crypto: hw_random - Add new Exynos RNG driver

Hi,

This is a follow up of my questions around exynos-rng [1].

Changes since v4:
=================
1. Patch 2/2: Use "stdrng" name, as suggested by Herbert.
2. Patch 2/2: Add Bartlomiej's reviewed-by.

Changes since v3:
=================
1. New patch: 1/2 for ALIGN_DOWN macro. The change in metag architecture was not compiled. Please test it.
2. Dropped patches touching ARM defconfig as they are not changing and they pollute this submission.
3. Utilize all seed provided by kcapi (suggested by Stephan Müller).
4. Drop dev->ctx (suggested by PrasannaKumar Muralidharan).
5. Remove any printks from set_seed callback as this might be a way for unprivileged user to pollute the log (suggested by Stephan).
6. Minor cleanups: initialize 'read' variable in exynos_rng_reseed() for readability (it is not strictly required).
7. Add review tags from Stephen and PrasannaKumar.

Changes since v2:
=================
1. Do not re-use random numbers for re-seed (neither for system resume nor for periodic re-seed). Instead the driver will just generate new random numbers (suggested by Stephan Müller).

Suspend path tested with suspend-to-freeze, not real suspend. Testing on Trats2 would be welcomed.

Changes since v1:
=================
1. Re-work the code for seeding after system resume, following suggestions and review by Stephan Müller.

2. Re-seed itself from time to time (every 100 ms), suggested by Stephan Müller.

3. Use a define for retries (Bartlomiej Zolnierkiewicz).
4. Add some docs.

Description:
============
The existing exynos-rng has many issues. The most important one is that it is a pseudo RNG device but uses hw_random interface which does not allow proper seeding.

The RNG module on Exynos4 requires seeding. On newer SoCs (like Exynos5420) it can seed itself from a true RNG. Converting the existing driver to use TRNG would effectively drop support for Exynos4 and break compatibility with existing users.

Instead I decided to convert it to crypto API. In the future I hope to add support for seeding from TRNG module.

Tested with app [2].

Patches are independent. I will take the defconfig changes (2/3 and 3/3) through samsung-soc tree.

Best regards,
Krzysztof

[1] https://www.spinics.net/lists/arm-kernel/msg569641.html
[2] https://www.spinics.net/lists/arm-kernel/msg571184.html

Krzysztof Kozlowski (2):
linux/kernel.h: Add ALIGN_DOWN macro
crypto: hw_random - Add new Exynos RNG driver

 MAINTAINERS                         |   8 +
 arch/metag/kernel/stacktrace.c      |   2 -
 drivers/char/hw_random/Kconfig      |  14 --
 drivers/char/hw_random/Makefile     |   1 -
 drivers/char/hw_random/exynos-rng.c | 231 ---------------------
 drivers/crypto/Kconfig              |  15 ++
 drivers/crypto/Makefile             |   1 +
 drivers/crypto/exynos-rng.c         | 389 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/udl/udl_fb.c        |   2 +-
 include/linux/kernel.h              |   1 +
 include/video/udlfb.h               |   2 +-
 11 files changed, 416 insertions(+), 250 deletions(-)
 delete mode 100644 drivers/char/hw_random/exynos-rng.c
 create mode 100644 drivers/crypto/exynos-rng.c

2.9.3

Few parts of kernel define their own macro for aligning down so provide a common define for this, with the same usage and assumptions as existing ALIGN.

Convert also three existing implementations to this one.

---

The metag change was not even compiled due to lack of cross compiler.

---
 arch/metag/kernel/stacktrace.c | 2 --
 drivers/gpu/drm/udl/udl_fb.c   | 2 +-
 include/linux/kernel.h         | 1 +
 include/video/udlfb.h          | 2 +-
 4 files changed, 3 insertions(+), 4 deletions(-)

index 91ffc4b75c33..09d67b7f51ca 100644
@@ -31,8 +31,6 @@ static void tbi_boing_init(void)
 }
 #endif
 
-#define ALIGN_DOWN(addr, size)  ((addr)&(~((size)-1)))
-
 /*
  * Unwind the current stack frame and store the new register values in the
  * structure passed as argument. Unwinding is equivalent to a function return,

index d05abc69e305..4a6500362564 100644
@@ -37,7 +37,7 @@ struct udl_fbdev {
 };
 
 #define DL_ALIGN_UP(x, a) ALIGN(x, a)
-#define DL_ALIGN_DOWN(x, a) ALIGN(x-(a-1), a)
+#define DL_ALIGN_DOWN(x, a) ALIGN_DOWN(x, a)
 
 /** Read the red component (0..255) of a 32 bpp colour. */
 #define DLO_RGB_GETRED(col) (uint8_t)((col) & 0xFF)

index 4c26dc3a8295..3d9f8420f973 100644
@@ -47,6 +47,7 @@
 
 /* @a is a power of 2 value */
 #define ALIGN(x, a)		__ALIGN_KERNEL((x), (a))
+#define ALIGN_DOWN(x, a)	__ALIGN_KERNEL((x) - ((a) - 1), (a))
 #define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
 #define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
 #define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)

index f9466fa54ba4..3ea90aea5617 100644
@@ -92,6 +92,6 @@ struct dlfb_data {
 
 /* remove these once align.h patch is taken into kernel */
 #define DL_ALIGN_UP(x, a) ALIGN(x, a)
-#define DL_ALIGN_DOWN(x, a) ALIGN(x-(a-1), a)
+#define DL_ALIGN_DOWN(x, a) ALIGN_DOWN(x, a)
 
 #endif

2.9.3

Replace existing hw_ranndom/exynos-rng driver with a new, reworked one. This is a driver for pseudo random number generator block which on Exynos4 chipsets must be seeded with some value. On newer Exynos5420 chipsets it might seed itself from true random number generator block but this is not implemented yet.

New driver is a complete rework to use the crypto ALGAPI instead of hw_random API. Rationale for the change:
1. hw_random interface is for true RNG devices.
2. The old driver was seeding itself with jiffies which is not a reliable source for randomness.
3. Device generates five random 32-bit numbers in each pass but old driver was returning only one 32-bit number thus its performance was reduced.

Compatibility with DeviceTree bindings is preserved.

New driver does not use runtime power management but manually enables and disables the clock when needed. This is preferred approach because using runtime PM just to toggle clock is huge overhead.

Another difference is reseeding itself with generated random data periodically and during resuming from system suspend (previously driver was re-seeding itself again with jiffies).

---
 MAINTAINERS                         |   8 +
 drivers/char/hw_random/Kconfig      |  14 --
 drivers/char/hw_random/Makefile     |   1 -
 drivers/char/hw_random/exynos-rng.c | 231 ---------------------
 drivers/crypto/Kconfig              |  15 ++
 drivers/crypto/Makefile             |   1 +
 drivers/crypto/exynos-rng.c         | 389 ++++++++++++++++++++++++++++++++++++
 7 files changed, 413 insertions(+), 246 deletions(-)
 delete mode 100644 drivers/char/hw_random/exynos-rng.c
 create mode 100644 drivers/crypto/exynos-rng.c

index affecc6d59f4..371fda859d43 100644
@@ -10977,6 +10977,14 @@ L:	alsa-devel-K7yf7f+aM1XWsZ/[email protected] (moderated for non-subscribers)
 S:	Supported
 F:	sound/soc/samsung/
 
+SAMSUNG EXYNOS PSEUDO RANDOM NUMBER GENERATOR (RNG) DRIVER
+M:	Krzysztof Kozlowski <[email protected]>
+L:	[email protected]
+L:	[email protected]
+S:	Maintained
+F:	drivers/crypto/exynos-rng.c
+F:	Documentation/devicetree/bindings/rng/samsung,exynos-rng4.txt
+
 SAMSUNG FRAMEBUFFER DRIVER
 M:	Jingoo Han <[email protected]>
 L:	[email protected]

index 0cafe08919c9..bdae802e7154 100644
@@ -294,20 +294,6 @@ config HW_RANDOM_POWERNV
 
 	  If unsure, say Y.
 
-config HW_RANDOM_EXYNOS
-	tristate "EXYNOS HW random number generator support"
-	depends on ARCH_EXYNOS || COMPILE_TEST
-	depends on HAS_IOMEM
-	default HW_RANDOM
-	---help---
-	  This driver provides kernel-side support for the Random Number
-	  Generator hardware found on EXYNOS SOCs.
-
-	  To compile this driver as a module, choose M here: the
-	  module will be called exynos-rng.
-
-	  If unsure, say Y.
-
 config HW_RANDOM_TPM
 	tristate "TPM HW Random Number Generator support"
 	depends on TCG_TPM

index 5f52b1e4e7be..6f1eecc2045c 100644
@@ -24,7 +24,6 @@ obj-$(CONFIG_HW_RANDOM_OCTEON) += octeon-rng.o
 obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
 obj-$(CONFIG_HW_RANDOM_POWERNV) += powernv-rng.o
-obj-$(CONFIG_HW_RANDOM_EXYNOS)	+= exynos-rng.o
 obj-$(CONFIG_HW_RANDOM_HISI)	+= hisi-rng.o
 obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
 obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o

index 1a60626937e4..7d1fdf6a751c 100644
@@ -388,6 +388,21 @@ config CRYPTO_DEV_MXC_SCC
 	  This option enables support for the Security Controller (SCC)
 	  found in Freescale i.MX25 chips.
 
+config CRYPTO_DEV_EXYNOS_RNG
+	tristate "EXYNOS HW pseudo random number generator support"
+	depends on ARCH_EXYNOS || COMPILE_TEST
+	depends on HAS_IOMEM
+	select CRYPTO_RNG
+	---help---
+	  This driver provides kernel-side support through the
+	  cryptographic API for the pseudo random number generator hardware
+	  found on Exynos SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called exynos-rng.
+
+	  If unsure, say Y.
+
 config CRYPTO_DEV_S5P
 	tristate "Support for Samsung S5PV210/Exynos crypto accelerator"
 	depends on ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST

index 41ca339e89d3..9603f1862b30 100644
@@ -6,6 +6,7 @@ obj-$(CONFIG_CRYPTO_DEV_CAVIUM_ZIP) += cavium/
 obj-$(CONFIG_CRYPTO_DEV_CCP) += ccp/
 obj-$(CONFIG_CRYPTO_DEV_CHELSIO) += chelsio/
 obj-$(CONFIG_CRYPTO_DEV_CPT) += cavium/cpt/
+obj-$(CONFIG_CRYPTO_DEV_EXYNOS_RNG) += exynos-rng.o
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM) += caam/
 obj-$(CONFIG_CRYPTO_DEV_GEODE) += geode-aes.o
 obj-$(CONFIG_CRYPTO_DEV_HIFN_795X) += hifn_795x.o

2.9.3

All applied. Thanks.

Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt