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When a CPU is unplugged, make sure to drop all per-CPU ipipe timer
devices when removing the CPU. Otherwise, we will corrupt the device
list when re-registering the host timer on CPU onlining.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

linux/ipipe_base.h was originally designed to circumvment #include
hell by exporting only a subset of core definitions with minimum
dependencies to other inner headers.

The latest code reorganization fixed this issue in a better way, and
linux/ipipe.h is currently the only direct reader of
linux/ipipe_base.h, so let's merge both headers back as linux/ipipe.h.

At least one arch, infamous x86, has a difference of NR_syscalls
depending on compat vs. native ABI. Account for that by introducing a
function that can deliver the currently valid syscall number if an arch
implements such a service. In all other cases, this change is
functionally no difference.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

This I-pipe hook reports the desired resumption mode to the subscriber:
resume all process tasks or just single-step a particular one? The use
case is to enable synchronous stopping / resuming of all head tasks of
a ptraced real-time process.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

A little bit inspired by the kernel's user return notifier, this
introduces an I-pipe hook before the kernel jumps back to a userspace
context from the root domain. The hook is design to allow a switch back
to the head domain, thus will not run through signal/preemption checks
when returning from the callback over head. It is guaranteed to fire on
return from interrupts and exceptions but may also fire on certain
syscall-return paths.

The first use case for the hook is resumption of ptraced tasks over
head if they were stopped in that domain.

This provides just the generic infrastructure, the invocation of
__ipipe_notify_user_intreturn as well as the definition of
TIP_USERINTRET are architecture-specific.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

__ipipe_migrate_head() should not BUG() unconditionally when failing
to schedule out a thread, but rather let the real-time core handle the
situation a bit more gracefully.

Only timers stolen away from the host kernel should be early acked by
the pipeline core. Otherwise, the regular IRQ handler associated to
the timer would duplicate the action. The IRQ line is left masked,
waiting for the IRQ flow handler to unmask it eventually.

Although we don't want to disable the hardware not to wreck the
outstanding timing requests managed by the co-kernel, we should
nevertheless notify it about entering the ONESHOT_STOPPED mode, so
that it may disable the host tick emulation.

There is no point in interposing on clock chip handlers for which
there was no support originally. In some cases (oneshot_stopped), we
may even get a kernel fault, jumping to a NULL address.

Interpose on non-NULL original handlers only.

Although we won't allow disabling the hardware when the clock event
logic switches a device to stopped mode - so that we won't affect the
timer logic running on the head stage unexpectedly -, we still have to
enable the hardware when switched (back) to oneshot mode, since it may
have been stopped prior to interposing on the device in
ipipe_timer_start().

Failing to do so would leave the hardware shut down for both regular
and Xenomai operations, with no mean to bring it up again.

Once the device was grabbed by ipipe_timer_start(), any pending host
tick programmed in the hardware is basically lost, unknown to the
co-kernel implementing the proxy handlers.

Schedule a host event with the latest target time programmed to have
the co-kernel know about the pending tick.

Handle requests for transitioning to deeper C-states the way Dovetail
does, which prevents us from losing the timer when grabbed by a
co-kernel, in presence of a CPUIDLE driver.

Those helpers affect both the real (in CPU) and virtual interrupt
states for the root stage, reconciling them.

At this chance, switch the min_delay_tick value to unsigned long to
match the corresponding clockevent definition.

Drop the legacy support for architectures not enabling the generic
clock event framework, which would only provide periodic timing.

We don't support any of those archs, and there is no point in running
a Xenomai co-kernel on a hardware not capable of handling oneshot
timing requests.

Now that stop_machine() guarantees fully atomic execution of the stop
routine via hard interrupt disabling, there is no point in using
ipipe_critical_enter/exit() for the same purpose in order to patch the
kernel text.

stop_machine() guarantees that all online CPUs are spinning
non-preemptible in a known code location before a subset of them may
safely run a stop-context function. This service is typically useful
for live patching the kernel code, or changing global memory mappings,
so that no activity could run in parallel until the system has
returned to a stable state after all stop-context operations have
completed.

When interrupt pipelining is enabled, we have to provide the same
guarantee by restoring hard interrupt disabling where virtualizing the
interrupt disable flag would defeat it.

The lockdep engine will check for the current interrupt state as part
of the locking validation process, which must encompass:

- the CPU interrupt state
- the current pipeline domain
- the virtual interrupt disable flag

so that we can traverse the tracepoints from any context sanely and
safely.

In addition trace_hardirqs_on_virt_caller() should be called by the
arch-dependent code when tracking the interrupt state before returning
to user-space after a kernel entry (exceptions, IRQ). This makes sure
that the tracking logic only applies to the root domain, and considers
the virtual disable flag exclusively.

For instance, the kernel may be entered when interrupts are (only)
virtually disabled for the root domain (i.e. stalled), and we should
tell the IRQ tracing logic that IRQs are about to be enabled back only
if the root domain is unstalled before leaving to user-space. In such
a context, the state of the interrupt bit in the CPU would be
irrelevant.

Fix up the PMU controller driver of the Marvell Dove SoC in order to
channel interrupts through the interrupt pipeline.

Fix up Synopsys's PCIE driver in order to channel interrupts through
the interrupt pipeline.

Fix up Altera's PCIE driver in order to channel interrupts through the
interrupt pipeline.

Fix up the pin controller driver of the Allwinner A1x SoCs in order to
channel interrupts through the interrupt pipeline.

Fix up the pin controller driver of the Broadcom 2835 SoC in order to
channel interrupts through the interrupt pipeline.

Fix up the pin controller driver of the Rockchip SoC in order to
channel interrupts through the interrupt pipeline.

Enable the serial driver for raw_printk() output.

Enable the serial driver for raw_printk() output.

Enable the serial driver for raw_printk() output.

Fix up Freescale's general power controller driver in order to channel
interrupts through the interrupt pipeline.

Fix up Broadcom's Generic Set Top Box (Level 2) interrupt controller
driver in order to channel interrupts through the interrupt pipeline.