bcc: support building with external libbpf package and older uapi lin…

…ux/bpf.h When building bcc with a relatively new packaged libbpf (0.8.1) and -DCMAKE_USE_LIBBPF_PACKAGE:BOOL=TRUE, multiple compilation failures are encountered due the fact the system uapi header in /usr/include/linux/bpf.h is not very recent (this is often the case for distros, which sync it via a kernel headers package quite conservatively due to use by glibc). With libbpf built via git submodule, the uapi header included in the libbpf package is used, so here a similar approach is proposed for the external package build. Instead of having to sync another file the already present compat/linux/virtual_bpf.h is used; we copy it to compat/linux/bpf.h (eliminating the string prefix/suffix on first/last lines). From there, we ensure that places that assume the presence of the libbpf git submodule point at compat/ as a location to find the uapi header. Signed-off-by: Alan Maguire <[email protected]>
ego · Oct 17, 2022 · e4bb4f3 · e4bb4f3
1 parent 981a947
commit e4bb4f3
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Showing 4 changed files with 18 additions and 0 deletions.
diff --git a/examples/cpp/CMakeLists.txt b/examples/cpp/CMakeLists.txt
@@ -4,7 +4,11 @@
 include_directories(${PROJECT_BINARY_DIR}/src/cc)
 include_directories(${PROJECT_SOURCE_DIR}/src/cc)
 include_directories(${PROJECT_SOURCE_DIR}/src/cc/api)
+if (CMAKE_USE_LIBBPF_PACKAGE AND LIBBPF_FOUND)
+include_directories(${PROJECT_SOURCE_DIR}/src/cc/compat)
+else()
 include_directories(${PROJECT_SOURCE_DIR}/src/cc/libbpf/include/uapi)
+endif()
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")

diff --git a/introspection/CMakeLists.txt b/introspection/CMakeLists.txt
@@ -3,7 +3,11 @@
 
 include_directories(${PROJECT_SOURCE_DIR}/src/cc)
 include_directories(${PROJECT_SOURCE_DIR}/src/cc/api)
+if (CMAKE_USE_LIBBPF_PACKAGE AND LIBBPF_FOUND)
+include_directories(${PROJECT_SOURCE_DIR}/src/cc/compat)
+else()
 include_directories(${PROJECT_SOURCE_DIR}/src/cc/libbpf/include/uapi)
+endif()
 
 option(INSTALL_INTROSPECTION "Install BPF introspection tools" ON)
 option(BPS_LINK_RT "Pass -lrt to linker when linking bps tool" ON)

diff --git a/src/cc/CMakeLists.txt b/src/cc/CMakeLists.txt
@@ -15,6 +15,12 @@ endif (LIBDEBUGINFOD_FOUND)
 # todo: if check for kernel version
 if (CMAKE_USE_LIBBPF_PACKAGE AND LIBBPF_FOUND)
  include_directories(${LIBBPF_INCLUDE_DIRS})
+ # create up-to-date linux/bpf.h from virtual_bpf.h (remove string wrapper);
+ # when libbpf is built as a submodule we use its version of linux/bpf.h
+ # so this does similar for the libbpf package, removing reliance on the
+ # system uapi header which can be out of date.
+ execute_process(COMMAND sh -c "cd ${CMAKE_CURRENT_SOURCE_DIR}/compat/linux && grep -ve '\\*\\*\\*\\*' virtual_bpf.h > bpf.h")
+ include_directories(${CMAKE_CURRENT_SOURCE_DIR}/compat)
 else()
  include_directories(${CMAKE_CURRENT_SOURCE_DIR}/libbpf/include)
  include_directories(${CMAKE_CURRENT_SOURCE_DIR}/libbpf/include/uapi)

diff --git a/tests/cc/CMakeLists.txt b/tests/cc/CMakeLists.txt
@@ -3,7 +3,11 @@
 
 include_directories(${PROJECT_SOURCE_DIR}/src/cc)
 include_directories(${PROJECT_SOURCE_DIR}/src/cc/api)
+if (CMAKE_USE_LIBBPF_PACKAGE AND LIBBPF_FOUND)
+include_directories(${PROJECT_SOURCE_DIR}/src/cc/compat)
+else()
 include_directories(${PROJECT_SOURCE_DIR}/src/cc/libbpf/include/uapi)
+endif()
 include_directories(${PROJECT_SOURCE_DIR}/tests/python/include)
 
 add_executable(test_static test_static.c)