From db516da95ce458f0cab5e7ae2db93fd821484d7d Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sun, 6 Nov 2022 16:02:43 +0100 Subject: [PATCH] hw_random: use add_hwgenerator_randomness() for early entropy Rather than calling add_device_randomness(), the add_early_randomness() function should use add_hwgenerator_randomness(), so that the early entropy can be potentially credited, which allows for the RNG to initialize earlier without having to wait for the kthread to come up. This requires some minor API refactoring, by adding a `sleep_after` parameter to add_hwgenerator_randomness(), so that we don't hit a blocking sleep from add_early_randomness(). Tested-by: AngeloGioacchino Del Regno Tested-by: Marek Szyprowski Reviewed-by: AngeloGioacchino Del Regno Reviewed-by: Dominik Brodowski Acked-by: Herbert Xu Signed-off-by: Jason A. Donenfeld --- drivers/char/hw_random/core.c | 8 +++++--- drivers/char/random.c | 12 ++++++------ include/linux/random.h | 2 +- 3 files changed, 12 insertions(+), 10 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index cc002b0c2f0c..63a0a8e4505d 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -69,8 +69,10 @@ static void add_early_randomness(struct hwrng *rng) mutex_lock(&reading_mutex); bytes_read = rng_get_data(rng, rng_fillbuf, 32, 0); mutex_unlock(&reading_mutex); - if (bytes_read > 0) - add_device_randomness(rng_fillbuf, bytes_read); + if (bytes_read > 0) { + size_t entropy = bytes_read * 8 * rng->quality / 1024; + add_hwgenerator_randomness(rng_fillbuf, bytes_read, entropy, false); + } } static inline void cleanup_rng(struct kref *kref) @@ -528,7 +530,7 @@ static int hwrng_fillfn(void *unused) /* Outside lock, sure, but y'know: randomness. */ add_hwgenerator_randomness((void *)rng_fillbuf, rc, - entropy >> 10); + entropy >> 10, true); } hwrng_fill = NULL; return 0; diff --git a/drivers/char/random.c b/drivers/char/random.c index a8476154d47e..94990b052f58 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -727,7 +727,7 @@ static void __cold _credit_init_bits(size_t bits) * the above entropy accumulation routines: * * void add_device_randomness(const void *buf, size_t len); - * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy); + * void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after); * void add_bootloader_randomness(const void *buf, size_t len); * void add_vmfork_randomness(const void *unique_vm_id, size_t len); * void add_interrupt_randomness(int irq); @@ -907,11 +907,11 @@ void add_device_randomness(const void *buf, size_t len) EXPORT_SYMBOL(add_device_randomness); /* - * Interface for in-kernel drivers of true hardware RNGs. - * Those devices may produce endless random bits and will be throttled - * when our pool is full. + * Interface for in-kernel drivers of true hardware RNGs. Those devices + * may produce endless random bits, so this function will sleep for + * some amount of time after, if the sleep_after parameter is true. */ -void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy) +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after) { mix_pool_bytes(buf, len); credit_init_bits(entropy); @@ -920,7 +920,7 @@ void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy) * Throttle writing to once every reseed interval, unless we're not yet * initialized or no entropy is credited. */ - if (!kthread_should_stop() && (crng_ready() || !entropy)) + if (sleep_after && !kthread_should_stop() && (crng_ready() || !entropy)) schedule_timeout_interruptible(crng_reseed_interval()); } EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); diff --git a/include/linux/random.h b/include/linux/random.h index 9455d93f5ba3..3b028c7ca065 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -17,7 +17,7 @@ void __init add_bootloader_randomness(const void *buf, size_t len); void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) __latent_entropy; void add_interrupt_randomness(int irq) __latent_entropy; -void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy); +void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after); #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) static inline void add_latent_entropy(void)