Re: [PATCH RFC 07/11] crypto: caam: check and use dma_map_sg() return code

["Horia Geantă" <horia.geanta@freescale.com>]

On 12/7/2015 9:12 PM, Russell King wrote:
> Strictly, dma_map_sg() may coalesce SG entries, but in practise on iMX
> hardware, this will never happen.  However, dma_map_sg() can fail, and
> we completely fail to check its return value.  So, fix this properly.
> 
> Arrange the code to map the scatterlist early, so we know how many
> scatter table entries to allocate, and then fill them in.  This allows
> us to keep relatively simple error cleanup paths.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Some tcrypt tests fail - looks like those with zero plaintext:
caam_jr ffe301000.jr: unable to map source for DMA
alg: hash: digest failed on test 1 for sha1-caam: ret=12
[...]

Need to be careful, dma_map_sg() returning zero is an error only if ptxt
is not null (alternatively src_nents returned by sg_nents_for_len()
could be checked).

> @@ -1091,7 +1102,7 @@ static int ahash_digest(struct ahash_request *req)
>  	u32 *sh_desc = ctx->sh_desc_digest, *desc;
>  	dma_addr_t ptr = ctx->sh_desc_digest_dma;
>  	int digestsize = crypto_ahash_digestsize(ahash);
> -	int src_nents, sec4_sg_bytes;
> +	int src_nents, mapped_nents, sec4_sg_bytes;
>  	dma_addr_t src_dma;
>  	struct ahash_edesc *edesc;
>  	int ret = 0;
> @@ -1099,9 +1110,14 @@ static int ahash_digest(struct ahash_request *req)
>  	int sh_len;
>  
>  	src_nents = sg_nents_for_len(req->src, req->nbytes);
> -	dma_map_sg(jrdev, req->src, src_nents, DMA_TO_DEVICE);
> -	if (src_nents > 1)
> -		sec4_sg_bytes = src_nents * sizeof(struct sec4_sg_entry);
> +	mapped_nents = dma_map_sg(jrdev, req->src, src_nents, DMA_TO_DEVICE);
> +	if (mapped_nents == 0) {
> +		dev_err(jrdev, "unable to map source for DMA\n");
> +		return -ENOMEM;
> +	}

This is at least one of the places where the error condition must change
to smth. like (src_nents != 0 && mapped_nents == 0).

Horia