| ====== |
| Kbuild |
| ====== |
| |
| |
| Output files |
| ============ |
| |
| modules.order |
| ------------- |
| This file records the order in which modules appear in Makefiles. This |
| is used by modprobe to deterministically resolve aliases that match |
| multiple modules. |
| |
| modules.builtin |
| --------------- |
| This file lists all modules that are built into the kernel. This is used |
| by modprobe to not fail when trying to load something builtin. |
| |
| modules.builtin.modinfo |
| ----------------------- |
| This file contains modinfo from all modules that are built into the kernel. |
| Unlike modinfo of a separate module, all fields are prefixed with module name. |
| |
| modules.builtin.ranges |
| ---------------------- |
| This file contains address offset ranges (per ELF section) for all modules |
| that are built into the kernel. Together with System.map, it can be used |
| to associate module names with symbols. |
| |
| Environment variables |
| ===================== |
| |
| KCPPFLAGS |
| --------- |
| Additional options to pass when preprocessing. The preprocessing options |
| will be used in all cases where kbuild does preprocessing including |
| building C files and assembler files. |
| |
| KAFLAGS |
| ------- |
| Additional options to the assembler (for built-in and modules). |
| |
| AFLAGS_MODULE |
| ------------- |
| Additional assembler options for modules. |
| |
| AFLAGS_KERNEL |
| ------------- |
| Additional assembler options for built-in. |
| |
| KCFLAGS |
| ------- |
| Additional options to the C compiler (for built-in and modules). |
| |
| KRUSTFLAGS |
| ---------- |
| Additional options to the Rust compiler (for built-in and modules). |
| |
| CFLAGS_KERNEL |
| ------------- |
| Additional options for $(CC) when used to compile |
| code that is compiled as built-in. |
| |
| CFLAGS_MODULE |
| ------------- |
| Additional module specific options to use for $(CC). |
| |
| RUSTFLAGS_KERNEL |
| ---------------- |
| Additional options for $(RUSTC) when used to compile |
| code that is compiled as built-in. |
| |
| RUSTFLAGS_MODULE |
| ---------------- |
| Additional module specific options to use for $(RUSTC). |
| |
| LDFLAGS_MODULE |
| -------------- |
| Additional options used for $(LD) when linking modules. |
| |
| HOSTCFLAGS |
| ---------- |
| Additional flags to be passed to $(HOSTCC) when building host programs. |
| |
| HOSTCXXFLAGS |
| ------------ |
| Additional flags to be passed to $(HOSTCXX) when building host programs. |
| |
| HOSTRUSTFLAGS |
| ------------- |
| Additional flags to be passed to $(HOSTRUSTC) when building host programs. |
| |
| HOSTLDFLAGS |
| ----------- |
| Additional flags to be passed when linking host programs. |
| |
| HOSTLDLIBS |
| ---------- |
| Additional libraries to link against when building host programs. |
| |
| .. _userkbuildflags: |
| |
| USERCFLAGS |
| ---------- |
| Additional options used for $(CC) when compiling userprogs. |
| |
| USERLDFLAGS |
| ----------- |
| Additional options used for $(LD) when linking userprogs. userprogs are linked |
| with CC, so $(USERLDFLAGS) should include "-Wl," prefix as applicable. |
| |
| KBUILD_KCONFIG |
| -------------- |
| Set the top-level Kconfig file to the value of this environment |
| variable. The default name is "Kconfig". |
| |
| KBUILD_VERBOSE |
| -------------- |
| Set the kbuild verbosity. Can be assigned same values as "V=...". |
| |
| See make help for the full list. |
| |
| Setting "V=..." takes precedence over KBUILD_VERBOSE. |
| |
| KBUILD_EXTMOD |
| ------------- |
| Set the directory to look for the kernel source when building external |
| modules. |
| |
| Setting "M=..." takes precedence over KBUILD_EXTMOD. |
| |
| KBUILD_OUTPUT |
| ------------- |
| Specify the output directory when building the kernel. |
| |
| This variable can also be used to point to the kernel output directory when |
| building external modules against a pre-built kernel in a separate build |
| directory. Please note that this does NOT specify the output directory for the |
| external modules themselves. |
| |
| The output directory can also be specified using "O=...". |
| |
| Setting "O=..." takes precedence over KBUILD_OUTPUT. |
| |
| KBUILD_EXTRA_WARN |
| ----------------- |
| Specify the extra build checks. The same value can be assigned by passing |
| W=... from the command line. |
| |
| See `make help` for the list of the supported values. |
| |
| Setting "W=..." takes precedence over KBUILD_EXTRA_WARN. |
| |
| KBUILD_DEBARCH |
| -------------- |
| For the deb-pkg target, allows overriding the normal heuristics deployed by |
| deb-pkg. Normally deb-pkg attempts to guess the right architecture based on |
| the UTS_MACHINE variable, and on some architectures also the kernel config. |
| The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian |
| architecture. |
| |
| KDOCFLAGS |
| --------- |
| Specify extra (warning/error) flags for kernel-doc checks during the build, |
| see scripts/kernel-doc for which flags are supported. Note that this doesn't |
| (currently) apply to documentation builds. |
| |
| ARCH |
| ---- |
| Set ARCH to the architecture to be built. |
| |
| In most cases the name of the architecture is the same as the |
| directory name found in the arch/ directory. |
| |
| But some architectures such as x86 and sparc have aliases. |
| |
| - x86: i386 for 32 bit, x86_64 for 64 bit |
| - parisc: parisc64 for 64 bit |
| - sparc: sparc32 for 32 bit, sparc64 for 64 bit |
| |
| CROSS_COMPILE |
| ------------- |
| Specify an optional fixed part of the binutils filename. |
| CROSS_COMPILE can be a part of the filename or the full path. |
| |
| CROSS_COMPILE is also used for ccache in some setups. |
| |
| CF |
| -- |
| Additional options for sparse. |
| |
| CF is often used on the command-line like this:: |
| |
| make CF=-Wbitwise C=2 |
| |
| INSTALL_PATH |
| ------------ |
| INSTALL_PATH specifies where to place the updated kernel and system map |
| images. Default is /boot, but you can set it to other values. |
| |
| INSTALLKERNEL |
| ------------- |
| Install script called when using "make install". |
| The default name is "installkernel". |
| |
| The script will be called with the following arguments: |
| |
| - $1 - kernel version |
| - $2 - kernel image file |
| - $3 - kernel map file |
| - $4 - default install path (use root directory if blank) |
| |
| The implementation of "make install" is architecture specific |
| and it may differ from the above. |
| |
| INSTALLKERNEL is provided to enable the possibility to |
| specify a custom installer when cross compiling a kernel. |
| |
| MODLIB |
| ------ |
| Specify where to install modules. |
| The default value is:: |
| |
| $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE) |
| |
| The value can be overridden in which case the default value is ignored. |
| |
| INSTALL_MOD_PATH |
| ---------------- |
| INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory |
| relocations required by build roots. This is not defined in the |
| makefile but the argument can be passed to make if needed. |
| |
| INSTALL_MOD_STRIP |
| ----------------- |
| INSTALL_MOD_STRIP, if defined, will cause modules to be |
| stripped after they are installed. If INSTALL_MOD_STRIP is '1', then |
| the default option --strip-debug will be used. Otherwise, |
| INSTALL_MOD_STRIP value will be used as the options to the strip command. |
| |
| INSTALL_HDR_PATH |
| ---------------- |
| INSTALL_HDR_PATH specifies where to install user space headers when |
| executing "make headers_*". |
| |
| The default value is:: |
| |
| $(objtree)/usr |
| |
| $(objtree) is the directory where output files are saved. |
| The output directory is often set using "O=..." on the commandline. |
| |
| The value can be overridden in which case the default value is ignored. |
| |
| INSTALL_DTBS_PATH |
| ----------------- |
| INSTALL_DTBS_PATH specifies where to install device tree blobs for |
| relocations required by build roots. This is not defined in the |
| makefile but the argument can be passed to make if needed. |
| |
| KBUILD_ABS_SRCTREE |
| -------------------------------------------------- |
| Kbuild uses a relative path to point to the tree when possible. For instance, |
| when building in the source tree, the source tree path is '.' |
| |
| Setting this flag requests Kbuild to use absolute path to the source tree. |
| There are some useful cases to do so, like when generating tag files with |
| absolute path entries etc. |
| |
| KBUILD_SIGN_PIN |
| --------------- |
| This variable allows a passphrase or PIN to be passed to the sign-file |
| utility when signing kernel modules, if the private key requires such. |
| |
| KBUILD_MODPOST_WARN |
| ------------------- |
| KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined |
| symbols in the final module linking stage. It changes such errors |
| into warnings. |
| |
| KBUILD_MODPOST_NOFINAL |
| ---------------------- |
| KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules. |
| This is solely useful to speed up test compiles. |
| |
| KBUILD_EXTRA_SYMBOLS |
| -------------------- |
| For modules that use symbols from other modules. |
| See more details in modules.rst. |
| |
| ALLSOURCE_ARCHS |
| --------------- |
| For tags/TAGS/cscope targets, you can specify more than one arch |
| to be included in the databases, separated by blank space. E.g.:: |
| |
| $ make ALLSOURCE_ARCHS="x86 mips arm" tags |
| |
| To get all available archs you can also specify all. E.g.:: |
| |
| $ make ALLSOURCE_ARCHS=all tags |
| |
| IGNORE_DIRS |
| ----------- |
| For tags/TAGS/cscope targets, you can choose which directories won't |
| be included in the databases, separated by blank space. E.g.:: |
| |
| $ make IGNORE_DIRS="drivers/gpu/drm/radeon tools" cscope |
| |
| KBUILD_BUILD_TIMESTAMP |
| ---------------------- |
| Setting this to a date string overrides the timestamp used in the |
| UTS_VERSION definition (uname -v in the running kernel). The value has to |
| be a string that can be passed to date -d. The default value |
| is the output of the date command at one point during build. |
| |
| KBUILD_BUILD_USER, KBUILD_BUILD_HOST |
| ------------------------------------ |
| These two variables allow to override the user@host string displayed during |
| boot and in /proc/version. The default value is the output of the commands |
| whoami and host, respectively. |
| |
| LLVM |
| ---- |
| If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead |
| of GCC and GNU binutils to build the kernel. |
