Add support for generating ecc private keys.

Generation of ecc private keys is helpful in a user-space to kernel
ecdh offload because the keys are not revealed to user-space. Private
key generation is also helpful to implement forward secrecy.

If the user provides a NULL ecc private key, the kernel will generate it
and further use it for ecdh.

Move ecdh's object files below drbg's. drbg must be present in the kernel
at the time of calling.
Signed-off-by: NTudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: NStephan Müller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

An ancient gcc bug (first reported in 2003) has apparently resurfaced
on MIPS, where kernelci.org reports an overly large stack frame in the
whirlpool hash algorithm:

crypto/wp512.c:987:1: warning: the frame size of 1112 bytes is larger than 1024 bytes [-Wframe-larger-than=]

With some testing in different configurations, I'm seeing large
variations in stack frames size up to 1500 bytes for what should have
around 300 bytes at most. I also checked the reference implementation,
which is essentially the same code but also comes with some test and
benchmarking infrastructure.

It seems that recent compiler versions on at least arm, arm64 and powerpc
have a partial fix for this problem, but enabling "-fsched-pressure", but
even with that fix they suffer from the issue to a certain degree. Some
testing on arm64 shows that the time needed to hash a given amount of
data is roughly proportional to the stack frame size here, which makes
sense given that the wp512 implementation is doing lots of loads for
table lookups, and the problem with the overly large stack is a result
of doing a lot more loads and stores for spilled registers (as seen from
inspecting the object code).

Disabling -fschedule-insns consistently fixes the problem for wp512,
in my collection of cross-compilers, the results are consistently better
or identical when comparing the stack sizes in this function, though
some architectures (notable x86) have schedule-insns disabled by
default.

The four columns are:
default: -O2
press:	 -O2 -fsched-pressure
nopress: -O2 -fschedule-insns -fno-sched-pressure
nosched: -O2 -no-schedule-insns (disables sched-pressure)

				default	press	nopress	nosched
alpha-linux-gcc-4.9.3		1136	848	1136	176
am33_2.0-linux-gcc-4.9.3	2100	2076	2100	2104
arm-linux-gnueabi-gcc-4.9.3	848	848	1048	352
cris-linux-gcc-4.9.3		272	272	272	272
frv-linux-gcc-4.9.3		1128	1000	1128	280
hppa64-linux-gcc-4.9.3		1128	336	1128	184
hppa-linux-gcc-4.9.3		644	308	644	276
i386-linux-gcc-4.9.3		352	352	352	352
m32r-linux-gcc-4.9.3		720	656	720	268
microblaze-linux-gcc-4.9.3	1108	604	1108	256
mips64-linux-gcc-4.9.3		1328	592	1328	208
mips-linux-gcc-4.9.3		1096	624	1096	240
powerpc64-linux-gcc-4.9.3	1088	432	1088	160
powerpc-linux-gcc-4.9.3		1080	584	1080	224
s390-linux-gcc-4.9.3		456	456	624	360
sh3-linux-gcc-4.9.3		292	292	292	292
sparc64-linux-gcc-4.9.3		992	240	992	208
sparc-linux-gcc-4.9.3		680	592	680	312
x86_64-linux-gcc-4.9.3		224	240	272	224
xtensa-linux-gcc-4.9.3		1152	704	1152	304

aarch64-linux-gcc-7.0.0		224	224	1104	208
arm-linux-gnueabi-gcc-7.0.1	824	824	1048	352
mips-linux-gcc-7.0.0		1120	648	1120	272
x86_64-linux-gcc-7.0.1		240	240	304	240

arm-linux-gnueabi-gcc-4.4.7	840			392
arm-linux-gnueabi-gcc-4.5.4	784	728	784	320
arm-linux-gnueabi-gcc-4.6.4	736	728	736	304
arm-linux-gnueabi-gcc-4.7.4	944	784	944	352
arm-linux-gnueabi-gcc-4.8.5	464	464	760	352
arm-linux-gnueabi-gcc-4.9.3	848	848	1048	352
arm-linux-gnueabi-gcc-5.3.1	824	824	1064	336
arm-linux-gnueabi-gcc-6.1.1	808	808	1056	344
arm-linux-gnueabi-gcc-7.0.1	824	824	1048	352

Trying the same test for serpent-generic, the picture is a bit different,
and while -fno-schedule-insns is generally better here than the default,
-fsched-pressure wins overall, so I picked that instead.

				default	press	nopress	nosched
alpha-linux-gcc-4.9.3		1392	864	1392	960
am33_2.0-linux-gcc-4.9.3	536	524	536	528
arm-linux-gnueabi-gcc-4.9.3	552	552	776	536
cris-linux-gcc-4.9.3		528	528	528	528
frv-linux-gcc-4.9.3		536	400	536	504
hppa64-linux-gcc-4.9.3		524	208	524	480
hppa-linux-gcc-4.9.3		768	472	768	508
i386-linux-gcc-4.9.3		564	564	564	564
m32r-linux-gcc-4.9.3		712	576	712	532
microblaze-linux-gcc-4.9.3	724	392	724	512
mips64-linux-gcc-4.9.3		720	384	720	496
mips-linux-gcc-4.9.3		728	384	728	496
powerpc64-linux-gcc-4.9.3	704	304	704	480
powerpc-linux-gcc-4.9.3		704	296	704	480
s390-linux-gcc-4.9.3		560	560	592	536
sh3-linux-gcc-4.9.3		540	540	540	540
sparc64-linux-gcc-4.9.3		544	352	544	496
sparc-linux-gcc-4.9.3		544	344	544	496
x86_64-linux-gcc-4.9.3		528	536	576	528
xtensa-linux-gcc-4.9.3		752	544	752	544

aarch64-linux-gcc-7.0.0		432	432	656	480
arm-linux-gnueabi-gcc-7.0.1	616	616	808	536
mips-linux-gcc-7.0.0		720	464	720	488
x86_64-linux-gcc-7.0.1		536	528	600	536

arm-linux-gnueabi-gcc-4.4.7	592			440
arm-linux-gnueabi-gcc-4.5.4	776	448	776	544
arm-linux-gnueabi-gcc-4.6.4	776	448	776	544
arm-linux-gnueabi-gcc-4.7.4	768	448	768	544
arm-linux-gnueabi-gcc-4.8.5	488	488	776	544
arm-linux-gnueabi-gcc-4.9.3	552	552	776	536
arm-linux-gnueabi-gcc-5.3.1	552	552	776	536
arm-linux-gnueabi-gcc-6.1.1	560	560	776	536
arm-linux-gnueabi-gcc-7.0.1	616	616	808	536

I did not do any runtime tests with serpent, so it is possible that stack
frame size does not directly correlate with runtime performance here and
it actually makes things worse, but it's more likely to help here, and
the reduced stack frame size is probably enough reason to apply the patch,
especially given that the crypto code is often used in deep call chains.

Link: https://kernelci.org/build/id/58797d7559b5149efdf6c3a9/logs/
Link: http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11488
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79149
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Lookup table based AES is sensitive to timing attacks, which is due to
the fact that such table lookups are data dependent, and the fact that
8 KB worth of tables covers a significant number of cachelines on any
architecture, resulting in an exploitable correlation between the key
and the processing time for known plaintexts.

For network facing algorithms such as CTR, CCM or GCM, this presents a
security risk, which is why arch specific AES ports are typically time
invariant, either through the use of special instructions, or by using
SIMD algorithms that don't rely on table lookups.

For generic code, this is difficult to achieve without losing too much
performance, but we can improve the situation significantly by switching
to an implementation that only needs 256 bytes of table data (the actual
S-box itself), which can be prefetched at the start of each block to
eliminate data dependent latencies.

This code encrypts at ~25 cycles per byte on ARM Cortex-A57 (while the
ordinary generic AES driver manages 18 cycles per byte on this
hardware). Decryption is substantially slower.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Both asn1 headers are included by rsa_helper.c, so rsa_helper.o
should explicitly depend on them.
Signed-off-by: NDavid Michael <david.michael@coreos.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch adds the simd skcipher helper which is meant to be
a replacement for ablk helper.  It replaces the underlying blkcipher
interface with skcipher, and also presents the top-level algorithm
as an skcipher.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Fix dependency between acomp and scomp that appears when acomp is
built as module
Signed-off-by: NGiovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add a synchronous back-end (scomp) to acomp. This allows to easily
expose the already present compression algorithms in LKCF via acomp.
Signed-off-by: NGiovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add acomp, an asynchronous compression api that uses scatterlist
buffers.
Signed-off-by: NGiovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch removes the old crypto_grab_skcipher helper and replaces
it with crypto_grab_skcipher2.

As this is the final entry point into givcipher this patch also
removes all traces of the top-level givcipher interface, including
all implicit IV generators such as chainiv.

The bottom-level givcipher interface remains until the drivers
using it are converted.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

* Implement ECDH under kpp API
 * Provide ECC software support for curve P-192 and
   P-256.
 * Add kpp test for ECDH with data generated by OpenSSL
Signed-off-by: NSalvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

* Implement MPI based Diffie-Hellman under kpp API
 * Test provided uses data generad by OpenSSL
Signed-off-by: NSalvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add key-agreement protocol primitives (kpp) API which allows to
implement primitives required by protocols such as DH and ECDH.
The API is composed mainly by the following functions
 * set_secret() - It allows the user to set his secret, also
   referred to as his private key, along with the parameters
   known to both parties involved in the key-agreement session.
 * generate_public_key() - It generates the public key to be sent to
   the other counterpart involved in the key-agreement session. The
   function has to be called after set_params() and set_secret()
 * generate_secret() - It generates the shared secret for the session

Other functions such as init() and exit() are provided for allowing
cryptographic hardware to be inizialized properly before use
Signed-off-by: NSalvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch adds the implementation of SHA3 algorithm
in software and it's based on original implementation
pushed in patch https://lwn.net/Articles/518415/ with
additional changes to match the padding rules specified
in SHA-3 specification.
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>
Signed-off-by: NRaveendra Padasalagi <raveendra.padasalagi@broadcom.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Now block cipher engines need to implement and maintain their own queue/thread
for processing requests, moreover currently helpers provided for only the queue
itself (in crypto_enqueue_request() and crypto_dequeue_request()) but they
don't help with the mechanics of driving the hardware (things like running the
request immediately, DMA map it or providing a thread to process the queue in)
even though a lot of that code really shouldn't vary that much from device to
device.

Thus this patch provides a mechanism for pushing requests to the hardware
as it becomes free that drivers could use. And this framework is patterned
on the SPI code and has worked out well there.
(https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/
 drivers/spi/spi.c?id=ffbbdd21)
Signed-off-by: NBaolin Wang <baolin.wang@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The generic crc32 implementation is currently called crc32.  This
is a problem because it clashes with the lib implementation of crc32.

This patch renames the crypto crc32 to crc32_generic so that it is
consistent with crc32c.  An alias for the driver is also added.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

It is unused now, so remove it.
Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch adds PKCS#1 v1.5 standard RSA padding as a separate template.
This way an RSA cipher with padding can be obtained by instantiating
"pkcs1pad(rsa)".  The reason for adding this is that RSA is almost
never used without this padding (or OAEP) so it will be needed for
either certificate work in the kernel or the userspace, and I also hear
that it is likely implemented by hardware RSA in which case hardware
implementations of the whole of pkcs1pad(rsa) can be provided.
Signed-off-by: NAndrew Zaborowski <andrew.zaborowski@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Hook keywrap source code into Kconfig and Makefile
Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Setkey function has been split into set_priv_key and set_pub_key.
Akcipher requests takes sgl for src and dst instead of void *.
Users of the API i.e. two existing RSA implementation and
test mgr code have been updated accordingly.
Signed-off-by: NTadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch introduces the crypto skcipher interface which aims
to replace both blkcipher and ablkcipher.

It's very similar to the existing ablkcipher interface.  The
main difference is the removal of the givcrypt interface.  In
order to make the transition easier for blkcipher users, there
is a helper SKCIPHER_REQUEST_ON_STACK which can be used to place
a request on the stack for synchronous transforms.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The Kconfig option NULL2 has been added as CRYPTO_MANAGER now
depends indirectly on NULL2.  However, the Makefile was not updated
to use the new option, resulting in potential build failures when
only NULL2 is enabled.

Fixes: 149a3971 ("crypto: aead - Add type-safe geniv init/exit helpers")
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The core of the Jitter RNG is intended to be compiled with -O0. To
ensure that the Jitter RNG can be compiled on all architectures,
separate out the RNG core into a stand-alone C file that can be compiled
with -O0 which does not depend on any kernel include file.

As no kernel includes can be used in the C file implementing the core
RNG, any dependencies on kernel code must be extracted.

A second file provides the link to the kernel and the kernel crypto API
that can be compiled with the regular compile options of the kernel.
Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add a new rsa generic SW implementation.
This implements only cryptographic primitives.
Signed-off-by: NTadeusz Struk <tadeusz.struk@intel.com>

Added select on ASN1.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Add Public Key Encryption API.
Signed-off-by: NTadeusz Struk <tadeusz.struk@intel.com>

Made CRYPTO_AKCIPHER invisible like other type config options.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Replace the global -O0 compiler flag from the Makefile with GCC
pragmas to mark only the functions required to be compiled without
optimizations.

This patch also adds a comment describing the rationale for the
functions chosen to be compiled without optimizations.
Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch removes krng so that DRBG can take its place.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This AEAD uses a chacha20 ablkcipher and a poly1305 ahash to construct the
ChaCha20-Poly1305 AEAD as defined in RFC7539. It supports both synchronous and
asynchronous operations, even if we currently have no async chacha20 or poly1305
drivers.
Signed-off-by: NMartin Willi <martin@strongswan.org>
Acked-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Poly1305 is a fast message authenticator designed by Daniel J. Bernstein.
It is further defined in RFC7539 as a building block for the ChaCha20-Poly1305
AEAD for use in IETF protocols.

This is a portable C implementation of the algorithm without architecture
specific optimizations, based on public domain code by Daniel J. Bernstein and
Andrew Moon.
Signed-off-by: NMartin Willi <martin@strongswan.org>
Acked-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

ChaCha20 is a high speed 256-bit key size stream cipher algorithm designed by
Daniel J. Bernstein. It is further specified in RFC7539 for use in IETF
protocols as a building block for the ChaCha20-Poly1305 AEAD.

This is a portable C implementation without any architecture specific
optimizations. It uses a 16-byte IV, which includes the 12-byte ChaCha20 nonce
prepended by the initial block counter. Some algorithms require an explicit
counter value, for example the mentioned AEAD construction.
Signed-off-by: NMartin Willi <martin@strongswan.org>
Acked-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

The CPU Jitter RNG provides a source of good entropy by
collecting CPU executing time jitter. The entropy in the CPU
execution time jitter is magnified by the CPU Jitter Random
Number Generator. The CPU Jitter Random Number Generator uses
the CPU execution timing jitter to generate a bit stream
which complies with different statistical measurements that
determine the bit stream is random.

The CPU Jitter Random Number Generator delivers entropy which
follows information theoretical requirements. Based on these
studies and the implementation, the caller can assume that
one bit of data extracted from the CPU Jitter Random Number
Generator holds one bit of entropy.

The CPU Jitter Random Number Generator provides a decentralized
source of entropy, i.e. every caller can operate on a private
state of the entropy pool.

The RNG does not have any dependencies on any other service
in the kernel. The RNG only needs a high-resolution time
stamp.

Further design details, the cryptographic assessment and
large array of test results are documented at
http://www.chronox.de/jent.html.

CC: Andreas Steffen <andreas.steffen@strongswan.org>
CC: Theodore Ts'o <tytso@mit.edu>
CC: Sandy Harris <sandyinchina@gmail.com>
Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch adds a new AEAD IV generator echainiv.  It is intended
to replace the existing skcipher IV generator eseqiv.

If the underlying AEAD algorithm is using the old AEAD interface,
then echainiv will simply use its IV generator.

Otherwise, echainiv will encrypt a counter just like eseqiv but
it'll first xor it against a previously stored IV similar to
chainiv.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Enable compilation of the AEAD AF_ALG support and provide a Kconfig
option to compile the AEAD AF_ALG support.
Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Enable compilation of the RNG AF_ALG support and provide a Kconfig
option to compile the RNG AF_ALG support.
Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch introduces the multi-buffer crypto daemon which is responsible
for submitting crypto jobs in a work queue to the responsible multi-buffer
crypto algorithm.  The idea of the multi-buffer algorihtm is to put
data streams from multiple jobs in a wide (AVX2) register and then
take advantage of SIMD instructions to do crypto computation on several
buffers simultaneously.

The multi-buffer crypto daemon is also responsbile for flushing the
remaining buffers to complete the computation if no new buffers arrive
for a while.
Signed-off-by: NTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch removes the build-time test that ensures at least one RNG
is set.  Instead we will simply not build drbg if no options are set
through Kconfig.

This also fixes a typo in the name of the Kconfig option CRYTPO_DRBG
(should be CRYPTO_DRBG).
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: NStephan Mueller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

We added the soft module dependency of crc32c module alias
to generic crc32c module so other hardware accelerated crc32c
modules could get loaded and used before the generic version.
We also renamed the crypto/crc32c.c containing the generic
crc32c crypto computation to crypto/crc32c_generic.c according
to convention.
Signed-off-by: NTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Disabling compiler optimizations can be fragile, since a new
optimization could be added to -O0 or -Os that breaks the assumptions
the code is making.

Instead of disabling compiler optimizations, use a dummy inline assembly
(based on RELOC_HIDE) to block the problematic kinds of optimization,
while still allowing other optimizations to be applied to the code.

The dummy inline assembly is added after every OR, and has the
accumulator variable as its input and output. The compiler is forced to
assume that the dummy inline assembly could both depend on the
accumulator variable and change the accumulator variable, so it is
forced to compute the value correctly before the inline assembly, and
cannot assume anything about its value after the inline assembly.

This change should be enough to make crypto_memneq work correctly (with
data-independent timing) even if it is inlined at its call sites. That
can be done later in a followup patch.

Compile-tested on x86_64.
Signed-off-by: NCesar Eduardo Barros <cesarb@cesarb.eti.br>
Acked-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

This patch provides a single place for information about hash algorithms,
such as hash sizes and kernel driver names, which will be used by IMA
and the public key code.

Changelog:
- Fix sparse and checkpatch warnings
- Move hash algo enums to uapi for userspace signing functions.
Signed-off-by: NDmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: NMimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: NHerbert Xu <herbert@gondor.apana.org.au>

When comparing MAC hashes, AEAD authentication tags, or other hash
values in the context of authentication or integrity checking, it
is important not to leak timing information to a potential attacker,
i.e. when communication happens over a network.

Bytewise memory comparisons (such as memcmp) are usually optimized so
that they return a nonzero value as soon as a mismatch is found. E.g,
on x86_64/i5 for 512 bytes this can be ~50 cyc for a full mismatch
and up to ~850 cyc for a full match (cold). This early-return behavior
can leak timing information as a side channel, allowing an attacker to
iteratively guess the correct result.

This patch adds a new method crypto_memneq ("memory not equal to each
other") to the crypto API that compares memory areas of the same length
in roughly "constant time" (cache misses could change the timing, but
since they don't reveal information about the content of the strings
being compared, they are effectively benign). Iow, best and worst case
behaviour take the same amount of time to complete (in contrast to
memcmp).

Note that crypto_memneq (unlike memcmp) can only be used to test for
equality or inequality, NOT for lexicographical order. This, however,
is not an issue for its use-cases within the crypto API.

We tried to locate all of the places in the crypto API where memcmp was
being used for authentication or integrity checking, and convert them
over to crypto_memneq.

crypto_memneq is declared noinline, placed in its own source file,
and compiled with optimizations that might increase code size disabled
("Os") because a smart compiler (or LTO) might notice that the return
value is always compared against zero/nonzero, and might then
reintroduce the same early-return optimization that we are trying to
avoid.

Using #pragma or __attribute__ optimization annotations of the code
for disabling optimization was avoided as it seems to be considered
broken or unmaintained for long time in GCC [1]. Therefore, we work
around that by specifying the compile flag for memneq.o directly in
the Makefile. We found that this seems to be most appropriate.

As we use ("Os"), this patch also provides a loop-free "fast-path" for
frequently used 16 byte digests. Similarly to kernel library string
functions, leave an option for future even further optimized architecture
specific assembler implementations.

This was a joint work of James Yonan and Daniel Borkmann. Also thanks
for feedback from Florian Weimer on this and earlier proposals [2].

  [1] http://gcc.gnu.org/ml/gcc/2012-07/msg00211.html
  [2] https://lkml.org/lkml/2013/2/10/131Signed-off-by: NJames Yonan <james@openvpn.net>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>