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Commit 25cf7f06 authored by Łukasz Stelmach's avatar Łukasz Stelmach Committed by Herbert Xu
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crypto: exynos - Introduce mutex to prevent concurrent access to hardware 



Hardware operations like reading random numbers and setting a seed need
to be conducted in a single thread. Therefore a mutex is required to
prevent multiple threads (processes) from accessing the hardware at the
same time.

The sequence of mutex_lock() and mutex_unlock() in the exynos_rng_reseed()
function enables switching between different threads waiting for the
driver to generate random numbers for them.

Signed-off-by: default avatarŁukasz Stelmach <l.stelmach@samsung.com>
Reviewed-by: default avatarKrzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 99c9acfe

drivers/crypto/exynos-rng.c

+21 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/err.h>

#include <linux/io.h>

#include <linux/module.h>

#include <linux/mutex.h>

#include <linux/of_device.h>

#include <linux/platform_device.h>
@@ -79,6 +80,7 @@ struct exynos_rng_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;
@@ -191,6 +193,10 @@ static void exynos_rng_reseed(struct exynos_rng_dev *rng) 
		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,
@@ -206,6 +212,7 @@ static int exynos_rng_generate(struct crypto_rng *tfm, 
	if (ret)

		return ret;



	mutex_lock(&rng->lock);

	do {

		ret = exynos_rng_get_random(rng, dst, dlen, &read);

		if (ret)
@@ -216,6 +223,7 @@ static int exynos_rng_generate(struct crypto_rng *tfm, 


		exynos_rng_reseed(rng);

	} while (dlen > 0);

	mutex_unlock(&rng->lock);



	clk_disable_unprepare(rng->clk);
@@ -233,7 +241,9 @@ static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed, 
	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);
@@ -278,6 +288,8 @@ static int exynos_rng_probe(struct platform_device *pdev) 


	rng->type = (enum exynos_prng_type)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)) {
@@ -328,9 +340,14 @@ static int __maybe_unused exynos_rng_suspend(struct device *dev) 
	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);
@@ -353,8 +370,12 @@ static int __maybe_unused exynos_rng_resume(struct device *dev) 
	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;