aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
-rw-r--r--Documentation/kbuild/makefiles.txt83
1 files changed, 43 insertions, 40 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 3d2f88ea14a5..b7d6abb501a6 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -22,7 +22,7 @@ This document describes the Linux kernel Makefiles.
22 === 4 Host Program support 22 === 4 Host Program support
23 --- 4.1 Simple Host Program 23 --- 4.1 Simple Host Program
24 --- 4.2 Composite Host Programs 24 --- 4.2 Composite Host Programs
25 --- 4.3 Defining shared libraries 25 --- 4.3 Defining shared libraries
26 --- 4.4 Using C++ for host programs 26 --- 4.4 Using C++ for host programs
27 --- 4.5 Controlling compiler options for host programs 27 --- 4.5 Controlling compiler options for host programs
28 --- 4.6 When host programs are actually built 28 --- 4.6 When host programs are actually built
@@ -69,7 +69,7 @@ architecture-specific information to the top Makefile.
69 69
70Each subdirectory has a kbuild Makefile which carries out the commands 70Each subdirectory has a kbuild Makefile which carries out the commands
71passed down from above. The kbuild Makefile uses information from the 71passed down from above. The kbuild Makefile uses information from the
72.config file to construct various file lists used by kbuild to build 72.config file to construct various file lists used by kbuild to build
73any built-in or modular targets. 73any built-in or modular targets.
74 74
75scripts/Makefile.* contains all the definitions/rules etc. that 75scripts/Makefile.* contains all the definitions/rules etc. that
@@ -203,9 +203,9 @@ more details, with real examples.
203 Example: 203 Example:
204 #fs/ext2/Makefile 204 #fs/ext2/Makefile
205 obj-$(CONFIG_EXT2_FS) += ext2.o 205 obj-$(CONFIG_EXT2_FS) += ext2.o
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
@@ -244,7 +244,7 @@ more details, with real examples.
244 For kbuild to actually recognize that there is a lib.a being built, 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 Use 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
@@ -408,7 +408,7 @@ more details, with real examples.
408 if first argument is not supported. 408 if first argument is not supported.
409 409
410 ld-option 410 ld-option
411 ld-option is used to check if $(CC) when used to link object files 411 ld-option is used to check if $(CC) when used to link object files
412 supports the given option. An optional second option may be 412 supports the given option. An optional second option may be
413 specified if first option are not supported. 413 specified if first option are not supported.
414 414
@@ -435,7 +435,7 @@ more details, with real examples.
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
438 cc-option-yn is used to check if gcc supports a given option 438 cc-option-yn is used to check if gcc supports a given option
439 and return 'y' if supported, otherwise 'n'. 439 and return 'y' if supported, otherwise 'n'.
440 440
441 Example: 441 Example:
@@ -443,7 +443,7 @@ more details, with real examples.
443 biarch := $(call cc-option-yn, -m32) 443 biarch := $(call cc-option-yn, -m32)
444 aflags-$(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 '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,
@@ -457,13 +457,13 @@ more details, with real examples.
457 cc-option-align = -malign 457 cc-option-align = -malign
458 gcc >= 3.00 458 gcc >= 3.00
459 cc-option-align = -falign 459 cc-option-align = -falign
460 460
461 Example: 461 Example:
462 CFLAGS += $(cc-option-align)-functions=4 462 CFLAGS += $(cc-option-align)-functions=4
463 463
464 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
465 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.
466 466
467 cc-version 467 cc-version
468 cc-version returns a numerical version of the $(CC) compiler version. 468 cc-version returns a numerical version of the $(CC) compiler version.
469 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
@@ -491,7 +491,7 @@ more details, with real examples.
491 491
492 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
493 $(CC) version is less than 4.2. 493 $(CC) version is less than 4.2.
494 cc-ifversion takes all the shell operators: 494 cc-ifversion takes all the shell operators:
495 -eq, -ne, -lt, -le, -gt, and -ge 495 -eq, -ne, -lt, -le, -gt, and -ge
496 The third parameter may be a text as in this example, but it may also 496 The third parameter may be a text as in this example, but it may also
497 be an expanded variable or a macro. 497 be an expanded variable or a macro.
@@ -507,7 +507,7 @@ The first step is to tell kbuild that a host program exists. This is
507done utilising the variable hostprogs-y. 507done utilising the variable hostprogs-y.
508 508
509The second step is to add an explicit dependency to the executable. 509The second step is to add an explicit dependency to the executable.
510This can be done in two ways. Either add the dependency in a rule, 510This can be done in two ways. Either add the dependency in a rule,
511or utilise the variable $(always). 511or utilise the variable $(always).
512Both possibilities are described in the following. 512Both possibilities are described in the following.
513 513
@@ -524,7 +524,7 @@ Both possibilities are described in the following.
524 Kbuild assumes in the above example that bin2hex is made from a single 524 Kbuild assumes in the above example that bin2hex is made from a single
525 c-source file named bin2hex.c located in the same directory as 525 c-source file named bin2hex.c located in the same directory as
526 the Makefile. 526 the Makefile.
527 527
528--- 4.2 Composite Host Programs 528--- 4.2 Composite Host Programs
529 529
530 Host programs can be made up based on composite objects. 530 Host programs can be made up based on composite objects.
@@ -535,7 +535,7 @@ Both possibilities are described in the following.
535 535
536 Example: 536 Example:
537 #scripts/lxdialog/Makefile 537 #scripts/lxdialog/Makefile
538 hostprogs-y := lxdialog 538 hostprogs-y := lxdialog
539 lxdialog-objs := checklist.o lxdialog.o 539 lxdialog-objs := checklist.o lxdialog.o
540 540
541 Objects with extension .o are compiled from the corresponding .c 541 Objects with extension .o are compiled from the corresponding .c
@@ -544,8 +544,8 @@ Both possibilities are described in the following.
544 Finally, the two .o files are linked to the executable, lxdialog. 544 Finally, the two .o files are linked to the executable, lxdialog.
545 Note: The syntax <executable>-y is not permitted for host-programs. 545 Note: The syntax <executable>-y is not permitted for host-programs.
546 546
547--- 4.3 Defining shared libraries 547--- 4.3 Defining shared libraries
548 548
549 Objects with extension .so are considered shared libraries, and 549 Objects with extension .so are considered shared libraries, and
550 will be compiled as position independent objects. 550 will be compiled as position independent objects.
551 Kbuild provides support for shared libraries, but the usage 551 Kbuild provides support for shared libraries, but the usage
@@ -558,7 +558,7 @@ Both possibilities are described in the following.
558 hostprogs-y := conf 558 hostprogs-y := conf
559 conf-objs := conf.o libkconfig.so 559 conf-objs := conf.o libkconfig.so
560 libkconfig-objs := expr.o type.o 560 libkconfig-objs := expr.o type.o
561 561
562 Shared libraries always require a corresponding -objs line, and 562 Shared libraries always require a corresponding -objs line, and
563 in the example above the shared library libkconfig is composed by 563 in the example above the shared library libkconfig is composed by
564 the two objects expr.o and type.o. 564 the two objects expr.o and type.o.
@@ -579,7 +579,7 @@ Both possibilities are described in the following.
579 579
580 In the example above the executable is composed of the C++ file 580 In the example above the executable is composed of the C++ file
581 qconf.cc - identified by $(qconf-cxxobjs). 581 qconf.cc - identified by $(qconf-cxxobjs).
582 582
583 If qconf is composed by a mixture of .c and .cc files, then an 583 If qconf is composed by a mixture of .c and .cc files, then an
584 additional line can be used to identify this. 584 additional line can be used to identify this.
585 585
@@ -588,7 +588,7 @@ Both possibilities are described in the following.
588 hostprogs-y := qconf 588 hostprogs-y := qconf
589 qconf-cxxobjs := qconf.o 589 qconf-cxxobjs := qconf.o
590 qconf-objs := check.o 590 qconf-objs := check.o
591 591
592--- 4.5 Controlling compiler options for host programs 592--- 4.5 Controlling compiler options for host programs
593 593
594 When compiling host programs, it is possible to set specific flags. 594 When compiling host programs, it is possible to set specific flags.
@@ -600,23 +600,23 @@ Both possibilities are described in the following.
600 Example: 600 Example:
601 #scripts/lxdialog/Makefile 601 #scripts/lxdialog/Makefile
602 HOST_EXTRACFLAGS += -I/usr/include/ncurses 602 HOST_EXTRACFLAGS += -I/usr/include/ncurses
603 603
604 To set specific flags for a single file the following construction 604 To set specific flags for a single file the following construction
605 is used: 605 is used:
606 606
607 Example: 607 Example:
608 #arch/ppc64/boot/Makefile 608 #arch/ppc64/boot/Makefile
609 HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE) 609 HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE)
610 610
611 It is also possible to specify additional options to the linker. 611 It is also possible to specify additional options to the linker.
612 612
613 Example: 613 Example:
614 #scripts/kconfig/Makefile 614 #scripts/kconfig/Makefile
615 HOSTLOADLIBES_qconf := -L$(QTDIR)/lib 615 HOSTLOADLIBES_qconf := -L$(QTDIR)/lib
616 616
617 When linking qconf, it will be passed the extra option 617 When linking qconf, it will be passed the extra option
618 "-L$(QTDIR)/lib". 618 "-L$(QTDIR)/lib".
619 619
620--- 4.6 When host programs are actually built 620--- 4.6 When host programs are actually built
621 621
622 Kbuild will only build host-programs when they are referenced 622 Kbuild will only build host-programs when they are referenced
@@ -631,7 +631,7 @@ Both possibilities are described in the following.
631 $(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist 631 $(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist
632 ( cd $(obj); ./gen-devlist ) < $< 632 ( cd $(obj); ./gen-devlist ) < $<
633 633
634 The target $(obj)/devlist.h will not be built before 634 The target $(obj)/devlist.h will not be built before
635 $(obj)/gen-devlist is updated. Note that references to 635 $(obj)/gen-devlist is updated. Note that references to
636 the host programs in special rules must be prefixed with $(obj). 636 the host programs in special rules must be prefixed with $(obj).
637 637
@@ -650,7 +650,7 @@ Both possibilities are described in the following.
650 650
651--- 4.7 Using hostprogs-$(CONFIG_FOO) 651--- 4.7 Using hostprogs-$(CONFIG_FOO)
652 652
653 A typcal pattern in a Kbuild file looks like this: 653 A typical pattern in a Kbuild file looks like this:
654 654
655 Example: 655 Example:
656 #scripts/Makefile 656 #scripts/Makefile
@@ -682,7 +682,8 @@ When executing "make clean", the two files "devlist.h classlist.h" will
682be deleted. Kbuild will assume files to be in same relative directory as the 682be deleted. Kbuild will assume files to be in same relative directory as the
683Makefile except if an absolute path is specified (path starting with '/'). 683Makefile except if an absolute path is specified (path starting with '/').
684 684
685To delete a directory hirachy use: 685To delete a directory hierarchy use:
686
686 Example: 687 Example:
687 #scripts/package/Makefile 688 #scripts/package/Makefile
688 clean-dirs := $(objtree)/debian/ 689 clean-dirs := $(objtree)/debian/
@@ -740,7 +741,7 @@ When kbuild executes, the following steps are followed (roughly):
7405) Recursively descend down in all directories listed in 7415) Recursively descend down in all directories listed in
741 init-* core* drivers-* net-* libs-* and build all targets. 742 init-* core* drivers-* net-* libs-* and build all targets.
742 - The values of the above variables are expanded in arch/$(ARCH)/Makefile. 743 - The values of the above variables are expanded in arch/$(ARCH)/Makefile.
7436) All object files are then linked and the resulting file vmlinux is 7446) All object files are then linked and the resulting file vmlinux is
744 located at the root of the obj tree. 745 located at the root of the obj tree.
745 The very first objects linked are listed in head-y, assigned by 746 The very first objects linked are listed in head-y, assigned by
746 arch/$(ARCH)/Makefile. 747 arch/$(ARCH)/Makefile.
@@ -762,7 +763,7 @@ When kbuild executes, the following steps are followed (roughly):
762 LDFLAGS := -m elf_s390 763 LDFLAGS := -m elf_s390
763 Note: EXTRA_LDFLAGS and LDFLAGS_$@ can be used to further customise 764 Note: EXTRA_LDFLAGS and LDFLAGS_$@ can be used to further customise
764 the flags used. See chapter 7. 765 the flags used. See chapter 7.
765 766
766 LDFLAGS_MODULE Options for $(LD) when linking modules 767 LDFLAGS_MODULE Options for $(LD) when linking modules
767 768
768 LDFLAGS_MODULE is used to set specific flags for $(LD) when 769 LDFLAGS_MODULE is used to set specific flags for $(LD) when
@@ -845,7 +846,7 @@ When kbuild executes, the following steps are followed (roughly):
845 $(CFLAGS_MODULE) contains extra C compiler flags used to compile code 846 $(CFLAGS_MODULE) contains extra C compiler flags used to compile code
846 for loadable kernel modules. 847 for loadable kernel modules.
847 848
848 849
849--- 6.2 Add prerequisites to archprepare: 850--- 6.2 Add prerequisites to archprepare:
850 851
851 The archprepare: rule is used to list prerequisites that need to be 852 The archprepare: rule is used to list prerequisites that need to be
@@ -869,7 +870,7 @@ When kbuild executes, the following steps are followed (roughly):
869 corresponding arch-specific section for modules; the module-building 870 corresponding arch-specific section for modules; the module-building
870 machinery is all architecture-independent. 871 machinery is all architecture-independent.
871 872
872 873
873 head-y, init-y, core-y, libs-y, drivers-y, net-y 874 head-y, init-y, core-y, libs-y, drivers-y, net-y
874 875
875 $(head-y) lists objects to be linked first in vmlinux. 876 $(head-y) lists objects to be linked first in vmlinux.
@@ -926,7 +927,7 @@ When kbuild executes, the following steps are followed (roughly):
926 #arch/i386/Makefile 927 #arch/i386/Makefile
927 define archhelp 928 define archhelp
928 echo '* bzImage - Image (arch/$(ARCH)/boot/bzImage)' 929 echo '* bzImage - Image (arch/$(ARCH)/boot/bzImage)'
929 endef 930 endif
930 931
931 When make is executed without arguments, the first goal encountered 932 When make is executed without arguments, the first goal encountered
932 will be built. In the top level Makefile the first goal present 933 will be built. In the top level Makefile the first goal present
@@ -938,7 +939,7 @@ When kbuild executes, the following steps are followed (roughly):
938 939
939 Example: 940 Example:
940 #arch/i386/Makefile 941 #arch/i386/Makefile
941 all: bzImage 942 all: bzImage
942 943
943 When "make" is executed without arguments, bzImage will be built. 944 When "make" is executed without arguments, bzImage will be built.
944 945
@@ -961,7 +962,7 @@ When kbuild executes, the following steps are followed (roughly):
961 In this example, extra-y is used to list object files that 962 In this example, extra-y is used to list object files that
962 shall be built, but shall not be linked as part of built-in.o. 963 shall be built, but shall not be linked as part of built-in.o.
963 964
964 965
965--- 6.6 Commands useful for building a boot image 966--- 6.6 Commands useful for building a boot image
966 967
967 Kbuild provides a few macros that are useful when building a 968 Kbuild provides a few macros that are useful when building a
@@ -995,7 +996,7 @@ When kbuild executes, the following steps are followed (roughly):
995 996
996 ld 997 ld
997 Link target. Often, LDFLAGS_$@ is used to set specific options to ld. 998 Link target. Often, LDFLAGS_$@ is used to set specific options to ld.
998 999
999 objcopy 1000 objcopy
1000 Copy binary. Uses OBJCOPYFLAGS usually specified in 1001 Copy binary. Uses OBJCOPYFLAGS usually specified in
1001 arch/$(ARCH)/Makefile. 1002 arch/$(ARCH)/Makefile.
@@ -1053,7 +1054,7 @@ When kbuild executes, the following steps are followed (roughly):
1053 BUILD arch/i386/boot/bzImage 1054 BUILD arch/i386/boot/bzImage
1054 1055
1055 will be displayed with "make KBUILD_VERBOSE=0". 1056 will be displayed with "make KBUILD_VERBOSE=0".
1056 1057
1057 1058
1058--- 6.8 Preprocessing linker scripts 1059--- 6.8 Preprocessing linker scripts
1059 1060
@@ -1062,19 +1063,19 @@ When kbuild executes, the following steps are followed (roughly):
1062 The script is a preprocessed variant of the file vmlinux.lds.S 1063 The script is a preprocessed variant of the file vmlinux.lds.S
1063 located in the same directory. 1064 located in the same directory.
1064 kbuild knows .lds files and includes a rule *lds.S -> *lds. 1065 kbuild knows .lds files and includes a rule *lds.S -> *lds.
1065 1066
1066 Example: 1067 Example:
1067 #arch/i386/kernel/Makefile 1068 #arch/i386/kernel/Makefile
1068 always := vmlinux.lds 1069 always := vmlinux.lds
1069 1070
1070 #Makefile 1071 #Makefile
1071 export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) 1072 export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
1072 1073
1073 The assigment to $(always) is used to tell kbuild to build the 1074 The assignment to $(always) is used to tell kbuild to build the
1074 target vmlinux.lds. 1075 target vmlinux.lds.
1075 The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the 1076 The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the
1076 specified options when building the target vmlinux.lds. 1077 specified options when building the target vmlinux.lds.
1077 1078
1078 When building the *.lds target, kbuild uses the variables: 1079 When building the *.lds target, kbuild uses the variables:
1079 CPPFLAGS : Set in top-level Makefile 1080 CPPFLAGS : Set in top-level Makefile
1080 EXTRA_CPPFLAGS : May be set in the kbuild makefile 1081 EXTRA_CPPFLAGS : May be set in the kbuild makefile
@@ -1180,3 +1181,5 @@ Language QA by Jan Engelhardt <jengelh@gmx.de>
1180- Generating offset header files. 1181- Generating offset header files.
1181- Add more variables to section 7? 1182- Add more variables to section 7?
1182 1183
1184
1185