Fix some typoes, and update some Makefile excerpts in the
makefiles.txt file, so that the examples reflect actual existing code.
Signed-off-by: Robert P. J. Day <[EMAIL PROTECTED]>
---
the biggest set of patches was to just replace out-of-date Makefile
snippets with existing snippets.
diff --git a/Documentation/kbuild/makefiles.txt
b/Documentation/kbuild/makefiles.txt
index 7a77533..af6c798 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -53,7 +53,7 @@ The Makefiles have five parts:
.config the kernel configuration file.
arch/$(ARCH)/Makefile the arch Makefile.
scripts/Makefile.* common rules etc. for all kbuild Makefiles.
- kbuild Makefiles there are about 500 of these.
+ kbuild Makefiles there are about 1000 of these.
The top Makefile reads the .config file, which comes from the kernel
configuration process.
@@ -277,9 +277,9 @@ more details, with real examples.
--- 3.7 Compilation flags
ccflags-y, asflags-y and ldflags-y
- The three flags listed above applies only to the kbuild makefile
+ The three flags listed above apply only to the kbuild makefile
where they are assigned. They are used for all the normal
- cc, as and ld invocation happenign during a recursive build.
+ cc, as and ld invocation happening during a recursive build.
Note: Flags with the same behaviour were previously named:
EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
They are yet supported but their use are deprecated.
@@ -287,9 +287,8 @@ more details, with real examples.
ccflags-y specifies options for compiling C files with $(CC).
Example:
- # drivers/sound/emu10k1/Makefile
- ccflags-y += -I$(obj)
- ccflags-$(DEBUG) += -DEMU10K1_DEBUG
+ #arch/x86/boot/Makefile
+ $(obj)/bzImage: ccflags-y := -D__BIG_KERNEL__
This variable is necessary because the top Makefile owns the
@@ -300,15 +299,15 @@ more details, with real examples.
when compiling assembly language source.
Example:
- #arch/x86_64/kernel/Makefile
- asflags-y := -traditional
+ #arch/x86/boot/Makefile
+ $(obj)/zImage: asflags-y := $(SVGA_MODE) $(RAMDISK)
ldflags-y is a string for per-directory options to $(LD).
Example:
- #arch/m68k/fpsp040/Makefile
- ldflags-y := -x
+ #arch/h8300/Makefile
+ LDFLAGS += $(ldflags-y)
CFLAGS_$@, AFLAGS_$@
@@ -398,9 +397,9 @@ more details, with real examples.
Example:
#arch/sh/Makefile
- cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
+ isaflags-y := $(call as-option,-Wa$(comma)-isa=$(isa-y),)
- In the above example, cflags-y will be assigned the option
+ In the above example, isaflags-y will be assigned the option
-Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
The second argument is optional, and if supplied will be used
if first argument is not supported.
@@ -411,10 +410,13 @@ more details, with real examples.
specified if first option are not supported.
Example:
- #arch/i386/kernel/Makefile
- vsyscall-flags += $(call ld-option,
-Wl$(comma)--hash-style=sysv)
+ #arch/x86/vdso/Makefile
+ vdso-flags = -fPIC -shared -Wl,-soname=linux-vdso.so.1 \
+ $(call ld-option, -Wl$(comma)--hash-style=sysv) \
+ -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096
+
- In the above example, vsyscall-flags will be assigned the option
+ In the above example, vdso-flags will use the option
-Wl$(comma)--hash-style=sysv if it is supported by $(CC).
The second argument is optional, and if supplied will be used
if first argument is not supported.
@@ -423,20 +425,19 @@ more details, with real examples.
as-instr checks if the assembler reports a specific instruction
and then outputs either option1 or option2
C escapes are supported in the test instruction
- Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
cc-option
cc-option is used to check if $(CC) supports a given option, and not
supported to use an optional second option.
Example:
- #arch/i386/Makefile
- cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
+ #arch/x86/Makefile_64
+ cflags-y += $(call cc-option,-funit-at-a-time)
- In the above example, cflags-y will be assigned the option
- -march=pentium-mmx if supported by $(CC), otherwise -march=i586.
- The second argument to cc-option is optional, and if omitted,
- cflags-y will be assigned no value if first option is not supported.
+ In the above example, cflags-y will have appended to it the
+ option -funit-at-a-time if supported by $(CC). The second
+ argument to cc-option is optional and, if omitted, will be
+ represented by no value if the first option is not supported.
Note: cc-option uses KBUILD_CFLAGS for $(CC) options
cc-option-yn
@@ -445,14 +446,16 @@ more details, with real examples.
Example:
#arch/ppc/Makefile
- biarch := $(call cc-option-yn, -m32)
- aflags-$(biarch) += -a32
- cflags-$(biarch) += -m32
-
- In the above example, $(biarch) is set to y if $(CC) supports the -m32
- option. When $(biarch) equals 'y', the expanded variables $(aflags-y)
- and $(cflags-y) will be assigned the values -a32 and -m32,
- respectively.
+ HAS_BIARCH := $(call cc-option-yn, -m32)
+ ifeq ($(HAS_BIARCH),y)
+ AS := $(AS) -a32
+ LD := $(LD) -m elf32ppc
+ CC := $(CC) -m32
+ endif
+
+ In the above example, $(HAS_BIARCH) is set to y if $(CC) supports
+ the -m32 option, which subsequently affects the values of $(AS),
+ $(LD) and $(CC).
Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options
cc-option-align
@@ -464,7 +467,13 @@ more details, with real examples.
gcc >= 3.00
cc-option-align = -falign
- Example:
+ The correct value is set automatically in scripts/Kbuild.include:
+ # cc-option-align
+ # Prefix align with either -falign or -malign
+ cc-option-align = $(subst -functions=0,,\
+ $(call cc-option,-falign-functions=0,-malign-functions=0))
+
+ Example usage:
KBUILD_CFLAGS += $(cc-option-align)-functions=4
In the above example, the option -falign-functions=4 is used for
@@ -475,18 +484,16 @@ more details, with real examples.
cc-version returns a numerical version of the $(CC) compiler version.
The format is <major><minor> where both are two digits. So for example
gcc 3.41 would return 0341.
- cc-version is useful when a specific $(CC) version is faulty in one
- area, for example -mregparm=3 was broken in some gcc versions
- even though the option was accepted by gcc.
Example:
- #arch/i386/Makefile
- cflags-y += $(shell \
- if [ $(call cc-version) -ge 0300 ] ; then \
- echo "-mregparm=3"; fi ;)
+ #arch/ia64/Makefile
+ ifeq ($(call cc-version),0304)
+ cflags-$(CONFIG_ITANIUM) += -mtune=merced
+ cflags-$(CONFIG_MCKINLEY) += -mtune=mckinley
+ endif
- In the above example, -mregparm=3 is only used for gcc version greater
- than or equal to gcc 3.0.
+ In the above example, the "cflags" variable(s) will have some
+ specific options appended if gcc 3.4 is being used.
cc-ifversion
cc-ifversion tests the version of $(CC) and equals last argument if
@@ -494,10 +501,10 @@ more details, with real examples.
Example:
#fs/reiserfs/Makefile
- ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
+ EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0400, -O1)
- In this example, ccflags-y will be assigned the value -O1 if the
- $(CC) version is less than 4.2.
+ In this example, EXTRA_CFLAGS will be assigned the value -O1 if the
+ $(CC) version is less than 4.0.
cc-ifversion takes all the shell operators:
-eq, -ne, -lt, -le, -gt, and -ge
The third parameter may be a text as in this example, but it may also
@@ -509,12 +516,16 @@ more details, with real examples.
cc-fullversion points out a more specific version than cc-version does.
Example:
- #arch/powerpc/Makefile
- $(Q)if test "$(call cc-fullversion)" = "040200" ; then \
+ @if test "$(call cc-fullversion)" = "040200" \
+ && test "x${CONFIG_MODULES}${CONFIG_PPC64}" = "xyy" ; then \
echo -n '*** GCC-4.2.0 cannot compile the 64-bit
powerpc ' ; \
+ echo 'kernel with modules enabled.' ; \
+ echo -n '*** Please use a different GCC version or ' ; \
+ echo 'disable kernel modules' ; \
false ; \
fi
+
In this example for a specific GCC version the build will error out
explaining
to the user why it stops.
@@ -533,11 +544,14 @@ more details, with real examples.
is already set then leave it with the old value.
Example:
- #arch/m68k/Makefile
+ #arch/mips/Makefile
ifneq ($(SUBARCH),$(ARCH))
- ifeq ($(CROSS_COMPILE),)
- CROSS_COMPILE := $(call cc-cross-prefix,
m68k-linux-gnu-)
- endif
+ ifeq ($(CROSS_COMPILE),)
+ CROSS_COMPILE := $(call cc-cross-prefix,
+ $(tool-archpref)-linux-
+ $(tool-archpref)-linux-gnu-
+ $(tool-archpref)-unknown-linux-gnu-)
+ endif
endif
=== 4 Host Program support
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA
http://crashcourse.ca
========================================================================
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