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Message-ID: <20161117080516.GA25394@Red>
Date: Thu, 17 Nov 2016 09:05:16 +0100
From: Corentin Labbe <clabbe.montjoie@...il.com>
To: PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, davem@...emloft.net,
maxime.ripard@...e-electrons.com, 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
On Tue, Oct 18, 2016 at 09:39:17PM +0530, PrasannaKumar Muralidharan wrote:
> Hi Corentin,
>
> I have a few minor comments.
>
> On 18 October 2016 at 18:04, Corentin Labbe <clabbe.montjoie@...il.com> wrote:
> > From: LABBE Corentin <clabbe.montjoie@...il.com>
> >
> > The Security System have a PRNG.
> > This patch add support for it as an hwrng.
> >
> > 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 | 14 +++++++
> > drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c | 70 ++++++++++++++++++++++++++++++++
> > drivers/crypto/sunxi-ss/sun4i-ss.h | 8 ++++
> > 5 files changed, 101 insertions(+)
> > create mode 100644 drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
> >
> > diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
> > index 4d2b81f..38f7aca 100644
> > --- a/drivers/crypto/Kconfig
> > +++ b/drivers/crypto/Kconfig
> > @@ -538,6 +538,14 @@ 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 HW_RANDOM
> > + help
> > + This driver 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 8f4c7a2..ca049ee 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-hwrng.o
> > diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-core.c b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> > index 3ac6c6c..fa739de 100644
> > --- a/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> > +++ b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> > @@ -359,6 +359,16 @@ static int sun4i_ss_probe(struct platform_device *pdev)
> > }
> > }
> > platform_set_drvdata(pdev, ss);
> > +
> > +#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
> > + /* Voluntarily made the PRNG optional */
> > + err = sun4i_ss_hwrng_register(&ss->hwrng);
> > + if (!err)
> > + dev_info(ss->dev, "sun4i-ss PRNG loaded");
> > + else
> > + dev_err(ss->dev, "sun4i-ss PRNG failed");
> > +#endif
> > +
> > return 0;
> > error_alg:
> > i--;
> > @@ -386,6 +396,10 @@ static int sun4i_ss_remove(struct platform_device *pdev)
> > int i;
> > struct sun4i_ss_ctx *ss = platform_get_drvdata(pdev);
> >
> > +#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
> > + sun4i_ss_hwrng_remove(&ss->hwrng);
> > +#endif
> > +
> > for (i = 0; i < ARRAY_SIZE(ss_algs); i++) {
> > switch (ss_algs[i].type) {
> > case CRYPTO_ALG_TYPE_ABLKCIPHER:
> > diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
> > new file mode 100644
> > index 0000000..95fadb7
> > --- /dev/null
> > +++ b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
> > @@ -0,0 +1,70 @@
> > +#include "sun4i-ss.h"
> > +
> > +static int sun4i_ss_hwrng_init(struct hwrng *hwrng)
> > +{
> > + struct sun4i_ss_ctx *ss;
> > +
> > + ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
> > + get_random_bytes(ss->seed, SS_SEED_LEN);
> > +
> > + return 0;
> > +}
> > +
> > +static int sun4i_ss_hwrng_read(struct hwrng *hwrng, void *buf,
> > + size_t max, bool wait)
> > +{
> > + int i;
> > + u32 v;
> > + u32 *data = buf;
> > + const u32 mode = SS_OP_PRNG | SS_PRNG_CONTINUE | SS_ENABLED;
> > + size_t len;
> > + struct sun4i_ss_ctx *ss;
> > +
> > + ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
> > + len = min_t(size_t, SS_DATA_LEN, max);
> > +
> > + spin_lock_bh(&ss->slock);
>
> Is spin_lock_bh really required here? I could see it is being used in
> sun4i-ss-hash.c but could not find any comment/info about the need.
>
No for sun4i-ss-hwrng it seems not required and work perfecly without _bh
> > + writel(mode, ss->base + SS_CTL);
> > +
> > + /* write the seed */
> > + for (i = 0; i < SS_SEED_LEN / 4; i++)
> > + writel(ss->seed[i], ss->base + SS_KEY0 + i * 4);
> > + writel(mode | SS_PRNG_START, ss->base + SS_CTL);
> > +
> > + /* Read the random data */
> > + readsl(ss->base + SS_TXFIFO, data, len / 4);
> > +
> > + if (len % 4 > 0) {
> > + v = readl(ss->base + SS_TXFIFO);
> > + memcpy(data + len / 4, &v, len % 4);
> > + }
>
> hwrng core asks for "rng_buffer_size()" of data which is a multiple of
> 4. So len % 4 will be 0. I think the above check is not required. Feel
> free to correct if I am wrong.
>
Agree, I removed that in v2
Thanks
Corentin Labbe
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