1====== 2Kbuild 3====== 4 5 6Output files 7============ 8 9modules.order 10------------- 11This file records the order in which modules appear in Makefiles. This 12is used by modprobe to deterministically resolve aliases that match 13multiple modules. 14 15modules.builtin 16--------------- 17This file lists all modules that are built into the kernel. This is used 18by modprobe to not fail when trying to load something builtin. 19 20modules.builtin.modinfo 21----------------------- 22This file contains modinfo from all modules that are built into the kernel. 23Unlike modinfo of a separate module, all fields are prefixed with module name. 24 25 26Environment variables 27===================== 28 29KCPPFLAGS 30--------- 31Additional options to pass when preprocessing. The preprocessing options 32will be used in all cases where kbuild does preprocessing including 33building C files and assembler files. 34 35KAFLAGS 36------- 37Additional options to the assembler (for built-in and modules). 38 39AFLAGS_MODULE 40------------- 41Additional assembler options for modules. 42 43AFLAGS_KERNEL 44------------- 45Additional assembler options for built-in. 46 47KCFLAGS 48------- 49Additional options to the C compiler (for built-in and modules). 50 51CFLAGS_KERNEL 52------------- 53Additional options for $(CC) when used to compile 54code that is compiled as built-in. 55 56CFLAGS_MODULE 57------------- 58Additional module specific options to use for $(CC). 59 60LDFLAGS_MODULE 61-------------- 62Additional options used for $(LD) when linking modules. 63 64HOSTCFLAGS 65---------- 66Additional flags to be passed to $(HOSTCC) when building host programs. 67 68HOSTCXXFLAGS 69------------ 70Additional flags to be passed to $(HOSTCXX) when building host programs. 71 72HOSTLDFLAGS 73----------- 74Additional flags to be passed when linking host programs. 75 76HOSTLDLIBS 77---------- 78Additional libraries to link against when building host programs. 79 80KBUILD_KCONFIG 81-------------- 82Set the top-level Kconfig file to the value of this environment 83variable. The default name is "Kconfig". 84 85KBUILD_VERBOSE 86-------------- 87Set the kbuild verbosity. Can be assigned same values as "V=...". 88 89See make help for the full list. 90 91Setting "V=..." takes precedence over KBUILD_VERBOSE. 92 93KBUILD_EXTMOD 94------------- 95Set the directory to look for the kernel source when building external 96modules. 97 98Setting "M=..." takes precedence over KBUILD_EXTMOD. 99 100KBUILD_OUTPUT 101------------- 102Specify the output directory when building the kernel. 103 104The output directory can also be specified using "O=...". 105 106Setting "O=..." takes precedence over KBUILD_OUTPUT. 107 108KBUILD_EXTRA_WARN 109----------------- 110Specify the extra build checks. The same value can be assigned by passing 111W=... from the command line. 112 113See `make help` for the list of the supported values. 114 115Setting "W=..." takes precedence over KBUILD_EXTRA_WARN. 116 117KBUILD_DEBARCH 118-------------- 119For the deb-pkg target, allows overriding the normal heuristics deployed by 120deb-pkg. Normally deb-pkg attempts to guess the right architecture based on 121the UTS_MACHINE variable, and on some architectures also the kernel config. 122The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian 123architecture. 124 125ARCH 126---- 127Set ARCH to the architecture to be built. 128 129In most cases the name of the architecture is the same as the 130directory name found in the arch/ directory. 131 132But some architectures such as x86 and sparc have aliases. 133 134- x86: i386 for 32 bit, x86_64 for 64 bit 135- sh: sh for 32 bit, sh64 for 64 bit 136- sparc: sparc32 for 32 bit, sparc64 for 64 bit 137 138CROSS_COMPILE 139------------- 140Specify an optional fixed part of the binutils filename. 141CROSS_COMPILE can be a part of the filename or the full path. 142 143CROSS_COMPILE is also used for ccache in some setups. 144 145CF 146-- 147Additional options for sparse. 148 149CF is often used on the command-line like this:: 150 151 make CF=-Wbitwise C=2 152 153INSTALL_PATH 154------------ 155INSTALL_PATH specifies where to place the updated kernel and system map 156images. Default is /boot, but you can set it to other values. 157 158INSTALLKERNEL 159------------- 160Install script called when using "make install". 161The default name is "installkernel". 162 163The script will be called with the following arguments: 164 165 - $1 - kernel version 166 - $2 - kernel image file 167 - $3 - kernel map file 168 - $4 - default install path (use root directory if blank) 169 170The implementation of "make install" is architecture specific 171and it may differ from the above. 172 173INSTALLKERNEL is provided to enable the possibility to 174specify a custom installer when cross compiling a kernel. 175 176MODLIB 177------ 178Specify where to install modules. 179The default value is:: 180 181 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) 182 183The value can be overridden in which case the default value is ignored. 184 185INSTALL_MOD_PATH 186---------------- 187INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory 188relocations required by build roots. This is not defined in the 189makefile but the argument can be passed to make if needed. 190 191INSTALL_MOD_STRIP 192----------------- 193INSTALL_MOD_STRIP, if defined, will cause modules to be 194stripped after they are installed. If INSTALL_MOD_STRIP is '1', then 195the default option --strip-debug will be used. Otherwise, 196INSTALL_MOD_STRIP value will be used as the options to the strip command. 197 198INSTALL_HDR_PATH 199---------------- 200INSTALL_HDR_PATH specifies where to install user space headers when 201executing "make headers_*". 202 203The default value is:: 204 205 $(objtree)/usr 206 207$(objtree) is the directory where output files are saved. 208The output directory is often set using "O=..." on the commandline. 209 210The value can be overridden in which case the default value is ignored. 211 212KBUILD_ABS_SRCTREE 213-------------------------------------------------- 214Kbuild uses a relative path to point to the tree when possible. For instance, 215when building in the source tree, the source tree path is '.' 216 217Setting this flag requests Kbuild to use absolute path to the source tree. 218There are some useful cases to do so, like when generating tag files with 219absolute path entries etc. 220 221KBUILD_SIGN_PIN 222--------------- 223This variable allows a passphrase or PIN to be passed to the sign-file 224utility when signing kernel modules, if the private key requires such. 225 226KBUILD_MODPOST_WARN 227------------------- 228KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined 229symbols in the final module linking stage. It changes such errors 230into warnings. 231 232KBUILD_MODPOST_NOFINAL 233---------------------- 234KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. 235This is solely useful to speed up test compiles. 236 237KBUILD_EXTRA_SYMBOLS 238-------------------- 239For modules that use symbols from other modules. 240See more details in modules.rst. 241 242ALLSOURCE_ARCHS 243--------------- 244For tags/TAGS/cscope targets, you can specify more than one arch 245to be included in the databases, separated by blank space. E.g.:: 246 247 $ make ALLSOURCE_ARCHS="x86 mips arm" tags 248 249To get all available archs you can also specify all. E.g.:: 250 251 $ make ALLSOURCE_ARCHS=all tags 252 253KBUILD_BUILD_TIMESTAMP 254---------------------- 255Setting this to a date string overrides the timestamp used in the 256UTS_VERSION definition (uname -v in the running kernel). The value has to 257be a string that can be passed to date -d. The default value 258is the output of the date command at one point during build. 259 260KBUILD_BUILD_USER, KBUILD_BUILD_HOST 261------------------------------------ 262These two variables allow to override the user@host string displayed during 263boot and in /proc/version. The default value is the output of the commands 264whoami and host, respectively. 265 266LLVM 267---- 268If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead 269of GCC and GNU binutils to build the kernel. 270