For some reason (ancient assembler?) the following build error is
reported by the kisskb:

  kisskb/src/arch/xtensa/kernel/entry.S: Error: unknown pseudo-op: `.bss':
  => 2176

Change abbreviated '.bss' to the full '.section .bss, "aw"' to fix this
error.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

When call0 userspace ABI support by probing is enabled instructions that
cause illegal instruction exception when PS.WOE is clear are retried
with PS.WOE set before calling c-level exception handler. Record user pc
at which PS.WOE was set in the fast exception handler and clear PS.WOE
in the c-level exception handler if we get there from the same address.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Don't use numeric labels for long jumps, use named local labels instead.
Avoid conditional label definition.
No functional changes.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

When fast_store_prohibited needs to go to the C-level exception handler
it leaves TLB entry that caused page fault in the TLB. If the faulting
task gets switched to a different CPU and completes page table update
there the TLB entry will get out of sync with the page table which may
cause a livelock on access to that page.
Invalidate faulting TLB entry on a slow path exit from the
fast_store_prohibited.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Define ARCH_HIBERNATION_POSSIBLE in Kconfig and implement hibernation
callbacks.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Current coprocessor support on xtensa only works correctly on
uniprocessor configurations. Make it work on SMP too and keep it lazy.

Make coprocessor_owner array per-CPU and move it to struct exc_table for
easy access from the fast_coprocessor exception handler. Allow task to
have live coprocessors only on single CPU, record this CPU number in the
struct thread_info::cp_owner_cpu. Change struct thread_info::cpenable
meaning to be 'coprocessors live on cp_owner_cpu'.
Introduce C-level coprocessor exception handler that flushes and
releases live coprocessors of the task taking 'coprocessor disabled'
exception and call it from the fast_coprocessor handler when the task
has live coprocessors on other CPU.
Make coprocessor_flush_all and coprocessor_release_all work correctly
when called from any CPU by sending IPI to the cp_owner_cpu. Add
function coprocessor_flush_release_all to do flush followed by release
atomically. Add function local_coprocessors_flush_release_all to flush
and release all coprocessors on the local CPU and use it to flush
coprocessor contexts from the CPU that goes offline.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Put user exit context tracking call on the common kernel entry/exit path
(function calls are impossible at earlier kernel entry stages because
PS.EXCM is not cleared yet). Put user entry context tracking call on the
user exit path. Syscalls go through this common code too, so nothing
specific needs to be done for them.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Using plain register names is prone to errors when code is changed and
new calls are added between the register load and use. Change plain
register names to abi_* names in the call-heavy part of the kernel exit
code to clearly indicate what's supposed to be preserved and what's not.
Re-align code while at it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Context tracking call must be done after hardirq tracking call,
otherwise lockdep_assert_irqs_disabled called from rcu_eqs_exit gives
a warning. To avoid context tracking logic duplication for IRQ/exception
entry paths move trace_hardirqs_off call back to common entry code.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

KERNEL_STACK_OVERFLOW_CHECK is incomplete and have never been enabled.
Remove it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>