Documentation / kbuild / kbuild.txt
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Based on kernel version 3.9. Page generated on 2013-05-02 23:09 EST.
1 Output files 2 3 modules.order 4 -------------------------------------------------- 5 This file records the order in which modules appear in Makefiles. This 6 is used by modprobe to deterministically resolve aliases that match 7 multiple modules. 8 9 modules.builtin 10 -------------------------------------------------- 11 This file lists all modules that are built into the kernel. This is used 12 by modprobe to not fail when trying to load something builtin. 13 14 15 Environment variables 16 17 KCPPFLAGS 18 -------------------------------------------------- 19 Additional options to pass when preprocessing. The preprocessing options 20 will be used in all cases where kbuild does preprocessing including 21 building C files and assembler files. 22 23 KAFLAGS 24 -------------------------------------------------- 25 Additional options to the assembler (for built-in and modules). 26 27 AFLAGS_MODULE 28 -------------------------------------------------- 29 Additional module specific options to use for $(AS). 30 31 AFLAGS_KERNEL 32 -------------------------------------------------- 33 Additional options for $(AS) when used for assembler 34 code for code that is compiled as built-in. 35 36 KCFLAGS 37 -------------------------------------------------- 38 Additional options to the C compiler (for built-in and modules). 39 40 CFLAGS_KERNEL 41 -------------------------------------------------- 42 Additional options for $(CC) when used to compile 43 code that is compiled as built-in. 44 45 CFLAGS_MODULE 46 -------------------------------------------------- 47 Additional module specific options to use for $(CC). 48 49 LDFLAGS_MODULE 50 -------------------------------------------------- 51 Additional options used for $(LD) when linking modules. 52 53 LDFLAGS_vmlinux 54 -------------------------------------------------- 55 Additional options passed to final link of vmlinux. 56 57 KBUILD_VERBOSE 58 -------------------------------------------------- 59 Set the kbuild verbosity. Can be assigned same values as "V=...". 60 See make help for the full list. 61 Setting "V=..." takes precedence over KBUILD_VERBOSE. 62 63 KBUILD_EXTMOD 64 -------------------------------------------------- 65 Set the directory to look for the kernel source when building external 66 modules. 67 The directory can be specified in several ways: 68 1) Use "M=..." on the command line 69 2) Environment variable KBUILD_EXTMOD 70 3) Environment variable SUBDIRS 71 The possibilities are listed in the order they take precedence. 72 Using "M=..." will always override the others. 73 74 KBUILD_OUTPUT 75 -------------------------------------------------- 76 Specify the output directory when building the kernel. 77 The output directory can also be specified using "O=...". 78 Setting "O=..." takes precedence over KBUILD_OUTPUT. 79 80 KBUILD_DEBARCH 81 -------------------------------------------------- 82 For the deb-pkg target, allows overriding the normal heuristics deployed by 83 deb-pkg. Normally deb-pkg attempts to guess the right architecture based on 84 the UTS_MACHINE variable, and on some architectures also the kernel config. 85 The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian 86 architecture. 87 88 ARCH 89 -------------------------------------------------- 90 Set ARCH to the architecture to be built. 91 In most cases the name of the architecture is the same as the 92 directory name found in the arch/ directory. 93 But some architectures such as x86 and sparc have aliases. 94 x86: i386 for 32 bit, x86_64 for 64 bit 95 sparc: sparc for 32 bit, sparc64 for 64 bit 96 97 CROSS_COMPILE 98 -------------------------------------------------- 99 Specify an optional fixed part of the binutils filename. 100 CROSS_COMPILE can be a part of the filename or the full path. 101 102 CROSS_COMPILE is also used for ccache in some setups. 103 104 CF 105 -------------------------------------------------- 106 Additional options for sparse. 107 CF is often used on the command-line like this: 108 109 make CF=-Wbitwise C=2 110 111 INSTALL_PATH 112 -------------------------------------------------- 113 INSTALL_PATH specifies where to place the updated kernel and system map 114 images. Default is /boot, but you can set it to other values. 115 116 INSTALLKERNEL 117 -------------------------------------------------- 118 Install script called when using "make install". 119 The default name is "installkernel". 120 121 The script will be called with the following arguments: 122 $1 - kernel version 123 $2 - kernel image file 124 $3 - kernel map file 125 $4 - default install path (use root directory if blank) 126 127 The implementation of "make install" is architecture specific 128 and it may differ from the above. 129 130 INSTALLKERNEL is provided to enable the possibility to 131 specify a custom installer when cross compiling a kernel. 132 133 MODLIB 134 -------------------------------------------------- 135 Specify where to install modules. 136 The default value is: 137 138 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) 139 140 The value can be overridden in which case the default value is ignored. 141 142 INSTALL_MOD_PATH 143 -------------------------------------------------- 144 INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory 145 relocations required by build roots. This is not defined in the 146 makefile but the argument can be passed to make if needed. 147 148 INSTALL_MOD_STRIP 149 -------------------------------------------------- 150 INSTALL_MOD_STRIP, if defined, will cause modules to be 151 stripped after they are installed. If INSTALL_MOD_STRIP is '1', then 152 the default option --strip-debug will be used. Otherwise, 153 INSTALL_MOD_STRIP value will be used as the options to the strip command. 154 155 INSTALL_FW_PATH 156 -------------------------------------------------- 157 INSTALL_FW_PATH specifies where to install the firmware blobs. 158 The default value is: 159 160 $(INSTALL_MOD_PATH)/lib/firmware 161 162 The value can be overridden in which case the default value is ignored. 163 164 INSTALL_HDR_PATH 165 -------------------------------------------------- 166 INSTALL_HDR_PATH specifies where to install user space headers when 167 executing "make headers_*". 168 The default value is: 169 170 $(objtree)/usr 171 172 $(objtree) is the directory where output files are saved. 173 The output directory is often set using "O=..." on the commandline. 174 175 The value can be overridden in which case the default value is ignored. 176 177 KBUILD_MODPOST_WARN 178 -------------------------------------------------- 179 KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined 180 symbols in the final module linking stage. It changes such errors 181 into warnings. 182 183 KBUILD_MODPOST_NOFINAL 184 -------------------------------------------------- 185 KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. 186 This is solely useful to speed up test compiles. 187 188 KBUILD_EXTRA_SYMBOLS 189 -------------------------------------------------- 190 For modules that use symbols from other modules. 191 See more details in modules.txt. 192 193 ALLSOURCE_ARCHS 194 -------------------------------------------------- 195 For tags/TAGS/cscope targets, you can specify more than one arch 196 to be included in the databases, separated by blank space. E.g.: 197 198 $ make ALLSOURCE_ARCHS="x86 mips arm" tags 199 200 To get all available archs you can also specify all. E.g.: 201 202 $ make ALLSOURCE_ARCHS=all tags 203 204 KBUILD_ENABLE_EXTRA_GCC_CHECKS 205 -------------------------------------------------- 206 If enabled over the make command line with "W=1", it turns on additional 207 gcc -W... options for more extensive build-time checking. 208 209 KBUILD_BUILD_TIMESTAMP 210 -------------------------------------------------- 211 Setting this to a date string overrides the timestamp used in the 212 UTS_VERSION definition (uname -v in the running kernel). The value has to 213 be a string that can be passed to date -d. The default value 214 is the output of the date command at one point during build. 215 216 KBUILD_BUILD_USER, KBUILD_BUILD_HOST 217 -------------------------------------------------- 218 These two variables allow to override the user@host string displayed during 219 boot and in /proc/version. The default value is the output of the commands 220 whoami and host, respectively. 221 222 KBUILD_LDS 223 -------------------------------------------------- 224 The linker script with full path. Assigned by the top-level Makefile. 225 226 KBUILD_VMLINUX_INIT 227 -------------------------------------------------- 228 All object files for the init (first) part of vmlinux. 229 Files specified with KBUILD_VMLINUX_INIT are linked first. 230 231 KBUILD_VMLINUX_MAIN 232 -------------------------------------------------- 233 All object files for the main part of vmlinux. 234 KBUILD_VMLINUX_INIT and KBUILD_VMLINUX_MAIN together specify 235 all the object files used to link vmlinux.
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