headers: Refactor kernel and arch headers.

This commit refactors kernel and arch headers to establish a boundary
between private and public interface headers.

The refactoring strategy used in this commit is detailed in the issue

This commit introduces the following major changes:

1. Establish a clear boundary between private and public headers by
  removing "kernel/include" and "arch/*/include" from the global
  include paths. Ideally, only kernel/ and arch/*/ source files should
  reference the headers in these directories. If these headers must be
  used by a component, these include paths shall be manually added to
  the CMakeLists.txt file of the component. This is intended to
  discourage applications from including private kernel and arch
  headers either knowingly and unknowingly.

  - kernel/include/ (PRIVATE)
    This directory contains the private headers that provide private
   kernel definitions which should not be visible outside the kernel
   and arch source code. All public kernel definitions must be added
   to an appropriate header located under include/.

  - arch/*/include/ (PRIVATE)
    This directory contains the private headers that provide private
   architecture-specific definitions which should not be visible
   outside the arch and kernel source code. All public architecture-
   specific definitions must be added to an appropriate header located
   under include/arch/*/.

  - include/ AND include/sys/ (PUBLIC)
    This directory contains the public headers that provide public
   kernel definitions which can be referenced by both kernel and
   application code.

  - include/arch/*/ (PUBLIC)
    This directory contains the public headers that provide public
   architecture-specific definitions which can be referenced by both
   kernel and application code.

2. Split arch_interface.h into "kernel-to-arch interface" and "public
  arch interface" divisions.

  - kernel/include/kernel_arch_interface.h
    * provides private "kernel-to-arch interface" definition.
    * includes arch/*/include/kernel_arch_func.h to ensure that the
     interface function implementations are always available.
    * includes sys/arch_interface.h so that public arch interface
     definitions are automatically included when including this file.

  - arch/*/include/kernel_arch_func.h
    * provides architecture-specific "kernel-to-arch interface"
     implementation.
    * only the functions that will be used in kernel and arch source
     files are defined here.

  - include/sys/arch_interface.h
    * provides "public arch interface" definition.
    * includes include/arch/arch_inlines.h to ensure that the
     architecture-specific public inline interface function
     implementations are always available.

  - include/arch/arch_inlines.h
    * includes architecture-specific arch_inlines.h in
     include/arch/*/arch_inline.h.

  - include/arch/*/arch_inline.h
    * provides architecture-specific "public arch interface" inline
     function implementation.
    * supersedes include/sys/arch_inline.h.

3. Refactor kernel and the existing architecture implementations.

  - Remove circular dependency of kernel and arch headers. The
   following general rules should be observed:

    * Never include any private headers from public headers
    * Never include kernel_internal.h in kernel_arch_data.h
    * Always include kernel_arch_data.h from kernel_arch_func.h
    * Never include kernel.h from kernel_struct.h either directly or
     indirectly. Only add the kernel structures that must be referenced
     from public arch headers in this file.

  - Relocate syscall_handler.h to include/ so it can be used in the
   public code. This is necessary because many user-mode public codes
   reference the functions defined in this header.

  - Relocate kernel_arch_thread.h to include/arch/*/thread.h. This is
   necessary to provide architecture-specific thread definition for
   'struct k_thread' in kernel.h.

  - Remove any private header dependencies from public headers using
   the following methods:

    * If dependency is not required, simply omit
    * If dependency is required,
      - Relocate a portion of the required dependencies from the
       private header to an appropriate public header OR
      - Relocate the required private header to make it public.

This commit supersedes #20047, addresses #19666, and fixes #3056.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

subsys/testsuite/ztest/include/arch/cpu.h

@@ -6,6 +6,18 @@
 
 /* This file exists as a hack around Zephyr's dependencies */
 
+/* Architecture thread structure */
+struct _callee_saved {
+};
+
+typedef struct _callee_saved _callee_saved_t;
+
+struct _thread_arch {
+};
+
+typedef struct _thread_arch _thread_arch_t;
+
+/* Architecture functions */
 static inline u32_t z_arch_k_cycle_get_32(void)
 {
 	return 0;
@@ -26,7 +38,7 @@ static inline bool z_arch_irq_unlocked(unsigned int key)
 	return 0;
 }
 
-#include <sys/arch_inlines.h>
+#include <sys/arch_interface.h>
 
 
 #endif /* ZEPHYR_SUBSYS_TESTSUITE_ZTEST_INCLUDE_ARCH_CPU_H */

subsys/testsuite/ztest/include/kernel_arch_thread.h

@@ -1,38 +0,0 @@
-/*
- * Copyright (c) 2017 Intel Corporation
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
-/**
- * @file
- * @brief Per-arch thread definition
- *
- * This file contains definitions for
- *
- *  struct _thread_arch
- *  struct _callee_saved
- *
- * necessary to instantiate instances of struct k_thread.
- */
-
-
-#ifndef _kernel_arch_thread__h_
-#define _kernel_arch_thread__h_
-
-#ifndef _ASMLANGUAGE
-
-struct _callee_saved {
-};
-
-typedef struct _callee_saved _callee_saved_t;
-
-struct _thread_arch {
-};
-
-typedef struct _thread_arch _thread_arch_t;
-
-#endif /* _ASMLANGUAGE */
-
-#endif /* _kernel_arch_thread__h_ */
-

subsys/testsuite/ztest/include/ztest.h

@@ -35,6 +35,7 @@
 #define CONFIG_NUM_COOP_PRIORITIES 16
 #define CONFIG_COOP_ENABLED 1
 #define CONFIG_PREEMPT_ENABLED 1
+#define CONFIG_MP_NUM_CPUS 1
 #define CONFIG_SYS_CLOCK_TICKS_PER_SEC 100
 #define CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC 10000000
 /* FIXME: Properly integrate with Zephyr's arch specific code */