Am Mittwoch, 27. Juni 2018, 07:08:53 CEST schrieb Vinod:
Hi Vinod,
> Thanks for the pointers, it helped me to test the driver :)
>
> I have two follow up question on crypto:
>
> - If there a way to avoid using a global variable in driver to hold the
> pointer for driver memory? Looks like exynos driver does that.
>
> I understand that the crypto callback don't provide driver context as
> they copy the data structures passed in registration API, but a simpler
> way to get driver context would be desirable.
Sure the kernel crypto API can and has to maintain a per-instance data
structure.
See the crypto/drbg.c for instance.
static int drbg_kcapi_random(struct crypto_rng *tfm,
const u8 *src, unsigned int slen,
u8 *dst, unsigned int dlen)
{
struct drbg_state *drbg = crypto_rng_ctx(tfm);
static int drbg_kcapi_seed(struct crypto_rng *tfm,
const u8 *seed, unsigned int slen)
{
struct drbg_state *drbg = crypto_rng_ctx(tfm);
The key is:
alg->base.cra_ctxsize = sizeof(struct drbg_state);
during initialization since the kernel crypto API allocates that buffer for
you and releases it during deallocation.
>
> - .seed seems to be mandatory, if I do not set it and even use
> .seedsize = 0, it panics at crypto_rng_reset(). So is .seed
> mandatory?
Well, seedsize = 0 just says that the RNG is ready to use after initialization
(i.e. it does not need to be seeded after initialization).
That does not preclude that a caller wants to reseed.
And yes, .seed must be set.
>
> Thanks
Ciao
Stephan
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