From: "H. Peter Anvin" <[email protected]> If we have arch_get_random_seed*(), try to use it for emergency refill of the entropy pool before giving up and blocking on /dev/random. It may or may not work in the moment, but if it does work, it will give the user better service than blocking will.
Signed-off-by: H. Peter Anvin <[email protected]> Acked-by: Ingo Molnar <[email protected]> --- drivers/char/random.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index b1d5ae2..f13f04b 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1297,6 +1297,34 @@ void rand_initialize_disk(struct gendisk *disk) } #endif +/* + * Attempt an emergency refill using arch_get_random_seed_long(). + * + * As with add_interrupt_randomness() be paranoid and only + * credit the output as 50% entropic. + */ +static int arch_random_refill(void) +{ + const unsigned int nlongs = 64; /* Arbitrary number */ + unsigned int n = 0; + unsigned int i; + unsigned long buf[nlongs]; + + for (i = 0; i < nlongs; i++) { + if (arch_get_random_seed_long(&buf[n])) + n++; + } + + if (n) { + unsigned int rand_bytes = n * sizeof(unsigned long); + + mix_pool_bytes(&input_pool, buf, rand_bytes, NULL); + credit_entropy_bits(&input_pool, rand_bytes*4); + } + + return n; +} + static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { @@ -1322,6 +1350,10 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) ENTROPY_BITS(&input_pool)); if (n == 0) { + /* Try an emergency refill */ + if (arch_random_refill()) + continue; + if (file->f_flags & O_NONBLOCK) { retval = -EAGAIN; break; -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
