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