| 1 | ====== |
| 2 | Kbuild |
| 3 | ====== |
| 4 | |
| 5 | |
| 6 | Output files |
| 7 | ============ |
| 8 | |
| 9 | modules.order |
| 10 | ------------- |
| 11 | This file records the order in which modules appear in Makefiles. This |
| 12 | is used by modprobe to deterministically resolve aliases that match |
| 13 | multiple modules. |
| 14 | |
| 15 | modules.builtin |
| 16 | --------------- |
| 17 | This file lists all modules that are built into the kernel. This is used |
| 18 | by modprobe to not fail when trying to load something builtin. |
| 19 | |
| 20 | modules.builtin.modinfo |
| 21 | ----------------------- |
| 22 | This file contains modinfo from all modules that are built into the kernel. |
| 23 | Unlike modinfo of a separate module, all fields are prefixed with module name. |
| 24 | |
| 25 | |
| 26 | Environment variables |
| 27 | ===================== |
| 28 | |
| 29 | KCPPFLAGS |
| 30 | --------- |
| 31 | Additional options to pass when preprocessing. The preprocessing options |
| 32 | will be used in all cases where kbuild does preprocessing including |
| 33 | building C files and assembler files. |
| 34 | |
| 35 | KAFLAGS |
| 36 | ------- |
| 37 | Additional options to the assembler (for built-in and modules). |
| 38 | |
| 39 | AFLAGS_MODULE |
| 40 | ------------- |
| 41 | Additional assembler options for modules. |
| 42 | |
| 43 | AFLAGS_KERNEL |
| 44 | ------------- |
| 45 | Additional assembler options for built-in. |
| 46 | |
| 47 | KCFLAGS |
| 48 | ------- |
| 49 | Additional options to the C compiler (for built-in and modules). |
| 50 | |
| 51 | KRUSTFLAGS |
| 52 | ---------- |
| 53 | Additional options to the Rust compiler (for built-in and modules). |
| 54 | |
| 55 | CFLAGS_KERNEL |
| 56 | ------------- |
| 57 | Additional options for $(CC) when used to compile |
| 58 | code that is compiled as built-in. |
| 59 | |
| 60 | CFLAGS_MODULE |
| 61 | ------------- |
| 62 | Additional module specific options to use for $(CC). |
| 63 | |
| 64 | RUSTFLAGS_KERNEL |
| 65 | ---------------- |
| 66 | Additional options for $(RUSTC) when used to compile |
| 67 | code that is compiled as built-in. |
| 68 | |
| 69 | RUSTFLAGS_MODULE |
| 70 | ---------------- |
| 71 | Additional module specific options to use for $(RUSTC). |
| 72 | |
| 73 | LDFLAGS_MODULE |
| 74 | -------------- |
| 75 | Additional options used for $(LD) when linking modules. |
| 76 | |
| 77 | HOSTCFLAGS |
| 78 | ---------- |
| 79 | Additional flags to be passed to $(HOSTCC) when building host programs. |
| 80 | |
| 81 | HOSTCXXFLAGS |
| 82 | ------------ |
| 83 | Additional flags to be passed to $(HOSTCXX) when building host programs. |
| 84 | |
| 85 | HOSTRUSTFLAGS |
| 86 | ------------- |
| 87 | Additional flags to be passed to $(HOSTRUSTC) when building host programs. |
| 88 | |
| 89 | HOSTLDFLAGS |
| 90 | ----------- |
| 91 | Additional flags to be passed when linking host programs. |
| 92 | |
| 93 | HOSTLDLIBS |
| 94 | ---------- |
| 95 | Additional libraries to link against when building host programs. |
| 96 | |
| 97 | .. _userkbuildflags: |
| 98 | |
| 99 | USERCFLAGS |
| 100 | ---------- |
| 101 | Additional options used for $(CC) when compiling userprogs. |
| 102 | |
| 103 | USERLDFLAGS |
| 104 | ----------- |
| 105 | Additional options used for $(LD) when linking userprogs. userprogs are linked |
| 106 | with CC, so $(USERLDFLAGS) should include "-Wl," prefix as applicable. |
| 107 | |
| 108 | KBUILD_KCONFIG |
| 109 | -------------- |
| 110 | Set the top-level Kconfig file to the value of this environment |
| 111 | variable. The default name is "Kconfig". |
| 112 | |
| 113 | KBUILD_VERBOSE |
| 114 | -------------- |
| 115 | Set the kbuild verbosity. Can be assigned same values as "V=...". |
| 116 | |
| 117 | See make help for the full list. |
| 118 | |
| 119 | Setting "V=..." takes precedence over KBUILD_VERBOSE. |
| 120 | |
| 121 | KBUILD_EXTMOD |
| 122 | ------------- |
| 123 | Set the directory to look for the kernel source when building external |
| 124 | modules. |
| 125 | |
| 126 | Setting "M=..." takes precedence over KBUILD_EXTMOD. |
| 127 | |
| 128 | KBUILD_OUTPUT |
| 129 | ------------- |
| 130 | Specify the output directory when building the kernel. |
| 131 | |
| 132 | The output directory can also be specified using "O=...". |
| 133 | |
| 134 | Setting "O=..." takes precedence over KBUILD_OUTPUT. |
| 135 | |
| 136 | KBUILD_EXTRA_WARN |
| 137 | ----------------- |
| 138 | Specify the extra build checks. The same value can be assigned by passing |
| 139 | W=... from the command line. |
| 140 | |
| 141 | See `make help` for the list of the supported values. |
| 142 | |
| 143 | Setting "W=..." takes precedence over KBUILD_EXTRA_WARN. |
| 144 | |
| 145 | KBUILD_DEBARCH |
| 146 | -------------- |
| 147 | For the deb-pkg target, allows overriding the normal heuristics deployed by |
| 148 | deb-pkg. Normally deb-pkg attempts to guess the right architecture based on |
| 149 | the UTS_MACHINE variable, and on some architectures also the kernel config. |
| 150 | The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian |
| 151 | architecture. |
| 152 | |
| 153 | ARCH |
| 154 | ---- |
| 155 | Set ARCH to the architecture to be built. |
| 156 | |
| 157 | In most cases the name of the architecture is the same as the |
| 158 | directory name found in the arch/ directory. |
| 159 | |
| 160 | But some architectures such as x86 and sparc have aliases. |
| 161 | |
| 162 | - x86: i386 for 32 bit, x86_64 for 64 bit |
| 163 | - sh: sh for 32 bit, sh64 for 64 bit |
| 164 | - sparc: sparc32 for 32 bit, sparc64 for 64 bit |
| 165 | |
| 166 | CROSS_COMPILE |
| 167 | ------------- |
| 168 | Specify an optional fixed part of the binutils filename. |
| 169 | CROSS_COMPILE can be a part of the filename or the full path. |
| 170 | |
| 171 | CROSS_COMPILE is also used for ccache in some setups. |
| 172 | |
| 173 | CF |
| 174 | -- |
| 175 | Additional options for sparse. |
| 176 | |
| 177 | CF is often used on the command-line like this:: |
| 178 | |
| 179 | make CF=-Wbitwise C=2 |
| 180 | |
| 181 | INSTALL_PATH |
| 182 | ------------ |
| 183 | INSTALL_PATH specifies where to place the updated kernel and system map |
| 184 | images. Default is /boot, but you can set it to other values. |
| 185 | |
| 186 | INSTALLKERNEL |
| 187 | ------------- |
| 188 | Install script called when using "make install". |
| 189 | The default name is "installkernel". |
| 190 | |
| 191 | The script will be called with the following arguments: |
| 192 | |
| 193 | - $1 - kernel version |
| 194 | - $2 - kernel image file |
| 195 | - $3 - kernel map file |
| 196 | - $4 - default install path (use root directory if blank) |
| 197 | |
| 198 | The implementation of "make install" is architecture specific |
| 199 | and it may differ from the above. |
| 200 | |
| 201 | INSTALLKERNEL is provided to enable the possibility to |
| 202 | specify a custom installer when cross compiling a kernel. |
| 203 | |
| 204 | MODLIB |
| 205 | ------ |
| 206 | Specify where to install modules. |
| 207 | The default value is:: |
| 208 | |
| 209 | $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) |
| 210 | |
| 211 | The value can be overridden in which case the default value is ignored. |
| 212 | |
| 213 | INSTALL_MOD_PATH |
| 214 | ---------------- |
| 215 | INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory |
| 216 | relocations required by build roots. This is not defined in the |
| 217 | makefile but the argument can be passed to make if needed. |
| 218 | |
| 219 | INSTALL_MOD_STRIP |
| 220 | ----------------- |
| 221 | INSTALL_MOD_STRIP, if defined, will cause modules to be |
| 222 | stripped after they are installed. If INSTALL_MOD_STRIP is '1', then |
| 223 | the default option --strip-debug will be used. Otherwise, |
| 224 | INSTALL_MOD_STRIP value will be used as the options to the strip command. |
| 225 | |
| 226 | INSTALL_HDR_PATH |
| 227 | ---------------- |
| 228 | INSTALL_HDR_PATH specifies where to install user space headers when |
| 229 | executing "make headers_*". |
| 230 | |
| 231 | The default value is:: |
| 232 | |
| 233 | $(objtree)/usr |
| 234 | |
| 235 | $(objtree) is the directory where output files are saved. |
| 236 | The output directory is often set using "O=..." on the commandline. |
| 237 | |
| 238 | The value can be overridden in which case the default value is ignored. |
| 239 | |
| 240 | KBUILD_ABS_SRCTREE |
| 241 | -------------------------------------------------- |
| 242 | Kbuild uses a relative path to point to the tree when possible. For instance, |
| 243 | when building in the source tree, the source tree path is '.' |
| 244 | |
| 245 | Setting this flag requests Kbuild to use absolute path to the source tree. |
| 246 | There are some useful cases to do so, like when generating tag files with |
| 247 | absolute path entries etc. |
| 248 | |
| 249 | KBUILD_SIGN_PIN |
| 250 | --------------- |
| 251 | This variable allows a passphrase or PIN to be passed to the sign-file |
| 252 | utility when signing kernel modules, if the private key requires such. |
| 253 | |
| 254 | KBUILD_MODPOST_WARN |
| 255 | ------------------- |
| 256 | KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined |
| 257 | symbols in the final module linking stage. It changes such errors |
| 258 | into warnings. |
| 259 | |
| 260 | KBUILD_MODPOST_NOFINAL |
| 261 | ---------------------- |
| 262 | KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. |
| 263 | This is solely useful to speed up test compiles. |
| 264 | |
| 265 | KBUILD_EXTRA_SYMBOLS |
| 266 | -------------------- |
| 267 | For modules that use symbols from other modules. |
| 268 | See more details in modules.rst. |
| 269 | |
| 270 | ALLSOURCE_ARCHS |
| 271 | --------------- |
| 272 | For tags/TAGS/cscope targets, you can specify more than one arch |
| 273 | to be included in the databases, separated by blank space. E.g.:: |
| 274 | |
| 275 | $ make ALLSOURCE_ARCHS="x86 mips arm" tags |
| 276 | |
| 277 | To get all available archs you can also specify all. E.g.:: |
| 278 | |
| 279 | $ make ALLSOURCE_ARCHS=all tags |
| 280 | |
| 281 | KBUILD_BUILD_TIMESTAMP |
| 282 | ---------------------- |
| 283 | Setting this to a date string overrides the timestamp used in the |
| 284 | UTS_VERSION definition (uname -v in the running kernel). The value has to |
| 285 | be a string that can be passed to date -d. The default value |
| 286 | is the output of the date command at one point during build. |
| 287 | |
| 288 | KBUILD_BUILD_USER, KBUILD_BUILD_HOST |
| 289 | ------------------------------------ |
| 290 | These two variables allow to override the user@host string displayed during |
| 291 | boot and in /proc/version. The default value is the output of the commands |
| 292 | whoami and host, respectively. |
| 293 | |
| 294 | LLVM |
| 295 | ---- |
| 296 | If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead |
| 297 | of GCC and GNU binutils to build the kernel. |