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Message-ID: <20170620095947.i3r3iym2cxz5jciw@flea.lan>
Date: Tue, 20 Jun 2017 11:59:47 +0200
From: Maxime Ripard <maxime.ripard@...e-electrons.com>
To: Corentin Labbe <clabbe.montjoie@...il.com>
Cc: herbert@...dor.apana.org.au, davem@...emloft.net, wens@...e.org,
linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] crypto: sun4i-ss: support the Security System PRNG
Hi,
On Tue, Jun 20, 2017 at 10:58:19AM +0200, Corentin Labbe wrote:
> The Security System have a PRNG, this patch add support for it via
> crypto_rng.
This might be a dumb question, but is the CRYPTO_RNG code really
supposed to be used with PRNG?
> Signed-off-by: Corentin Labbe <clabbe.montjoie@...il.com>
> ---
> drivers/crypto/Kconfig | 8 +++++
> drivers/crypto/sunxi-ss/Makefile | 1 +
> drivers/crypto/sunxi-ss/sun4i-ss-core.c | 30 ++++++++++++++++++
> drivers/crypto/sunxi-ss/sun4i-ss-prng.c | 56 +++++++++++++++++++++++++++++++++
> drivers/crypto/sunxi-ss/sun4i-ss.h | 9 ++++++
> 5 files changed, 104 insertions(+)
> create mode 100644 drivers/crypto/sunxi-ss/sun4i-ss-prng.c
>
> diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
> index ab82536d64e2..bde0b102eb70 100644
> --- a/drivers/crypto/Kconfig
> +++ b/drivers/crypto/Kconfig
> @@ -618,6 +618,14 @@ config CRYPTO_DEV_SUN4I_SS
> To compile this driver as a module, choose M here: the module
> will be called sun4i-ss.
>
> +config CRYPTO_DEV_SUN4I_SS_PRNG
> + bool "Support for Allwinner Security System PRNG"
> + depends on CRYPTO_DEV_SUN4I_SS
> + select CRYPTO_RNG
> + help
> + Select this option if you to provides kernel-side support for
> + the Pseudo-Random Number Generator found in the Security System.
> +
> config CRYPTO_DEV_ROCKCHIP
> tristate "Rockchip's Cryptographic Engine driver"
> depends on OF && ARCH_ROCKCHIP
> diff --git a/drivers/crypto/sunxi-ss/Makefile b/drivers/crypto/sunxi-ss/Makefile
> index 8f4c7a273141..ccb893219079 100644
> --- a/drivers/crypto/sunxi-ss/Makefile
> +++ b/drivers/crypto/sunxi-ss/Makefile
> @@ -1,2 +1,3 @@
> obj-$(CONFIG_CRYPTO_DEV_SUN4I_SS) += sun4i-ss.o
> sun4i-ss-y += sun4i-ss-core.o sun4i-ss-hash.o sun4i-ss-cipher.o
> +sun4i-ss-$(CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG) += sun4i-ss-prng.o
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-core.c b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> index 02ad8256e900..d6bb2991c000 100644
> --- a/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> @@ -213,6 +213,23 @@ static struct sun4i_ss_alg_template ss_algs[] = {
> }
> }
> },
> +#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
> +{
> + .type = CRYPTO_ALG_TYPE_RNG,
> + .alg.rng = {
> + .base = {
> + .cra_name = "stdrng",
> + .cra_driver_name = "sun4i_ss_rng",
> + .cra_priority = 300,
> + .cra_ctxsize = 0,
> + .cra_module = THIS_MODULE,
> + },
> + .generate = sun4i_ss_prng_generate,
> + .seed = sun4i_ss_prng_seed,
> + .seedsize = SS_SEED_LEN,
> + }
> +},
> +#endif
> };
>
> static int sun4i_ss_probe(struct platform_device *pdev)
> @@ -355,6 +372,13 @@ static int sun4i_ss_probe(struct platform_device *pdev)
> goto error_alg;
> }
> break;
> + case CRYPTO_ALG_TYPE_RNG:
> + err = crypto_register_rng(&ss_algs[i].alg.rng);
> + if (err) {
> + dev_err(ss->dev, "Fail to register %s\n",
> + ss_algs[i].alg.rng.base.cra_name);
> + }
> + break;
> }
> }
> platform_set_drvdata(pdev, ss);
> @@ -369,6 +393,9 @@ static int sun4i_ss_probe(struct platform_device *pdev)
> case CRYPTO_ALG_TYPE_AHASH:
> crypto_unregister_ahash(&ss_algs[i].alg.hash);
> break;
> + case CRYPTO_ALG_TYPE_RNG:
> + crypto_unregister_rng(&ss_algs[i].alg.rng);
> + break;
> }
> }
> if (ss->reset)
> @@ -393,6 +420,9 @@ static int sun4i_ss_remove(struct platform_device *pdev)
> case CRYPTO_ALG_TYPE_AHASH:
> crypto_unregister_ahash(&ss_algs[i].alg.hash);
> break;
> + case CRYPTO_ALG_TYPE_RNG:
> + crypto_unregister_rng(&ss_algs[i].alg.rng);
> + break;
> }
> }
>
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-prng.c b/drivers/crypto/sunxi-ss/sun4i-ss-prng.c
> new file mode 100644
> index 000000000000..3941587def6b
> --- /dev/null
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss-prng.c
> @@ -0,0 +1,56 @@
> +#include "sun4i-ss.h"
> +
> +int sun4i_ss_prng_seed(struct crypto_rng *tfm, const u8 *seed,
> + unsigned int slen)
> +{
> + struct sun4i_ss_alg_template *algt;
> + struct rng_alg *alg = crypto_rng_alg(tfm);
> +
> + algt = container_of(alg, struct sun4i_ss_alg_template, alg.rng);
> + memcpy(algt->ss->seed, seed, slen);
> +
> + return 0;
> +}
> +
> +int sun4i_ss_prng_generate(struct crypto_rng *tfm, const u8 *src,
> + unsigned int slen, u8 *dst, unsigned int dlen)
> +{
> + struct sun4i_ss_alg_template *algt;
> + struct rng_alg *alg = crypto_rng_alg(tfm);
> + int i;
> + u32 v;
> + u32 *data = (u32 *)dst;
> + const u32 mode = SS_OP_PRNG | SS_PRNG_CONTINUE | SS_ENABLED;
> + size_t len;
> + struct sun4i_ss_ctx *ss;
> + unsigned int todo = (dlen / 4) * 4;
> +
> + algt = container_of(alg, struct sun4i_ss_alg_template, alg.rng);
> + ss = algt->ss;
> +
> + spin_lock(&ss->slock);
> +
> + writel(mode, ss->base + SS_CTL);
> +
> + while (todo > 0) {
> + /* write the seed */
> + for (i = 0; i < SS_SEED_LEN / 4; i++)
> + writel(ss->seed[i], ss->base + SS_KEY0 + i * 4);
> +
> + /* Read the random data */
> + len = min_t(size_t, SS_DATA_LEN, todo);
> + readsl(ss->base + SS_TXFIFO, data, len / 4);
> + data += len / 4;
> + todo -= len;
> +
> + /* Update the seed */
> + for (i = 0; i < SS_SEED_LEN / 4; i++) {
> + v = readl(ss->base + SS_KEY0 + i * 4);
> + ss->seed[i] = v;
> + }
> + }
> +
> + writel(0, ss->base + SS_CTL);
> + spin_unlock(&ss->slock);
> + return dlen;
> +}
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss.h b/drivers/crypto/sunxi-ss/sun4i-ss.h
> index a0e1efc1cb2a..293632b1cf27 100644
> --- a/drivers/crypto/sunxi-ss/sun4i-ss.h
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss.h
> @@ -32,6 +32,7 @@
> #include <crypto/aes.h>
> #include <crypto/des.h>
> #include <crypto/internal/rng.h>
> +#include <crypto/rng.h>
>
> #define SS_CTL 0x00
> #define SS_KEY0 0x04
> @@ -127,6 +128,9 @@
> #define SS_RXFIFO_EMP_INT_ENABLE (1 << 2)
> #define SS_TXFIFO_AVA_INT_ENABLE (1 << 0)
>
> +#define SS_SEED_LEN (192 / 8)
> +#define SS_DATA_LEN (160 / 8)
> +
> struct sun4i_ss_ctx {
> void __iomem *base;
> int irq;
> @@ -136,6 +140,7 @@ struct sun4i_ss_ctx {
> struct device *dev;
> struct resource *res;
> spinlock_t slock; /* control the use of the device */
> + u32 seed[SS_SEED_LEN / 4];
Shouldn't you define SS_SEED_LEN in bits, and then use either
BITS_PER_BYTE and BITS_PER_LONG so that it's obvious what you're doing
?
And you could also make that variable defined based on the option,
otherwise you'll always allocate that array, even if you're not using
it.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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