Add Kconfig symbol, asm/mtd-xip.h header and define related macros:
xip_cpu_idle, xip_irqpending, xip_currtime and xip_elapsed_since.
Append .xiptext to the vectors when separate vectors are configured
because otherwise they are appended to the data and data may not even be
executable in XIP configuration.

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

Idle code is very like entry code in that RCU isn't available. As
such, add a little validation.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195540.373461409@infradead.org

Whether xtensa cores start from primary or secondary reset vector is
configurable and may be chosen by board designer or controlled at
runtime. When secondary reset vector is unused its location in memory
may not be writable.
Make secondary reset vector support conditional and don't build and load
secondary reset vector code when it is disabled.

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

There's no need in window overflow/underflow/alloca exception handlers
or window spill code when neither kernel nor userspace support windowed
registers. Don't build or link it.

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

Allow vectors to be either merged into the kernel .text or put at a
fixed virtual address independently of XIP option. Drop option that
puts vectors at a fixed offset from the kernel text. Add choice to
Kconfig.
Vectors at fixed virtual address may be useful for XIP-aware MTD support
and for noMMU configurations with available IRAM. Configurations without
VECBASE register must put their vectors at specific locations regardless
of the selected option. All other configurations should happily use
merged vectors.

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

There's no real dependency between SMP and XIP, allow them to be
selected together. Always define 2- and 4-argument SECTION_VECTOR
macros, always use 4-argument macro for the secondary reset vector and
always define relocation entry for it.

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

On XIP kernels it makes sense to have exception vectors and fast
exception handlers together (in a fast memory). In addition, with MTD
XIP support both vectors and fast exception handlers must be outside of
the FLASH.

Add section .exception.text and move fast exception handlers to it.
Put it together with vectors when vectors are outside of the .text.

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

Pull Xtensa updates from Max Filippov:

 - add support for execute in place (XIP) kernels

 - improvements in inline assembly: use named arguments and "m"
   constraints where possible

 - improve stack dumping

 - clean up system_call code and syscall tracing

 - various small fixes and cleanups

* tag 'xtensa-20191201' of git://github.com/jcmvbkbc/linux-xtensa: (30 commits)
  xtensa: clean up system_call/xtensa_rt_sigreturn interaction
  xtensa: fix system_call interaction with ptrace
  xtensa: rearrange syscall tracing
  xtensa: fix syscall_set_return_value
  xtensa: drop unneeded headers from coprocessor.S
  xtensa: entry: Remove unneeded need_resched() loop
  xtensa: use MEMBLOCK_ALLOC_ANYWHERE for KASAN shadow map
  xtensa: fix TLB sanity checker
  xtensa: get rid of __ARCH_USE_5LEVEL_HACK
  xtensa: mm: fix PMD folding implementation
  xtensa: make stack dump size configurable
  xtensa: improve stack dumping
  xtensa: use "m" constraint instead of "r" in futex.h assembly
  xtensa: use "m" constraint instead of "a" in cmpxchg.h assembly
  xtensa: use named assembly arguments in cmpxchg.h
  xtensa: use "m" constraint instead of "a" in atomic.h assembly
  xtensa: use named assembly arguments in atomic.h
  xtensa: use "m" constraint instead of "a" in bitops.h assembly
  xtensa: use named assembly arguments in bitops.h
  xtensa: use macros to generate *_bit and test_and_*_bit functions
  ...

Section .fixup contains pieces of code, merge it with the rest of the
.text section.

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

XIP (eXecute In Place) kernel image is the image that can be run
directly from ROM, using RAM only for writable data.

XIP xtensa kernel differs from regular xtensa kernel in the following
ways:
- it has exception/IRQ vectors merged into text section. No vectors
  relocation takes place at kernel startup.
- .data/.bss location must be specified in the kernel configuration,
  its content is copied there in the _startup function.
- .init.text is merged with the rest of text and is executed from ROM.
- when MMU is used the virtual address where the kernel will be mapped
  must be specified in the kernel configuration. It may be in the KSEG
  or in the KIO, __pa macro is adjusted to be able to handle both.

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