[RFC PATCH 1/3] hw_random: allow RNG devices to give early randomness after a delay
From: Amit Shah <hidden>
Date: 2014-07-14 04:36:50
Also in:
lkml
Subsystem:
hardware random number generator core, the rest · Maintainers:
Olivia Mackall, Herbert Xu, Linus Torvalds
Some RNG devices may not be ready to give early randomness at probe() time, and hence lose out on the opportunity to contribute to system randomness at boot- or device hotplug- time. This commit schedules a delayed work item for such devices, and fetches early randomness after a delay. Currently the delay is 500ms, which is enough for the lone device that needs such treatment: virtio-rng. CC: Kees Cook <redacted> CC: Jason Cooper <redacted> CC: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Amit Shah <redacted> --- drivers/char/hw_random/core.c | 20 +++++++++++++++++++- include/linux/hw_random.h | 8 ++++++++ 2 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index c4419ea..2a765fd 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c@@ -63,7 +63,7 @@ static size_t rng_buffer_size(void) return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES; } -static void add_early_randomness(struct hwrng *rng) +static void get_early_randomness(struct hwrng *rng) { unsigned char bytes[16]; int bytes_read;
@@ -79,6 +79,21 @@ static void add_early_randomness(struct hwrng *rng) add_device_randomness(bytes, bytes_read); } +static void sched_init_random(struct work_struct *work) +{ + struct hwrng *rng = container_of(work, struct hwrng, dwork.work); + + get_early_randomness(rng); +} + +static void add_early_randomness(struct hwrng *rng) +{ + if (!(rng->flags & HWRNG_DELAY_READ_AT_INIT)) + return get_early_randomness(rng); + + schedule_delayed_work(&rng->dwork, msecs_to_jiffies(500)); +} + static inline int hwrng_init(struct hwrng *rng) { if (rng->init) {
@@ -351,6 +366,7 @@ int hwrng_register(struct hwrng *rng) goto out_unlock; } + INIT_DELAYED_WORK(&rng->dwork, sched_init_random); old_rng = current_rng; if (!old_rng) { err = hwrng_init(rng);
@@ -362,6 +378,7 @@ int hwrng_register(struct hwrng *rng) if (!old_rng) { err = register_miscdev(); if (err) { + cancel_delayed_work_sync(&rng->dwork); hwrng_cleanup(rng); current_rng = NULL; goto out_unlock;
@@ -395,6 +412,7 @@ void hwrng_unregister(struct hwrng *rng) mutex_lock(&rng_mutex); list_del(&rng->list); + cancel_delayed_work_sync(&rng->dwork); if (current_rng == rng) { hwrng_cleanup(rng); if (list_empty(&rng_list)) {
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index b4b0eef..8f7370d 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h@@ -14,6 +14,11 @@ #include <linux/types.h> #include <linux/list.h> +#include <linux/workqueue.h> + +#define HWRNG_DELAY_READ_AT_INIT BIT(0) /* Schedule delayed work to fetch + * initial randomness instead of doing + * it at ->init()-time */ /** * struct hwrng - Hardware Random Number Generator driver
@@ -28,6 +33,7 @@ * Must not be NULL. *OBSOLETE* * @read: New API. drivers can fill up to max bytes of data * into the buffer. The buffer is aligned for any type. + * @flags: Per-device flags. * @priv: Private data, for use by the RNG driver. */ struct hwrng {
@@ -37,9 +43,11 @@ struct hwrng { int (*data_present)(struct hwrng *rng, int wait); int (*data_read)(struct hwrng *rng, u32 *data); int (*read)(struct hwrng *rng, void *data, size_t max, bool wait); + unsigned int flags; unsigned long priv; /* internal. */ + struct delayed_work dwork; struct list_head list; };
--
1.9.3