If you google around about how to build an osx kext you will find very few results, a few email messages saying not to bother or that it it impossible.<\/p>\n
So what’s all the voodoo about. \u00a0A few defines, some linker options, some compiler options. Also a special info.c file and Info.plist.<\/p>\n
Note: if you want to sign your kernel module you will need to apply to apple for a special kernel module code signing certificate.<\/p>\n
Setup basic cmake project. We need 3.8 or newer to use\u00a0BUNDLE_EXTENSION for the .kext bundle type.<\/p>\n
cmake_minimum_required (VERSION 3.8)\r\n\r\nproject (example)<\/pre>\nSetup some variables for later. These are both optional if you use the default system sdk or you don’t want to code sign.<\/p>\n
set(CODE_SIGN_ID \"Developer ID Application: Your Name. (XYZZYYZYZY)\")\r\nset(CMAKE_OSX_SYSROOT \/Applications\/Xcode.app\/Contents\/Developer\/Platforms\/MacOSX.platform\/Developer\/SDKs\/MacOSX10.10.sdk\/)\r\n<\/pre>\nAdd a debug preprocessor def. This is optional.<\/p>\n
if(CMAKE_BUILD_TYPE MATCHES Debug)\r\n add_definitions(-DDEBUG)\r\nendif()<\/pre>\nAdd the special preprocessor defines to access internal kernel structures.<\/p>\n
add_definitions(\r\n -DKERNEL\r\n -DKERNEL_PRIVATE\r\n -DDRIVER_PRIVATE\r\n -DAPPLE\r\n -DNeXT\r\n)<\/pre>\nAdd include directories for osx kernel headers and private headers.<\/p>\n
include_directories(\r\n ${CMAKE_OSX_SYSROOT}\/System\/Library\/Frameworks\/Kernel.framework\/PrivateHeaders\r\n ${CMAKE_OSX_SYSROOT}\/System\/Library\/Frameworks\/Kernel.framework\/Headers\r\n)<\/pre>\nAdd an executable bundle target.<\/p>\n
add_executable(\r\n ${PROJECT_NAME}\r\n MACOSX_BUNDLE\r\n example.c\r\n example_info.c\r\n Info.plist\r\n)<\/pre>\nSet the target bundle extension to “kext” and the plist file.<\/p>\n
set_target_properties(${PROJECT_NAME} PROPERTIES BUNDLE_EXTENSION kext MACOSX_BUNDLE_INFO_PLIST ${PROJECT_SOURCE_DIR}\/Info.plist)<\/pre>\nSet a million compile options. \u00a0These were taken from a minimal xcode project.<\/p>\n
Note: The\u00a0-mmacosx-version-min=10.10 can be removed or changed to support older versions of OSX.<\/p>\n
add_compile_options(${PROJECT_NAME}\r\n -x c -arch x86_64 -fmessage-length=0\r\n -fdiagnostics-show-note-include-stack\r\n -fmacro-backtrace-limit=0 -nostdinc\r\n -std=gnu99 -fmodules -gmodules\r\n -Wnon-modular-include-in-framework-module\r\n -Werror=non-modular-include-in-framework-module\r\n -fno-builtin -Wno-trigraphs -msoft-float -O0 -fno-common\r\n -mkernel -Wno-missing-field-initializers -Wno-missing-prototypes\r\n -Werror=return-type -Wdocumentation -Wunreachable-code\r\n -Werror=deprecated-objc-isa-usage -Werror=objc-root-class\r\n -Wno-missing-braces -Wparentheses -Wswitch -Wunused-function\r\n -Wno-unused-label -Wno-unused-parameter -Wunused-variable -Wunused-value\r\n -Wempty-body -Wconditional-uninitialized -Wno-unknown-pragmas\r\n -Wno-shadow -Wno-four-char-constants -Wno-conversion -Wconstant-conversion\r\n -Wint-conversion -Wbool-conversion -Wenum-conversion -Wshorten-64-to-32\r\n -Wpointer-sign -Wno-newline-eof\r\n -fasm-blocks -fstrict-aliasing -Wdeprecated-declarations\r\n -mmacosx-version-min=10.10 -Wno-sign-conversion\r\n -Winfinite-recursion -iquote\r\n)<\/pre>\n<\/p>\n
Add the libraries required for the kernel module and linker options.<\/p>\n
Note: The\u00a0-mmacosx-version-min=10.10 can be removed or changed to support older versions of OSX.<\/p>\n
target_link_libraries(${PROJECT_NAME}\r\n \"-lkmodc++\"\r\n \"-lkmod\"\r\n \"-lcc_kext\"\r\n \"-arch x86_64\"\r\n \"-mmacosx-version-min=10.10\"\r\n \"-nostdlib\"\r\n \"-Xlinker -object_path_lto\"\r\n \"-Xlinker -export_dynamic\"\r\n \"-Xlinker -kext\"\r\n)<\/pre>\nAdd a custom target to sign the kernel module. \u00a0This can be skipped if code signing isn’t needed.<\/p>\n
add_custom_command (TARGET ${PROJECT_NAME} POST_BUILD\r\n COMMENT \"Code Signing Kext With: ${CODE_SIGN_ID}\"\r\n VERBATIM\r\n COMMAND\r\n \/usr\/bin\/codesign -s \"${CODE_SIGN_ID}\" \"${CMAKE_CURRENT_BINARY_DIR}\/${PROJECT_NAME}.kext\"\r\n)<\/pre>\nThe example.c file:<\/p>\n
#include <sys\/kernel_types.h>\r\n#include <sys\/systm.h>\r\n\r\nkern_return_t example_start(kmod_info_t * ki, void *d) {\r\n printf(\"Loaded example\\n\");\r\n return KERN_SUCCESS;\r\n}\r\n\r\nkern_return_t example_stop(kmod_info_t *ki, void *d) {\r\n printf(\"example unloading.\\n\");\r\n return KERN_SUCCESS;\r\n}<\/pre>\nThe example_info.c File. \u00a0This is usually generated by xcode during the build process.<\/p>\n
It just sets the main entry points to example_start and example_stop<\/p>\n
#include <mach\/mach_types.h>\r\n\r\nextern kern_return_t _start(kmod_info_t *ki, void *data);\r\nextern kern_return_t _stop(kmod_info_t *ki, void *data);\r\n__private_extern__ kern_return_t example_start(kmod_info_t *ki, void *data);\r\n__private_extern__ kern_return_t example_stop(kmod_info_t *ki, void *data);\r\n\r\n__attribute__((visibility(\"default\"))) KMOD_EXPLICIT_DECL(com.example, \"1.0.0d1\", _start, _stop)\r\n__private_extern__ kmod_start_func_t *_realmain = example_start;\r\n__private_extern__ kmod_stop_func_t *_antimain = example_stop;\r\n__private_extern__ int _kext_apple_cc = __APPLE_CC__ ;<\/pre>\n<\/p>\n
The complete cmake file.<\/p>\n
cmake_minimum_required (VERSION 3.8)\r\n\r\nproject (example)\r\n\r\nset(CODE_SIGN_ID \"Developer ID Application: Your Name. (XYZZYYZYZY)\")\r\nset(CMAKE_OSX_SYSROOT \/Applications\/Xcode.app\/Contents\/Developer\/Platforms\/MacOSX.platform\/Developer\/SDKs\/MacOSX10.11.sdk\/)\r\n\r\n\r\nif(CMAKE_BUILD_TYPE MATCHES Debug)\r\n\tadd_definitions(-DDEBUG)\r\nendif()\r\n\r\nadd_definitions(\r\n\t-DKERNEL\r\n\t-DKERNEL_PRIVATE\r\n\t-DDRIVER_PRIVATE\r\n\t-DAPPLE\r\n\t-DNeXT\r\n)\r\n\r\ninclude_directories(\r\n\t${CMAKE_OSX_SYSROOT}\/System\/Library\/Frameworks\/Kernel.framework\/PrivateHeaders\r\n\t${CMAKE_OSX_SYSROOT}\/System\/Library\/Frameworks\/Kernel.framework\/Headers\r\n)\r\n\r\nadd_executable(\r\n\t${PROJECT_NAME}\r\n\tMACOSX_BUNDLE\r\n\texample.c\r\n\texample_info.c\r\n\tInfo.plist\r\n)\r\n\r\nset_target_properties(${PROJECT_NAME} PROPERTIES BUNDLE_EXTENSION kext MACOSX_BUNDLE_INFO_PLIST ${PROJECT_SOURCE_DIR}\/Info.plist)\r\n\r\n\r\nadd_compile_options(${PROJECT_NAME}\r\n\t-x c -arch x86_64 -fmessage-length=0\r\n\t-fdiagnostics-show-note-include-stack\r\n\t-fmacro-backtrace-limit=0 -nostdinc\r\n\t-std=gnu99 -fmodules -gmodules\r\n\t-Wnon-modular-include-in-framework-module\r\n\t-Werror=non-modular-include-in-framework-module\r\n\t-fno-builtin -Wno-trigraphs -msoft-float -O0 -fno-common\r\n\t-mkernel -Wno-missing-field-initializers -Wno-missing-prototypes\r\n\t-Werror=return-type -Wdocumentation -Wunreachable-code\r\n\t-Werror=deprecated-objc-isa-usage -Werror=objc-root-class\r\n\t-Wno-missing-braces -Wparentheses -Wswitch -Wunused-function\r\n\t-Wno-unused-label -Wno-unused-parameter -Wunused-variable -Wunused-value\r\n\t-Wempty-body -Wconditional-uninitialized -Wno-unknown-pragmas\r\n\t-Wno-shadow -Wno-four-char-constants -Wno-conversion -Wconstant-conversion\r\n\t-Wint-conversion -Wbool-conversion -Wenum-conversion -Wshorten-64-to-32\r\n\t-Wpointer-sign -Wno-newline-eof\r\n\t-fasm-blocks -fstrict-aliasing -Wdeprecated-declarations\r\n\t-mmacosx-version-min=10.11 -Wno-sign-conversion\r\n\t-Winfinite-recursion -iquote\r\n)\r\n\r\n# delete this to not code sign\r\ntarget_link_libraries(${PROJECT_NAME} \r\n\t\"-lkmodc++\"\r\n\t\"-lkmod\"\r\n\t\"-lcc_kext\"\r\n\t\"-arch x86_64\"\r\n\t\"-mmacosx-version-min=10.11\"\r\n\t\"-nostdlib\"\r\n\t\"-Xlinker -object_path_lto\"\r\n\t\"-Xlinker -export_dynamic\"\r\n\t\"-Xlinker -kext\"\r\n)\r\n<\/pre>\nThe magic Info.plist file. \u00a0All references to “example” will need to match the binary and com.example items.<\/p>\n
<?xml version=\"1.0\" encoding=\"UTF-8\"?>\r\n<!DOCTYPE plist PUBLIC \"-\/\/Apple\/\/DTD PLIST 1.0\/\/EN\" \"http:\/\/www.apple.com\/DTDs\/PropertyList-1.0.dtd\">\r\n<plist version=\"1.0\">\r\n<dict>\r\n\t<key>BuildMachineOSBuild<\/key>\r\n\t<string>15G31<\/string>\r\n\t<key>CFBundleDevelopmentRegion<\/key>\r\n\t<string>en<\/string>\r\n\t<key>CFBundleExecutable<\/key>\r\n\t<string>example<\/string>\r\n\t<key>CFBundleIdentifier<\/key>\r\n\t<string>com.example<\/string>\r\n\t<key>CFBundleInfoDictionaryVersion<\/key>\r\n\t<string>6.0<\/string>\r\n\t<key>CFBundleName<\/key>\r\n\t<string>example<\/string>\r\n\t<key>CFBundlePackageType<\/key>\r\n\t<string>KEXT<\/string>\r\n\t<key>CFBundleShortVersionString<\/key>\r\n\t<string>1.0<\/string>\r\n\t<key>CFBundleSupportedPlatforms<\/key>\r\n\t<array>\r\n\t\t<string>MacOSX<\/string>\r\n\t<\/array>\r\n\t<key>CFBundleVersion<\/key>\r\n\t<string>1<\/string>\r\n\t<key>DTCompiler<\/key>\r\n\t<string>com.apple.compilers.llvm.clang.1_0<\/string>\r\n\t<key>DTPlatformBuild<\/key>\r\n\t<string>8A218a<\/string>\r\n\t<key>DTPlatformVersion<\/key>\r\n\t<string>GM<\/string>\r\n\t<key>DTSDKBuild<\/key>\r\n\t<string>16A300<\/string>\r\n\t<key>DTSDKName<\/key>\r\n\t<string>macosx10.12<\/string>\r\n\t<key>DTXcode<\/key>\r\n\t<string>0800<\/string>\r\n\t<key>DTXcodeBuild<\/key>\r\n\t<string>8A218a<\/string>\r\n\t<key>NSHumanReadableCopyright<\/key>\r\n\t<string>Copyright \u00a9 2017 Someone. All rights reserved.<\/string>\r\n\t<key>OSBundleLibraries<\/key>\r\n\t<dict>\r\n\t\t<key>com.apple.kpi.bsd<\/key>\r\n\t\t<string>8.0.0<\/string>\r\n\t\t<key>com.apple.kpi.libkern<\/key>\r\n\t\t<string>8.0.0<\/string>\r\n\t\t<key>com.apple.kpi.mach<\/key>\r\n\t\t<string>8.0.0<\/string>\r\n\t<\/dict>\r\n<\/dict>\r\n<\/plist>\r\n<\/pre>\n<\/p>\n
GitHub Repository with the example.<\/a><\/p>\n
<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
If you google around about how to build an osx kext you will find very few results, a few email messages saying not to bother or that it it impossible. So what’s all the voodoo about. \u00a0A few defines, some linker options, some compiler options. Also a special info.c file and Info.plist. Note: if you … Continue reading Building an Apple OSX Kernel Module With CMake – C\/C++<\/span>