true;
> +
> +	err1 = s5p_hash_update(req);
> +	if (err1 == -EINPROGRESS || err1 == -EBUSY)
> +		return err1;
> +
> +	/*
> +	 * final() has to be always called to cleanup resources even if
> +	 * update() failed, except EINPROGRESS or calculate digest for small
> +	 * size
> +	 */
> +	err2 = s5p_hash_final(req);
> +
> +	return err1 ?: err2;

See a note below.

[snip]

> +/**
> + * s5p_hash_digest - calculate digest from req->src
> + * @req:	AHASH request
> + *
> + * Return values: see s5p_hash_final above.
> + */
> +static int s5p_hash_digest(struct ahash_request *req)
> +{
> +	return s5p_hash_init(req) ?: s5p_hash_finup(req);

Now I got it, this ?: notation is invalid according to C99 and thus it
confused me, but GCC has an extension to support it, so, it's up to you
if you leave it as is or change it to comply with C99. If it ever causes
any troubles, it'll be easy to fix, and I'm fine if you leave it as is,
because it is understandable to GCC.

[snip]

> +/**
> + * s5p_hash_import - import hash state
> + * @req:	AHASH request
> + * @in:		buffer with state to be imported from
> + */
> +static int s5p_hash_import(struct ahash_request *req, const void *in)
> +{
> +	struct s5p_hash_reqctx *ctx = ahash_request_ctx(req);
> +	struct crypto_ahash *tfm = crypto_ahash_reqtfm(req);
> +	struct s5p_hash_ctx *tctx = crypto_ahash_ctx(tfm);
> +	const struct s5p_hash_reqctx *ctx_in = in;
> +
> +	memcpy(ctx, in, sizeof(*ctx) + BUFLEN);
> +	if (ctx_in->bufcnt < 0 || ctx_in->bufcnt > BUFLEN) {

Now "ctx_in->bufcnt < 0" condition can be removed, moreover it
will eliminate a warning reproted by the compiler:

drivers/crypto/s5p-sss.c:1748:21: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (ctx_in->bufcnt < 0 || ctx_in->bufcnt > BUFLEN) {
                     ^

--
With best wishes,
Vladimir