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
53LDFLAGS_vmlinux
54--------------------------------------------------
55Additional options passed to final link of vmlinux.
56
57KBUILD_VERBOSE
58--------------------------------------------------
59Set the kbuild verbosity. Can be assigned same values as "V=...".
60See make help for the full list.
61Setting "V=..." takes precedence over KBUILD_VERBOSE.
62
63KBUILD_EXTMOD
64--------------------------------------------------
65Set the directory to look for the kernel source when building external
66modules.
67The directory can be specified in several ways:
681) Use "M=..." on the command line
692) Environment variable KBUILD_EXTMOD
703) Environment variable SUBDIRS
71The possibilities are listed in the order they take precedence.
72Using "M=..." will always override the others.
73
74KBUILD_OUTPUT
75--------------------------------------------------
76Specify the output directory when building the kernel.
77The output directory can also be specified using "O=...".
78Setting "O=..." takes precedence over KBUILD_OUTPUT.
79
80KBUILD_DEBARCH
81--------------------------------------------------
82For the deb-pkg target, allows overriding the normal heuristics deployed by
83deb-pkg. Normally deb-pkg attempts to guess the right architecture based on
84the UTS_MACHINE variable, and on some architectures also the kernel config.
85The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian
86architecture.
87
88ARCH
89--------------------------------------------------
90Set ARCH to the architecture to be built.
91In most cases the name of the architecture is the same as the
92directory name found in the arch/ directory.
93But some architectures such as x86 and sparc have aliases.
94x86: i386 for 32 bit, x86_64 for 64 bit
95sparc: sparc for 32 bit, sparc64 for 64 bit
96
97CROSS_COMPILE
98--------------------------------------------------
99Specify an optional fixed part of the binutils filename.
100CROSS_COMPILE can be a part of the filename or the full path.
101
102CROSS_COMPILE is also used for ccache in some setups.
103
104CF
105--------------------------------------------------
106Additional options for sparse.
107CF is often used on the command-line like this:
108
109    make CF=-Wbitwise C=2
110
111INSTALL_PATH
112--------------------------------------------------
113INSTALL_PATH specifies where to place the updated kernel and system map
114images. Default is /boot, but you can set it to other values.
115
116INSTALLKERNEL
117--------------------------------------------------
118Install script called when using "make install".
119The default name is "installkernel".
120
121The 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
127The implementation of "make install" is architecture specific
128and it may differ from the above.
129
130INSTALLKERNEL is provided to enable the possibility to
131specify a custom installer when cross compiling a kernel.
132
133MODLIB
134--------------------------------------------------
135Specify where to install modules.
136The default value is:
137
138     $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
139
140The value can be overridden in which case the default value is ignored.
141
142INSTALL_MOD_PATH
143--------------------------------------------------
144INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
145relocations required by build roots.  This is not defined in the
146makefile but the argument can be passed to make if needed.
147
148INSTALL_MOD_STRIP
149--------------------------------------------------
150INSTALL_MOD_STRIP, if defined, will cause modules to be
151stripped after they are installed.  If INSTALL_MOD_STRIP is '1', then
152the default option --strip-debug will be used.  Otherwise,
153INSTALL_MOD_STRIP value will be used as the options to the strip command.
154
155INSTALL_FW_PATH
156--------------------------------------------------
157INSTALL_FW_PATH specifies where to install the firmware blobs.
158The default value is:
159
160    $(INSTALL_MOD_PATH)/lib/firmware
161
162The value can be overridden in which case the default value is ignored.
163
164INSTALL_HDR_PATH
165--------------------------------------------------
166INSTALL_HDR_PATH specifies where to install user space headers when
167executing "make headers_*".
168The default value is:
169
170    $(objtree)/usr
171
172$(objtree) is the directory where output files are saved.
173The output directory is often set using "O=..." on the commandline.
174
175The value can be overridden in which case the default value is ignored.
176
177KBUILD_SIGN_PIN
178--------------------------------------------------
179This variable allows a passphrase or PIN to be passed to the sign-file
180utility when signing kernel modules, if the private key requires such.
181
182KBUILD_MODPOST_WARN
183--------------------------------------------------
184KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
185symbols in the final module linking stage. It changes such errors
186into warnings.
187
188KBUILD_MODPOST_NOFINAL
189--------------------------------------------------
190KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
191This is solely useful to speed up test compiles.
192
193KBUILD_EXTRA_SYMBOLS
194--------------------------------------------------
195For modules that use symbols from other modules.
196See more details in modules.txt.
197
198ALLSOURCE_ARCHS
199--------------------------------------------------
200For tags/TAGS/cscope targets, you can specify more than one arch
201to be included in the databases, separated by blank space. E.g.:
202
203    $ make ALLSOURCE_ARCHS="x86 mips arm" tags
204
205To get all available archs you can also specify all. E.g.:
206
207    $ make ALLSOURCE_ARCHS=all tags
208
209KBUILD_ENABLE_EXTRA_GCC_CHECKS
210--------------------------------------------------
211If enabled over the make command line with "W=1", it turns on additional
212gcc -W... options for more extensive build-time checking.
213
214KBUILD_BUILD_TIMESTAMP
215--------------------------------------------------
216Setting this to a date string overrides the timestamp used in the
217UTS_VERSION definition (uname -v in the running kernel). The value has to
218be a string that can be passed to date -d. The default value
219is the output of the date command at one point during build.
220
221KBUILD_BUILD_USER, KBUILD_BUILD_HOST
222--------------------------------------------------
223These two variables allow to override the user@host string displayed during
224boot and in /proc/version. The default value is the output of the commands
225whoami and host, respectively.
226
227KBUILD_LDS
228--------------------------------------------------
229The linker script with full path. Assigned by the top-level Makefile.
230
231KBUILD_VMLINUX_INIT
232--------------------------------------------------
233All object files for the init (first) part of vmlinux.
234Files specified with KBUILD_VMLINUX_INIT are linked first.
235
236KBUILD_VMLINUX_MAIN
237--------------------------------------------------
238All object files for the main part of vmlinux.
239KBUILD_VMLINUX_INIT and KBUILD_VMLINUX_MAIN together specify
240all the object files used to link vmlinux.
241