This merge contains the user-visible, ABI-breaking changes that we want
to make sure we have in Linux before our first release. Highlights
include:

* VDSO entries for clock_get/gettimeofday/getcpu have been added. These
are simple syscalls now, but we want to let glibc use them from the
start so we can make them faster later.
* A VDSO entry for instruction cache flushing has been added so
userspace can flush the instruction cache.
* The VDSO symbol versions for __vdso_cmpxchg{32,64} have been removed,
as those VDSO entries don't actually exist.

Conflicts:
arch/riscv/include/asm/tlbflush.h

This patch set is the result of some feedback that filtered through
after our original patch set was reviewed, some of which was the result
of me missing some email. It contains:

* A new READ_ONCE in arch_spin_is_locked()
* __test_and_op_bit_ord() is now actually ordered
* Improvements to various comments
* Removal of some dead code

We used to have some cmpxchg syscalls. They're no longer there, so we
no longer need the include.

CC: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

This was removed from the other architectures in commit
952111d7db02 ("arch: Remove spin_unlock_wait() arch-specific
definitions"). That landed between when we got upstream and when our
patches were reviewed, so this is a followup patch.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

Despite RISC-V having a direct 'fence.i' instruction available to
userspace (which we can't trap!), that's not actually viable when
running on Linux because the kernel might schedule a process on another
hart. There is no way for userspace to handle this without invoking the
kernel (as it doesn't know the thread->hart mappings), so we've defined
a RISC-V specific system call to flush the instruction cache.

This patch adds both a system call and a VDSO entry. If possible, we'd
like to avoid having the system call be considered part of the
user-facing ABI and instead restrict that to the VDSO entry -- both just
in general to avoid having additional user-visible ABI to maintain, and
because we'd prefer that users just call the VDSO entry because there
might be a better way to do this in the future (ie, one that doesn't
require entering the kernel).

Signed-off-by: Andrew Waterman <andrew@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

Pull ARM fixes from Russell King:

- LPAE fixes for kernel-readonly regions

- Fix for get_user_pages_fast on LPAE systems

- avoid tying decompressor to a particular platform if DEBUG_LL is
enabled

- BUG if we attempt to return to userspace but the to-be-restored PSR
value keeps us in privileged mode (defeating an issue that ftracetest
found)

* 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm:
ARM: BUG if jumping to usermode address in kernel mode
ARM: 8722/1: mm: make STRICT_KERNEL_RWX effective for LPAE
ARM: 8721/1: mm: dump: check hardware RO bit for LPAE
ARM: make decompressor debug output user selectable
ARM: fix get_user_pages_fast

This is just a comment change, but it's one that bit me on the mailing
list. It turns out that issuing a `sfence.vma` enforces instruction
cache ordering in addition to TLB ordering. This isn't explicitly
called out in the ISA manual, but Andrew will be making that more clear
in a future revision.

CC: Andrew Waterman <andrew@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

The RISC-V ISA allows for instruction caches that are not coherent WRT
stores, even on a single hart. As a result, we need to explicitly flush
the instruction cache whenever marking a dirty page as executable in
order to preserve the correct system behavior.

Local instruction caches aren't that scary (our implementations actually
flush the cache, but RISC-V is defined to allow higher-performance
implementations to exist), but RISC-V defines no way to perform an
instruction cache shootdown. When explicitly asked to do so we can
shoot down remote instruction caches via an IPI, but this is a bit on
the slow side.

Instead of requiring an IPI to all harts whenever marking a page as
executable, we simply flush the currently running harts. In order to
maintain correct behavior, we additionally mark every other hart as
needing a deferred instruction cache which will be taken before anything
runs on it.

Signed-off-by: Andrew Waterman <andrew@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

Pull irq fixes from Thomas Glexiner:

- unbreak the irq trigger type check for legacy platforms

- a handful fixes for ARM GIC v3/4 interrupt controllers

- a few trivial fixes all over the place

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
genirq/matrix: Make - vs ?: Precedence explicit
irqchip/imgpdc: Use resource_size function on resource object
irqchip/qcom: Fix u32 comparison with value less than zero
irqchip/exiu: Fix return value check in exiu_init()
irqchip/gic-v3-its: Remove artificial dependency on PCI
irqchip/gic-v4: Add forward definition of struct irq_domain_ops
irqchip/gic-v3: pr_err() strings should end with newlines
irqchip/s3c24xx: pr_err() strings should end with newlines
irqchip/gic-v3: Fix ppi-partitions lookup
irqchip/gic-v4: Clear IRQ_DISABLE_UNLAZY again if mapping fails
genirq: Track whether the trigger type has been set

Detect if we are returning to usermode via the normal kernel exit paths
but the saved PSR value indicates that we are in kernel mode. This
could occur due to corrupted stack state, which has been observed with
"ftracetest".

This ensures that we catch the problem case before we get to user code.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

This was just incorrect in the original version.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

For now these are just placeholders that execute the syscall. We will
later optimize them to avoid kernel crossings, but we'd like to have the
VDSO entries from the first released kernel version to make the ABI
simpler.

Signed-off-by: Andrew Waterman <andrew@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>