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