Documentation/kbuild/kbuild.txt

   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.