cmake: Add dependency to LibELF

Add a new a `FindLibElf.cmake` package, and use it to link the main
`libbcc` library against the system's LibELF. This library will be used
to re-implement functionality that was previously dependent on
`binutils`.

CMakeLists.txt

@@ -47,6 +47,8 @@ if(NOT DEFINED BCC_KERNEL_MODULES_DIR)
   set(BCC_KERNEL_MODULES_DIR "/lib/modules")
 endif()
 
+find_package(LibElf REQUIRED)
+
 # Set to non-zero if system installs kernel headers with split source and build
 # directories in /lib/modules/`uname -r`/. This is the case for debian and
 # suse, to the best of my knowledge.

cmake/FindLibElf.cmake

+# - Try to find libelf
+# Once done this will define
+#
+#  LIBELF_FOUND - system has libelf
+#  LIBELF_INCLUDE_DIRS - the libelf include directory
+#  LIBELF_LIBRARIES - Link these to use libelf
+#  LIBELF_DEFINITIONS - Compiler switches required for using libelf
+#
+#  Copyright (c) 2008 Bernhard Walle <bernhard.walle@gmx.de>
+#
+#  Redistribution and use is allowed according to the terms of the New
+#  BSD license.
+#  For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+#
+
+
+if (LIBELF_LIBRARIES AND LIBELF_INCLUDE_DIRS)
+  set (LibElf_FIND_QUIETLY TRUE)
+endif (LIBELF_LIBRARIES AND LIBELF_INCLUDE_DIRS)
+
+find_path (LIBELF_INCLUDE_DIRS
+  NAMES
+    libelf.h
+  PATHS
+    /usr/include
+    /usr/include/libelf
+    /usr/local/include
+    /usr/local/include/libelf
+    /opt/local/include
+    /opt/local/include/libelf
+    /sw/include
+    /sw/include/libelf
+    ENV CPATH)
+
+find_library (LIBELF_LIBRARIES
+  NAMES
+    elf
+  PATHS
+    /usr/lib
+    /usr/local/lib
+    /opt/local/lib
+    /sw/lib
+    ENV LIBRARY_PATH
+    ENV LD_LIBRARY_PATH)
+
+include (FindPackageHandleStandardArgs)
+
+
+# handle the QUIETLY and REQUIRED arguments and set LIBELF_FOUND to TRUE if all listed variables are TRUE
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(LibElf DEFAULT_MSG
+  LIBELF_LIBRARIES
+  LIBELF_INCLUDE_DIRS)
+
+SET(CMAKE_REQUIRED_LIBRARIES elf)
+INCLUDE(CheckCXXSourceCompiles)
+CHECK_CXX_SOURCE_COMPILES("#include <libelf.h>
+int main() {
+  Elf *e = (Elf*)0;
+  size_t sz;
+  elf_getshdrstrndx(e, &sz);
+  return 0;
+}" ELF_GETSHDRSTRNDX)
+
+mark_as_advanced(LIBELF_INCLUDE_DIRS LIBELF_LIBRARIES ELF_GETSHDRSTRNDX)

src/cc/CMakeLists.txt

@@ -8,6 +8,7 @@ include_directories(${CMAKE_CURRENT_BINARY_DIR}/frontends/b)
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/frontends/b)
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/frontends/clang)
 include_directories(${LLVM_INCLUDE_DIRS})
+include_directories(${LIBELF_INCLUDE_DIRS})
 # todo: if check for kernel version
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/compat)
 add_definitions(${LLVM_DEFINITIONS})
@@ -52,8 +53,8 @@ set(clang_libs ${libclangFrontend} ${libclangSerialization} ${libclangDriver} ${
   ${libclangAST} ${libclangLex} ${libclangBasic})
 
 # Link against LLVM libraries
-target_link_libraries(bcc-shared b_frontend clang_frontend ${clang_libs} ${expanded_libs})
-target_link_libraries(bcc-static b_frontend clang_frontend bcc-loader-static ${clang_libs} ${expanded_libs})
+target_link_libraries(bcc-shared b_frontend clang_frontend ${clang_libs} ${expanded_libs} ${LIBELF_LIBRARIES})
+target_link_libraries(bcc-static b_frontend clang_frontend bcc-loader-static ${clang_libs} ${expanded_libs} ${LIBELF_LIBRARIES})
 
 install(TARGETS bcc-shared LIBRARY COMPONENT libbcc
   DESTINATION ${CMAKE_INSTALL_LIBDIR})