kbuild: allow assignment to {A,C,LD}FLAGS_MODULE on the command line
[linux-2.6-block.git] / Documentation / kbuild / kbuild.txt
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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
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15Environment variables
16
17KCPPFLAGS
18--------------------------------------------------
19Additional options to pass when preprocessing. The preprocessing options
df291fa9 20will be used in all cases where kbuild does preprocessing including
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21building C files and assembler files.
22
23KAFLAGS
24--------------------------------------------------
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25Additional options to the assembler (for built-in and modules).
26
27AFLAGS_MODULE
28--------------------------------------------------
29Addtional module specific options to use for $(AS).
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30
31KCFLAGS
32--------------------------------------------------
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33Additional options to the C compiler (for built-in and modules).
34
35CFLAGS_MODULE
36--------------------------------------------------
37Addtional module specific options to use for $(CC).
38
39LDFLAGS_MODULE
40--------------------------------------------------
41Additional options used for $(LD) when linking modules.
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42
43KBUILD_VERBOSE
44--------------------------------------------------
df291fa9 45Set the kbuild verbosity. Can be assigned same values as "V=...".
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46See make help for the full list.
47Setting "V=..." takes precedence over KBUILD_VERBOSE.
48
49KBUILD_EXTMOD
50--------------------------------------------------
51Set the directory to look for the kernel source when building external
52modules.
53The directory can be specified in several ways:
541) Use "M=..." on the command line
552) Environmnet variable KBUILD_EXTMOD
563) Environmnet variable SUBDIRS
57The possibilities are listed in the order they take precedence.
58Using "M=..." will always override the others.
59
60KBUILD_OUTPUT
61--------------------------------------------------
62Specify the output directory when building the kernel.
63The output directory can also be specificed using "O=...".
df291fa9 64Setting "O=..." takes precedence over KBUILD_OUTPUT.
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65
66ARCH
67--------------------------------------------------
68Set ARCH to the architecture to be built.
69In most cases the name of the architecture is the same as the
70directory name found in the arch/ directory.
df291fa9 71But some architectures such as x86 and sparc have aliases.
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72x86: i386 for 32 bit, x86_64 for 64 bit
73sparc: sparc for 32 bit, sparc64 for 64 bit
74
75CROSS_COMPILE
76--------------------------------------------------
77Specify an optional fixed part of the binutils filename.
78CROSS_COMPILE can be a part of the filename or the full path.
79
e8d400a9 80CROSS_COMPILE is also used for ccache in some setups.
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81
82CF
83--------------------------------------------------
84Additional options for sparse.
85CF is often used on the command-line like this:
86
87 make CF=-Wbitwise C=2
88
89INSTALL_PATH
90--------------------------------------------------
91INSTALL_PATH specifies where to place the updated kernel and system map
df291fa9 92images. Default is /boot, but you can set it to other values.
acc08b51 93
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94INSTALLKERNEL
95--------------------------------------------------
96Install script called when using "make install".
97The default name is "installkernel".
98
99The script will be called with the following arguments:
100 $1 - kernel version
101 $2 - kernel image file
102 $3 - kernel map file
103 $4 - default install path (use root directory if blank)
104
105The implmentation of "make install" is architecture specific
106and it may differ from the above.
107
108INSTALLKERNEL is provided to enable the possibility to
109specify a custom installer when cross compiling a kernel.
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110
111MODLIB
112--------------------------------------------------
113Specify where to install modules.
114The default value is:
115
116 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
117
118The value can be overridden in which case the default value is ignored.
119
120INSTALL_MOD_PATH
121--------------------------------------------------
122INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
123relocations required by build roots. This is not defined in the
124makefile but the argument can be passed to make if needed.
125
126INSTALL_MOD_STRIP
127--------------------------------------------------
128INSTALL_MOD_STRIP, if defined, will cause modules to be
129stripped after they are installed. If INSTALL_MOD_STRIP is '1', then
130the default option --strip-debug will be used. Otherwise,
131INSTALL_MOD_STRIP will used as the options to the strip command.
132
133INSTALL_FW_PATH
134--------------------------------------------------
df291fa9 135INSTALL_FW_PATH specifies where to install the firmware blobs.
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136The default value is:
137
138 $(INSTALL_MOD_PATH)/lib/firmware
139
140The value can be overridden in which case the default value is ignored.
141
142INSTALL_HDR_PATH
143--------------------------------------------------
df291fa9 144INSTALL_HDR_PATH specifies where to install user space headers when
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145executing "make headers_*".
146The default value is:
147
148 $(objtree)/usr
149
150$(objtree) is the directory where output files are saved.
151The output directory is often set using "O=..." on the commandline.
152
153The value can be overridden in which case the default value is ignored.
154
155KBUILD_MODPOST_WARN
156--------------------------------------------------
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157KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
158symbols in the final module linking stage. It changes such errors
159into warnings.
acc08b51 160
df291fa9 161KBUILD_MODPOST_NOFINAL
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162--------------------------------------------------
163KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
df291fa9 164This is solely useful to speed up test compiles.
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165
166KBUILD_EXTRA_SYMBOLS
167--------------------------------------------------
df291fa9 168For modules that use symbols from other modules.
acc08b51 169See more details in modules.txt.
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170
171ALLSOURCE_ARCHS
172--------------------------------------------------
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173For tags/TAGS/cscope targets, you can specify more than one arch
174to be included in the databases, separated by blank space. E.g.:
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175
176 $ make ALLSOURCE_ARCHS="x86 mips arm" tags
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177
178To get all available archs you can also specify all. E.g.:
179
180 $ make ALLSOURCE_ARCHS=all tags