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 modules.builtin.ranges 26 ---------------------- 27 This file contains address offset ranges (per ELF section) for all modules 28 that are built into the kernel. Together with System.map, it can be used 29 to associate module names with symbols. 30 31 Environment variables 32 ===================== 33 34 KCPPFLAGS 35 --------- 36 Additional options to pass when preprocessing. The preprocessing options 37 will be used in all cases where kbuild does preprocessing including 38 building C files and assembler files. 39 40 KAFLAGS 41 ------- 42 Additional options to the assembler (for built-in and modules). 43 44 AFLAGS_MODULE 45 ------------- 46 Additional assembler options for modules. 47 48 AFLAGS_KERNEL 49 ------------- 50 Additional assembler options for built-in. 51 52 KCFLAGS 53 ------- 54 Additional options to the C compiler (for built-in and modules). 55 56 KRUSTFLAGS 57 ---------- 58 Additional options to the Rust compiler (for built-in and modules). 59 60 CFLAGS_KERNEL 61 ------------- 62 Additional options for $(CC) when used to compile 63 code that is compiled as built-in. 64 65 CFLAGS_MODULE 66 ------------- 67 Additional module specific options to use for $(CC). 68 69 RUSTFLAGS_KERNEL 70 ---------------- 71 Additional options for $(RUSTC) when used to compile 72 code that is compiled as built-in. 73 74 RUSTFLAGS_MODULE 75 ---------------- 76 Additional module specific options to use for $(RUSTC). 77 78 LDFLAGS_MODULE 79 -------------- 80 Additional options used for $(LD) when linking modules. 81 82 HOSTCFLAGS 83 ---------- 84 Additional flags to be passed to $(HOSTCC) when building host programs. 85 86 HOSTCXXFLAGS 87 ------------ 88 Additional flags to be passed to $(HOSTCXX) when building host programs. 89 90 HOSTRUSTFLAGS 91 ------------- 92 Additional flags to be passed to $(HOSTRUSTC) when building host programs. 93 94 HOSTLDFLAGS 95 ----------- 96 Additional flags to be passed when linking host programs. 97 98 HOSTLDLIBS 99 ---------- 100 Additional libraries to link against when building host programs. 101 102 .. _userkbuildflags: 103 104 USERCFLAGS 105 ---------- 106 Additional options used for $(CC) when compiling userprogs. 107 108 USERLDFLAGS 109 ----------- 110 Additional options used for $(LD) when linking userprogs. userprogs are linked 111 with CC, so $(USERLDFLAGS) should include "-Wl," prefix as applicable. 112 113 KBUILD_KCONFIG 114 -------------- 115 Set the top-level Kconfig file to the value of this environment 116 variable. The default name is "Kconfig". 117 118 KBUILD_VERBOSE 119 -------------- 120 Set the kbuild verbosity. Can be assigned same values as "V=...". 121 122 See make help for the full list. 123 124 Setting "V=..." takes precedence over KBUILD_VERBOSE. 125 126 KBUILD_EXTMOD 127 ------------- 128 Set the directory to look for the kernel source when building external 129 modules. 130 131 Setting "M=..." takes precedence over KBUILD_EXTMOD. 132 133 KBUILD_OUTPUT 134 ------------- 135 Specify the output directory when building the kernel. 136 137 This variable can also be used to point to the kernel output directory when 138 building external modules against a pre-built kernel in a separate build 139 directory. Please note that this does NOT specify the output directory for the 140 external modules themselves. 141 142 The output directory can also be specified using "O=...". 143 144 Setting "O=..." takes precedence over KBUILD_OUTPUT. 145 146 KBUILD_EXTRA_WARN 147 ----------------- 148 Specify the extra build checks. The same value can be assigned by passing 149 W=... from the command line. 150 151 See `make help` for the list of the supported values. 152 153 Setting "W=..." takes precedence over KBUILD_EXTRA_WARN. 154 155 KBUILD_DEBARCH 156 -------------- 157 For the deb-pkg target, allows overriding the normal heuristics deployed by 158 deb-pkg. Normally deb-pkg attempts to guess the right architecture based on 159 the UTS_MACHINE variable, and on some architectures also the kernel config. 160 The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian 161 architecture. 162 163 KDOCFLAGS 164 --------- 165 Specify extra (warning/error) flags for kernel-doc checks during the build, 166 see scripts/kernel-doc for which flags are supported. Note that this doesn't 167 (currently) apply to documentation builds. 168 169 ARCH 170 ---- 171 Set ARCH to the architecture to be built. 172 173 In most cases the name of the architecture is the same as the 174 directory name found in the arch/ directory. 175 176 But some architectures such as x86 and sparc have aliases. 177 178 - x86: i386 for 32 bit, x86_64 for 64 bit 179 - parisc: parisc64 for 64 bit 180 - sparc: sparc32 for 32 bit, sparc64 for 64 bit 181 182 CROSS_COMPILE 183 ------------- 184 Specify an optional fixed part of the binutils filename. 185 CROSS_COMPILE can be a part of the filename or the full path. 186 187 CROSS_COMPILE is also used for ccache in some setups. 188 189 CF 190 -- 191 Additional options for sparse. 192 193 CF is often used on the command-line like this:: 194 195 make CF=-Wbitwise C=2 196 197 INSTALL_PATH 198 ------------ 199 INSTALL_PATH specifies where to place the updated kernel and system map 200 images. Default is /boot, but you can set it to other values. 201 202 INSTALLKERNEL 203 ------------- 204 Install script called when using "make install". 205 The default name is "installkernel". 206 207 The script will be called with the following arguments: 208 209 - $1 - kernel version 210 - $2 - kernel image file 211 - $3 - kernel map file 212 - $4 - default install path (use root directory if blank) 213 214 The implementation of "make install" is architecture specific 215 and it may differ from the above. 216 217 INSTALLKERNEL is provided to enable the possibility to 218 specify a custom installer when cross compiling a kernel. 219 220 MODLIB 221 ------ 222 Specify where to install modules. 223 The default value is:: 224 225 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) 226 227 The value can be overridden in which case the default value is ignored. 228 229 INSTALL_MOD_PATH 230 ---------------- 231 INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory 232 relocations required by build roots. This is not defined in the 233 makefile but the argument can be passed to make if needed. 234 235 INSTALL_MOD_STRIP 236 ----------------- 237 INSTALL_MOD_STRIP, if defined, will cause modules to be 238 stripped after they are installed. If INSTALL_MOD_STRIP is '1', then 239 the default option --strip-debug will be used. Otherwise, 240 INSTALL_MOD_STRIP value will be used as the options to the strip command. 241 242 INSTALL_HDR_PATH 243 ---------------- 244 INSTALL_HDR_PATH specifies where to install user space headers when 245 executing "make headers_*". 246 247 The default value is:: 248 249 $(objtree)/usr 250 251 $(objtree) is the directory where output files are saved. 252 The output directory is often set using "O=..." on the commandline. 253 254 The value can be overridden in which case the default value is ignored. 255 256 INSTALL_DTBS_PATH 257 ----------------- 258 INSTALL_DTBS_PATH specifies where to install device tree blobs for 259 relocations required by build roots. This is not defined in the 260 makefile but the argument can be passed to make if needed. 261 262 KBUILD_ABS_SRCTREE 263 -------------------------------------------------- 264 Kbuild uses a relative path to point to the tree when possible. For instance, 265 when building in the source tree, the source tree path is '.' 266 267 Setting this flag requests Kbuild to use absolute path to the source tree. 268 There are some useful cases to do so, like when generating tag files with 269 absolute path entries etc. 270 271 KBUILD_SIGN_PIN 272 --------------- 273 This variable allows a passphrase or PIN to be passed to the sign-file 274 utility when signing kernel modules, if the private key requires such. 275 276 KBUILD_MODPOST_WARN 277 ------------------- 278 KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined 279 symbols in the final module linking stage. It changes such errors 280 into warnings. 281 282 KBUILD_MODPOST_NOFINAL 283 ---------------------- 284 KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. 285 This is solely useful to speed up test compiles. 286 287 KBUILD_EXTRA_SYMBOLS 288 -------------------- 289 For modules that use symbols from other modules. 290 See more details in modules.rst. 291 292 ALLSOURCE_ARCHS 293 --------------- 294 For tags/TAGS/cscope targets, you can specify more than one arch 295 to be included in the databases, separated by blank space. E.g.:: 296 297 $ make ALLSOURCE_ARCHS="x86 mips arm" tags 298 299 To get all available archs you can also specify all. E.g.:: 300 301 $ make ALLSOURCE_ARCHS=all tags 302 303 IGNORE_DIRS 304 ----------- 305 For tags/TAGS/cscope targets, you can choose which directories won't 306 be included in the databases, separated by blank space. E.g.:: 307 308 $ make IGNORE_DIRS="drivers/gpu/drm/radeon tools" cscope 309 310 KBUILD_BUILD_TIMESTAMP 311 ---------------------- 312 Setting this to a date string overrides the timestamp used in the 313 UTS_VERSION definition (uname -v in the running kernel). The value has to 314 be a string that can be passed to date -d. The default value 315 is the output of the date command at one point during build. 316 317 KBUILD_BUILD_USER, KBUILD_BUILD_HOST 318 ------------------------------------ 319 These two variables allow to override the user@host string displayed during 320 boot and in /proc/version. The default value is the output of the commands 321 whoami and host, respectively. 322 323 LLVM 324 ---- 325 If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead 326 of GCC and GNU binutils to build the kernel.
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