diff options
Diffstat (limited to 'Documentation/kbuild')
-rw-r--r-- | Documentation/kbuild/makefiles.txt | 184 |
1 files changed, 94 insertions, 90 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 0706699c9da9..3d2f88ea14a5 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt | |||
@@ -86,7 +86,7 @@ any kernel Makefiles (or any other source files). | |||
86 | 86 | ||
87 | *Normal developers* are people who work on features such as device | 87 | *Normal developers* are people who work on features such as device |
88 | drivers, file systems, and network protocols. These people need to | 88 | drivers, file systems, and network protocols. These people need to |
89 | maintain the kbuild Makefiles for the subsystem that they are | 89 | maintain the kbuild Makefiles for the subsystem they are |
90 | working on. In order to do this effectively, they need some overall | 90 | working on. In order to do this effectively, they need some overall |
91 | knowledge about the kernel Makefiles, plus detailed knowledge about the | 91 | knowledge about the kernel Makefiles, plus detailed knowledge about the |
92 | public interface for kbuild. | 92 | public interface for kbuild. |
@@ -104,10 +104,10 @@ This document is aimed towards normal developers and arch developers. | |||
104 | === 3 The kbuild files | 104 | === 3 The kbuild files |
105 | 105 | ||
106 | Most Makefiles within the kernel are kbuild Makefiles that use the | 106 | Most Makefiles within the kernel are kbuild Makefiles that use the |
107 | kbuild infrastructure. This chapter introduce the syntax used in the | 107 | kbuild infrastructure. This chapter introduces the syntax used in the |
108 | kbuild makefiles. | 108 | kbuild makefiles. |
109 | The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can | 109 | The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can |
110 | be used and if both a 'Makefile' and a 'Kbuild' file exists then the 'Kbuild' | 110 | be used and if both a 'Makefile' and a 'Kbuild' file exists, then the 'Kbuild' |
111 | file will be used. | 111 | file will be used. |
112 | 112 | ||
113 | Section 3.1 "Goal definitions" is a quick intro, further chapters provide | 113 | Section 3.1 "Goal definitions" is a quick intro, further chapters provide |
@@ -124,7 +124,7 @@ more details, with real examples. | |||
124 | Example: | 124 | Example: |
125 | obj-y += foo.o | 125 | obj-y += foo.o |
126 | 126 | ||
127 | This tell kbuild that there is one object in that directory named | 127 | This tell kbuild that there is one object in that directory, named |
128 | foo.o. foo.o will be built from foo.c or foo.S. | 128 | foo.o. foo.o will be built from foo.c or foo.S. |
129 | 129 | ||
130 | If foo.o shall be built as a module, the variable obj-m is used. | 130 | If foo.o shall be built as a module, the variable obj-m is used. |
@@ -140,7 +140,7 @@ more details, with real examples. | |||
140 | --- 3.2 Built-in object goals - obj-y | 140 | --- 3.2 Built-in object goals - obj-y |
141 | 141 | ||
142 | The kbuild Makefile specifies object files for vmlinux | 142 | The kbuild Makefile specifies object files for vmlinux |
143 | in the lists $(obj-y). These lists depend on the kernel | 143 | in the $(obj-y) lists. These lists depend on the kernel |
144 | configuration. | 144 | configuration. |
145 | 145 | ||
146 | Kbuild compiles all the $(obj-y) files. It then calls | 146 | Kbuild compiles all the $(obj-y) files. It then calls |
@@ -154,8 +154,8 @@ more details, with real examples. | |||
154 | Link order is significant, because certain functions | 154 | Link order is significant, because certain functions |
155 | (module_init() / __initcall) will be called during boot in the | 155 | (module_init() / __initcall) will be called during boot in the |
156 | order they appear. So keep in mind that changing the link | 156 | order they appear. So keep in mind that changing the link |
157 | order may e.g. change the order in which your SCSI | 157 | order may e.g. change the order in which your SCSI |
158 | controllers are detected, and thus you disks are renumbered. | 158 | controllers are detected, and thus your disks are renumbered. |
159 | 159 | ||
160 | Example: | 160 | Example: |
161 | #drivers/isdn/i4l/Makefile | 161 | #drivers/isdn/i4l/Makefile |
@@ -206,8 +206,8 @@ more details, with real examples. | |||
206 | ext2-y := balloc.o bitmap.o | 206 | ext2-y := balloc.o bitmap.o |
207 | ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o | 207 | ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o |
208 | 208 | ||
209 | In this example xattr.o is only part of the composite object | 209 | In this example, xattr.o is only part of the composite object |
210 | ext2.o, if $(CONFIG_EXT2_FS_XATTR) evaluates to 'y'. | 210 | ext2.o if $(CONFIG_EXT2_FS_XATTR) evaluates to 'y'. |
211 | 211 | ||
212 | Note: Of course, when you are building objects into the kernel, | 212 | Note: Of course, when you are building objects into the kernel, |
213 | the syntax above will also work. So, if you have CONFIG_EXT2_FS=y, | 213 | the syntax above will also work. So, if you have CONFIG_EXT2_FS=y, |
@@ -221,16 +221,16 @@ more details, with real examples. | |||
221 | 221 | ||
222 | --- 3.5 Library file goals - lib-y | 222 | --- 3.5 Library file goals - lib-y |
223 | 223 | ||
224 | Objects listed with obj-* are used for modules or | 224 | Objects listed with obj-* are used for modules, or |
225 | combined in a built-in.o for that specific directory. | 225 | combined in a built-in.o for that specific directory. |
226 | There is also the possibility to list objects that will | 226 | There is also the possibility to list objects that will |
227 | be included in a library, lib.a. | 227 | be included in a library, lib.a. |
228 | All objects listed with lib-y are combined in a single | 228 | All objects listed with lib-y are combined in a single |
229 | library for that directory. | 229 | library for that directory. |
230 | Objects that are listed in obj-y and additional listed in | 230 | Objects that are listed in obj-y and additionaly listed in |
231 | lib-y will not be included in the library, since they will anyway | 231 | lib-y will not be included in the library, since they will anyway |
232 | be accessible. | 232 | be accessible. |
233 | For consistency objects listed in lib-m will be included in lib.a. | 233 | For consistency, objects listed in lib-m will be included in lib.a. |
234 | 234 | ||
235 | Note that the same kbuild makefile may list files to be built-in | 235 | Note that the same kbuild makefile may list files to be built-in |
236 | and to be part of a library. Therefore the same directory | 236 | and to be part of a library. Therefore the same directory |
@@ -241,11 +241,11 @@ more details, with real examples. | |||
241 | lib-y := checksum.o delay.o | 241 | lib-y := checksum.o delay.o |
242 | 242 | ||
243 | This will create a library lib.a based on checksum.o and delay.o. | 243 | This will create a library lib.a based on checksum.o and delay.o. |
244 | For kbuild to actually recognize that there is a lib.a being build | 244 | For kbuild to actually recognize that there is a lib.a being built, |
245 | the directory shall be listed in libs-y. | 245 | the directory shall be listed in libs-y. |
246 | See also "6.3 List directories to visit when descending". | 246 | See also "6.3 List directories to visit when descending". |
247 | 247 | ||
248 | Usage of lib-y is normally restricted to lib/ and arch/*/lib. | 248 | Use of lib-y is normally restricted to lib/ and arch/*/lib. |
249 | 249 | ||
250 | --- 3.6 Descending down in directories | 250 | --- 3.6 Descending down in directories |
251 | 251 | ||
@@ -255,7 +255,7 @@ more details, with real examples. | |||
255 | invoke make recursively in subdirectories, provided you let it know of | 255 | invoke make recursively in subdirectories, provided you let it know of |
256 | them. | 256 | them. |
257 | 257 | ||
258 | To do so obj-y and obj-m are used. | 258 | To do so, obj-y and obj-m are used. |
259 | ext2 lives in a separate directory, and the Makefile present in fs/ | 259 | ext2 lives in a separate directory, and the Makefile present in fs/ |
260 | tells kbuild to descend down using the following assignment. | 260 | tells kbuild to descend down using the following assignment. |
261 | 261 | ||
@@ -353,8 +353,8 @@ more details, with real examples. | |||
353 | Special rules are used when the kbuild infrastructure does | 353 | Special rules are used when the kbuild infrastructure does |
354 | not provide the required support. A typical example is | 354 | not provide the required support. A typical example is |
355 | header files generated during the build process. | 355 | header files generated during the build process. |
356 | Another example is the architecture specific Makefiles which | 356 | Another example are the architecture specific Makefiles which |
357 | needs special rules to prepare boot images etc. | 357 | need special rules to prepare boot images etc. |
358 | 358 | ||
359 | Special rules are written as normal Make rules. | 359 | Special rules are written as normal Make rules. |
360 | Kbuild is not executing in the directory where the Makefile is | 360 | Kbuild is not executing in the directory where the Makefile is |
@@ -387,22 +387,22 @@ more details, with real examples. | |||
387 | 387 | ||
388 | --- 3.11 $(CC) support functions | 388 | --- 3.11 $(CC) support functions |
389 | 389 | ||
390 | The kernel may be build with several different versions of | 390 | The kernel may be built with several different versions of |
391 | $(CC), each supporting a unique set of features and options. | 391 | $(CC), each supporting a unique set of features and options. |
392 | kbuild provide basic support to check for valid options for $(CC). | 392 | kbuild provide basic support to check for valid options for $(CC). |
393 | $(CC) is useally the gcc compiler, but other alternatives are | 393 | $(CC) is useally the gcc compiler, but other alternatives are |
394 | available. | 394 | available. |
395 | 395 | ||
396 | as-option | 396 | as-option |
397 | as-option is used to check if $(CC) when used to compile | 397 | as-option is used to check if $(CC) -- when used to compile |
398 | assembler (*.S) files supports the given option. An optional | 398 | assembler (*.S) files -- supports the given option. An optional |
399 | second option may be specified if first option are not supported. | 399 | second option may be specified if the first option is not supported. |
400 | 400 | ||
401 | Example: | 401 | Example: |
402 | #arch/sh/Makefile | 402 | #arch/sh/Makefile |
403 | cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),) | 403 | cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),) |
404 | 404 | ||
405 | In the above example cflags-y will be assinged the the option | 405 | In the above example, cflags-y will be assigned the option |
406 | -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC). | 406 | -Wa$(comma)-isa=$(isa-y) if it is supported by $(CC). |
407 | The second argument is optional, and if supplied will be used | 407 | The second argument is optional, and if supplied will be used |
408 | if first argument is not supported. | 408 | if first argument is not supported. |
@@ -422,7 +422,7 @@ more details, with real examples. | |||
422 | if first argument is not supported. | 422 | if first argument is not supported. |
423 | 423 | ||
424 | cc-option | 424 | cc-option |
425 | cc-option is used to check if $(CC) support a given option, and not | 425 | cc-option is used to check if $(CC) supports a given option, and not |
426 | supported to use an optional second option. | 426 | supported to use an optional second option. |
427 | 427 | ||
428 | Example: | 428 | Example: |
@@ -430,8 +430,8 @@ more details, with real examples. | |||
430 | cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586) | 430 | cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586) |
431 | 431 | ||
432 | In the above example cflags-y will be assigned the option | 432 | In the above example cflags-y will be assigned the option |
433 | -march=pentium-mmx if supported by $(CC), otherwise -march-i586. | 433 | -march=pentium-mmx if supported by $(CC), otherwise -march=i586. |
434 | The second argument to cc-option is optional, and if omitted | 434 | The second argument to cc-option is optional, and if omitted, |
435 | cflags-y will be assigned no value if first option is not supported. | 435 | cflags-y will be assigned no value if first option is not supported. |
436 | 436 | ||
437 | cc-option-yn | 437 | cc-option-yn |
@@ -444,14 +444,15 @@ more details, with real examples. | |||
444 | aflags-$(biarch) += -a32 | 444 | aflags-$(biarch) += -a32 |
445 | cflags-$(biarch) += -m32 | 445 | cflags-$(biarch) += -m32 |
446 | 446 | ||
447 | In the above example $(biarch) is set to y if $(CC) supports the -m32 | 447 | In the above example, $(biarch) is set to y if $(CC) supports the -m32 |
448 | option. When $(biarch) equals to y the expanded variables $(aflags-y) | 448 | option. When $(biarch) equals 'y', the expanded variables $(aflags-y) |
449 | and $(cflags-y) will be assigned the values -a32 and -m32. | 449 | and $(cflags-y) will be assigned the values -a32 and -m32, |
450 | respectively. | ||
450 | 451 | ||
451 | cc-option-align | 452 | cc-option-align |
452 | gcc version >= 3.0 shifted type of options used to speify | 453 | gcc versions >= 3.0 changed the type of options used to specify |
453 | alignment of functions, loops etc. $(cc-option-align) whrn used | 454 | alignment of functions, loops etc. $(cc-option-align), when used |
454 | as prefix to the align options will select the right prefix: | 455 | as prefix to the align options, will select the right prefix: |
455 | gcc < 3.00 | 456 | gcc < 3.00 |
456 | cc-option-align = -malign | 457 | cc-option-align = -malign |
457 | gcc >= 3.00 | 458 | gcc >= 3.00 |
@@ -460,15 +461,15 @@ more details, with real examples. | |||
460 | Example: | 461 | Example: |
461 | CFLAGS += $(cc-option-align)-functions=4 | 462 | CFLAGS += $(cc-option-align)-functions=4 |
462 | 463 | ||
463 | In the above example the option -falign-functions=4 is used for | 464 | In the above example, the option -falign-functions=4 is used for |
464 | gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used. | 465 | gcc >= 3.00. For gcc < 3.00, -malign-functions=4 is used. |
465 | 466 | ||
466 | cc-version | 467 | cc-version |
467 | cc-version return a numerical version of the $(CC) compiler version. | 468 | cc-version returns a numerical version of the $(CC) compiler version. |
468 | The format is <major><minor> where both are two digits. So for example | 469 | The format is <major><minor> where both are two digits. So for example |
469 | gcc 3.41 would return 0341. | 470 | gcc 3.41 would return 0341. |
470 | cc-version is useful when a specific $(CC) version is faulty in one | 471 | cc-version is useful when a specific $(CC) version is faulty in one |
471 | area, for example the -mregparm=3 were broken in some gcc version | 472 | area, for example -mregparm=3 was broken in some gcc versions |
472 | even though the option was accepted by gcc. | 473 | even though the option was accepted by gcc. |
473 | 474 | ||
474 | Example: | 475 | Example: |
@@ -477,18 +478,18 @@ more details, with real examples. | |||
477 | if [ $(call cc-version) -ge 0300 ] ; then \ | 478 | if [ $(call cc-version) -ge 0300 ] ; then \ |
478 | echo "-mregparm=3"; fi ;) | 479 | echo "-mregparm=3"; fi ;) |
479 | 480 | ||
480 | In the above example -mregparm=3 is only used for gcc version greater | 481 | In the above example, -mregparm=3 is only used for gcc version greater |
481 | than or equal to gcc 3.0. | 482 | than or equal to gcc 3.0. |
482 | 483 | ||
483 | cc-ifversion | 484 | cc-ifversion |
484 | cc-ifversion test the version of $(CC) and equals last argument if | 485 | cc-ifversion tests the version of $(CC) and equals last argument if |
485 | version expression is true. | 486 | version expression is true. |
486 | 487 | ||
487 | Example: | 488 | Example: |
488 | #fs/reiserfs/Makefile | 489 | #fs/reiserfs/Makefile |
489 | EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1) | 490 | EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1) |
490 | 491 | ||
491 | In this example EXTRA_CFLAGS will be assigned the value -O1 if the | 492 | In this example, EXTRA_CFLAGS will be assigned the value -O1 if the |
492 | $(CC) version is less than 4.2. | 493 | $(CC) version is less than 4.2. |
493 | cc-ifversion takes all the shell operators: | 494 | cc-ifversion takes all the shell operators: |
494 | -eq, -ne, -lt, -le, -gt, and -ge | 495 | -eq, -ne, -lt, -le, -gt, and -ge |
@@ -529,7 +530,7 @@ Both possibilities are described in the following. | |||
529 | Host programs can be made up based on composite objects. | 530 | Host programs can be made up based on composite objects. |
530 | The syntax used to define composite objects for host programs is | 531 | The syntax used to define composite objects for host programs is |
531 | similar to the syntax used for kernel objects. | 532 | similar to the syntax used for kernel objects. |
532 | $(<executeable>-objs) list all objects used to link the final | 533 | $(<executeable>-objs) lists all objects used to link the final |
533 | executable. | 534 | executable. |
534 | 535 | ||
535 | Example: | 536 | Example: |
@@ -538,9 +539,9 @@ Both possibilities are described in the following. | |||
538 | lxdialog-objs := checklist.o lxdialog.o | 539 | lxdialog-objs := checklist.o lxdialog.o |
539 | 540 | ||
540 | Objects with extension .o are compiled from the corresponding .c | 541 | Objects with extension .o are compiled from the corresponding .c |
541 | files. In the above example checklist.c is compiled to checklist.o | 542 | files. In the above example, checklist.c is compiled to checklist.o |
542 | and lxdialog.c is compiled to lxdialog.o. | 543 | and lxdialog.c is compiled to lxdialog.o. |
543 | Finally the two .o files are linked to the executable, lxdialog. | 544 | Finally, the two .o files are linked to the executable, lxdialog. |
544 | Note: The syntax <executable>-y is not permitted for host-programs. | 545 | Note: The syntax <executable>-y is not permitted for host-programs. |
545 | 546 | ||
546 | --- 4.3 Defining shared libraries | 547 | --- 4.3 Defining shared libraries |
@@ -594,7 +595,7 @@ Both possibilities are described in the following. | |||
594 | The programs will always be compiled utilising $(HOSTCC) passed | 595 | The programs will always be compiled utilising $(HOSTCC) passed |
595 | the options specified in $(HOSTCFLAGS). | 596 | the options specified in $(HOSTCFLAGS). |
596 | To set flags that will take effect for all host programs created | 597 | To set flags that will take effect for all host programs created |
597 | in that Makefile use the variable HOST_EXTRACFLAGS. | 598 | in that Makefile, use the variable HOST_EXTRACFLAGS. |
598 | 599 | ||
599 | Example: | 600 | Example: |
600 | #scripts/lxdialog/Makefile | 601 | #scripts/lxdialog/Makefile |
@@ -613,7 +614,8 @@ Both possibilities are described in the following. | |||
613 | #scripts/kconfig/Makefile | 614 | #scripts/kconfig/Makefile |
614 | HOSTLOADLIBES_qconf := -L$(QTDIR)/lib | 615 | HOSTLOADLIBES_qconf := -L$(QTDIR)/lib |
615 | 616 | ||
616 | When linking qconf it will be passed the extra option "-L$(QTDIR)/lib". | 617 | When linking qconf, it will be passed the extra option |
618 | "-L$(QTDIR)/lib". | ||
617 | 619 | ||
618 | --- 4.6 When host programs are actually built | 620 | --- 4.6 When host programs are actually built |
619 | 621 | ||
@@ -648,7 +650,7 @@ Both possibilities are described in the following. | |||
648 | 650 | ||
649 | --- 4.7 Using hostprogs-$(CONFIG_FOO) | 651 | --- 4.7 Using hostprogs-$(CONFIG_FOO) |
650 | 652 | ||
651 | A typcal pattern in a Kbuild file lok like this: | 653 | A typcal pattern in a Kbuild file looks like this: |
652 | 654 | ||
653 | Example: | 655 | Example: |
654 | #scripts/Makefile | 656 | #scripts/Makefile |
@@ -656,13 +658,13 @@ Both possibilities are described in the following. | |||
656 | 658 | ||
657 | Kbuild knows about both 'y' for built-in and 'm' for module. | 659 | Kbuild knows about both 'y' for built-in and 'm' for module. |
658 | So if a config symbol evaluate to 'm', kbuild will still build | 660 | So if a config symbol evaluate to 'm', kbuild will still build |
659 | the binary. In other words Kbuild handle hostprogs-m exactly | 661 | the binary. In other words, Kbuild handles hostprogs-m exactly |
660 | like hostprogs-y. But only hostprogs-y is recommend used | 662 | like hostprogs-y. But only hostprogs-y is recommended to be used |
661 | when no CONFIG symbol are involved. | 663 | when no CONFIG symbols are involved. |
662 | 664 | ||
663 | === 5 Kbuild clean infrastructure | 665 | === 5 Kbuild clean infrastructure |
664 | 666 | ||
665 | "make clean" deletes most generated files in the src tree where the kernel | 667 | "make clean" deletes most generated files in the obj tree where the kernel |
666 | is compiled. This includes generated files such as host programs. | 668 | is compiled. This includes generated files such as host programs. |
667 | Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always), | 669 | Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always), |
668 | $(extra-y) and $(targets). They are all deleted during "make clean". | 670 | $(extra-y) and $(targets). They are all deleted during "make clean". |
@@ -723,29 +725,29 @@ be visited during "make clean". | |||
723 | 725 | ||
724 | The top level Makefile sets up the environment and does the preparation, | 726 | The top level Makefile sets up the environment and does the preparation, |
725 | before starting to descend down in the individual directories. | 727 | before starting to descend down in the individual directories. |
726 | The top level makefile contains the generic part, whereas the | 728 | The top level makefile contains the generic part, whereas |
727 | arch/$(ARCH)/Makefile contains what is required to set-up kbuild | 729 | arch/$(ARCH)/Makefile contains what is required to set up kbuild |
728 | to the said architecture. | 730 | for said architecture. |
729 | To do so arch/$(ARCH)/Makefile sets a number of variables, and defines | 731 | To do so, arch/$(ARCH)/Makefile sets up a number of variables and defines |
730 | a few targets. | 732 | a few targets. |
731 | 733 | ||
732 | When kbuild executes the following steps are followed (roughly): | 734 | When kbuild executes, the following steps are followed (roughly): |
733 | 1) Configuration of the kernel => produced .config | 735 | 1) Configuration of the kernel => produce .config |
734 | 2) Store kernel version in include/linux/version.h | 736 | 2) Store kernel version in include/linux/version.h |
735 | 3) Symlink include/asm to include/asm-$(ARCH) | 737 | 3) Symlink include/asm to include/asm-$(ARCH) |
736 | 4) Updating all other prerequisites to the target prepare: | 738 | 4) Updating all other prerequisites to the target prepare: |
737 | - Additional prerequisites are specified in arch/$(ARCH)/Makefile | 739 | - Additional prerequisites are specified in arch/$(ARCH)/Makefile |
738 | 5) Recursively descend down in all directories listed in | 740 | 5) Recursively descend down in all directories listed in |
739 | init-* core* drivers-* net-* libs-* and build all targets. | 741 | init-* core* drivers-* net-* libs-* and build all targets. |
740 | - The value of the above variables are extended in arch/$(ARCH)/Makefile. | 742 | - The values of the above variables are expanded in arch/$(ARCH)/Makefile. |
741 | 6) All object files are then linked and the resulting file vmlinux is | 743 | 6) All object files are then linked and the resulting file vmlinux is |
742 | located at the root of the src tree. | 744 | located at the root of the obj tree. |
743 | The very first objects linked are listed in head-y, assigned by | 745 | The very first objects linked are listed in head-y, assigned by |
744 | arch/$(ARCH)/Makefile. | 746 | arch/$(ARCH)/Makefile. |
745 | 7) Finally the architecture specific part does any required post processing | 747 | 7) Finally, the architecture specific part does any required post processing |
746 | and builds the final bootimage. | 748 | and builds the final bootimage. |
747 | - This includes building boot records | 749 | - This includes building boot records |
748 | - Preparing initrd images and the like | 750 | - Preparing initrd images and thelike |
749 | 751 | ||
750 | 752 | ||
751 | --- 6.1 Set variables to tweak the build to the architecture | 753 | --- 6.1 Set variables to tweak the build to the architecture |
@@ -770,7 +772,7 @@ When kbuild executes the following steps are followed (roughly): | |||
770 | LDFLAGS_vmlinux Options for $(LD) when linking vmlinux | 772 | LDFLAGS_vmlinux Options for $(LD) when linking vmlinux |
771 | 773 | ||
772 | LDFLAGS_vmlinux is used to specify additional flags to pass to | 774 | LDFLAGS_vmlinux is used to specify additional flags to pass to |
773 | the linker when linking the final vmlinux. | 775 | the linker when linking the final vmlinux image. |
774 | LDFLAGS_vmlinux uses the LDFLAGS_$@ support. | 776 | LDFLAGS_vmlinux uses the LDFLAGS_$@ support. |
775 | 777 | ||
776 | Example: | 778 | Example: |
@@ -780,7 +782,7 @@ When kbuild executes the following steps are followed (roughly): | |||
780 | OBJCOPYFLAGS objcopy flags | 782 | OBJCOPYFLAGS objcopy flags |
781 | 783 | ||
782 | When $(call if_changed,objcopy) is used to translate a .o file, | 784 | When $(call if_changed,objcopy) is used to translate a .o file, |
783 | then the flags specified in OBJCOPYFLAGS will be used. | 785 | the flags specified in OBJCOPYFLAGS will be used. |
784 | $(call if_changed,objcopy) is often used to generate raw binaries on | 786 | $(call if_changed,objcopy) is often used to generate raw binaries on |
785 | vmlinux. | 787 | vmlinux. |
786 | 788 | ||
@@ -792,7 +794,7 @@ When kbuild executes the following steps are followed (roughly): | |||
792 | $(obj)/image: vmlinux FORCE | 794 | $(obj)/image: vmlinux FORCE |
793 | $(call if_changed,objcopy) | 795 | $(call if_changed,objcopy) |
794 | 796 | ||
795 | In this example the binary $(obj)/image is a binary version of | 797 | In this example, the binary $(obj)/image is a binary version of |
796 | vmlinux. The usage of $(call if_changed,xxx) will be described later. | 798 | vmlinux. The usage of $(call if_changed,xxx) will be described later. |
797 | 799 | ||
798 | AFLAGS $(AS) assembler flags | 800 | AFLAGS $(AS) assembler flags |
@@ -809,7 +811,7 @@ When kbuild executes the following steps are followed (roughly): | |||
809 | Default value - see top level Makefile | 811 | Default value - see top level Makefile |
810 | Append or modify as required per architecture. | 812 | Append or modify as required per architecture. |
811 | 813 | ||
812 | Often the CFLAGS variable depends on the configuration. | 814 | Often, the CFLAGS variable depends on the configuration. |
813 | 815 | ||
814 | Example: | 816 | Example: |
815 | #arch/i386/Makefile | 817 | #arch/i386/Makefile |
@@ -830,7 +832,7 @@ When kbuild executes the following steps are followed (roughly): | |||
830 | ... | 832 | ... |
831 | 833 | ||
832 | 834 | ||
833 | The first examples utilises the trick that a config option expands | 835 | The first example utilises the trick that a config option expands |
834 | to 'y' when selected. | 836 | to 'y' when selected. |
835 | 837 | ||
836 | CFLAGS_KERNEL $(CC) options specific for built-in | 838 | CFLAGS_KERNEL $(CC) options specific for built-in |
@@ -846,15 +848,15 @@ When kbuild executes the following steps are followed (roughly): | |||
846 | 848 | ||
847 | --- 6.2 Add prerequisites to archprepare: | 849 | --- 6.2 Add prerequisites to archprepare: |
848 | 850 | ||
849 | The archprepare: rule is used to list prerequisites that needs to be | 851 | The archprepare: rule is used to list prerequisites that need to be |
850 | built before starting to descend down in the subdirectories. | 852 | built before starting to descend down in the subdirectories. |
851 | This is usual header files containing assembler constants. | 853 | This is usually used for header files containing assembler constants. |
852 | 854 | ||
853 | Example: | 855 | Example: |
854 | #arch/arm/Makefile | 856 | #arch/arm/Makefile |
855 | archprepare: maketools | 857 | archprepare: maketools |
856 | 858 | ||
857 | In this example the file target maketools will be processed | 859 | In this example, the file target maketools will be processed |
858 | before descending down in the subdirectories. | 860 | before descending down in the subdirectories. |
859 | See also chapter XXX-TODO that describe how kbuild supports | 861 | See also chapter XXX-TODO that describe how kbuild supports |
860 | generating offset header files. | 862 | generating offset header files. |
@@ -870,15 +872,16 @@ When kbuild executes the following steps are followed (roughly): | |||
870 | 872 | ||
871 | head-y, init-y, core-y, libs-y, drivers-y, net-y | 873 | head-y, init-y, core-y, libs-y, drivers-y, net-y |
872 | 874 | ||
873 | $(head-y) list objects to be linked first in vmlinux. | 875 | $(head-y) lists objects to be linked first in vmlinux. |
874 | $(libs-y) list directories where a lib.a archive can be located. | 876 | $(libs-y) lists directories where a lib.a archive can be located. |
875 | The rest list directories where a built-in.o object file can be located. | 877 | The rest lists directories where a built-in.o object file can be |
878 | located. | ||
876 | 879 | ||
877 | $(init-y) objects will be located after $(head-y). | 880 | $(init-y) objects will be located after $(head-y). |
878 | Then the rest follows in this order: | 881 | Then the rest follows in this order: |
879 | $(core-y), $(libs-y), $(drivers-y) and $(net-y). | 882 | $(core-y), $(libs-y), $(drivers-y) and $(net-y). |
880 | 883 | ||
881 | The top level Makefile define values for all generic directories, | 884 | The top level Makefile defines values for all generic directories, |
882 | and arch/$(ARCH)/Makefile only adds architecture specific directories. | 885 | and arch/$(ARCH)/Makefile only adds architecture specific directories. |
883 | 886 | ||
884 | Example: | 887 | Example: |
@@ -915,9 +918,9 @@ When kbuild executes the following steps are followed (roughly): | |||
915 | "$(Q)$(MAKE) $(build)=<dir>" is the recommended way to invoke | 918 | "$(Q)$(MAKE) $(build)=<dir>" is the recommended way to invoke |
916 | make in a subdirectory. | 919 | make in a subdirectory. |
917 | 920 | ||
918 | There are no rules for naming of the architecture specific targets, | 921 | There are no rules for naming architecture specific targets, |
919 | but executing "make help" will list all relevant targets. | 922 | but executing "make help" will list all relevant targets. |
920 | To support this $(archhelp) must be defined. | 923 | To support this, $(archhelp) must be defined. |
921 | 924 | ||
922 | Example: | 925 | Example: |
923 | #arch/i386/Makefile | 926 | #arch/i386/Makefile |
@@ -928,8 +931,8 @@ When kbuild executes the following steps are followed (roughly): | |||
928 | When make is executed without arguments, the first goal encountered | 931 | When make is executed without arguments, the first goal encountered |
929 | will be built. In the top level Makefile the first goal present | 932 | will be built. In the top level Makefile the first goal present |
930 | is all:. | 933 | is all:. |
931 | An architecture shall always per default build a bootable image. | 934 | An architecture shall always, per default, build a bootable image. |
932 | In "make help" the default goal is highlighted with a '*'. | 935 | In "make help", the default goal is highlighted with a '*'. |
933 | Add a new prerequisite to all: to select a default goal different | 936 | Add a new prerequisite to all: to select a default goal different |
934 | from vmlinux. | 937 | from vmlinux. |
935 | 938 | ||
@@ -955,7 +958,7 @@ When kbuild executes the following steps are followed (roughly): | |||
955 | #arch/i386/kernel/Makefile | 958 | #arch/i386/kernel/Makefile |
956 | extra-y := head.o init_task.o | 959 | extra-y := head.o init_task.o |
957 | 960 | ||
958 | In this example extra-y is used to list object files that | 961 | In this example, extra-y is used to list object files that |
959 | shall be built, but shall not be linked as part of built-in.o. | 962 | shall be built, but shall not be linked as part of built-in.o. |
960 | 963 | ||
961 | 964 | ||
@@ -972,8 +975,8 @@ When kbuild executes the following steps are followed (roughly): | |||
972 | target: source(s) FORCE | 975 | target: source(s) FORCE |
973 | $(call if_changed,ld/objcopy/gzip) | 976 | $(call if_changed,ld/objcopy/gzip) |
974 | 977 | ||
975 | When the rule is evaluated it is checked to see if any files | 978 | When the rule is evaluated, it is checked to see if any files |
976 | needs an update, or the commandline has changed since last | 979 | needs an update, or the command line has changed since the last |
977 | invocation. The latter will force a rebuild if any options | 980 | invocation. The latter will force a rebuild if any options |
978 | to the executable have changed. | 981 | to the executable have changed. |
979 | Any target that utilises if_changed must be listed in $(targets), | 982 | Any target that utilises if_changed must be listed in $(targets), |
@@ -991,7 +994,7 @@ When kbuild executes the following steps are followed (roughly): | |||
991 | #WRONG!# $(call if_changed, ld/objcopy/gzip) | 994 | #WRONG!# $(call if_changed, ld/objcopy/gzip) |
992 | 995 | ||
993 | ld | 996 | ld |
994 | Link target. Often LDFLAGS_$@ is used to set specific options to ld. | 997 | Link target. Often, LDFLAGS_$@ is used to set specific options to ld. |
995 | 998 | ||
996 | objcopy | 999 | objcopy |
997 | Copy binary. Uses OBJCOPYFLAGS usually specified in | 1000 | Copy binary. Uses OBJCOPYFLAGS usually specified in |
@@ -1010,10 +1013,10 @@ When kbuild executes the following steps are followed (roughly): | |||
1010 | $(obj)/setup $(obj)/bootsect: %: %.o FORCE | 1013 | $(obj)/setup $(obj)/bootsect: %: %.o FORCE |
1011 | $(call if_changed,ld) | 1014 | $(call if_changed,ld) |
1012 | 1015 | ||
1013 | In this example there are two possible targets, requiring different | 1016 | In this example, there are two possible targets, requiring different |
1014 | options to the linker. the linker options are specified using the | 1017 | options to the linker. The linker options are specified using the |
1015 | LDFLAGS_$@ syntax - one for each potential target. | 1018 | LDFLAGS_$@ syntax - one for each potential target. |
1016 | $(targets) are assinged all potential targets, herby kbuild knows | 1019 | $(targets) are assinged all potential targets, by which kbuild knows |
1017 | the targets and will: | 1020 | the targets and will: |
1018 | 1) check for commandline changes | 1021 | 1) check for commandline changes |
1019 | 2) delete target during make clean | 1022 | 2) delete target during make clean |
@@ -1027,7 +1030,7 @@ When kbuild executes the following steps are followed (roughly): | |||
1027 | 1030 | ||
1028 | --- 6.7 Custom kbuild commands | 1031 | --- 6.7 Custom kbuild commands |
1029 | 1032 | ||
1030 | When kbuild is executing with KBUILD_VERBOSE=0 then only a shorthand | 1033 | When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand |
1031 | of a command is normally displayed. | 1034 | of a command is normally displayed. |
1032 | To enable this behaviour for custom commands kbuild requires | 1035 | To enable this behaviour for custom commands kbuild requires |
1033 | two variables to be set: | 1036 | two variables to be set: |
@@ -1045,7 +1048,7 @@ When kbuild executes the following steps are followed (roughly): | |||
1045 | $(call if_changed,image) | 1048 | $(call if_changed,image) |
1046 | @echo 'Kernel: $@ is ready' | 1049 | @echo 'Kernel: $@ is ready' |
1047 | 1050 | ||
1048 | When updating the $(obj)/bzImage target the line: | 1051 | When updating the $(obj)/bzImage target, the line |
1049 | 1052 | ||
1050 | BUILD arch/i386/boot/bzImage | 1053 | BUILD arch/i386/boot/bzImage |
1051 | 1054 | ||
@@ -1054,11 +1057,11 @@ When kbuild executes the following steps are followed (roughly): | |||
1054 | 1057 | ||
1055 | --- 6.8 Preprocessing linker scripts | 1058 | --- 6.8 Preprocessing linker scripts |
1056 | 1059 | ||
1057 | When the vmlinux image is build the linker script: | 1060 | When the vmlinux image is built, the linker script |
1058 | arch/$(ARCH)/kernel/vmlinux.lds is used. | 1061 | arch/$(ARCH)/kernel/vmlinux.lds is used. |
1059 | The script is a preprocessed variant of the file vmlinux.lds.S | 1062 | The script is a preprocessed variant of the file vmlinux.lds.S |
1060 | located in the same directory. | 1063 | located in the same directory. |
1061 | kbuild knows .lds file and includes a rule *lds.S -> *lds. | 1064 | kbuild knows .lds files and includes a rule *lds.S -> *lds. |
1062 | 1065 | ||
1063 | Example: | 1066 | Example: |
1064 | #arch/i386/kernel/Makefile | 1067 | #arch/i386/kernel/Makefile |
@@ -1068,11 +1071,11 @@ When kbuild executes the following steps are followed (roughly): | |||
1068 | export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) | 1071 | export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) |
1069 | 1072 | ||
1070 | The assigment to $(always) is used to tell kbuild to build the | 1073 | The assigment to $(always) is used to tell kbuild to build the |
1071 | target: vmlinux.lds. | 1074 | target vmlinux.lds. |
1072 | The assignment to $(CPPFLAGS_vmlinux.lds) tell kbuild to use the | 1075 | The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the |
1073 | specified options when building the target vmlinux.lds. | 1076 | specified options when building the target vmlinux.lds. |
1074 | 1077 | ||
1075 | When building the *.lds target kbuild used the variakles: | 1078 | When building the *.lds target, kbuild uses the variables: |
1076 | CPPFLAGS : Set in top-level Makefile | 1079 | CPPFLAGS : Set in top-level Makefile |
1077 | EXTRA_CPPFLAGS : May be set in the kbuild makefile | 1080 | EXTRA_CPPFLAGS : May be set in the kbuild makefile |
1078 | CPPFLAGS_$(@F) : Target specific flags. | 1081 | CPPFLAGS_$(@F) : Target specific flags. |
@@ -1147,7 +1150,7 @@ The top Makefile exports the following variables: | |||
1147 | 1150 | ||
1148 | === 8 Makefile language | 1151 | === 8 Makefile language |
1149 | 1152 | ||
1150 | The kernel Makefiles are designed to run with GNU Make. The Makefiles | 1153 | The kernel Makefiles are designed to be run with GNU Make. The Makefiles |
1151 | use only the documented features of GNU Make, but they do use many | 1154 | use only the documented features of GNU Make, but they do use many |
1152 | GNU extensions. | 1155 | GNU extensions. |
1153 | 1156 | ||
@@ -1169,10 +1172,11 @@ is the right choice. | |||
1169 | Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net> | 1172 | Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net> |
1170 | Updates by Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de> | 1173 | Updates by Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de> |
1171 | Updates by Sam Ravnborg <sam@ravnborg.org> | 1174 | Updates by Sam Ravnborg <sam@ravnborg.org> |
1175 | Language QA by Jan Engelhardt <jengelh@gmx.de> | ||
1172 | 1176 | ||
1173 | === 10 TODO | 1177 | === 10 TODO |
1174 | 1178 | ||
1175 | - Describe how kbuild support shipped files with _shipped. | 1179 | - Describe how kbuild supports shipped files with _shipped. |
1176 | - Generating offset header files. | 1180 | - Generating offset header files. |
1177 | - Add more variables to section 7? | 1181 | - Add more variables to section 7? |
1178 | 1182 | ||