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