Now that we guarantee that SYSCLK is running at the optimal rate when
hw_params succeeds, and that it will continue running at that rate,
SYSCLK will always be an integer multiple of BCLK. So we can always
pick the exact divider, not just the closest divider.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-14-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The codec's clock input is shared among all AIFs, and shared with other
audio-related hardware in the SoC, including I2S and SPDIF controllers.
To ensure sample rates selected by userspace or by codec2codec DAI links
are maintained, the clock rate must be protected while it is in use.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20201014061941.4306-13-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

While another stream is active, only allow userspace to use sample rates
that are compatible with the current SYSCLK frequency. This ensures the
actual sample rate will always match what is given in hw_params.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-12-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The sun8i codec has three clock/sample rate domains:
 - The AIF1 domain, with a sample rate equal to AIF1 LRCK
 - The AIF2 domain, with a sample rate equal to AIF2 LRCK
 - The SYSCLK domain, containing the ADC, DAC, and effects (AGC/DRC),
   with a sample rate given by a divisor from SYSCLK. The divisor is
   controlled by the AIF1_FS or AIF2_FS field in SYS_SR_CTRL, depending
   on if SYSCLK's source is AIF1CLK or AIF2CLK, respectively. The exact
   sample rate depends on if SYSCLK is running at 22.6 MHz or 24.6 MHz.

When an AIF (currently only AIF1) is active, the ADC and DAC should run
at that sample rate to avoid artifacting. Sample rate conversion is only
available when multiple AIFs are active and are routed to each other;
this means the sample rate conversion hardware usually cannot be used.

Only attach the event hook to the channel 0 AIF widgets, since we only
need one event when a DAI stream starts or stops. Channel 0 is always
brought up with a DAI stream, regardless of the number of channels in
the stream.

The ADC and DAC (along with their effects blocks) can be used even if
no AIFs are in use. In that case, we should select an appropriate sample
rate divisor, instead of keeping the last-used AIF sample rate.
44.1/48 kHz was chosen to balance audio quality and power consumption.

Since the sample rate is tied to active AIF paths, disabling pmdown_time
allows switching to the optimal sample rate immediately, instead of
after a 5 second delay.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20201014061941.4306-11-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The system sample rate programmed into the hardware is really a clock
divider from SYSCLK to the ADC and DAC. Since we support two SYSCLK
frequencies, we can use all sample rates corresponding to one of those
frequencies divided by any available divisor.

This commit enables support for those sample rates. It also stops
advertising support for a 64 kHz sample rate, which is not supported.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-10-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The AIFs have a single register controlling DAI parameters in both
directions, including BCLK/LRCK divisor and word size. The DAIs produce
only noise or silence if any of these parameters is wrong. Therefore, we
need to enforce symmetry for these parameters, so starting a new
substream will not break an existing substream.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-9-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Now that BCLK and LRCK rate calculations in the driver can handle any
hardware-supported slot width and number of slots, allow overriding
those parameters from the device tree.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-8-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Previously, the BCLK divisor calculation assumed zero padding and
exactly two slots. In order to support the TDM slot binding and
20/24-bit word sizes, those assumptions must be removed.

Due to hardware limitations, the BCLK/LRCK ratio is not as simple as
"slot_width * slots". However, the correct value is already calculated
elsewhere in this function, since it must also be programmed into the
hardware. Reuse that value to calculate the correct SYSCLK/BCLK divisor.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-7-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The codec supports only power-of-two BCLK/LRCK divisors. If either the
slot width or the number of slots is not a power of two, the LRCK
divisor must be rounded up to provide enough space. To do that, use
order_base_2 (instead of ilog2, which rounds down).

Since the rounded divisor is also needed for setting the SYSCLK/BCLK
divisor, return the order base 2 instead of fully calculating the
hardware register encoding.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-6-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The hardware supports 8 to 24-bit word sizes on all three of its DAIs,
only one of which is connected to the CPU DAI. Program the word size
based on the actual selected format, instead of assuming limitations
from another driver (which, incedentally, has patches pending to remove
that limitation).
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-5-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

When using the I2S, LEFT_J, or RIGHT_J format, the hardware supports
independent BCLK and LRCK inversion control. When using DSP_A or DSP_B,
LRCK inversion is not supported. The register bit is repurposed to
select between DSP_A and DSP_B. Extend the driver to support this.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20201014061941.4306-4-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

The LRCK inversion bit has a different meaning in DSP mode: it selects
between the DSP A and DSP B formats. To support this, we need to know if
the selected format is a DSP format. One easy way to do this is to set
the format field before the clock inversion fields.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-3-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

In preparation for adding additional DAIs to this component, convert the
DAI driver definition to an array. Since this changes all of the lines
in the definition anyway, let's move it closer to the ops function
definitions, instead of on the far side of the DAPM arrays. And while
moving the DAI driver ops, rename the set_fmt hook to match the usual
naming scheme.

Give the existing DAI an explicit ID and more meaningful stream names,
so it will remain unique as more DAIs are added. The AIF widget streams
must be updated to match.
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20201014061941.4306-2-samuel@sholland.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

    https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.plSigned-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@gooogle.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tid_addr is not a "pointer to (pointer to int in userspace)"; it is in
fact a "pointer to (pointer to int in userspace) in userspace".  So
sparse rightfully complains about passing a kernel pointer to
put_user().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 453431a5 ("mm, treewide: rename kzfree() to
kfree_sensitive()") renamed kzfree() to kfree_sensitive(),
but it left a compatibility definition of kzfree() to avoid
being too disruptive.

Since then a few more instances of kzfree() have slipped in.

Just get rid of them and remove the compatibility definition
once and for all.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

If set, use the environment variable GIT_DIR to change the default .git
location of the kernel git tree.

If GIT_DIR is unset, keep using the current ".git" default.

Link: https://lkml.kernel.org/r/c5e23b45562373d632fccb8bc04e563abba4dd1d.camel@perches.comSigned-off-by: Joe Perches <joe@perches.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull timer fixes from Thomas Gleixner:
 "A time namespace fix and a matching selftest. The futex absolute
  timeouts which are based on CLOCK_MONOTONIC require time namespace
  corrected. This was missed in the original time namesapce support"

* tag 'timers-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  selftests/timens: Add a test for futex()
  futex: Adjust absolute futex timeouts with per time namespace offset

Pull scheduler fixes from Thomas Gleixner:
 "Two scheduler fixes:

   - A trivial build fix for sched_feat() to compile correctly with
     CONFIG_JUMP_LABEL=n

   - Replace a zero lenght array with a flexible array"

* tag 'sched-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/features: Fix !CONFIG_JUMP_LABEL case
  sched: Replace zero-length array with flexible-array

Pull perf fix from Thomas Gleixner:
 "A single fix to compute the field offset of the SNOOPX bit in the data
  source bitmask of perf events correctly"

* tag 'perf-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf: correct SNOOPX field offset

Pull locking fix from Thomas Gleixner:
 "Just a trivial fix for kernel-doc warnings"

* tag 'locking-urgent-2020-10-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/seqlocks: Fix kernel-doc warnings

Pull NTB fixes from Jon Mason.

* tag 'ntb-5.10' of git://github.com/jonmason/ntb:
  NTB: Use struct_size() helper in devm_kzalloc()
  ntb: intel: Fix memleak in intel_ntb_pci_probe
  NTB: hw: amd: fix an issue about leak system resources

Pull i2c fix from Wolfram Sang:
 "Regression fix for rc1 and stable kernels as well"

* 'i2c/for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: core: Restore acpi_walk_dep_device_list() getting called after registering the ACPI i2c devs

Pull more cifs updates from Steve French:
 "Add support for stat of various special file types (WSL reparse points
  for char, block, fifo)"

* tag '5.10-rc-smb3-fixes-part2' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: update internal module version number
  smb3: add some missing definitions from MS-FSCC
  smb3: remove two unused variables
  smb3: add support for stat of WSL reparse points for special file types

Pull more parisc updates from Helge Deller:

 - During this merge window O_NONBLOCK was changed to become 000200000,
   but we missed that the syscalls timerfd_create(), signalfd4(),
   eventfd2(), pipe2(), inotify_init1() and userfaultfd() do a strict
   bit-wise check of the flags parameter.

   To provide backward compatibility with existing userspace we
   introduce parisc specific wrappers for those syscalls which filter
   out the old O_NONBLOCK value and replaces it with the new one.

 - Prevent HIL bus driver to get stuck when keyboard or mouse isn't
   attached

 - Improve error return codes when setting rtc time

 - Minor documentation fix in pata_ns87415.c

* 'parisc-5.10-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  ata: pata_ns87415.c: Document support on parisc with superio chip
  parisc: Add wrapper syscalls to fix O_NONBLOCK flag usage
  hil/parisc: Disable HIL driver when it gets stuck
  parisc: Improve error return codes when setting rtc time

Pull more xen updates from Juergen Gross:

 - a series for the Xen pv block drivers adding module parameters for
   better control of resource usge

 - a cleanup series for the Xen event driver

* tag 'for-linus-5.10b-rc1c-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  Documentation: add xen.fifo_events kernel parameter description
  xen/events: unmask a fifo event channel only if it was masked
  xen/events: only register debug interrupt for 2-level events
  xen/events: make struct irq_info private to events_base.c
  xen: remove no longer used functions
  xen-blkfront: Apply changed parameter name to the document
  xen-blkfront: add a parameter for disabling of persistent grants
  xen-blkback: add a parameter for disabling of persistent grants

Pull SafeSetID updates from Micah Morton:
 "The changes are mostly contained to within the SafeSetID LSM, with the
  exception of a few 1-line changes to change some ns_capable() calls to
  ns_capable_setid() -- causing a flag (CAP_OPT_INSETID) to be set that
  is examined by SafeSetID code and nothing else in the kernel.

  The changes to SafeSetID internally allow for setting up GID
  transition security policies, as already existed for UIDs"

* tag 'safesetid-5.10' of git://github.com/micah-morton/linux:
  LSM: SafeSetID: Fix warnings reported by test bot
  LSM: SafeSetID: Add GID security policy handling
  LSM: Signal to SafeSetID when setting group IDs

Pull random32 updates from Willy Tarreau:
 "Make prandom_u32() less predictable.

  This is the cleanup of the latest series of prandom_u32
  experimentations consisting in using SipHash instead of Tausworthe to
  produce the randoms used by the network stack.

  The changes to the files were kept minimal, and the controversial
  commit that used to take noise from the fast_pool (f227e3ec) was
  reverted. Instead, a dedicated "net_rand_noise" per_cpu variable is
  fed from various sources of activities (networking, scheduling) to
  perturb the SipHash state using fast, non-trivially predictable data,
  instead of keeping it fully deterministic. The goal is essentially to
  make any occasional memory leakage or brute-force attempt useless.

  The resulting code was verified to be very slightly faster on x86_64
  than what is was with the controversial commit above, though this
  remains barely above measurement noise. It was also tested on i386 and
  arm, and build- tested only on arm64"

Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/

* tag '20201024-v4-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/wtarreau/prandom:
  random32: add a selftest for the prandom32 code
  random32: add noise from network and scheduling activity
  random32: make prandom_u32() output unpredictable

Commit 21653a41 ("i2c: core: Call i2c_acpi_install_space_handler()
before i2c_acpi_register_devices()")'s intention was to only move the
acpi_install_address_space_handler() call to the point before where
the ACPI declared i2c-children of the adapter where instantiated by
i2c_acpi_register_devices().

But i2c_acpi_install_space_handler() had a call to
acpi_walk_dep_device_list() hidden (that is I missed it) at the end
of it, so as an unwanted side-effect now acpi_walk_dep_device_list()
was also being called before i2c_acpi_register_devices().

Move the acpi_walk_dep_device_list() call to the end of
i2c_acpi_register_devices(), so that it is once again called *after*
the i2c_client-s hanging of the adapter have been created.

This fixes the Microsoft Surface Go 2 hanging at boot.

Fixes: 21653a41 ("i2c: core: Call i2c_acpi_install_space_handler() before i2c_acpi_register_devices()")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=209627Reported-by: Rainer Finke <rainer@finke.cc>
Reported-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Suggested-by: Maximilian Luz <luzmaximilian@gmail.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Pull block fixes from Jens Axboe:

 - NVMe pull request from Christoph
     - rdma error handling fixes (Chao Leng)
     - fc error handling and reconnect fixes (James Smart)
     - fix the qid displace when tracing ioctl command (Keith Busch)
     - don't use BLK_MQ_REQ_NOWAIT for passthru (Chaitanya Kulkarni)
     - fix MTDT for passthru (Logan Gunthorpe)
     - blacklist Write Same on more devices (Kai-Heng Feng)
     - fix an uninitialized work struct (zhenwei pi)"

 - lightnvm out-of-bounds fix (Colin)

 - SG allocation leak fix (Doug)

 - rnbd fixes (Gioh, Guoqing, Jack)

 - zone error translation fixes (Keith)

 - kerneldoc markup fix (Mauro)

 - zram lockdep fix (Peter)

 - Kill unused io_context members (Yufen)

 - NUMA memory allocation cleanup (Xianting)

 - NBD config wakeup fix (Xiubo)

* tag 'block-5.10-2020-10-24' of git://git.kernel.dk/linux-block: (27 commits)
  block: blk-mq: fix a kernel-doc markup
  nvme-fc: shorten reconnect delay if possible for FC
  nvme-fc: wait for queues to freeze before calling update_hr_hw_queues
  nvme-fc: fix error loop in create_hw_io_queues
  nvme-fc: fix io timeout to abort I/O
  null_blk: use zone status for max active/open
  nvmet: don't use BLK_MQ_REQ_NOWAIT for passthru
  nvmet: cleanup nvmet_passthru_map_sg()
  nvmet: limit passthru MTDS by BIO_MAX_PAGES
  nvmet: fix uninitialized work for zero kato
  nvme-pci: disable Write Zeroes on Sandisk Skyhawk
  nvme: use queuedata for nvme_req_qid
  nvme-rdma: fix crash due to incorrect cqe
  nvme-rdma: fix crash when connect rejected
  block: remove unused members for io_context
  blk-mq: remove the calling of local_memory_node()
  zram: Fix __zram_bvec_{read,write}() locking order
  skd_main: remove unused including <linux/version.h>
  sgl_alloc_order: fix memory leak
  lightnvm: fix out-of-bounds write to array devices->info[]
  ...

Pull io_uring fixes from Jens Axboe:

 - fsize was missed in previous unification of work flags

 - Few fixes cleaning up the flags unification creds cases (Pavel)

 - Fix NUMA affinities for completely unplugged/replugged node for io-wq

 - Two fallout fixes from the set_fs changes. One local to io_uring, one
   for the splice entry point that io_uring uses.

 - Linked timeout fixes (Pavel)

 - Removal of ->flush() ->files work-around that we don't need anymore
   with referenced files (Pavel)

 - Various cleanups (Pavel)

* tag 'io_uring-5.10-2020-10-24' of git://git.kernel.dk/linux-block:
  splice: change exported internal do_splice() helper to take kernel offset
  io_uring: make loop_rw_iter() use original user supplied pointers
  io_uring: remove req cancel in ->flush()
  io-wq: re-set NUMA node affinities if CPUs come online
  io_uring: don't reuse linked_timeout
  io_uring: unify fsize with def->work_flags
  io_uring: fix racy REQ_F_LINK_TIMEOUT clearing
  io_uring: do poll's hash_node init in common code
  io_uring: inline io_poll_task_handler()
  io_uring: remove extra ->file check in poll prep
  io_uring: make cached_cq_overflow non atomic_t
  io_uring: inline io_fail_links()
  io_uring: kill ref get/drop in personality init
  io_uring: flags-based creds init in queue

Pull libata fixes from Jens Axboe:
 "Two minor libata fixes:

   - Fix a DMA boundary mask regression for sata_rcar (Geert)

   - kerneldoc markup fix (Mauro)"

* tag 'libata-5.10-2020-10-24' of git://git.kernel.dk/linux-block:
  ata: fix some kernel-doc markups
  ata: sata_rcar: Fix DMA boundary mask

Pull misc vfs updates from Al Viro:
 "Assorted stuff all over the place (the largest group here is
  Christoph's stat cleanups)"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: remove KSTAT_QUERY_FLAGS
  fs: remove vfs_stat_set_lookup_flags
  fs: move vfs_fstatat out of line
  fs: implement vfs_stat and vfs_lstat in terms of vfs_fstatat
  fs: remove vfs_statx_fd
  fs: omfs: use kmemdup() rather than kmalloc+memcpy
  [PATCH] reduce boilerplate in fsid handling
  fs: Remove duplicated flag O_NDELAY occurring twice in VALID_OPEN_FLAGS
  selftests: mount: add nosymfollow tests
  Add a "nosymfollow" mount option.

Pull dma-mapping fixes from Christoph Hellwig:

 - document the new dma_{alloc,free}_pages() API

 - two fixups for the dma-mapping.h split

* tag 'dma-mapping-5.10-1' of git://git.infradead.org/users/hch/dma-mapping:
  dma-mapping: document dma_{alloc,free}_pages
  dma-mapping: move more functions to dma-map-ops.h
  ARM/sa1111: add a missing include of dma-map-ops.h

Pull KVM fixes from Paolo Bonzini:
 "Two fixes for this merge window, and an unrelated bugfix for a host
  hang"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: ioapic: break infinite recursion on lazy EOI
  KVM: vmx: rename pi_init to avoid conflict with paride
  KVM: x86/mmu: Avoid modulo operator on 64-bit value to fix i386 build

Pull x86 SEV-ES fixes from Borislav Petkov:
 "Three fixes to SEV-ES to correct setting up the new early pagetable on
  5-level paging machines, to always map boot_params and the kernel
  cmdline, and disable stack protector for ../compressed/head{32,64}.c.
  (Arvind Sankar)"

* tag 'x86_seves_fixes_for_v5.10_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/boot/64: Explicitly map boot_params and command line
  x86/head/64: Disable stack protection for head$(BITS).o
  x86/boot/64: Initialize 5-level paging variables earlier

Given that this code is new, let's add a selftest for it as well.
It doesn't rely on fixed sets, instead it picks 1024 numbers and
verifies that they're not more correlated than desired.

Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
Cc: George Spelvin <lkml@sdf.org>
Cc: Amit Klein <aksecurity@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

With the removal of the interrupt perturbations in previous random32
change (random32: make prandom_u32() output unpredictable), the PRNG
has become 100% deterministic again. While SipHash is expected to be
way more robust against brute force than the previous Tausworthe LFSR,
there's still the risk that whoever has even one temporary access to
the PRNG's internal state is able to predict all subsequent draws till
the next reseed (roughly every minute). This may happen through a side
channel attack or any data leak.

This patch restores the spirit of commit f227e3ec ("random32: update
the net random state on interrupt and activity") in that it will perturb
the internal PRNG's statee using externally collected noise, except that
it will not pick that noise from the random pool's bits nor upon
interrupt, but will rather combine a few elements along the Tx path
that are collectively hard to predict, such as dev, skb and txq
pointers, packet length and jiffies values. These ones are combined
using a single round of SipHash into a single long variable that is
mixed with the net_rand_state upon each invocation.

The operation was inlined because it produces very small and efficient
code, typically 3 xor, 2 add and 2 rol. The performance was measured
to be the same (even very slightly better) than before the switch to
SipHash; on a 6-core 12-thread Core i7-8700k equipped with a 40G NIC
(i40e), the connection rate dropped from 556k/s to 555k/s while the
SYN cookie rate grew from 5.38 Mpps to 5.45 Mpps.

Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
Cc: George Spelvin <lkml@sdf.org>
Cc: Amit Klein <aksecurity@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>