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2022-11-18hwrng: core - treat default_quality as a maximum and default to 1024Jason A. Donenfeld1-1/+1
Most hw_random devices return entropy which is assumed to be of full quality, but driver authors don't bother setting the quality knob. Some hw_random devices return less than full quality entropy, and then driver authors set the quality knob. Therefore, the entropy crediting should be opt-out rather than opt-in per-driver, to reflect the actual reality on the ground. For example, the two Raspberry Pi RNG drivers produce full entropy randomness, and both EDK2 and U-Boot's drivers for these treat them as such. The result is that EFI then uses these numbers and passes the to Linux, and Linux credits them as boot, thereby initializing the RNG. Yet, in Linux, the quality knob was never set to anything, and so on the chance that Linux is booted without EFI, nothing is ever credited. That's annoying. The same pattern appears to repeat itself throughout various drivers. In fact, very very few drivers have bothered setting quality=1024. Looking at the git history of existing drivers and corresponding mailing list discussion, this conclusion tracks. There's been a decent amount of discussion about drivers that set quality < 1024 -- somebody read and interepreted a datasheet, or made some back of the envelope calculation somehow. But there's been very little, if any, discussion about most drivers where the quality is just set to 1024 or unset (or set to 1000 when the authors misunderstood the API and assumed it was base-10 rather than base-2); in both cases the intent was fairly clear of, "this is a hardware random device; it's fine." So let's invert this logic. A hw_random struct's quality knob now controls the maximum quality a driver can produce, or 0 to specify 1024. Then, the module-wide switch called "default_quality" is changed to represent the maximum quality of any driver. By default it's 1024, and the quality of any particular driver is then given by: min(default_quality, rng->quality ?: 1024); This way, the user can still turn this off for weird reasons (and we can replace whatever driver-specific disabling hacks existed in the past), yet we get proper crediting for relevant RNGs. Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2022-08-19hwrng: core - let sleep be interrupted when unregistering hwrngJason A. Donenfeld1-0/+3
There are two deadlock scenarios that need addressing, which cause problems when the computer goes to sleep, the interface is set down, and hwrng_unregister() is called. When the deadlock is hit, sleep is delayed for tens of seconds, causing it to fail. These scenarios are: 1) The hwrng kthread can't be stopped while it's sleeping, because it uses msleep_interruptible() which does not react to kthread_stop. 2) A normal user thread can't be interrupted by hwrng_unregister() while it's sleeping, because hwrng_unregister() is called from elsewhere. We solve both issues by add a completion object called dying that fulfils waiters once we have started the process in hwrng_unregister. At the same time, we should cleanup a common and useless dmesg splat in the same area. Cc: <stable@vger.kernel.org> Reported-by: Gregory Erwin <gregerwin256@gmail.com> Fixes: fcd09c90c3c5 ("ath9k: use hw_random API instead of directly dumping into random.c") Link: https://lore.kernel.org/all/CAO+Okf6ZJC5-nTE_EJUGQtd8JiCkiEHytGgDsFGTEjs0c00giw@mail.gmail.com/ Link: https://lore.kernel.org/lkml/CAO+Okf5k+C+SE6pMVfPf-d8MfVPVq4PO7EY8Hys_DVXtent3HA@mail.gmail.com/ Link: https://bugs.archlinux.org/task/75138 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Toke Høiland-Jørgensen <toke@toke.dk> Acked-by: Kalle Valo <kvalo@kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2022-02-21random: pull add_hwgenerator_randomness() declaration into random.hJason A. Donenfeld1-2/+0
add_hwgenerator_randomness() is a function implemented and documented inside of random.c. It is the way that hardware RNGs push data into it. Therefore, it should be declared in random.h. Otherwise sparse complains with: random.c:1137:6: warning: symbol 'add_hwgenerator_randomness' was not declared. Should it be static? The alternative would be to include hw_random.h into random.c, but that wouldn't really be good for anything except slowing down compile time. Cc: Matt Mackall <mpm@selenic.com> Cc: Theodore Ts'o <tytso@mit.edu> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Reviewed-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-02-21random: make more consistent use of integer typesJason A. Donenfeld1-1/+1
We've been using a flurry of int, unsigned int, size_t, and ssize_t. Let's unify all of this into size_t where it makes sense, as it does in most places, and leave ssize_t for return values with possible errors. In addition, keeping with the convention of other functions in this file, functions that are dealing with raw bytes now take void * consistently instead of a mix of that and u8 *, because much of the time we're actually passing some other structure that is then interpreted as bytes by the function. We also take the opportunity to fix the outdated and incorrect comment in get_random_bytes_arch(). Cc: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Reviewed-by: Jann Horn <jannh@google.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2019-07-15docs: admin-guide: add a series of orphaned documentsMauro Carvalho Chehab1-1/+1
There are lots of documents that belong to the admin-guide but are on random places (most under Documentation root dir). Move them to the admin guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
2018-10-05hwrng: core - document the quality fieldMichael S. Tsirkin1-1/+2
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: 0f734e6e768 ("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>
2016-11-21hwrng: Make explicit that max >= 32 alwaysPrasannaKumar Muralidharan1-2/+1
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>
2016-08-24hwrng: core - Improve description of the ->read() interfaceDaniel Thompson1-1/+3
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>
2015-03-16hwrng: add devm_* interfacesDmitry Torokhov1-0/+4
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>
2014-12-26hwrng: core - Use struct completion for cleanup_doneHerbert Xu1-1/+2
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>
2014-12-22hwrng: fix unregister race.Rusty Russell1-0/+1
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>
2014-12-22hwrng: use reference counts on each struct hwrng.Rusty Russell1-0/+2
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>
2014-07-15hwrng: add per-device entropy deratingTorsten Duwe1-0/+3
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>
2014-07-15random: add_hwgenerator_randomness() for feeding entropy from devicesTorsten Duwe1-0/+2
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>
2011-05-25hwrng: fix spelling mistake in header commentSasha Levin1-1/+1
Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Matt Mackall <mpm@selenic.com> Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2009-12-01hwrng: core - Replace u32 in driver API with byte arrayIan Molton1-2/+5
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>
2008-04-30Remove "#ifdef __KERNEL__" checks from unexported headersRobert P. J. Day1-2/+0
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>
2008-04-20PM: Remove destroy_suspended_device()Rafael J. Wysocki1-9/+1
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>
2008-02-05HWRNG: add possibility to remove hwrng devices during suspend/resumeRafael J. Wysocki1-1/+9
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>
2008-01-11[HWRNG]: move status polling loop to data_present callbacksPatrick McHardy1-1/+1
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>
2006-06-26[PATCH] Add new generic HW RNG coreMichael Buesch1-0/+50
Signed-off-by: Michael Buesch <mb@bu3sch.de> Cc: Jeff Garzik <jeff@garzik.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>