1 ====== 1 ======
2 Kbuild 2 Kbuild
3 ====== 3 ======
4 4
5 5
6 Output files 6 Output files
7 ============ 7 ============
8 8
9 modules.order 9 modules.order
10 ------------- 10 -------------
11 This file records the order in which modules a 11 This file records the order in which modules appear in Makefiles. This
12 is used by modprobe to deterministically resol 12 is used by modprobe to deterministically resolve aliases that match
13 multiple modules. 13 multiple modules.
14 14
15 modules.builtin 15 modules.builtin
16 --------------- 16 ---------------
17 This file lists all modules that are built int 17 This file lists all modules that are built into the kernel. This is used
18 by modprobe to not fail when trying to load so 18 by modprobe to not fail when trying to load something builtin.
19 19
20 modules.builtin.modinfo 20 modules.builtin.modinfo
21 ----------------------- 21 -----------------------
22 This file contains modinfo from all modules th 22 This file contains modinfo from all modules that are built into the kernel.
23 Unlike modinfo of a separate module, all field 23 Unlike modinfo of a separate module, all fields are prefixed with module name.
24 24
25 modules.builtin.ranges <<
26 ---------------------- <<
27 This file contains address offset ranges (per <<
28 that are built into the kernel. Together with <<
29 to associate module names with symbols. <<
30 25
31 Environment variables 26 Environment variables
32 ===================== 27 =====================
33 28
34 KCPPFLAGS 29 KCPPFLAGS
35 --------- 30 ---------
36 Additional options to pass when preprocessing. 31 Additional options to pass when preprocessing. The preprocessing options
37 will be used in all cases where kbuild does pr 32 will be used in all cases where kbuild does preprocessing including
38 building C files and assembler files. 33 building C files and assembler files.
39 34
40 KAFLAGS 35 KAFLAGS
41 ------- 36 -------
42 Additional options to the assembler (for built 37 Additional options to the assembler (for built-in and modules).
43 38
44 AFLAGS_MODULE 39 AFLAGS_MODULE
45 ------------- 40 -------------
46 Additional assembler options for modules. 41 Additional assembler options for modules.
47 42
48 AFLAGS_KERNEL 43 AFLAGS_KERNEL
49 ------------- 44 -------------
50 Additional assembler options for built-in. 45 Additional assembler options for built-in.
51 46
52 KCFLAGS 47 KCFLAGS
53 ------- 48 -------
54 Additional options to the C compiler (for buil 49 Additional options to the C compiler (for built-in and modules).
55 50
56 KRUSTFLAGS <<
57 ---------- <<
58 Additional options to the Rust compiler (for b <<
59 <<
60 CFLAGS_KERNEL 51 CFLAGS_KERNEL
61 ------------- 52 -------------
62 Additional options for $(CC) when used to comp 53 Additional options for $(CC) when used to compile
63 code that is compiled as built-in. 54 code that is compiled as built-in.
64 55
65 CFLAGS_MODULE 56 CFLAGS_MODULE
66 ------------- 57 -------------
67 Additional module specific options to use for 58 Additional module specific options to use for $(CC).
68 59
69 RUSTFLAGS_KERNEL <<
70 ---------------- <<
71 Additional options for $(RUSTC) when used to c <<
72 code that is compiled as built-in. <<
73 <<
74 RUSTFLAGS_MODULE <<
75 ---------------- <<
76 Additional module specific options to use for <<
77 <<
78 LDFLAGS_MODULE 60 LDFLAGS_MODULE
79 -------------- 61 --------------
80 Additional options used for $(LD) when linking 62 Additional options used for $(LD) when linking modules.
81 63
82 HOSTCFLAGS 64 HOSTCFLAGS
83 ---------- 65 ----------
84 Additional flags to be passed to $(HOSTCC) whe 66 Additional flags to be passed to $(HOSTCC) when building host programs.
85 67
86 HOSTCXXFLAGS 68 HOSTCXXFLAGS
87 ------------ 69 ------------
88 Additional flags to be passed to $(HOSTCXX) wh 70 Additional flags to be passed to $(HOSTCXX) when building host programs.
89 71
90 HOSTRUSTFLAGS <<
91 ------------- <<
92 Additional flags to be passed to $(HOSTRUSTC) <<
93 <<
94 HOSTLDFLAGS 72 HOSTLDFLAGS
95 ----------- 73 -----------
96 Additional flags to be passed when linking hos 74 Additional flags to be passed when linking host programs.
97 75
98 HOSTLDLIBS 76 HOSTLDLIBS
99 ---------- 77 ----------
100 Additional libraries to link against when buil 78 Additional libraries to link against when building host programs.
101 79
102 .. _userkbuildflags: <<
103 <<
104 USERCFLAGS <<
105 ---------- <<
106 Additional options used for $(CC) when compili <<
107 <<
108 USERLDFLAGS <<
109 ----------- <<
110 Additional options used for $(LD) when linking <<
111 with CC, so $(USERLDFLAGS) should include "-Wl <<
112 <<
113 KBUILD_KCONFIG 80 KBUILD_KCONFIG
114 -------------- 81 --------------
115 Set the top-level Kconfig file to the value of 82 Set the top-level Kconfig file to the value of this environment
116 variable. The default name is "Kconfig". 83 variable. The default name is "Kconfig".
117 84
118 KBUILD_VERBOSE 85 KBUILD_VERBOSE
119 -------------- 86 --------------
120 Set the kbuild verbosity. Can be assigned same 87 Set the kbuild verbosity. Can be assigned same values as "V=...".
121 88
122 See make help for the full list. 89 See make help for the full list.
123 90
124 Setting "V=..." takes precedence over KBUILD_V 91 Setting "V=..." takes precedence over KBUILD_VERBOSE.
125 92
126 KBUILD_EXTMOD 93 KBUILD_EXTMOD
127 ------------- 94 -------------
128 Set the directory to look for the kernel sourc 95 Set the directory to look for the kernel source when building external
129 modules. 96 modules.
130 97
131 Setting "M=..." takes precedence over KBUILD_E 98 Setting "M=..." takes precedence over KBUILD_EXTMOD.
132 99
133 KBUILD_OUTPUT 100 KBUILD_OUTPUT
134 ------------- 101 -------------
135 Specify the output directory when building the 102 Specify the output directory when building the kernel.
136 103
137 This variable can also be used to point to the <<
138 building external modules against a pre-built <<
139 directory. Please note that this does NOT spec <<
140 external modules themselves. <<
141 <<
142 The output directory can also be specified usi 104 The output directory can also be specified using "O=...".
143 105
144 Setting "O=..." takes precedence over KBUILD_O 106 Setting "O=..." takes precedence over KBUILD_OUTPUT.
145 107
146 KBUILD_EXTRA_WARN 108 KBUILD_EXTRA_WARN
147 ----------------- 109 -----------------
148 Specify the extra build checks. The same value 110 Specify the extra build checks. The same value can be assigned by passing
149 W=... from the command line. 111 W=... from the command line.
150 112
151 See `make help` for the list of the supported 113 See `make help` for the list of the supported values.
152 114
153 Setting "W=..." takes precedence over KBUILD_E 115 Setting "W=..." takes precedence over KBUILD_EXTRA_WARN.
154 116
155 KBUILD_DEBARCH 117 KBUILD_DEBARCH
156 -------------- 118 --------------
157 For the deb-pkg target, allows overriding the 119 For the deb-pkg target, allows overriding the normal heuristics deployed by
158 deb-pkg. Normally deb-pkg attempts to guess th 120 deb-pkg. Normally deb-pkg attempts to guess the right architecture based on
159 the UTS_MACHINE variable, and on some architec 121 the UTS_MACHINE variable, and on some architectures also the kernel config.
160 The value of KBUILD_DEBARCH is assumed (not ch 122 The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian
161 architecture. 123 architecture.
162 124
163 KDOCFLAGS <<
164 --------- <<
165 Specify extra (warning/error) flags for kernel <<
166 see scripts/kernel-doc for which flags are sup <<
167 (currently) apply to documentation builds. <<
168 <<
169 ARCH 125 ARCH
170 ---- 126 ----
171 Set ARCH to the architecture to be built. 127 Set ARCH to the architecture to be built.
172 128
173 In most cases the name of the architecture is 129 In most cases the name of the architecture is the same as the
174 directory name found in the arch/ directory. 130 directory name found in the arch/ directory.
175 131
176 But some architectures such as x86 and sparc h 132 But some architectures such as x86 and sparc have aliases.
177 133
178 - x86: i386 for 32 bit, x86_64 for 64 bit 134 - x86: i386 for 32 bit, x86_64 for 64 bit
179 - parisc: parisc64 for 64 bit !! 135 - sh: sh for 32 bit, sh64 for 64 bit
180 - sparc: sparc32 for 32 bit, sparc64 for 64 bi 136 - sparc: sparc32 for 32 bit, sparc64 for 64 bit
181 137
182 CROSS_COMPILE 138 CROSS_COMPILE
183 ------------- 139 -------------
184 Specify an optional fixed part of the binutils 140 Specify an optional fixed part of the binutils filename.
185 CROSS_COMPILE can be a part of the filename or 141 CROSS_COMPILE can be a part of the filename or the full path.
186 142
187 CROSS_COMPILE is also used for ccache in some 143 CROSS_COMPILE is also used for ccache in some setups.
188 144
189 CF 145 CF
190 -- 146 --
191 Additional options for sparse. 147 Additional options for sparse.
192 148
193 CF is often used on the command-line like this 149 CF is often used on the command-line like this::
194 150
195 make CF=-Wbitwise C=2 151 make CF=-Wbitwise C=2
196 152
197 INSTALL_PATH 153 INSTALL_PATH
198 ------------ 154 ------------
199 INSTALL_PATH specifies where to place the upda 155 INSTALL_PATH specifies where to place the updated kernel and system map
200 images. Default is /boot, but you can set it t 156 images. Default is /boot, but you can set it to other values.
201 157
202 INSTALLKERNEL 158 INSTALLKERNEL
203 ------------- 159 -------------
204 Install script called when using "make install 160 Install script called when using "make install".
205 The default name is "installkernel". 161 The default name is "installkernel".
206 162
207 The script will be called with the following a 163 The script will be called with the following arguments:
208 164
209 - $1 - kernel version 165 - $1 - kernel version
210 - $2 - kernel image file 166 - $2 - kernel image file
211 - $3 - kernel map file 167 - $3 - kernel map file
212 - $4 - default install path (use root direc 168 - $4 - default install path (use root directory if blank)
213 169
214 The implementation of "make install" is archit 170 The implementation of "make install" is architecture specific
215 and it may differ from the above. 171 and it may differ from the above.
216 172
217 INSTALLKERNEL is provided to enable the possib 173 INSTALLKERNEL is provided to enable the possibility to
218 specify a custom installer when cross compilin 174 specify a custom installer when cross compiling a kernel.
219 175
220 MODLIB 176 MODLIB
221 ------ 177 ------
222 Specify where to install modules. 178 Specify where to install modules.
223 The default value is:: 179 The default value is::
224 180
225 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELR 181 $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
226 182
227 The value can be overridden in which case the 183 The value can be overridden in which case the default value is ignored.
228 184
229 INSTALL_MOD_PATH 185 INSTALL_MOD_PATH
230 ---------------- 186 ----------------
231 INSTALL_MOD_PATH specifies a prefix to MODLIB 187 INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
232 relocations required by build roots. This is 188 relocations required by build roots. This is not defined in the
233 makefile but the argument can be passed to mak 189 makefile but the argument can be passed to make if needed.
234 190
235 INSTALL_MOD_STRIP 191 INSTALL_MOD_STRIP
236 ----------------- 192 -----------------
237 INSTALL_MOD_STRIP, if defined, will cause modu 193 INSTALL_MOD_STRIP, if defined, will cause modules to be
238 stripped after they are installed. If INSTALL 194 stripped after they are installed. If INSTALL_MOD_STRIP is '1', then
239 the default option --strip-debug will be used. 195 the default option --strip-debug will be used. Otherwise,
240 INSTALL_MOD_STRIP value will be used as the op 196 INSTALL_MOD_STRIP value will be used as the options to the strip command.
241 197
242 INSTALL_HDR_PATH 198 INSTALL_HDR_PATH
243 ---------------- 199 ----------------
244 INSTALL_HDR_PATH specifies where to install us 200 INSTALL_HDR_PATH specifies where to install user space headers when
245 executing "make headers_*". 201 executing "make headers_*".
246 202
247 The default value is:: 203 The default value is::
248 204
249 $(objtree)/usr 205 $(objtree)/usr
250 206
251 $(objtree) is the directory where output files 207 $(objtree) is the directory where output files are saved.
252 The output directory is often set using "O=... 208 The output directory is often set using "O=..." on the commandline.
253 209
254 The value can be overridden in which case the 210 The value can be overridden in which case the default value is ignored.
255 211
256 INSTALL_DTBS_PATH <<
257 ----------------- <<
258 INSTALL_DTBS_PATH specifies where to install d <<
259 relocations required by build roots. This is <<
260 makefile but the argument can be passed to mak <<
261 <<
262 KBUILD_ABS_SRCTREE 212 KBUILD_ABS_SRCTREE
263 ---------------------------------------------- 213 --------------------------------------------------
264 Kbuild uses a relative path to point to the tr 214 Kbuild uses a relative path to point to the tree when possible. For instance,
265 when building in the source tree, the source t 215 when building in the source tree, the source tree path is '.'
266 216
267 Setting this flag requests Kbuild to use absol 217 Setting this flag requests Kbuild to use absolute path to the source tree.
268 There are some useful cases to do so, like whe 218 There are some useful cases to do so, like when generating tag files with
269 absolute path entries etc. 219 absolute path entries etc.
270 220
271 KBUILD_SIGN_PIN 221 KBUILD_SIGN_PIN
272 --------------- 222 ---------------
273 This variable allows a passphrase or PIN to be 223 This variable allows a passphrase or PIN to be passed to the sign-file
274 utility when signing kernel modules, if the pr 224 utility when signing kernel modules, if the private key requires such.
275 225
276 KBUILD_MODPOST_WARN 226 KBUILD_MODPOST_WARN
277 ------------------- 227 -------------------
278 KBUILD_MODPOST_WARN can be set to avoid errors 228 KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
279 symbols in the final module linking stage. It 229 symbols in the final module linking stage. It changes such errors
280 into warnings. 230 into warnings.
281 231
282 KBUILD_MODPOST_NOFINAL 232 KBUILD_MODPOST_NOFINAL
283 ---------------------- 233 ----------------------
284 KBUILD_MODPOST_NOFINAL can be set to skip the 234 KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
285 This is solely useful to speed up test compile 235 This is solely useful to speed up test compiles.
286 236
287 KBUILD_EXTRA_SYMBOLS 237 KBUILD_EXTRA_SYMBOLS
288 -------------------- 238 --------------------
289 For modules that use symbols from other module 239 For modules that use symbols from other modules.
290 See more details in modules.rst. 240 See more details in modules.rst.
291 241
292 ALLSOURCE_ARCHS 242 ALLSOURCE_ARCHS
293 --------------- 243 ---------------
294 For tags/TAGS/cscope targets, you can specify 244 For tags/TAGS/cscope targets, you can specify more than one arch
295 to be included in the databases, separated by 245 to be included in the databases, separated by blank space. E.g.::
296 246
297 $ make ALLSOURCE_ARCHS="x86 mips arm" tags 247 $ make ALLSOURCE_ARCHS="x86 mips arm" tags
298 248
299 To get all available archs you can also specif 249 To get all available archs you can also specify all. E.g.::
300 250
301 $ make ALLSOURCE_ARCHS=all tags 251 $ make ALLSOURCE_ARCHS=all tags
302 <<
303 IGNORE_DIRS <<
304 ----------- <<
305 For tags/TAGS/cscope targets, you can choose w <<
306 be included in the databases, separated by bla <<
307 <<
308 $ make IGNORE_DIRS="drivers/gpu/drm/radeon <<
309 252
310 KBUILD_BUILD_TIMESTAMP 253 KBUILD_BUILD_TIMESTAMP
311 ---------------------- 254 ----------------------
312 Setting this to a date string overrides the ti 255 Setting this to a date string overrides the timestamp used in the
313 UTS_VERSION definition (uname -v in the runnin 256 UTS_VERSION definition (uname -v in the running kernel). The value has to
314 be a string that can be passed to date -d. The 257 be a string that can be passed to date -d. The default value
315 is the output of the date command at one point 258 is the output of the date command at one point during build.
316 259
317 KBUILD_BUILD_USER, KBUILD_BUILD_HOST 260 KBUILD_BUILD_USER, KBUILD_BUILD_HOST
318 ------------------------------------ 261 ------------------------------------
319 These two variables allow to override the user 262 These two variables allow to override the user@host string displayed during
320 boot and in /proc/version. The default value i 263 boot and in /proc/version. The default value is the output of the commands
321 whoami and host, respectively. 264 whoami and host, respectively.
322 265
323 LLVM 266 LLVM
324 ---- 267 ----
325 If this variable is set to 1, Kbuild will use 268 If this variable is set to 1, Kbuild will use Clang and LLVM utilities instead
326 of GCC and GNU binutils to build the kernel. 269 of GCC and GNU binutils to build the kernel.
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