[PATCH] crypto: exynos-rng - Remove exynos-rng driver

[PATCH] crypto: exynos-rng - Remove exynos-rng driver

[Eric Biggers]

This driver has no purpose.  It doesn't feed into the Linux RNG, nor
does it implement the hwrng interface.  It is accessible only via the
"rng" algorithm type of AF_ALG, which isn't used in practice.  Everyone
uses either the Linux RNG, or rarely /dev/hwrng.

Moreover, this is a PRNG whose only source of entropy is the 160-bit
seed the user passes in.  So this can be used only by a user who already
has a source of cryptographically secure random numbers, such as
/dev/random.  Which they can, and do, just use in the first place.

Just remove this driver.  There's no need to keep useless code around.

Note that the other crypto_rng drivers in drivers/crypto/ are similarly
unused and are being removed too.  This commit just handles exynos-rng.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 MAINTAINERS                         |   8 -
 arch/arm/configs/exynos_defconfig   |   1 -
 arch/arm/configs/multi_v7_defconfig |   1 -
 drivers/crypto/Kconfig              |  18 --
 drivers/crypto/Makefile             |   1 -
 drivers/crypto/exynos-rng.c         | 399 ----------------------------
 6 files changed, 428 deletions(-)
 delete mode 100644 drivers/crypto/exynos-rng.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 882214b0e7db..a7f2762baac1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23701,18 +23701,10 @@ L:	linux-samsung-soc@vger.kernel.org
 S:	Supported
 F:	Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml
 F:	drivers/mailbox/exynos-mailbox.c
 F:	include/linux/mailbox/exynos-message.h
 
-SAMSUNG EXYNOS PSEUDO RANDOM NUMBER GENERATOR (RNG) DRIVER
-M:	Krzysztof Kozlowski <krzk@kernel.org>
-L:	linux-crypto@vger.kernel.org
-L:	linux-samsung-soc@vger.kernel.org
-S:	Maintained
-F:	Documentation/devicetree/bindings/rng/samsung,exynos4-rng.yaml
-F:	drivers/crypto/exynos-rng.c
-
 SAMSUNG EXYNOS TRUE RANDOM NUMBER GENERATOR (TRNG) DRIVER
 M:	Łukasz Stelmach <l.stelmach@samsung.com>
 L:	linux-samsung-soc@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/rng/samsung,exynos5250-trng.yaml
diff --git a/arch/arm/configs/exynos_defconfig b/arch/arm/configs/exynos_defconfig
index 84070e9698e8..8b072a5c0a5e 100644
--- a/arch/arm/configs/exynos_defconfig
+++ b/arch/arm/configs/exynos_defconfig
@@ -362,11 +362,10 @@ CONFIG_CRYPTO_LZ4=m
 CONFIG_CRYPTO_USER_API_HASH=m
 CONFIG_CRYPTO_USER_API_SKCIPHER=m
 CONFIG_CRYPTO_USER_API_RNG=m
 CONFIG_CRYPTO_USER_API_AEAD=m
 CONFIG_CRYPTO_AES_ARM_BS=m
-CONFIG_CRYPTO_DEV_EXYNOS_RNG=y
 CONFIG_CRYPTO_DEV_S5P=y
 CONFIG_DMA_CMA=y
 CONFIG_CMA_SIZE_MBYTES=96
 CONFIG_FONTS=y
 CONFIG_FONT_7x14=y
diff --git a/arch/arm/configs/multi_v7_defconfig b/arch/arm/configs/multi_v7_defconfig
index bcc9aabc1202..3672dd12df60 100644
--- a/arch/arm/configs/multi_v7_defconfig
+++ b/arch/arm/configs/multi_v7_defconfig
@@ -1327,11 +1327,10 @@ CONFIG_CRYPTO_GHASH_ARM_CE=m
 CONFIG_CRYPTO_AES=m
 CONFIG_CRYPTO_AES_ARM_BS=m
 CONFIG_CRYPTO_AES_ARM_CE=m
 CONFIG_CRYPTO_DEV_SUN4I_SS=m
 CONFIG_CRYPTO_DEV_FSL_CAAM=m
-CONFIG_CRYPTO_DEV_EXYNOS_RNG=m
 CONFIG_CRYPTO_DEV_S5P=m
 CONFIG_CRYPTO_DEV_ATMEL_AES=m
 CONFIG_CRYPTO_DEV_ATMEL_TDES=m
 CONFIG_CRYPTO_DEV_ATMEL_SHA=m
 CONFIG_CRYPTO_DEV_MARVELL_CESA=m
diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index 3449b3c9c6ad..39c7b195bb33 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -373,25 +373,10 @@ config CRYPTO_DEV_SAHARA
 	select CRYPTO_ENGINE
 	help
 	  This option enables support for the SAHARA HW crypto accelerator
 	  found in some Freescale i.MX 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
 	depends on HAS_IOMEM
 	select CRYPTO_AES
@@ -402,20 +387,17 @@ config CRYPTO_DEV_S5P
 	  algorithms execution.
 
 config CRYPTO_DEV_EXYNOS_HASH
 	bool "Support for Samsung Exynos HASH accelerator"
 	depends on CRYPTO_DEV_S5P
-	depends on !CRYPTO_DEV_EXYNOS_RNG && CRYPTO_DEV_EXYNOS_RNG!=m
 	select CRYPTO_SHA1
 	select CRYPTO_MD5
 	select CRYPTO_SHA256
 	help
 	  Select this to offload Exynos from HASH MD5/SHA1/SHA256.
 	  This will select software SHA1, MD5 and SHA256 as they are
 	  needed for small and zero-size messages.
-	  HASH algorithms will be disabled if EXYNOS_RNG
-	  is enabled due to hw conflict.
 
 config CRYPTO_DEV_NX
 	bool "Support for IBM PowerPC Nest (NX) cryptographic acceleration"
 	depends on PPC64
 	help
diff --git a/drivers/crypto/Makefile b/drivers/crypto/Makefile
index 283bbc650b5b..e141ab0dd741 100644
--- a/drivers/crypto/Makefile
+++ b/drivers/crypto/Makefile
@@ -9,11 +9,10 @@ obj-$(CONFIG_CRYPTO_DEV_ATMEL_I2C) += atmel-i2c.o
 obj-$(CONFIG_CRYPTO_DEV_ATMEL_ECC) += atmel-ecc.o
 obj-$(CONFIG_CRYPTO_DEV_ATMEL_SHA204A) += atmel-sha204a.o
 obj-$(CONFIG_CRYPTO_DEV_CCP) += ccp/
 obj-$(CONFIG_CRYPTO_DEV_CCREE) += ccree/
 obj-$(CONFIG_CRYPTO_DEV_CHELSIO) += chelsio/
-obj-$(CONFIG_CRYPTO_DEV_EXYNOS_RNG) += exynos-rng.o
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM_COMMON) += caam/
 obj-$(CONFIG_CRYPTO_DEV_GEODE) += geode-aes.o
 obj-$(CONFIG_CRYPTO_DEV_HIFN_795X) += hifn_795x.o
 obj-$(CONFIG_CRYPTO_DEV_IMGTEC_HASH) += img-hash.o
 obj-$(CONFIG_CRYPTO_DEV_MARVELL) += marvell/
diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c
deleted file mode 100644
index 2aaa98f9b44e..000000000000
--- a/drivers/crypto/exynos-rng.c
+++ /dev/null
@@ -1,399 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * exynos-rng.c - Random Number Generator driver for the Exynos
- *
- * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org>
- *
- * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c:
- * Copyright (C) 2012 Samsung Electronics
- * Jonghwa Lee <jonghwa3.lee@samsung.com>
- */
-
-#include <linux/clk.h>
-#include <linux/crypto.h>
-#include <linux/err.h>
-#include <linux/io.h>
-#include <linux/module.h>
-#include <linux/mutex.h>
-#include <linux/of.h>
-#include <linux/platform_device.h>
-
-#include <crypto/internal/rng.h>
-
-#define EXYNOS_RNG_CONTROL		0x0
-#define EXYNOS_RNG_STATUS		0x10
-
-#define EXYNOS_RNG_SEED_CONF		0x14
-#define EXYNOS_RNG_GEN_PRNG	        BIT(1)
-
-#define EXYNOS_RNG_SEED_BASE		0x140
-#define EXYNOS_RNG_SEED(n)		(EXYNOS_RNG_SEED_BASE + (n * 0x4))
-#define EXYNOS_RNG_OUT_BASE		0x160
-#define EXYNOS_RNG_OUT(n)		(EXYNOS_RNG_OUT_BASE + (n * 0x4))
-
-/* EXYNOS_RNG_CONTROL bit fields */
-#define EXYNOS_RNG_CONTROL_START	0x18
-/* EXYNOS_RNG_STATUS bit fields */
-#define EXYNOS_RNG_STATUS_SEED_SETTING_DONE	BIT(1)
-#define EXYNOS_RNG_STATUS_RNG_DONE		BIT(5)
-
-/* Five seed and output registers, each 4 bytes */
-#define EXYNOS_RNG_SEED_REGS		5
-#define EXYNOS_RNG_SEED_SIZE		(EXYNOS_RNG_SEED_REGS * 4)
-
-enum exynos_prng_type {
-	EXYNOS_PRNG_UNKNOWN = 0,
-	EXYNOS_PRNG_EXYNOS4,
-	EXYNOS_PRNG_EXYNOS5,
-};
-
-/*
- * Driver re-seeds itself with generated random numbers to hinder
- * backtracking of the original seed.
- *
- * Time for next re-seed in ms.
- */
-#define EXYNOS_RNG_RESEED_TIME		1000
-#define EXYNOS_RNG_RESEED_BYTES		65536
-
-/*
- * In polling mode, do not wait infinitely for the engine to finish the work.
- */
-#define EXYNOS_RNG_WAIT_RETRIES		100
-
-/* Context for crypto */
-struct exynos_rng_ctx {
-	struct exynos_rng_dev		*rng;
-};
-
-/* Device associated memory */
-struct exynos_rng_dev {
-	struct device			*dev;
-	enum exynos_prng_type		type;
-	void __iomem			*mem;
-	struct clk			*clk;
-	struct mutex 			lock;
-	/* Generated numbers stored for seeding during resume */
-	u8				seed_save[EXYNOS_RNG_SEED_SIZE];
-	unsigned int			seed_save_len;
-	/* Time of last seeding in jiffies */
-	unsigned long			last_seeding;
-	/* Bytes generated since last seeding */
-	unsigned long			bytes_seeding;
-};
-
-static struct exynos_rng_dev *exynos_rng_dev;
-
-static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
-{
-	return readl_relaxed(rng->mem + offset);
-}
-
-static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset)
-{
-	writel_relaxed(val, rng->mem + offset);
-}
-
-static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
-			       const u8 *seed, unsigned int slen)
-{
-	u32 val;
-	int i;
-
-	/* Round seed length because loop iterates over full register size */
-	slen = ALIGN_DOWN(slen, 4);
-
-	if (slen < EXYNOS_RNG_SEED_SIZE)
-		return -EINVAL;
-
-	for (i = 0; i < slen ; i += 4) {
-		unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS;
-
-		val = seed[i] << 24;
-		val |= seed[i + 1] << 16;
-		val |= seed[i + 2] << 8;
-		val |= seed[i + 3] << 0;
-
-		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg));
-	}
-
-	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
-	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
-		dev_warn(rng->dev, "Seed setting not finished\n");
-		return -EIO;
-	}
-
-	rng->last_seeding = jiffies;
-	rng->bytes_seeding = 0;
-
-	return 0;
-}
-
-/*
- * Start the engine and poll for finish.  Then read from output registers
- * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated
- * random data (EXYNOS_RNG_SEED_SIZE).
- *
- * On success: return 0 and store number of read bytes under 'read' address.
- * On error: return -ERRNO.
- */
-static int exynos_rng_get_random(struct exynos_rng_dev *rng,
-				 u8 *dst, unsigned int dlen,
-				 unsigned int *read)
-{
-	int retry = EXYNOS_RNG_WAIT_RETRIES;
-
-	if (rng->type == EXYNOS_PRNG_EXYNOS4) {
-		exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
-				  EXYNOS_RNG_CONTROL);
-	} else if (rng->type == EXYNOS_PRNG_EXYNOS5) {
-		exynos_rng_writel(rng, EXYNOS_RNG_GEN_PRNG,
-				  EXYNOS_RNG_SEED_CONF);
-	}
-
-	while (!(exynos_rng_readl(rng,
-			EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
-		cpu_relax();
-
-	if (!retry)
-		return -ETIMEDOUT;
-
-	/* Clear status bit */
-	exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
-			  EXYNOS_RNG_STATUS);
-	*read = min_t(size_t, dlen, EXYNOS_RNG_SEED_SIZE);
-	memcpy_fromio(dst, rng->mem + EXYNOS_RNG_OUT_BASE, *read);
-	rng->bytes_seeding += *read;
-
-	return 0;
-}
-
-/* Re-seed itself from time to time */
-static void exynos_rng_reseed(struct exynos_rng_dev *rng)
-{
-	unsigned long next_seeding = rng->last_seeding + \
-				     msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME);
-	unsigned long now = jiffies;
-	unsigned int read = 0;
-	u8 seed[EXYNOS_RNG_SEED_SIZE];
-
-	if (time_before(now, next_seeding) &&
-	    rng->bytes_seeding < EXYNOS_RNG_RESEED_BYTES)
-		return;
-
-	if (exynos_rng_get_random(rng, seed, sizeof(seed), &read))
-		return;
-
-	exynos_rng_set_seed(rng, seed, read);
-
-	/* Let others do some of their job. */
-	mutex_unlock(&rng->lock);
-	mutex_lock(&rng->lock);
-}
-
-static int exynos_rng_generate(struct crypto_rng *tfm,
-			       const u8 *src, unsigned int slen,
-			       u8 *dst, unsigned int dlen)
-{
-	struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
-	struct exynos_rng_dev *rng = ctx->rng;
-	unsigned int read = 0;
-	int ret;
-
-	ret = clk_prepare_enable(rng->clk);
-	if (ret)
-		return ret;
-
-	mutex_lock(&rng->lock);
-	do {
-		ret = exynos_rng_get_random(rng, dst, dlen, &read);
-		if (ret)
-			break;
-
-		dlen -= read;
-		dst += read;
-
-		exynos_rng_reseed(rng);
-	} while (dlen > 0);
-	mutex_unlock(&rng->lock);
-
-	clk_disable_unprepare(rng->clk);
-
-	return ret;
-}
-
-static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
-			   unsigned int slen)
-{
-	struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
-	struct exynos_rng_dev *rng = ctx->rng;
-	int ret;
-
-	ret = clk_prepare_enable(rng->clk);
-	if (ret)
-		return ret;
-
-	mutex_lock(&rng->lock);
-	ret = exynos_rng_set_seed(ctx->rng, seed, slen);
-	mutex_unlock(&rng->lock);
-
-	clk_disable_unprepare(rng->clk);
-
-	return ret;
-}
-
-static int exynos_rng_kcapi_init(struct crypto_tfm *tfm)
-{
-	struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm);
-
-	ctx->rng = exynos_rng_dev;
-
-	return 0;
-}
-
-static struct rng_alg exynos_rng_alg = {
-	.generate		= exynos_rng_generate,
-	.seed			= exynos_rng_seed,
-	.seedsize		= EXYNOS_RNG_SEED_SIZE,
-	.base			= {
-		.cra_name		= "stdrng",
-		.cra_driver_name	= "exynos_rng",
-		.cra_priority		= 300,
-		.cra_ctxsize		= sizeof(struct exynos_rng_ctx),
-		.cra_module		= THIS_MODULE,
-		.cra_init		= exynos_rng_kcapi_init,
-	}
-};
-
-static int exynos_rng_probe(struct platform_device *pdev)
-{
-	struct exynos_rng_dev *rng;
-	int ret;
-
-	if (exynos_rng_dev)
-		return -EEXIST;
-
-	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
-	if (!rng)
-		return -ENOMEM;
-
-	rng->type = (uintptr_t)of_device_get_match_data(&pdev->dev);
-
-	mutex_init(&rng->lock);
-
-	rng->dev = &pdev->dev;
-	rng->clk = devm_clk_get(&pdev->dev, "secss");
-	if (IS_ERR(rng->clk)) {
-		dev_err(&pdev->dev, "Couldn't get clock.\n");
-		return PTR_ERR(rng->clk);
-	}
-
-	rng->mem = devm_platform_ioremap_resource(pdev, 0);
-	if (IS_ERR(rng->mem))
-		return PTR_ERR(rng->mem);
-
-	platform_set_drvdata(pdev, rng);
-
-	exynos_rng_dev = rng;
-
-	ret = crypto_register_rng(&exynos_rng_alg);
-	if (ret) {
-		dev_err(&pdev->dev,
-			"Couldn't register rng crypto alg: %d\n", ret);
-		exynos_rng_dev = NULL;
-	}
-
-	return ret;
-}
-
-static void exynos_rng_remove(struct platform_device *pdev)
-{
-	crypto_unregister_rng(&exynos_rng_alg);
-
-	exynos_rng_dev = NULL;
-}
-
-static int __maybe_unused exynos_rng_suspend(struct device *dev)
-{
-	struct exynos_rng_dev *rng = dev_get_drvdata(dev);
-	int ret;
-
-	/* If we were never seeded then after resume it will be the same */
-	if (!rng->last_seeding)
-		return 0;
-
-	rng->seed_save_len = 0;
-	ret = clk_prepare_enable(rng->clk);
-	if (ret)
-		return ret;
-
-	mutex_lock(&rng->lock);
-
-	/* Get new random numbers and store them for seeding on resume. */
-	exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save),
-			      &(rng->seed_save_len));
-
-	mutex_unlock(&rng->lock);
-
-	dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n",
-		rng->seed_save_len);
-
-	clk_disable_unprepare(rng->clk);
-
-	return 0;
-}
-
-static int __maybe_unused exynos_rng_resume(struct device *dev)
-{
-	struct exynos_rng_dev *rng = dev_get_drvdata(dev);
-	int ret;
-
-	/* Never seeded so nothing to do */
-	if (!rng->last_seeding)
-		return 0;
-
-	ret = clk_prepare_enable(rng->clk);
-	if (ret)
-		return ret;
-
-	mutex_lock(&rng->lock);
-
-	ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);
-
-	mutex_unlock(&rng->lock);
-
-	clk_disable_unprepare(rng->clk);
-
-	return ret;
-}
-
-static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend,
-			 exynos_rng_resume);
-
-static const struct of_device_id exynos_rng_dt_match[] = {
-	{
-		.compatible = "samsung,exynos4-rng",
-		.data = (const void *)EXYNOS_PRNG_EXYNOS4,
-	}, {
-		.compatible = "samsung,exynos5250-prng",
-		.data = (const void *)EXYNOS_PRNG_EXYNOS5,
-	},
-	{ },
-};
-MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
-
-static struct platform_driver exynos_rng_driver = {
-	.driver		= {
-		.name	= "exynos-rng",
-		.pm	= &exynos_rng_pm_ops,
-		.of_match_table = exynos_rng_dt_match,
-	},
-	.probe		= exynos_rng_probe,
-	.remove		= exynos_rng_remove,
-};
-
-module_platform_driver(exynos_rng_driver);
-
-MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver");
-MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>");
-MODULE_LICENSE("GPL v2");

base-commit: 5624ea54f3ba5c83d2e5503411a31a8be0278c1e
-- 
2.54.0