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1Environment variables
2
3KCPPFLAGS
4--------------------------------------------------
5Additional options to pass when preprocessing. The preprocessing options
6will be used in all cases where kbuild do preprocessing including
7building C files and assembler files.
8
9KAFLAGS
10--------------------------------------------------
11Additional options to the assembler.
12
13KCFLAGS
14--------------------------------------------------
15Additional options to the C compiler.
16
17KBUILD_VERBOSE
18--------------------------------------------------
19Set the kbuild verbosity. Can be assinged same values as "V=...".
20See make help for the full list.
21Setting "V=..." takes precedence over KBUILD_VERBOSE.
22
23KBUILD_EXTMOD
24--------------------------------------------------
25Set the directory to look for the kernel source when building external
26modules.
27The directory can be specified in several ways:
281) Use "M=..." on the command line
292) Environmnet variable KBUILD_EXTMOD
303) Environmnet variable SUBDIRS
31The possibilities are listed in the order they take precedence.
32Using "M=..." will always override the others.
33
34KBUILD_OUTPUT
35--------------------------------------------------
36Specify the output directory when building the kernel.
37The output directory can also be specificed using "O=...".
38Setting "O=..." takes precedence over KBUILD_OUTPUT
39
40ARCH
41--------------------------------------------------
42Set ARCH to the architecture to be built.
43In most cases the name of the architecture is the same as the
44directory name found in the arch/ directory.
45But some architectures suach as x86 and sparc has aliases.
46x86: i386 for 32 bit, x86_64 for 64 bit
47sparc: sparc for 32 bit, sparc64 for 64 bit
48
49CROSS_COMPILE
50--------------------------------------------------
51Specify an optional fixed part of the binutils filename.
52CROSS_COMPILE can be a part of the filename or the full path.
53
54CROSS_COMPILE is also used for ccache is some setups.
55
56CF
57--------------------------------------------------
58Additional options for sparse.
59CF is often used on the command-line like this:
60
61 make CF=-Wbitwise C=2
62
63INSTALL_PATH
64--------------------------------------------------
65INSTALL_PATH specifies where to place the updated kernel and system map
66images. Default is /boot, but you can set it to other values
67
68
69MODLIB
70--------------------------------------------------
71Specify where to install modules.
72The default value is:
73
74 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
75
76The value can be overridden in which case the default value is ignored.
77
78INSTALL_MOD_PATH
79--------------------------------------------------
80INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
81relocations required by build roots. This is not defined in the
82makefile but the argument can be passed to make if needed.
83
84INSTALL_MOD_STRIP
85--------------------------------------------------
86INSTALL_MOD_STRIP, if defined, will cause modules to be
87stripped after they are installed. If INSTALL_MOD_STRIP is '1', then
88the default option --strip-debug will be used. Otherwise,
89INSTALL_MOD_STRIP will used as the options to the strip command.
90
91INSTALL_FW_PATH
92--------------------------------------------------
93INSTALL_FW_PATH specify where to install the firmware blobs.
94The default value is:
95
96 $(INSTALL_MOD_PATH)/lib/firmware
97
98The value can be overridden in which case the default value is ignored.
99
100INSTALL_HDR_PATH
101--------------------------------------------------
102INSTALL_HDR_PATH specify where to install user space headers when
103executing "make headers_*".
104The default value is:
105
106 $(objtree)/usr
107
108$(objtree) is the directory where output files are saved.
109The output directory is often set using "O=..." on the commandline.
110
111The value can be overridden in which case the default value is ignored.
112
113KBUILD_MODPOST_WARN
114--------------------------------------------------
115KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined
116symbols in the final module linking stage.
117
118KBUILD_MODPOST_FINAL
119--------------------------------------------------
120KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
121This is solely usefull to speed up test compiles.
122
123KBUILD_EXTRA_SYMBOLS
124--------------------------------------------------
125For modules use symbols from another modules.
126See more details in modules.txt.