quality field is currently documented as being 'per mill'. In fact the
math involved is:
add_hwgenerator_randomness((void *)rng_fillbuf, rc,
rc * current_quality * 8 >> 10);
thus the actual definition is "bits of entropy per 1024 bits of input".
The current documentation seems to have confused multiple people
in the past, let's fix the documentation to match code.
An alternative is to change core to match driver expectations, replacing
rc * current_quality * 8 >> 10
with
rc * current_quality / 1000
but that has performance costs, so probably isn't a good option.
Fixes: 0f734e6e76 ("hwrng: add per-device entropy derating")
Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As hw_random core calls ->read with max > 32 or more, make it explicit.
Also remove checks involving 'max' being less than 8.
Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Currently, very few RNG drivers support single byte reads using the
->read() interface. Of the 14 drivers in drivers/char/hw_random that
support this interface only three of these actually support max == 1.
The other behaviours vary between return 0, return 2, return 4 and return
-EIO).
This is not a problem in practice because the core hw_random code never
performs a read shorter than 16 bytes. The documentation for this function
already contrains the alignment of the buffer pointer, so let's also
guarantee that the buffer is at least as large as its alignment.
This constraint is intended to be the weakest guarantee neccessary to
allow driver writers to safely simplify their code.
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This change adds devm_hwrng_register and devm_hwrng_unregister which
use can simplify error unwinding and unbinding code paths in device
drivers.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
There is no point in doing a manual completion for cleanup_done
when struct completion fits in perfectly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The previous patch added one potential problem: we can still be
reading from a hwrng when it's unregistered. Add a wait for zero
in the hwrng_unregister path.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
current_rng holds one reference, and we bump it every time we want
to do a read from it.
This means we only hold the rng_mutex to grab or drop a reference,
so accessing /sys/devices/virtual/misc/hw_random/rng_current doesn't
block on read of /dev/hwrng.
Using a kref is overkill (we're always under the rng_mutex), but
a standard pattern.
This also solves the problem that the hwrng_fillfn thread was
accessing current_rng without a lock, which could change (eg. to NULL)
underneath it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch introduces a derating factor to struct hwrng for
the random bits going into the kernel input pool, and a common
default derating for drivers which do not specify one.
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
This patch adds an interface to the random pool for feeding entropy
in-kernel.
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
This patch implements a new method by which hw_random hardware drivers
can pass data to the core more efficiently, using a shared buffer.
The old methods have been retained as a compatability layer until all the
drivers have been updated.
Signed-off-by: Ian Molton <ian.molton@collabora.co.uk>
Acked-by: Matt Mackall <mpm@selenic.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Remove the "#ifdef __KERNEL__" tests from unexported header files in
linux/include whose entire contents are wrapped in that preprocessor
test.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After 2.6.24 there was a plan to make the PM core acquire all device
semaphores during a suspend/hibernation to protect itself from
concurrent operations involving device objects. That proved to be
too heavy-handed and we found a better way to achieve the goal, but
before it happened, we had introduced the functions
device_pm_schedule_removal() and destroy_suspended_device() to allow
drivers to "safely" destroy a suspended device and we had adapted some
drivers to use them. Now that these functions are no longer necessary,
it seems reasonable to remove them and modify their users to use the
normal device unregistration instead.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Make it possible to unregister a Hardware Random Number Generator
device object in a safe way during a suspend/resume cycle.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Michael Buesch <mb@bu3sch.de>
Cc: Michael Buesch <mb@bu3sch.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "John W. Linville" <linville@tuxdriver.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Len Brown <lenb@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Handle waiting for new random within the drivers themselves, this allows to
use better suited timeouts for the individual rngs.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Michael S. Tsirkin