The random longs to be pulled by arch_get_random_long() are
prepared in an 4K buffer which is filled from the NIST 800-90
compliant s390 drbg. By default the random long buffer is refilled
256 times before the drbg itself needs a reseed. The reseed of the
drbg is done with 32 bytes fetched from the high quality (but slow)
trng which is assumed to deliver 100% entropy. So the 32 * 8 = 256
bits of entropy are spread over 256 * 4KB = 1MB serving 131072
arch_get_random_long() invocations before reseeded.
How often the 4K random long buffer is refilled with the drbg
before the drbg is reseeded can be adjusted. There is a module
parameter 's390_arch_rnd_long_drbg_reseed' accessible via
/sys/module/arch_random/parameters/rndlong_drbg_reseed
or as kernel command line parameter
arch_random.rndlong_drbg_reseed=<value>
This parameter tells how often the drbg fills the 4K buffer before
it is re-seeded by fresh entropy from the trng.
A value of 16 results in reseeding the drbg at every 16 * 4 KB = 64
KB with 32 bytes of fresh entropy pulled from the trng. So a value
of 16 would result in 256 bits entropy per 64 KB.
A value of 256 results in 1MB of drbg output before a reseed of the
drbg is done. So this would spread the 256 bits of entropy among 1MB.
Setting this parameter to 0 forces the reseed to take place every
time the 4K buffer is depleted, so the entropy rises to 256 bits
entropy per 4K or 0.5 bit entropy per arch_get_random_long(). With
setting this parameter to negative values all this effort is
disabled, arch_get_random long() returns false and thus indicating
that the arch_get_random_long() feature is disabled at all.
arch_get_random_long() is used by random.c among others to provide
an initial hash value to be mixed with the entropy pool on every
random data pull. For about 64 bytes read from /dev/urandom there
is one call to arch_get_random_long(). So these additional random
long values count for performance of /dev/urandom with measurable
but low penalty.
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
We must not use the pointer output without validating the
success of the random read.
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200110145422.49141-11-broonie@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
These symbols are currently part of the generic archrandom.h
interface, but are currently unused and can be removed.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200110145422.49141-4-broonie@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
The arch_get_random_seed_long() invocation done by the random device
driver is done in interrupt context and may be invoked very very
frequently. The existing s390 arch_get_random_seed*() implementation
uses the PRNO(TRNG) instruction which produces excellent high quality
entropy but is relatively slow and thus expensive.
This fix reworks the arch_get_random_seed* implementation. It
introduces a buffer concept to decouple the delivery of random data
via arch_get_random_seed*() from the generation of new random
bytes. The buffer of random data is filled asynchronously by a
workqueue thread.
If there are enough bytes in the buffer the s390_arch_random_generate()
just delivers these bytes. Otherwise false is returned until the worker
thread refills the buffer.
The worker fills the rng buffer by pulling fresh entropy from the
high quality (but slow) true hardware random generator. This entropy
is then spread over the buffer with an pseudo random generator.
As the arch_get_random_seed_long() fetches 8 bytes and the calling
function add_interrupt_randomness() counts this as 1 bit entropy the
distribution needs to make sure there is in fact 1 bit entropy
contained in 8 bytes of the buffer. The current values pull 32 byte
entropy and scatter this into a 2048 byte buffer. So 8 byte in the
buffer will contain 1 bit of entropy.
The worker thread is rescheduled based on the charge level of the
buffer but at least with 500 ms delay to avoid too much cpu consumption.
So the max. amount of rng data delivered via arch_get_random_seed is
limited to 4Kb per second.
Signed-off-by: Harald Freudenberger <freude@de.ibm.com>
Reviewed-by: Patrick Steuer <patrick.steuer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Pull s390 updates from Heiko Carstens:
"Since Martin is on vacation you get the s390 pull request for the
v4.15 merge window this time from me.
Besides a lot of cleanups and bug fixes these are the most important
changes:
- a new regset for runtime instrumentation registers
- hardware accelerated AES-GCM support for the aes_s390 module
- support for the new CEX6S crypto cards
- support for FORTIFY_SOURCE
- addition of missing z13 and new z14 instructions to the in-kernel
disassembler
- generate opcode tables for the in-kernel disassembler out of a
simple text file instead of having to manually maintain those
tables
- fast memset16, memset32 and memset64 implementations
- removal of named saved segment support
- hardware counter support for z14
- queued spinlocks and queued rwlocks implementations for s390
- use the stack_depth tracking feature for s390 BPF JIT
- a new s390_sthyi system call which emulates the sthyi (store
hypervisor information) instruction
- removal of the old KVM virtio transport
- an s390 specific CPU alternatives implementation which is used in
the new spinlock code"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (88 commits)
MAINTAINERS: add virtio-ccw.h to virtio/s390 section
s390/noexec: execute kexec datamover without DAT
s390: fix transactional execution control register handling
s390/bpf: take advantage of stack_depth tracking
s390: simplify transactional execution elf hwcap handling
s390/zcrypt: Rework struct ap_qact_ap_info.
s390/virtio: remove unused header file kvm_virtio.h
s390: avoid undefined behaviour
s390/disassembler: generate opcode tables from text file
s390/disassembler: remove insn_to_mnemonic()
s390/dasd: avoid calling do_gettimeofday()
s390: vfio-ccw: Do not attempt to free no-op, test and tic cda.
s390: remove named saved segment support
s390/archrandom: Reconsider s390 arch random implementation
s390/pci: do not require AIS facility
s390/qdio: sanitize put_indicator
s390/qdio: use atomic_cmpxchg
s390/nmi: avoid using long-displacement facility
s390: pass endianness info to sparse
s390/decompressor: remove informational messages
...
The reworked version of the random device driver now calls
the arch_get_random_* functions on a very high frequency.
It does about 100.000 calls to arch_get_random_long for
providing 10 MB via /dev/urandom. Each invocation was
fetching entropy from the hardware random generator which
has a rate limit of about 4 MB/s. As the trng invocation
waits until enough entropy is gathered, the random device
driver is slowed down dramatically.
The s390 true random generator is not designed for such
a high rate. The TRNG is more designed to be used together
with the arch_get_random_seed_* functions. This is similar
to the way how powerpc has implemented their arch random
functionality.
This patch removes the invocations of the s390 TRNG for
arch_get_random_long() and arch_get_random_int() but leaving
the invocations for arch_get_random_seed_long() and
arch_get_random_seed_int(). So the s390 arch random
implementation now contributes high quality entropy to
the kernel random device for reseeding.
Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This patch introduces s390 specific arch random functionality.
There exists a generic kernel API for arch specific random
number implementation (see include/linux/random.h). Here
comes the header file and a very small static code part
implementing the arch_random_* API based on the TRNG
subfunction coming with the reworked PRNG instruction.
The arch random implementation hooks into the kernel
initialization and checks for availability of the TRNG
function. In accordance to the arch random API all functions
return false if the TRNG is not available. Otherwise the new
high quality entropy source provides fresh random on each
invocation.
The s390 arch random feature build is controlled via
CONFIG_ARCH_RANDOM. This config option located in
arch/s390/Kconfig is enabled by default and appears
as entry "s390 architectural random number generation API"
in the submenu "Processor type and features" for s390 builds.
Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Harald Freudenberger
Richard Henderson
Harald Freudenberger
Linus Torvalds
Harald Freudenberger
Greg Kroah-Hartman