KBUILD_CPPFLAGS is defined differently depending on whether the main
compiler is clang or not. This means that it is not possible to build
the compat vDSO with GCC if the rest of the kernel is built with clang.

Define VDSO_CPPFLAGS directly to break this dependency and allow a clang
kernel to build a compat vDSO with GCC:

  $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
    CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- CC=clang \
    COMPATCC=arm-linux-gnueabihf-gcc
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

There's no need to export COMPATCC, so just define it locally in the
vdso32/Makefile, which is the only place where it is used.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Rather than force the use of GCC for the compat cross-compiler, instead
extract the target from CROSS_COMPILE_COMPAT and pass it to clang if the
main compiler is clang.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arm64 was the last architecture using CROSS_COMPILE_COMPAT_VDSO config
option. With this patch series the dependency in the architecture has
been removed.

Remove CROSS_COMPILE_COMPAT_VDSO from the Unified vDSO library code.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

The jump labels are not used in vdso32 since it is not possible to run
runtime patching on them.

Remove the configuration option from the Makefile.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Older versions of binutils (prior to 2.24) do not support the "ISHLD"
option for memory barrier instructions, which leads to a build failure
when assembling the vdso32 library.

Add a compilation time mechanism that detects if binutils supports those
instructions and configure the kernel accordingly.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Will Deacon <will@kernel.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Moving over to the generic C implementation of the vDSO inadvertently
left some stale files behind which are no longer used. Remove them.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

The .config file and the generated include/config/auto.conf can
end up out of sync after a set of commands since
CONFIG_CROSS_COMPILE_COMPAT_VDSO is not updated correctly.

The sequence can be reproduced as follows:

$ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig
[...]
$ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig
[set CONFIG_CROSS_COMPILE_COMPAT_VDSO="arm-linux-gnueabihf-"]
$ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-

Which results in:

arch/arm64/Makefile:62: CROSS_COMPILE_COMPAT not defined or empty,
the compat vDSO will not be built

even though the compat vDSO has been built:

$ file arch/arm64/kernel/vdso32/vdso.so
arch/arm64/kernel/vdso32/vdso.so: ELF 32-bit LSB pie executable, ARM,
EABI5 version 1 (SYSV), dynamically linked,
BuildID[sha1]=c67f6c786f2d2d6f86c71f708595594aa25247f6, stripped

A similar case that involves changing the configuration parameter
multiple times can be reconducted to the same family of problems.

Remove the use of CONFIG_CROSS_COMPILE_COMPAT_VDSO altogether and
instead rely on the cross-compiler prefix coming from the environment
via CROSS_COMPILE_COMPAT, much like we do for the rest of the kernel.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Will Deacon <will@kernel.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

When detecting a spurious EL1 translation fault, we attempt to compare
ESR_EL1.DFSC with PAR_EL1.FST. We erroneously use FIELD_PREP() to
extract PAR_EL1.FST, when we should be using FIELD_GET().

In the wise words of Robin Murphy:

| FIELD_GET() is a UBFX, FIELD_PREP() is a BFI

Using FIELD_PREP() means that that dfsc & ESR_ELx_FSC_TYPE is always
zero, and hence not equal to ESR_ELx_FSC_FAULT. Thus we detect any
unhandled translation fault as spurious.

... so let's use FIELD_GET() to ensure we don't decide all translation
faults are spurious. ESR_EL1.DFSC occupies bits [5:0], and requires no
shifting.

Fixes: 42f91093 ("arm64: mm: Ignore spurious translation faults taken from the kernel")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Robin Murphy <robin.murphy@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

CPUs affected by Neoverse-N1 #1542419 may execute a stale instruction if
it was recently modified. The affected sequence requires freshly written
instructions to be executable before a branch to them is updated.

There are very few places in the kernel that modify executable text,
all but one come with sufficient synchronisation:
 * The module loader's flush_module_icache() calls flush_icache_range(),
   which does a kick_all_cpus_sync()
 * bpf_int_jit_compile() calls flush_icache_range().
 * Kprobes calls aarch64_insn_patch_text(), which does its work in
   stop_machine().
 * static keys and ftrace both patch between nops and branches to
   existing kernel code (not generated code).

The affected sequence is the interaction between ftrace and modules.
The module PLT is cleaned using __flush_icache_range() as the trampoline
shouldn't be executable until we update the branch to it.

Drop the double-underscore so that this path runs kick_all_cpus_sync()
too.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Commit bd82d4bd ("arm64: Fix incorrect irqflag restore for priority
masking") added a macro to the entry.S call paths that leave the
PSTATE.I bit set. This tells the pPNMI masking logic that interrupts
are masked by the CPU, not by the PMR. This value is read back by
local_daif_save().

Commit bd82d4bd added this call to el0_svc, as el0_svc_handler
is called with interrupts masked. el0_svc_compat was missed, but should
be covered in the same way as both of these paths end up in
el0_svc_common(), which expects to unmask interrupts.

Fixes: bd82d4bd ("arm64: Fix incorrect irqflag restore for priority masking")
Signed-off-by: James Morse <james.morse@arm.com>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Signed-off-by: Will Deacon <will@kernel.org>

If we take an unhandled fault in the kernel, we call show_pte() to dump
the {PGDP,PGD,PUD,PMD,PTE} values for the corresponding page table walk,
where the PGDP value is virt_to_phys(mm->pgd).

The boot-time and runtime kernel page tables, init_pg_dir and
swapper_pg_dir respectively, are kernel symbols. Thus, it is not valid
to call virt_to_phys() on either of these, though we'll do so if we take
a fault on a TTBR1 address.

When CONFIG_DEBUG_VIRTUAL is not selected, virt_to_phys() will silently
fix this up. However, when CONFIG_DEBUG_VIRTUAL is selected, this
results in splats as below. Depending on when these occur, they can
happen to suppress information needed to debug the original unhandled
fault, such as the backtrace:

| Unable to handle kernel paging request at virtual address ffff7fffec73cf0f
| Mem abort info:
|   ESR = 0x96000004
|   EC = 0x25: DABT (current EL), IL = 32 bits
|   SET = 0, FnV = 0
|   EA = 0, S1PTW = 0
| Data abort info:
|   ISV = 0, ISS = 0x00000004
|   CM = 0, WnR = 0
| ------------[ cut here ]------------
| virt_to_phys used for non-linear address: 00000000102c9dbe (swapper_pg_dir+0x0/0x1000)
| WARNING: CPU: 1 PID: 7558 at arch/arm64/mm/physaddr.c:15 __virt_to_phys+0xe0/0x170 arch/arm64/mm/physaddr.c:12
| Kernel panic - not syncing: panic_on_warn set ...
| SMP: stopping secondary CPUs
| Dumping ftrace buffer:
|    (ftrace buffer empty)
| Kernel Offset: disabled
| CPU features: 0x0002,23000438
| Memory Limit: none
| Rebooting in 1 seconds..

We can avoid this by ensuring that we call __pa_symbol() for
init_mm.pgd, as this will always be a kernel symbol. As the dumped
{PGD,PUD,PMD,PTE} values are the raw values from the relevant entries we
don't need to handle these specially.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

The HWCAP framework will detect a new capability based on the sanitized
version of the ID registers.

Sanitization is based on a whitelist, so any field not described will end
up to be zeroed.

At the moment, ID_AA64ISAR1_EL1.FRINTTS is not described in
ftr_id_aa64isar1. This means the field will be zeroed and therefore the
userspace will not be able to see the HWCAP even if the hardware
supports the feature.

This can be fixed by describing the field in ftr_id_aa64isar1.

Fixes: ca9503fc ("arm64: Expose FRINT capabilities to userspace")
Signed-off-by: Julien Grall <julien.grall@arm.com>
Cc: mark.brown@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

As of ac7c3e4f ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly"),
inline functions are no longer annotated with '__always_inline', which
allows the compiler to decide whether inlining is really a good idea or
not. Although this is a great idea on paper, the reality is that AArch64
GCC prior to 9.1 has been shown to get confused when creating an
out-of-line copy of a function passing explicit 'register' variables
into an inline assembly block:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91111

It's not clear whether this is specific to arm64 or not but, for now,
ensure that all of our functions using 'register' variables are marked
as '__always_inline' so that the old behaviour is effectively preserved.

Hopefully other architectures are luckier with their compilers.

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Will Deacon <will@kernel.org>

Sphinx generates the following warnings for the arm64 doc
pages:

Documentation/arm64/memory.rst:158: WARNING: Unexpected indentation.
Documentation/arm64/memory.rst:162: WARNING: Unexpected indentation.

These indentations warnings can be resolved by utilising code
hightlighting instead.
Signed-off-by: Adam Zerella <adam.zerella@gmail.com>
Signed-off-by: Will Deacon <will@kernel.org>

The system which has SVE feature crashed because of
the memory pointed by task->thread.sve_state was destroyed
by someone.

That is because sve_state is freed while the forking the
child process. The child process has the pointer of sve_state
which is same as the parent's because the child's task_struct
is copied from the parent's one. If the copy_process()
fails as an error on somewhere, for example, copy_creds(),
then the sve_state is freed even if the parent is alive.
The flow is as follows.

copy_process
        p = dup_task_struct
            => arch_dup_task_struct
                *dst = *src;  // copy the entire region.
:
        retval = copy_creds
        if (retval < 0)
                goto bad_fork_free;
:
bad_fork_free:
...
        delayed_free_task(p);
          => free_task
             => arch_release_task_struct
                => fpsimd_release_task
                   => __sve_free
                      => kfree(task->thread.sve_state);
                         // free the parent's sve_state

Move child's sve_state = NULL and clearing TIF_SVE flag
to arch_dup_task_struct() so that the child doesn't free the
parent's one.
There is no need to wait until copy_process() to clear TIF_SVE for
dst, because the thread flags for dst are initialized already by
copying the src task_struct.
This change simplifies the code, so get rid of comments that are no
longer needed.

As a note, arm64 used to have thread_info on the stack. So it
would not be possible to clear TIF_SVE until the stack is initialized.
From commit c02433dd ("arm64: split thread_info from task stack"),
the thread_info is part of the task, so it should be valid to modify
the flag from arch_dup_task_struct().

Cc: stable@vger.kernel.org # 4.15.x-
Fixes: bc0ee476 ("arm64/sve: Core task context handling")
Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reported-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Suggested-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Tested-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

Commit 73f38166 ("arm64: Advertise mitigation of Spectre-v2, or lack
thereof") renamed the caller of the install_bp_hardening_cb() function
but forgot to update a comment, which can be confusing when trying to
follow the code flow.

Fixes: 73f38166 ("arm64: Advertise mitigation of Spectre-v2, or lack thereof")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Will Deacon <will@kernel.org>

Pull btrfs fixes from David Sterba:
 "A bunch of fixes that accumulated in recent weeks, mostly material for
  stable.

  Summary:

   - fix for regression from 5.3 that prevents to use balance convert
     with single profile

   - qgroup fixes: rescan race, accounting leak with multiple writers,
     potential leak after io failure recovery

   - fix for use after free in relocation (reported by KASAN)

   - other error handling fixups"

* tag 'for-5.4-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: qgroup: Fix reserved data space leak if we have multiple reserve calls
  btrfs: qgroup: Fix the wrong target io_tree when freeing reserved data space
  btrfs: Fix a regression which we can't convert to SINGLE profile
  btrfs: relocation: fix use-after-free on dead relocation roots
  Btrfs: fix race setting up and completing qgroup rescan workers
  Btrfs: fix missing error return if writeback for extent buffer never started
  btrfs: adjust dirty_metadata_bytes after writeback failure of extent buffer
  Btrfs: fix selftests failure due to uninitialized i_mode in test inodes

Pull csky updates from Guo Ren:
 "This round of csky subsystem just some fixups:

   - Fix mb() synchronization problem

   - Fix dma_alloc_coherent with PAGE_SO attribute

   - Fix cache_op failed when cross memory ZONEs

   - Optimize arch_sync_dma_for_cpu/device with dma_inv_range

   - Fix ioremap function losing

   - Fix arch_get_unmapped_area() implementation

   - Fix defer cache flush for 610

   - Support kernel non-aligned access

   - Fix 610 vipt cache flush mechanism

   - Fix add zero_fp fixup perf backtrace panic

   - Move static keyword to the front of declaration

   - Fix csky_pmu.max_period assignment

   - Use generic free_initrd_mem()

   - entry: Remove unneeded need_resched() loop"

* tag 'csky-for-linus-5.4-rc1' of git://github.com/c-sky/csky-linux:
  csky: Move static keyword to the front of declaration
  csky: entry: Remove unneeded need_resched() loop
  csky: Fixup csky_pmu.max_period assignment
  csky: Fixup add zero_fp fixup perf backtrace panic
  csky: Use generic free_initrd_mem()
  csky: Fixup 610 vipt cache flush mechanism
  csky: Support kernel non-aligned access
  csky: Fixup defer cache flush for 610
  csky: Fixup arch_get_unmapped_area() implementation
  csky: Fixup ioremap function losing
  csky: Optimize arch_sync_dma_for_cpu/device with dma_inv_range
  csky/dma: Fixup cache_op failed when cross memory ZONEs
  csky: Fixup dma_alloc_coherent with PAGE_SO attribute
  csky: Fixup mb() synchronization problem

Pull ARM SoC fixes from Olof Johansson:
 "A few fixes that have trickled in through the merge window:

   - Video fixes for OMAP due to panel-dpi driver removal

   - Clock fixes for OMAP that broke no-idle quirks + nfsroot on DRA7

   - Fixing arch version on ASpeed ast2500

   - Two fixes for reset handling on ARM SCMI"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc:
  ARM: aspeed: ast2500 is ARMv6K
  reset: reset-scmi: add missing handle initialisation
  firmware: arm_scmi: reset: fix reset_state assignment in scmi_domain_reset
  bus: ti-sysc: Remove unpaired sysc_clkdm_deny_idle()
  ARM: dts: logicpd-som-lv: Fix i2c2 and i2c3 Pin mux
  ARM: dts: am3517-evm: Fix missing video
  ARM: dts: logicpd-torpedo-baseboard: Fix missing video
  ARM: omap2plus_defconfig: Fix missing video
  bus: ti-sysc: Fix handling of invalid clocks
  bus: ti-sysc: Fix clock handling for no-idle quirks

Pull tracing fixes from Steven Rostedt:
 "A few more tracing fixes:

   - Fix a buffer overflow by checking nr_args correctly in probes

   - Fix a warning that is reported by clang

   - Fix a possible memory leak in error path of filter processing

   - Fix the selftest that checks for failures, but wasn't failing

   - Minor clean up on call site output of a memory trace event"

* tag 'trace-v5.4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  selftests/ftrace: Fix same probe error test
  mm, tracing: Print symbol name for call_site in trace events
  tracing: Have error path in predicate_parse() free its allocated memory
  tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN macro
  tracing/probe: Fix to check the difference of nr_args before adding probe

Pull more MMC updates from Ulf Hansson:
 "A couple more updates/fixes for MMC:

   - sdhci-pci: Add Genesys Logic GL975x support

   - sdhci-tegra: Recover loss in throughput for DMA

   - sdhci-of-esdhc: Fix DMA bug"

* tag 'mmc-v5.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc:
  mmc: host: sdhci-pci: Add Genesys Logic GL975x support
  mmc: tegra: Implement ->set_dma_mask()
  mmc: sdhci: Let drivers define their DMA mask
  mmc: sdhci-of-esdhc: set DMA snooping based on DMA coherence
  mmc: sdhci: improve ADMA error reporting

Move the static keyword to the front of declaration of
csky_pmu_of_device_ids, and resolve the following compiler
warning that can be seen when building with warnings
enabled (W=1):

arch/csky/kernel/perf_event.c:1340:1: warning:
  ‘static’ is not at beginning of declaration [-Wold-style-declaration]
Signed-off-by: Krzysztof Wilczynski <kw@linux.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

Since the enabling and disabling of IRQs within preempt_schedule_irq()
is contained in a need_resched() loop, we don't need the outer arch
code loop.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

Pull Documentation/process update from Greg KH:
 "Here are two small Documentation/process/embargoed-hardware-issues.rst
  file updates that missed my previous char/misc pull request.

  The first one adds an Intel representative for the process, and the
  second one cleans up the text a bit more when it comes to how the
  disclosure rules work, as it was a bit confusing to some companies"

* tag 'char-misc-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  Documentation/process: Clarify disclosure rules
  Documentation/process: Volunteer as the ambassador for Intel

Pull more vfs updates from Al Viro:
 "A couple of misc patches"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  afs dynroot: switch to simple_dir_operations
  fs/handle.c - fix up kerneldoc

Pull more cifs updates from Steve French:
 "Fixes from the recent SMB3 Test events and Storage Developer
  Conference (held the last two weeks).

  Here are nine smb3 patches including an important patch for debugging
  traces with wireshark, with three patches marked for stable.

  Additional fixes from last week to better handle some newly discovered
  reparse points, and a fix the create/mkdir path for setting the mode
  more atomically (in SMB3 Create security descriptor context), and one
  for path name processing are still being tested so are not included
  here"

* tag '5.4-rc-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  CIFS: Fix oplock handling for SMB 2.1+ protocols
  smb3: missing ACL related flags
  smb3: pass mode bits into create calls
  smb3: Add missing reparse tags
  CIFS: fix max ea value size
  fs/cifs/sess.c: Remove set but not used variable 'capabilities'
  fs/cifs/smb2pdu.c: Make SMB2_notify_init static
  smb3: fix leak in "open on server" perf counter
  smb3: allow decryption keys to be dumped by admin for debugging

The csky_pmu.max_period has type u64, and BIT() can only return
32 bits unsigned long on C-SKY. The initialization for max_period
will be incorrect when count_width is bigger than 32.

Use BIT_ULL()
Signed-off-by: Mao Han <han_mao@c-sky.com>
Signed-off-by: Guo Ren <ren_guo@c-sky.com>

We need set fp zero to let backtrace know the end. The patch fixup perf
callchain panic problem, because backtrace didn't know what is the end
of fp.
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Reported-by: Mao Han <han_mao@c-sky.com>

The csky implementation of free_initrd_mem() is an open-coded version of
free_reserved_area() without poisoning.

Remove it and make csky use the generic version of free_initrd_mem().
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

Merge active entropy generation updates.

This is admittedly partly "for discussion".  We need to have a way
forward for the boot time deadlocks where user space ends up waiting for
more entropy, but no entropy is forthcoming because the system is
entirely idle just waiting for something to happen.

While this was triggered by what is arguably a user space bug with
GDM/gnome-session asking for secure randomness during early boot, when
they didn't even need any such truly secure thing, the issue ends up
being that our "getrandom()" interface is prone to that kind of
confusion, because people don't think very hard about whether they want
to block for sufficient amounts of entropy.

The approach here-in is to decide to not just passively wait for entropy
to happen, but to start actively collecting it if it is missing.  This
is not necessarily always possible, but if the architecture has a CPU
cycle counter, there is a fair amount of noise in the exact timings of
reasonably complex loads.

We may end up tweaking the load and the entropy estimates, but this
should be at least a reasonable starting point.

As part of this, we also revert the revert of the ext4 IO pattern
improvement that ended up triggering the reported lack of external
entropy.

* getrandom() active entropy waiting:
  Revert "Revert "ext4: make __ext4_get_inode_loc plug""
  random: try to actively add entropy rather than passively wait for it

This reverts commit 72dbcf72.

Instead of waiting forever for entropy that may just not happen, we now
try to actively generate entropy when required, and are thus hopefully
avoiding the problem that caused the nice ext4 IO pattern fix to be
reverted.

So revert the revert.

Cc: Ahmed S. Darwish <darwish.07@gmail.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Alexander E. Patrakov <patrakov@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

For 5.3 we had to revert a nice ext4 IO pattern improvement, because it
caused a bootup regression due to lack of entropy at bootup together
with arguably broken user space that was asking for secure random
numbers when it really didn't need to.

See commit 72dbcf72 (Revert "ext4: make __ext4_get_inode_loc plug").

This aims to solve the issue by actively generating entropy noise using
the CPU cycle counter when waiting for the random number generator to
initialize.  This only works when you have a high-frequency time stamp
counter available, but that's the case on all modern x86 CPU's, and on
most other modern CPU's too.

What we do is to generate jitter entropy from the CPU cycle counter
under a somewhat complex load: calling the scheduler while also
guaranteeing a certain amount of timing noise by also triggering a
timer.

I'm sure we can tweak this, and that people will want to look at other
alternatives, but there's been a number of papers written on jitter
entropy, and this should really be fairly conservative by crediting one
bit of entropy for every timer-induced jump in the cycle counter.  Not
because the timer itself would be all that unpredictable, but because
the interaction between the timer and the loop is going to be.

Even if (and perhaps particularly if) the timer actually happens on
another CPU, the cacheline interaction between the loop that reads the
cycle counter and the timer itself firing is going to add perturbations
to the cycle counter values that get mixed into the entropy pool.

As Thomas pointed out, with a modern out-of-order CPU, even quite simple
loops show a fair amount of hard-to-predict timing variability even in
the absense of external interrupts.  But this tries to take that further
by actually having a fairly complex interaction.

This is not going to solve the entropy issue for architectures that have
no CPU cycle counter, but it's not clear how (and if) that is solvable,
and the hardware in question is largely starting to be irrelevant.  And
by doing this we can at least avoid some of the even more contentious
approaches (like making the entropy waiting time out in order to avoid
the possibly unbounded waiting).

Cc: Ahmed Darwish <darwish.07@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Nicholas Mc Guire <hofrat@opentech.at>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Alexander E. Patrakov <patrakov@gmail.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'fixes-5.4-merge-window' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into arm/fixes

Fixes for omap variants

Few fixes for ti-sysc interconnect target module driver for no-idle
quirks that caused nfsroot to fail on some dra7 boards.

And let's fixes to get LCD working again for logicpd board that got
broken a while back with removal of panel-dpi driver. We need to now
use generic CONFIG_DRM_PANEL_SIMPLE instead.

* tag 'fixes-5.4-merge-window' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  bus: ti-sysc: Remove unpaired sysc_clkdm_deny_idle()
  ARM: dts: logicpd-som-lv: Fix i2c2 and i2c3 Pin mux
  ARM: dts: am3517-evm: Fix missing video
  ARM: dts: logicpd-torpedo-baseboard: Fix missing video
  ARM: omap2plus_defconfig: Fix missing video
  bus: ti-sysc: Fix handling of invalid clocks
  bus: ti-sysc: Fix clock handling for no-idle quirks

Link: https://lore.kernel.org/r/pull-1568819401-72461@atomide.comSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'scmi-fixes-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into arm/fixes

ARM SCMI fixes for v5.4

Couple of fixes: one in scmi reset driver initialising missed scmi handle
and an other in scmi reset API implementation fixing the assignment of
reset state

* tag 'scmi-fixes-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  reset: reset-scmi: add missing handle initialisation
  firmware: arm_scmi: reset: fix reset_state assignment in scmi_domain_reset

Link: https://lore.kernel.org/r/20190918142139.GA4370@bogusSigned-off-by: Olof Johansson <olof@lixom.net>

More libnvdimm updates from Dan Williams:

 - Complete the reworks to interoperate with powerpc dynamic huge page
   sizes

 - Fix a crash due to missed accounting for the powerpc 'struct
   page'-memmap mapping granularity

 - Fix badblock initialization for volatile (DRAM emulated) pmem ranges

 - Stop triggering request_key() notifications to userspace when
   NVDIMM-security is disabled / not present

 - Miscellaneous small fixups

* tag 'libnvdimm-fixes-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  libnvdimm/region: Enable MAP_SYNC for volatile regions
  libnvdimm: prevent nvdimm from requesting key when security is disabled
  libnvdimm/region: Initialize bad block for volatile namespaces
  libnvdimm/nfit_test: Fix acpi_handle redefinition
  libnvdimm/altmap: Track namespace boundaries in altmap
  libnvdimm: Fix endian conversion issues 
  libnvdimm/dax: Pick the right alignment default when creating dax devices
  powerpc/book3s64: Export has_transparent_hugepage() related functions.

Pull thermal SoC updates from Eduardo Valentin:
 "This is a really small pull in the midst of a lot of pending patches.

  We are in the middle of restructuring how we are maintaining the
  thermal subsystem, as per discussion in our last LPC. For now, I am
  sending just some changes that were pending in my tree. Looking
  forward to get a more streamlined process in the next merge window"

* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal:
  thermal: db8500: Rewrite to be a pure OF sensor
  thermal: db8500: Use dev helper variable
  thermal: db8500: Finalize device tree conversion
  thermal: thermal_mmio: remove some dead code

Pull  more i2c updates from Wolfram Sang:

 - make Lenovo Yoga C630 boot now that the dependencies are merged

 - restore BlockProcessCall for i801, accidently removed in this merge
   window

 - a bugfix for the riic driver

 - an improvement to the slave-eeprom driver which should have been in
   the first pull request but sadly got lost in the process

* 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: slave-eeprom: Add read only mode
  i2c: i801: Bring back Block Process Call support for certain platforms
  i2c: riic: Clear NACK in tend isr
  i2c: qcom-geni: Disable DMA processing on the Lenovo Yoga C630

Pull iommu fixes from Joerg Roedel:
 "A couple of fixes for the AMD IOMMU driver have piled up:

   - Some fixes for the reworked IO page-table which caused memory leaks
     or did not allow to downgrade mappings under some conditions.

   - Locking fixes to fix a couple of possible races around accessing
     'struct protection_domain'. The races got introduced when the
     dma-ops path became lock-less in the fast-path"

* tag 'iommu-fixes-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu:
  iommu/amd: Lock code paths traversing protection_domain->dev_list
  iommu/amd: Lock dev_data in attach/detach code paths
  iommu/amd: Check for busy devices earlier in attach_device()
  iommu/amd: Take domain->lock for complete attach/detach path
  iommu/amd: Remove amd_iommu_devtable_lock
  iommu/amd: Remove domain->updated
  iommu/amd: Wait for completion of IOTLB flush in attach_device
  iommu/amd: Unmap all L7 PTEs when downgrading page-sizes
  iommu/amd: Introduce first_pte_l7() helper
  iommu/amd: Fix downgrading default page-sizes in alloc_pte()
  iommu/amd: Fix pages leak in free_pagetable()