[BUILD] rewrite CMake build system to track changes of source files

This change restructures the source code directories, separates shared
form non-shared application code and adds CMake dependencies. These
dependencies allow the tracking of changes and trigger a rebuild of
those build targets where changed files are involved.

WARNING: Note that the support of the DNBD3_SERVER_AFL build option is
not supported yet. Thus, the option should be never turned on.

4 files changed, 111 insertions, 0 deletions

diff --git a/cmake/GenerateVersion.cmake b/cmake/GenerateVersion.cmake
new file mode 100644
index 0000000..e336489
--- /dev/null
+++ b/cmake/GenerateVersion.cmake
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2020 Manuel Bentele <development@manuel-bentele.de>
+#
+
+# get Git short hash and tag of latest repository commit
+execute_process(COMMAND git describe HEAD
+                OUTPUT_VARIABLE DNBD3_VERSION
+                OUTPUT_STRIP_TRAILING_WHITESPACE)
+if(DNBD3_VERSION STREQUAL "")
+    set(DNBD3_VERSION "unknown")
+endif(DNBD3_VERSION STREQUAL "")
+
+# write dnbd3 version into a new C source file based on the specified version template
+configure_file(${VERSION_INPUT_FILE} ${VERSION_OUTPUT_FILE})
diff --git a/cmake/Kernel.cmake b/cmake/Kernel.cmake
new file mode 100644
index 0000000..232c298
--- /dev/null
+++ b/cmake/Kernel.cmake
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# CMake macros to build and install Linux kernel modules
+# Copyright (C) 2020 Manuel Bentele <development@manuel-bentele.de>
+#
+
+# macro to define kernel module targets
+macro(add_kernel_module MODULE_NAME KERNEL_BUILD_DIR KERNEL_INSTALL_DIR MODULE_MACRO MODULE_SOURCE_FILES MODULE_HEADER_FILES BUILD_SOURCE_FILE)
+    # create directory for kernel module
+    file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME})
+    # copy build source file
+    get_filename_component(BUILD_SOURCE_FILENAME ${BUILD_SOURCE_FILE} NAME)
+    add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${BUILD_SOURCE_FILENAME}
+                       COMMAND ${CMAKE_COMMAND} -E copy_if_different ${BUILD_SOURCE_FILE} ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}
+                       DEPENDS ${BUILD_SOURCE_FILE})
+    set(BUILD_SOURCE_FILE_PREPARED ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${BUILD_SOURCE_FILENAME})
+    # copy source files
+    foreach(MODULE_SOURCE_FILE ${MODULE_SOURCE_FILES})
+        get_filename_component(MODULE_SOURCE_FILENAME ${MODULE_SOURCE_FILE} NAME)
+        add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_SOURCE_FILENAME}
+                           COMMAND ${CMAKE_COMMAND} -E copy_if_different ${MODULE_SOURCE_FILE} ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}
+                           DEPENDS ${MODULE_SOURCE_FILE})
+        set(MODULE_SOURCE_FILES_PREPARED ${MODULE_SOURCE_FILES_PREPARED}
+                                         ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_SOURCE_FILENAME})
+    endforeach()
+    # copy header files
+    foreach(MODULE_HEADER_FILE ${MODULE_HEADER_FILES})
+        get_filename_component(MODULE_HEADER_FILENAME ${MODULE_HEADER_FILE} NAME)
+        add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_HEADER_FILENAME}
+                           COMMAND ${CMAKE_COMMAND} -E copy_if_different ${MODULE_HEADER_FILE} ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}
+                           DEPENDS ${MODULE_HEADER_FILE})
+        set(MODULE_HEADER_FILES_PREPARED ${MODULE_HEADER_FILES_PREPARED}
+                                         ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_HEADER_FILENAME})
+    endforeach()
+    # check if module depends on another module
+    if(NOT ${ARGV7} STREQUAL "")
+        set(MODULE_EXTRA_SYMBOLS ${CMAKE_CURRENT_BINARY_DIR}/${ARGV7}/Module.symvers)
+    endif()
+    # define build command
+    set(MODULE_BUILD_COMMAND ${CMAKE_MAKE_PROGRAM} ${MODULE_MACRO}
+                                                   -C ${KERNEL_BUILD_DIR}
+                                                    M=${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME} modules
+                                                    EXTRA_CFLAGS=${KERNEL_C_FLAGS}
+                                                    KBUILD_EXTRA_SYMBOLS=${MODULE_EXTRA_SYMBOLS})
+    add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_NAME}.ko
+                       COMMAND ${MODULE_BUILD_COMMAND}
+                       WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}
+                       COMMENT "Build kernel module ${MODULE_NAME}"
+                       DEPENDS ${BUILD_SOURCE_FILE_PREPARED} ${MODULE_HEADER_FILES_PREPARED} ${MODULE_SOURCE_FILES_PREPARED}
+                       VERBATIM)
+    add_custom_target(${MODULE_NAME} ALL DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_NAME}.ko ${ARGV7})
+    # install kernel module
+    install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${MODULE_NAME}/${MODULE_NAME}.ko
+            DESTINATION ${KERNEL_INSTALL_DIR}
+            PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
+            COMPONENT kernel)
+endmacro(add_kernel_module)
diff --git a/cmake/KernelVersion.cmake b/cmake/KernelVersion.cmake
new file mode 100644
index 0000000..1ded072
--- /dev/null
+++ b/cmake/KernelVersion.cmake
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2020 Manuel Bentele <development@manuel-bentele.de>
+#
+
+# get Linux kernel version from KERNEL_BUILD_DIR string
+macro(get_kernel_version LINUX_KERNEL_VERSION KERNEL_BUILD_DIR)
+    string(REGEX MATCH "[0-9]+\\.[0-9]+\\.[0-9]+" LINUX_KERNEL_VERSION ${KERNEL_BUILD_DIR})
+    if(LINUX_KERNEL_VERSION STREQUAL "")
+        set(LINUX_KERNEL_VERSION "unknown")
+    endif(LINUX_KERNEL_VERSION STREQUAL "")
+endmacro(get_kernel_version LINUX_KERNEL_VERSION KERNEL_BUILD_DIR)
diff --git a/cmake/ProjectVersion.cmake b/cmake/ProjectVersion.cmake
new file mode 100644
index 0000000..108505d
--- /dev/null
+++ b/cmake/ProjectVersion.cmake
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2020 Manuel Bentele <development@manuel-bentele.de>
+#
+
+macro(gen_project_version VERSION_INPUT_FILE VERSION_OUTPUT_FILE)
+    get_filename_component(VERSION_OUTPUT_FILENAME ${VERSION_OUTPUT_FILE} NAME)
+    # command that will trigger a rebuild of version.c every time
+    add_custom_command(OUTPUT regenerate-version-file
+                       COMMAND ${CMAKE_COMMAND} -E sleep 0
+                       COMMENT "Trigger generating ${VERSION_OUTPUT_FILENAME}")
+
+    # call the GenerateVersion.cmake file to generate the version.c file
+    add_custom_command(OUTPUT ${VERSION_OUTPUT_FILE}
+                       COMMAND ${CMAKE_COMMAND} -D VERSION_INPUT_FILE=${VERSION_INPUT_FILE}
+                                                -D VERSION_OUTPUT_FILE=${VERSION_OUTPUT_FILE}
+                                                -P ${PROJECT_MODULES_DIR}/GenerateVersion.cmake
+                       COMMENT "Generating ${VERSION_OUTPUT_FILENAME}"
+                       DEPENDS regenerate-version-file)
+    add_custom_target(dnbd3-generate-version DEPENDS ${VERSION_OUTPUT_FILE})
+
+    # create target to expose project version
+    add_library(dnbd3-version INTERFACE)
+    target_include_directories(dnbd3-version INTERFACE ${PROJECT_INCLUDE_TMP_DIR})
+    add_dependencies(dnbd3-version dnbd3-generate-version)
+
+endmacro(gen_project_version VERSION_INPUT_FILE VERSION_OUTPUT_FILE)