libelf.cmake

# SPDX-License-Identifier: Apache-2.0
#
# Copyright (C) 2023 The Falco Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
# specific language governing permissions and limitations under the License.
#

option(USE_BUNDLED_LIBELF "Enable building of the bundled libelf" ${USE_BUNDLED_DEPS})
option(USE_SHARED_LIBELF "When not using bundled libelf, link it dynamically" ON)

if(LIBELF_INCLUDE)
    # we already have LIBELF
elseif(NOT USE_BUNDLED_LIBELF)
    find_path(LIBELF_INCLUDE elf.h PATH_SUFFIXES elf)
    if(BUILD_SHARED_LIBS OR USE_SHARED_LIBELF)
        set(LIBELF_LIB_SUFFIX ${CMAKE_SHARED_LIBRARY_SUFFIX})
    else()
        set(LIBELF_LIB_SUFFIX ${CMAKE_STATIC_LIBRARY_SUFFIX})
    endif()
    find_library(LIBELF_LIB NAMES libelf${LIBELF_LIB_SUFFIX})
    if(LIBELF_LIB)
        message(STATUS "Found LIBELF: include: ${LIBELF_INCLUDE}, lib: ${LIBELF_LIB}")
    else()
        message(FATAL_ERROR "Couldn't find system libelf")
    endif()
    # We add a custom target, in this way we can always depend on `libelf`
    # without distinguishing between "bundled" and "not-bundled" case
    add_custom_target(libelf)
else()
    if(BUILD_SHARED_LIBS)
        set(LIBELF_LIB_SUFFIX ${CMAKE_SHARED_LIBRARY_SUFFIX})
    else()
        set(LIBELF_LIB_SUFFIX ${CMAKE_STATIC_LIBRARY_SUFFIX})
    endif()
    set(LIBELF_CFLAGS "-I${ZLIB_INCLUDE}")
    if (ENABLE_PIC)
        set(LIBELF_CFLAGS "${LIBELF_CFLAGS} -fPIC")
    endif()
    set(LIBELF_SRC "${PROJECT_BINARY_DIR}/libelf-prefix/src")
    set(LIBELF_INCLUDE "${LIBELF_SRC}/libelf/libelf")
    set(LIBELF_LIB "${LIBELF_SRC}/libelf/libelf/libelf${LIBELF_LIB_SUFFIX}")
    ExternalProject_Add(
            libelf
            PREFIX "${PROJECT_BINARY_DIR}/libelf-prefix"
            DEPENDS zlib
            URL "https://sourceware.org/elfutils/ftp/0.189/elfutils-0.189.tar.bz2"
            URL_HASH "SHA256=39bd8f1a338e2b7cd4abc3ff11a0eddc6e690f69578a57478d8179b4148708c8"
            CONFIGURE_COMMAND ./configure LDFLAGS=-L${ZLIB_SRC} "CFLAGS=${LIBELF_CFLAGS}" --enable-deterministic-archives --disable-debuginfod --disable-libdebuginfod --without-zstd
            BUILD_IN_SOURCE 1
            BUILD_COMMAND make -C lib libeu.a
            COMMAND make -C libelf libelf${LIBELF_LIB_SUFFIX}
            INSTALL_COMMAND ""
            UPDATE_COMMAND ""
            BUILD_BYPRODUCTS ${LIBELF_LIB}
    )
    message(STATUS "Using bundled libelf: include'${LIBELF_INCLUDE}', lib: ${LIBELF_LIB}")
    install(FILES "${LIBELF_LIB}" DESTINATION "${CMAKE_INSTALL_LIBDIR}/${LIBS_PACKAGE_NAME}"
            COMPONENT "libs-deps")
    install(DIRECTORY "${LIBELF_INCLUDE}" DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${LIBS_PACKAGE_NAME}"
            COMPONENT "libs-deps")
endif()

# We add a custom target, in this way we can always depend on `libelf`
# without distinguishing between "bundled" and "not-bundled" case
if(NOT TARGET libelf)
    add_custom_target(libelf)
endif()

include_directories(${LIBELF_INCLUDE})