CMake: Add ability to use system-installed libbpf rather than ExternalProject_Add

CMakeLists.txt

@@ -31,14 +31,18 @@ cmake_policy(SET CMP0048 NEW)
 # set the project name - version is MAJOR.MINOR.PATCH.RELEASE - releases start at 1
 #
 if (DEFINED ENV{VERSION})
-  project(ProcDumpForLinux VERSION $ENV{VERSION})
+  project(ProcDumpForLinux VERSION $ENV{VERSION} LANGUAGES C CXX)
 else()
-  project(ProcDumpForLinux VERSION 0.0.0)
+  project(ProcDumpForLinux VERSION 0.0.0 LANGUAGES C CXX)
 endif()
 
 set(PROJECT_VERSION_TWEAK 0)
 file(READ "dist/changelog" CHANGE_LOG)
 
+option(PROCDUMP_DISABLE_SYSTEM_LIBBPF "Don't attempt to use an installed libbpf" OFF)
+
+include(GNUInstallDirs)
+
 #
 # enable Debug while pre-release; disable Debug in post-release
 #
@@ -191,8 +195,17 @@ target_include_directories(procdump PUBLIC
                            ${procdump_ebpf_SOURCE_DIR}
                           )
 
-add_dependencies(procdump libbpf procdump_ebpf)
-target_link_libraries(procdump ${libbpf_SOURCE_DIR}/src/libbpf.a elf z pthread)
+add_dependencies(procdump procdump_ebpf)
+
+list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake")
+find_package(Threads REQUIRED)
+find_package(ZLIB REQUIRED)
+find_package(Libelf REQUIRED)
+target_link_libraries(procdump
+	Libelf::Libelf
+	ZLIB::ZLIB
+	Threads::Threads
+)
 
 #
 # Copy integration test directory
@@ -235,17 +248,37 @@ add_custom_target(rpm
 # Make ProcDump eBPF program
 #
 
-# Fetch libbpf
-include(ExternalProject)
+# Attempt to use system-installed libbpf
+if(NOT PROCDUMP_DISABLE_SYSTEM_LIBBPF)
+  find_package(Bpf COMPONENTS libbpf)
+  if(Bpf_FOUND)
+    set(libbpf_LINK Bpf::libbpf)
+    set(libbpf_INCLUDE "${Bpf_INCLUDE_DIRS}")
+  endif()
+endif()
+
+if(NOT Bpf_FOUND)
+  # Fetch libbpf
+  include(ExternalProject)
+
+  ExternalProject_Add(libbpf
+      GIT_REPOSITORY https://github.com/libbpf/libbpf.git
+      GIT_TAG v1.2.2
+      PREFIX ./libbpf
+      CONFIGURE_COMMAND ""
+      BUILD_COMMAND
+        cd ../libbpf/src &&
+        bash -c "CFLAGS=\"-g -O2 -Werror -Wall -fPIC\" make"
+      INSTALL_COMMAND
+        cd ../libbpf/src && bash -c "DESTDIR=<INSTALL_DIR> make install"
+      )
+  set(libbpf_LINK "${libbpf_BINARY_DIR}/usr/${CMAKE_INSTALL_LIBDIR}/libbpf.a")
+  set(libbpf_INCLUDE "${libbpf_BINARY_DIR}/usr/include")
+endif()
+# We always need to find the bpftool program
+find_package(Bpf REQUIRED COMPONENTS bpftool)
 
-ExternalProject_Add(libbpf
-    GIT_REPOSITORY https://github.com/libbpf/libbpf.git
-    GIT_TAG v1.2.2
-    PREFIX ./libbpf
-    CONFIGURE_COMMAND ""
-    BUILD_COMMAND cd ../libbpf/src && bash -c "CFLAGS=\"-g -O2 -Werror -Wall -fPIC\" make"
-    INSTALL_COMMAND ""
-    )
+target_link_libraries(procdump ${libbpf_LINK})
 
 # set binaries and options for clang and llc
 set(CLANG "clang")
@@ -274,19 +307,33 @@ set(CLANG_INCLUDES
                    -I "/usr/include/x86_64-linux-gnu"
                    -I "${CMAKE_SOURCE_DIR}"
                    -I "${CMAKE_BINARY_DIR}"
-                   -I "${libbpf_SOURCE_DIR}/src"
+                   -I "${libbpf_INCLUDE}"
                    )
 
-add_custom_target(procdump_ebpf
-                  DEPENDS procdump_ebpf.o
-                 )
+add_custom_command(OUTPUT procdump_ebpf.o
+  COMMAND "${CLANG}" -nostdinc -isystem `gcc -print-file-name=include` ${CLANG_INCLUDES} ${CLANG_DEFINES} -O2 ${CLANG_OPTIONS} -target bpf -fno-stack-protector -c "${procdump_ebpf_SOURCE_DIR}/procdump_ebpf.c" -o "procdump_ebpf.o"
+  COMMENT "Building EBPF object procdump_ebpf.o"
+  DEPENDS ${procdump_ebpf_SOURCE_DIR}/procdump_ebpf.c
+  WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
+)
+add_custom_command(OUTPUT procdump.ebpf.o
+  COMMAND Bpf::bpftool gen object procdump.ebpf.o procdump_ebpf.o
+  COMMENT "Generating procdump.ebpf.o"
+  DEPENDS procdump_ebpf.o
+  WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
+)
 
-add_dependencies(procdump_ebpf libbpf)
+add_custom_command(OUTPUT procdump_ebpf.skel.h
+  COMMAND Bpf::bpftool gen skeleton "procdump.ebpf.o" name "procdump_ebpf" > "procdump_ebpf.skel.h"
+  COMMENT "Writing EBPF header procdump_ebpf.skel.h"
+  DEPENDS procdump.ebpf.o
+  WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
+)
 
-add_custom_command(OUTPUT procdump_ebpf.o
-                   COMMAND "${CLANG}" -nostdinc -isystem `gcc -print-file-name=include` ${CLANG_INCLUDES} ${CLANG_DEFINES} -O2 ${CLANG_OPTIONS} -target bpf -fno-stack-protector -c "${procdump_ebpf_SOURCE_DIR}/procdump_ebpf.c" -o "procdump_ebpf.o" && bpftool gen object procdump.ebpf.o procdump_ebpf.o && bpftool gen skeleton "procdump.ebpf.o" name "procdump_ebpf" > "procdump_ebpf.skel.h"
-                   COMMENT "Building EBPF object procdump_ebpf.o"
-                   DEPENDS ${procdump_ebpf_SOURCE_DIR}/procdump_ebpf.c
-                  )
+add_custom_target(procdump_ebpf DEPENDS
+  procdump_ebpf.o
+  procdump.ebpf.o
+  procdump_ebpf.skel.h
+)
 
-set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES procdump.ebpf.o)
+add_dependencies(procdump_ebpf ${libbpf_LINK})

cmake/FindBpf.cmake

@@ -0,0 +1,138 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+FindBpf
+----------
+
+Find libbpf headers and library, and bpftool executable.
+
+Imported Targets
+^^^^^^^^^^^^^^^^
+
+``Bpf::libbpf``
+  The libbpf library, if found.
+``Bpf::bpftool``
+  The bpftool executable, if found.
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+This will define some or all of the following variables
+in your project (depending on components selected):
+
+``Bpf_FOUND``
+  true if (the requested version of) libbpf and/or the bpftool
+  program are available.
+``Bpf_VERSION``
+  the version of libbpf.
+``Bpf_LIBRARIES``
+  the libraries to link against to use libbpf.
+``Bpf_INCLUDE_DIRS``
+  where to find the libbpf headers.
+``Bpf_COMPILE_OPTIONS``
+  this should be passed to target_compile_options(), if the
+  target is not used for linking
+``Bpf_BPFTOOL_EXECUTABLE``
+  the location of the bpftool binary.
+
+#]=======================================================================]
+
+if(NOT Bpf_FIND_COMPONENTS)
+  set(Bpf_FIND_COMPONENTS libbpf bpftool)
+endif()
+set(_required)
+
+if(libbpf IN_LIST Bpf_FIND_COMPONENTS)
+  # Use pkg-config to get the directories and then use these values
+  # in the FIND_PATH() and FIND_LIBRARY() calls
+  find_package(PkgConfig QUIET)
+  pkg_check_modules(PKG_Bpf QUIET libbpf)
+
+  set(Bpf_COMPILE_OPTIONS ${PKG_Bpf_CFLAGS_OTHER})
+  set(Bpf_VERSION ${PKG_Bpf_VERSION})
+
+  find_path(Bpf_INCLUDE_DIR
+    NAMES
+      bpf/libbpf.h
+    HINTS
+      ${PKG_Bpf_INCLUDE_DIRS}
+  )
+  mark_as_advanced(Bpf_INCLUDE_DIR)
+
+  find_library(Bpf_LIBRARY
+    NAMES
+      bpf
+    HINTS
+      ${PKG_Bpf_LIBRARY_DIRS}
+  )
+  mark_as_advanced(Bpf_LIBRARY)
+
+  if(Bpf_INCLUDE_DIR AND Bpf_LIBRARY)
+    set(Bpf_libbpf_FOUND TRUE)
+  endif()
+
+  list(APPEND _required Bpf_LIBRARY Bpf_INCLUDE_DIR)
+  set(_version Bpf_VERSION)
+
+  set(Bpf_LIBRARIES ${Bpf_LIBRARY})
+  set(Bpf_INCLUDE_DIRS ${Bpf_INCLUDE_DIR})
+endif()
+
+if(bpftool IN_LIST Bpf_FIND_COMPONENTS)
+  find_program(Bpf_BPFTOOL_EXECUTABLE
+    NAMES
+      bpftool
+  )
+  mark_as_advanced(Bpf_BPFTOOL_EXECUTABLE)
+
+  if(Bpf_BPFTOOL_EXECUTABLE)
+    set(Bpf_bpftool_FOUND TRUE)
+  endif()
+  list(APPEND _required Bpf_BPFTOOL_EXECUTABLE)
+  set(Bpf_BPFTOOL_EXECUTABLE ${Bpf_BPFTOOL_EXECUTABLE})
+endif()
+
+include(FindPackageHandleStandardArgs)
+
+# From CMake 3.18, HANDLE_COMPONENTS makes REQUIRED_VARS optional
+if(CMAKE_VERSION VERSION_LESS "3.18")
+  set(_required_vars
+    REQUIRED_VARS
+      ${_required}
+  )
+else()
+  set(_required_vars)
+endif()
+
+if(DEFINED _version)
+  set(_version_var
+    VERSION_VAR ${_version}
+  )
+else()
+  set(_version_var)
+endif()
+
+find_package_handle_standard_args(Bpf
+  FOUND_VAR
+    Bpf_FOUND
+  ${_version_var}
+  ${_required_vars}
+  HANDLE_COMPONENTS
+)
+
+if(Bpf_FOUND AND Bpf_LIBRARY AND NOT TARGET Bpf::libbpf)
+    add_library(Bpf::libbpf UNKNOWN IMPORTED)
+    set_target_properties(Bpf::libbpf PROPERTIES
+      IMPORTED_LOCATION "${Bpf_LIBRARY}"
+      INTERFACE_COMPILE_OPTIONS "${Bpf_COMPILE_OPTIONS}"
+      INTERFACE_INCLUDE_DIRECTORIES "${Bpf_INCLUDE_DIR}"
+    )
+endif()
+
+if(Bpf_FOUND AND Bpf_BPFTOOL_EXECUTABLE AND NOT TARGET Bpf::bpftool)
+    add_executable(Bpf::bpftool IMPORTED)
+    set_target_properties(Bpf::bpftool PROPERTIES
+      IMPORTED_LOCATION "${Bpf_BPFTOOL_EXECUTABLE}"
+    )
+endif()

cmake/FindLibelf.cmake

@@ -0,0 +1,82 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+FindLibelf
+----------
+
+Find libelf headers and library.
+
+Imported Targets
+^^^^^^^^^^^^^^^^
+
+``Libelf::Libelf``
+  The libelf library, if found.
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+This will define the following variables in your project:
+
+``Libelf_FOUND``
+  true if (the requested version of) Libelf is available.
+``Libelf_VERSION``
+  the version of Libelf.
+``Libelf_LIBRARIES``
+  the libraries to link against to use Libelf.
+``Libelf_INCLUDE_DIRS``
+  where to find the Libelf headers.
+``Libelf_COMPILE_OPTIONS``
+  this should be passed to target_compile_options(), if the
+  target is not used for linking
+
+#]=======================================================================]
+
+
+# Use pkg-config to get the directories and then use these values
+# in the FIND_PATH() and FIND_LIBRARY() calls
+find_package(PkgConfig QUIET)
+pkg_check_modules(PKG_Libelf QUIET libelf)
+
+set(Libelf_COMPILE_OPTIONS ${PKG_Libelf_CFLAGS_OTHER})
+set(Libelf_VERSION ${PKG_Libelf_VERSION})
+
+find_path(Libelf_INCLUDE_DIR
+  NAMES
+    libelf.h
+  HINTS
+    ${PKG_Libelf_INCLUDE_DIRS}
+)
+find_library(Libelf_LIBRARY
+  NAMES
+    elf
+  HINTS
+    ${PKG_Libelf_LIBRARY_DIRS}
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(Libelf
+  FOUND_VAR
+    Libelf_FOUND
+  REQUIRED_VARS
+    Libelf_LIBRARY
+    Libelf_INCLUDE_DIR
+  VERSION_VAR
+    Libelf_VERSION
+)
+
+if(Libelf_FOUND AND NOT TARGET Libelf::Libelf)
+  add_library(Libelf::Libelf UNKNOWN IMPORTED)
+  set_target_properties(Libelf::Libelf PROPERTIES
+    IMPORTED_LOCATION "${Libelf_LIBRARY}"
+    INTERFACE_COMPILE_OPTIONS "${Libelf_COMPILE_OPTIONS}"
+    INTERFACE_INCLUDE_DIRECTORIES "${Libelf_INCLUDE_DIR}"
+  )
+endif()
+
+mark_as_advanced(Libelf_LIBRARY Libelf_INCLUDE_DIR)
+
+if(Libelf_FOUND)
+  set(Libelf_LIBRARIES ${Libelf_LIBRARY})
+  set(Libelf_INCLUDE_DIRS ${Libelf_INCLUDE_DIR})
+endif()

ebpf/procdump_ebpf.h

@@ -18,8 +18,8 @@
 #define __PROCDUMP_EBPF_H__
 
 #include "vmlinux.h"
-#include <bpf_helpers.h>
-#include <usdt.bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/usdt.bpf.h>
 
 #define USER_STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP | BPF_F_USER_STACK)
 #define ARGS_HASH_SIZE 10240
@@ -66,4 +66,4 @@ struct {
 	__uint(max_entries, 10 * 1024 * 1024 /* 10 MB */);
 } ringBuffer SEC(".maps");
 
-#endif // __PROCDUMP_EBPF_H__
+#endif // __PROCDUMP_EBPF_H__