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<HTML
><HEAD
><TITLE
>Linux Makefiles</TITLE
><META
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>Linux i386 Boot Code HOWTO</TH
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>Prev</A
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><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="makefiles"
></A
>2. Linux Makefiles</H1
><P
>&#13; Before perusing Linux code, we should get some basic idea about
how Linux is composed, compiled and linked.
A straightforward way to achieve this goal is to understand Linux makefiles.
Check <A
HREF="http://lxr.linux.no/source?v=2.4.20"
TARGET="_top"
>&#13; Cross-Referencing Linux</A
> if you prefer online source browsing.
</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="linux_makefile"
></A
>2.1. linux/Makefile</H2
><P
>&#13; Here are some well-known targets in this top-level makefile:
<P
></P
><UL
><LI
><P
>&#13; <EM
>xconfig, menuconfig, config, oldconfig</EM
>:
generate kernel configuration file
<TT
CLASS="filename"
>linux/.config</TT
>;
</P
></LI
><LI
><P
>&#13; <EM
>depend, dep</EM
>: generate dependency files, like
<TT
CLASS="filename"
>linux/.depend</TT
>,
<TT
CLASS="filename"
>linux/.hdepend</TT
> and
<TT
CLASS="filename"
>.depend</TT
> in subdirectories;
</P
></LI
><LI
><P
>&#13; <EM
>vmlinux</EM
>: generate resident kernel image
<TT
CLASS="filename"
>linux/vmlinux</TT
>, the most important target;
</P
></LI
><LI
><P
>&#13; <EM
>modules, modules_install</EM
>:
generate and install modules in
<TT
CLASS="filename"
>/lib/modules/$(KERNELRELEASE)</TT
>;
</P
></LI
><LI
><P
>&#13; <EM
>tags</EM
>: generate tag file
<TT
CLASS="filename"
>linux/tags</TT
>, for source browsing with
<A
HREF="http://vim.sourceforge.net"
TARGET="_top"
>vim</A
>.
</P
></LI
></UL
>
</P
><P
>&#13; Overview of <TT
CLASS="filename"
>linux/Makefile</TT
> is outlined below:
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="programlisting"
>include .depend
include .config
include arch/i386/Makefile
vmlinux: generate linux/vmlinux
/* entry point "stext" defined in arch/i386/kernel/head.S */
$(LD) -T $(TOPDIR)/arch/i386/vmlinux.lds -e stext
/* $(HEAD) */
+ from arch/i386/Makefile
arch/i386/kernel/head.o
arch/i386/kernel/init_task.o
init/main.o
init/version.o
init/do_mounts.o
--start-group
/* $(CORE_FILES) */
+ from arch/i386/Makefile
arch/i386/kernel/kernel.o
arch/i386/mm/mm.o
kernel/kernel.o
mm/mm.o
fs/fs.o
ipc/ipc.o
/* $(DRIVERS) */
drivers/...
char/char.o
block/block.o
misc/misc.o
net/net.o
media/media.o
cdrom/driver.o
and other static linked drivers
+ from arch/i386/Makefile
arch/i386/math-emu/math.o (ifdef CONFIG_MATH_EMULATION)
/* $(NETWORKS) */
net/network.o
/* $(LIBS) */
+ from arch/i386/Makefile
arch/i386/lib/lib.a
lib/lib.a
--end-group
-o vmlinux
$(NM) vmlinux | grep ... | sort &#62; System.map
tags: generate linux/tags for vim
modules: generate modules
modules_install: install modules
clean mrproper distclean: clean up build directory
psdocs pdfdocs htmldocs mandocs: generate kernel documents
include Rules.make
rpm: generate an rpm</PRE
></FONT
></TD
></TR
></TABLE
>
"--start-group" and "--end-group" are <B
CLASS="command"
>ld</B
>
command line options to resolve symbol reference problem. Refer to
<A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_2.html#SEC3"
TARGET="_top"
>&#13; Using LD, the GNU linker: Command Line Options</A
> for details.
</P
><P
>&#13; <TT
CLASS="filename"
>Rules.make</TT
> contains rules which are shared
between multiple Makefiles.
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="vmlinux.lds"
></A
>2.2. linux/arch/i386/vmlinux.lds</H2
><P
>&#13; After compilation, <B
CLASS="command"
>ld</B
> combines a number of
object and archive files, relocates their data and
ties up symbol references.
<TT
CLASS="filename"
>linux/arch/i386/vmlinux.lds</TT
> is designated by
<TT
CLASS="filename"
>linux/Makefile</TT
> as the linker script used
in linking the resident kernel image <TT
CLASS="filename"
>linux/vmlinux</TT
>.
</P
><P
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="programlisting"
>/* ld script to make i386 Linux kernel
* Written by Martin Mares &#60;mj@atrey.karlin.mff.cuni.cz&#62;;
*/
OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
OUTPUT_ARCH(i386)
/* "ENTRY" is overridden by command line option "-e stext" in linux/Makefile */
ENTRY(_start)
/* Output file (linux/vmlinux) layout.
* Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC17"
TARGET="_top"
>Using LD, the GNU linker: Specifying Output Sections</A
> */
SECTIONS
{
/* Output section .text starts at address 3G+1M.
* Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC10"
TARGET="_top"
>Using LD, the GNU linker: The Location Counter</A
> */
. = 0xC0000000 + 0x100000;
_text = .; /* Text and read-only data */
.text : {
*(.text)
*(.fixup)
*(.gnu.warning)
} = 0x9090
/* Unallocated holes filled with 0x9090, i.e. opcode for "NOP NOP".
* Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC21"
TARGET="_top"
>Using LD, the GNU linker: Optional Section Attributes</A
> */
_etext = .; /* End of text section */
.rodata : { *(.rodata) *(.rodata.*) }
.kstrtab : { *(.kstrtab) }
/* Aligned to next 16-bytes boundary.
* Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC14"
TARGET="_top"
>Using LD, the GNU linker: Arithmetic Functions</A
> */
. = ALIGN(16); /* Exception table */
__start___ex_table = .;
__ex_table : { *(__ex_table) }
__stop___ex_table = .;
__start___ksymtab = .; /* Kernel symbol table */
__ksymtab : { *(__ksymtab) }
__stop___ksymtab = .;
.data : { /* Data */
*(.data)
CONSTRUCTORS
}
/* For "CONSTRUCTORS", refer to
* <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC26"
TARGET="_top"
>Using LD, the GNU linker: Option Commands</A
> */
_edata = .; /* End of data section */
. = ALIGN(8192); /* init_task */
.data.init_task : { *(.data.init_task) }
. = ALIGN(4096); /* Init code and data */
__init_begin = .;
.text.init : { *(.text.init) }
.data.init : { *(.data.init) }
. = ALIGN(16);
__setup_start = .;
.setup.init : { *(.setup.init) }
__setup_end = .;
__initcall_start = .;
.initcall.init : { *(.initcall.init) }
__initcall_end = .;
. = ALIGN(4096);
__init_end = .;
. = ALIGN(4096);
.data.page_aligned : { *(.data.idt) }
. = ALIGN(32);
.data.cacheline_aligned : { *(.data.cacheline_aligned) }
__bss_start = .; /* BSS */
.bss : {
*(.bss)
}
_end = . ;
/* Output section /DISCARD/ will not be included in the final link output.
* Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC18"
TARGET="_top"
>Using LD, the GNU linker: Section Definitions</A
> */
/* Sections to be discarded */
/DISCARD/ : {
*(.text.exit)
*(.data.exit)
*(.exitcall.exit)
}
/* The following output sections are addressed at memory location 0.
* Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC21"
TARGET="_top"
>Using LD, the GNU linker: Optional Section Attributes</A
> */
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
.stab.excl 0 : { *(.stab.excl) }
.stab.exclstr 0 : { *(.stab.exclstr) }
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
}</PRE
></FONT
></TD
></TR
></TABLE
>
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="i386_makefile"
></A
>2.3. linux/arch/i386/Makefile</H2
><P
>&#13; <TT
CLASS="filename"
>linux/arch/i386/Makefile</TT
> is included by
<TT
CLASS="filename"
>linux/Makefile</TT
> to provide i386 specific
items and terms.
</P
><P
>&#13; All the following targets depend on target <EM
>vmlinux</EM
>
of <TT
CLASS="filename"
>linux/Makefile</TT
>.
They are accomplished by making corresponding targets in
<TT
CLASS="filename"
>linux/arch/i386/boot/Makefile</TT
> with some options.
<DIV
CLASS="table"
><A
NAME="AEN153"
></A
><P
><B
>Table 1. Targets in linux/arch/i386/Makefile</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Target</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Command</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>zImage
<A
NAME="AEN163"
HREF="#FTN.AEN163"
><SPAN
CLASS="footnote"
>[a]</SPAN
></A
>
</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>@$(MAKE) -C arch/i386/boot zImage</B
>
<A
NAME="AEN169"
HREF="#FTN.AEN169"
><SPAN
CLASS="footnote"
>[b]</SPAN
></A
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bzImage</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>@$(MAKE) -C arch/i386/boot bzImage</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>zlilo</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>@$(MAKE) -C arch/i386/boot BOOTIMAGE=zImage zlilo</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bzlilo</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>@$(MAKE) -C arch/i386/boot BOOTIMAGE=bzImage zlilo</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>zdisk</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>@$(MAKE) -C arch/i386/boot BOOTIMAGE=zImage zdisk</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bzdisk</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>@$(MAKE) -C arch/i386/boot BOOTIMAGE=bzImage zdisk</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>install</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>@$(MAKE) -C arch/i386/boot BOOTIMAGE=bzImage install</B
>
</TD
></TR
></TBODY
><TR
><TD
COLSPAN="2"
>Notes:<BR><A
NAME="FTN.AEN163"
>a. </A
>
<EM
>zImage</EM
> alias:
<EM
>compressed</EM
>;
<BR><A
NAME="FTN.AEN169"
>b. </A
>
"-C" is a MAKE command line option
to change directory before reading makefiles;
<BR>Refer to
<A
HREF="http://www.gnu.org/software/make/manual/html_chapter/make_9.html#SEC102"
TARGET="_top"
>&#13; GNU make: Summary of Options</A
> and
<A
HREF="http://www.gnu.org/software/make/manual/html_chapter/make_5.html#SEC58"
TARGET="_top"
>&#13; GNU make: Recursive Use of make</A
>.
<BR></TD
></TR
></TABLE
></DIV
>
</P
><P
>&#13; It is worth noticing that this makefile redefines
some environment variables which are exported by
<TT
CLASS="filename"
>linux/Makefile</TT
>, specifically:
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="programlisting"
>OBJCOPY=$(CROSS_COMPILE)objcopy -O binary -R .note -R .comment -S</PRE
></FONT
></TD
></TR
></TABLE
>
The effect will be passed to subdirectory makefiles and
will change the tool's behavior. Refer to
<A
HREF="http://www.gnu.org/software/binutils/manual/html_chapter/binutils_3.html"
TARGET="_top"
>&#13; GNU Binary Utilities: objcopy</A
>
for <B
CLASS="command"
>objcopy</B
> command line option details.
</P
><P
>&#13; Not sure why <EM
>$(LIBS)</EM
> includes
"$(TOPDIR)/arch/i386/lib/lib.a" twice:
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="programlisting"
>LIBS := $(TOPDIR)/arch/i386/lib/lib.a $(LIBS) $(TOPDIR)/arch/i386/lib/lib.a</PRE
></FONT
></TD
></TR
></TABLE
>
It may be employed to work around linking problems with some toolchains.
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="i386_boot_makefile"
></A
>2.4. linux/arch/i386/boot/Makefile</H2
><P
>&#13; <TT
CLASS="filename"
>linux/arch/i386/boot/Makefile</TT
> is somehow
independent as it is not included by either
<TT
CLASS="filename"
>linux/arch/i386/Makefile</TT
>
or <TT
CLASS="filename"
>linux/Makefile</TT
>.
</P
><P
>&#13; However, they do have some relationship:
<P
></P
><UL
><LI
><P
>&#13; <TT
CLASS="filename"
>linux/Makefile</TT
>: provides resident kernel image
<TT
CLASS="filename"
>linux/vmlinux</TT
>;
</P
></LI
><LI
><P
>&#13; <TT
CLASS="filename"
>linux/arch/i386/boot/Makefile</TT
>:
provides bootstrap;
</P
></LI
><LI
><P
>&#13; <TT
CLASS="filename"
>linux/arch/i386/Makefile</TT
>:
makes sure <TT
CLASS="filename"
>linux/vmlinux</TT
> is ready
before the bootstrap is constructed,
and exports targets (like <EM
>bzImage</EM
>)
to <TT
CLASS="filename"
>linux/Makefile</TT
>.
</P
></LI
></UL
>
</P
><P
>&#13; $(BOOTIMAGE) value, which is for target <EM
>zdisk, zlilo</EM
>
or <EM
>zdisk</EM
>, comes from
<TT
CLASS="filename"
>linux/arch/i386/Makefile</TT
>.
</P
><P
>&#13; <DIV
CLASS="table"
><A
NAME="AEN232"
></A
><P
><B
>Table 2. Targets in linux/arch/i386/boot/Makefile</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Target</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Command</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>zImage</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>$(OBJCOPY) compressed/vmlinux compressed/vmlinux.out
tools/build bootsect setup compressed/vmlinux.out $(ROOT_DEV) &#62; zImage</PRE
></FONT
></TD
></TR
></TABLE
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bzImage</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>$(OBJCOPY) compressed/bvmlinux compressed/bvmlinux.out
tools/build -b bbootsect bsetup compressed/bvmlinux.out $(ROOT_DEV) \
&#62; bzImage</PRE
></FONT
></TD
></TR
></TABLE
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>zdisk</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>dd bs=8192 if=$(BOOTIMAGE) of=/dev/fd0</PRE
></FONT
></TD
></TR
></TABLE
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>zlilo</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>if [ -f $(INSTALL_PATH)/vmlinuz ]; then mv $(INSTALL_PATH)/vmlinuz
$(INSTALL_PATH)/vmlinuz.old; fi
if [ -f $(INSTALL_PATH)/System.map ]; then mv $(INSTALL_PATH)/System.map
$(INSTALL_PATH)/System.old; fi
cat $(BOOTIMAGE) &#62; $(INSTALL_PATH)/vmlinuz
cp $(TOPDIR)/System.map $(INSTALL_PATH)/
if [ -x /sbin/lilo ]; then /sbin/lilo; else /etc/lilo/install; fi</PRE
></FONT
></TD
></TR
></TABLE
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>install</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>sh -x ./install.sh $(KERNELRELEASE) $(BOOTIMAGE) $(TOPDIR)/System.map
"$(INSTALL_PATH)"</PRE
></FONT
></TD
></TR
></TABLE
>
</TD
></TR
></TBODY
></TABLE
></DIV
>
<B
CLASS="command"
>tools/build</B
> builds boot image
<EM
>zImage</EM
> from
{bootsect, setup, compressed/vmlinux.out}, or
<EM
>bzImage</EM
> from
{bbootsect, bsetup, compressed/bvmlinux,out}.
<TT
CLASS="filename"
>linux/Makefile</TT
> "export ROOT_DEV = CURRENT".
Note that $(OBJCOPY) has been redefined by
<TT
CLASS="filename"
>linux/arch/i386/Makefile</TT
>
in <A
HREF="makefiles.html#i386_makefile"
>Section 2.3</A
>.
</P
><P
>&#13; <DIV
CLASS="table"
><A
NAME="AEN267"
></A
><P
><B
>Table 3. Supporting targets in linux/arch/i386/boot/Makefile</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Target: Prerequisites</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Command</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>compressed/vmlinux: linux/vmlinux</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>@$(MAKE) -C compressed vmlinux</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>compressed/bvmlinux: linux/vmlinux</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>@$(MAKE) -C compressed bvmlinux</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>tools/build: tools/build.c</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(HOSTCC) $(HOSTCFLAGS) -o $@ $&#60; -I$(TOPDIR)/include</B
>
<A
NAME="AEN287"
HREF="#FTN.AEN287"
><SPAN
CLASS="footnote"
>[a]</SPAN
></A
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bootsect: bootsect.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13; <B
CLASS="command"
>$(LD) -Ttext 0x0 -s --oformat binary bootsect.o</B
>
<A
NAME="AEN294"
HREF="#FTN.AEN294"
><SPAN
CLASS="footnote"
>[b]</SPAN
></A
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bootsect.o: bootsect.s</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>$(AS) -o $@ $&#60;</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bootsect.s: bootsect.S ...</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(CPP) $(CPPFLAGS) -traditional $(SVGA_MODE) $(RAMDISK) $&#60; -o $@</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bbootsect: bbootsect.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(LD) -Ttext 0x0 -s --oformat binary $&#60; -o $@</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bbootsect.o: bbootsect.s</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>$(AS) -o $@ $&#60;</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bbootsect.s: bootsect.S ...</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(CPP) $(CPPFLAGS) -D__BIG_KERNEL__ -traditional $(SVGA_MODE) $(RAMDISK) $&#60; -o $@</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>setup: setup.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(LD) -Ttext 0x0 -s --oformat binary -e begtext -o $@ $&#60;</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>setup.o: setup.s</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>$(AS) -o $@ $&#60;</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>setup.s: setup.S video.S ...</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(CPP) $(CPPFLAGS) -D__ASSEMBLY__ -traditional $(SVGA_MODE) $(RAMDISK) $&#60; -o $@</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bsetup: bsetup.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(LD) -Ttext 0x0 -s --oformat binary -e begtext -o $@ $&#60;</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bsetup.o: bsetup.s</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
CLASS="command"
>$(AS) -o $@ $&#60;</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bsetup.s: setup.S video.S ...</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(CPP) $(CPPFLAGS) -D__BIG_KERNEL__ -D__ASSEMBLY__ -traditional $(SVGA_MODE) $(RAMDISK) $&#60; -o $@</B
>
</TD
></TR
></TBODY
><TR
><TD
COLSPAN="2"
>Notes:<BR><A
NAME="FTN.AEN287"
>a. </A
>
"$@" means target, "$&#60;" means first prerequisite; Refer to
<A
HREF="http://www.gnu.org/software/make/manual/html_chapter/make_10.html#SEC111"
TARGET="_top"
>&#13; GNU make: Automatic Variables</A
>;
<BR><A
NAME="FTN.AEN294"
>b. </A
>
"--oformat binary" asks for raw binary output,
which is identical to the memory dump of the executable;
Refer to <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_2.html#SEC3"
TARGET="_top"
>Using LD, the GNU linker: Command Line Options</A
>.
<BR></TD
></TR
></TABLE
></DIV
>
Note that it has "-D__BIG_KERNEL__" when compile
<TT
CLASS="filename"
>bootsect.S</TT
> to <TT
CLASS="filename"
>bbootsect.s</TT
>, and
<TT
CLASS="filename"
>setup.S</TT
> to <TT
CLASS="filename"
>bsetup.s</TT
>.
They must be Place Independent Code (PIC), thus what "-Ttext" option is
doesn't matter.
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="i386_boot_compressed_makefile"
></A
>2.5. linux/arch/i386/boot/compressed/Makefile</H2
><P
>&#13; This makefile handles image (de)compression mechanism.
</P
><P
>&#13; It is good to separate (de)compression from bootstrap.
This divide-and-conquer solution allows us to easily improve
(de)compression mechanism or to adopt a new bootstrap method.
</P
><P
>&#13; Directory
<TT
CLASS="filename"
>linux/arch/i386/boot/compressed/</TT
>
contains two source files:
<TT
CLASS="filename"
>head.S</TT
> and <TT
CLASS="filename"
>misc.c</TT
>.
</P
><P
>&#13; <DIV
CLASS="table"
><A
NAME="AEN354"
></A
><P
><B
>Table 4. Targets in linux/arch/i386/boot/compressed/Makefile</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Target</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Command</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>vmlinux<A
NAME="AEN364"
HREF="#FTN.AEN364"
><SPAN
CLASS="footnote"
>[a]</SPAN
></A
>
</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(LD) -Ttext 0x1000 -e startup_32 -o vmlinux head.o misc.o piggy.o</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>bvmlinux</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(LD) -Ttext 0x100000 -e startup_32 -o bvmlinux head.o misc.o piggy.o</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>head.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<B
CLASS="command"
>$(CC) $(AFLAGS) -traditional -c head.S</B
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>misc.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>$(CC) $(CFLAGS) -DKBUILD_BASENAME=$(subst $(comma),_,$(subst -,_,$(*F)))
-c misc.c<A
NAME="AEN382"
HREF="#FTN.AEN382"
><SPAN
CLASS="footnote"
>[b]</SPAN
></A
></PRE
></FONT
></TD
></TR
></TABLE
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>piggy.o</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>tmppiggy=_tmp_$$$$piggy; \
rm -f $$tmppiggy $$tmppiggy.gz $$tmppiggy.lnk; \
$(OBJCOPY) $(SYSTEM) $$tmppiggy; \
gzip -f -9 &#60; $$tmppiggy &#62; $$tmppiggy.gz; \
echo "SECTIONS { .data : { input_len = .; \
LONG(input_data_end - input_data) input_data = .; \
*(.data) input_data_end = .; }}" &#62; $$tmppiggy.lnk; \
$(LD) -r -o piggy.o -b binary $$tmppiggy.gz -b elf32-i386 \
-T $$tmppiggy.lnk; \
rm -f $$tmppiggy $$tmppiggy.gz $$tmppiggy.lnk</PRE
></FONT
></TD
></TR
></TABLE
></TD
></TR
></TBODY
><TR
><TD
COLSPAN="2"
>Notes:<BR><A
NAME="FTN.AEN364"
>a. </A
>
Target <EM
>vmlinux</EM
> here is different from
that defined in <TT
CLASS="filename"
>linux/Makefile</TT
>;
<BR><A
NAME="FTN.AEN382"
>b. </A
>"subst" is a MAKE function; Refer to
<A
HREF="http://www.gnu.org/software/make/manual/html_chapter/make_8.html#SEC85"
TARGET="_top"
>GNU make: Functions for String Substitution and Analysis</A
>.
<BR></TD
></TR
></TABLE
></DIV
>
</P
><P
>&#13; <TT
CLASS="filename"
>piggy.o</TT
> contains
variable <EM
>input_len</EM
>
and gzipped <TT
CLASS="filename"
>linux/vmlinux</TT
>.
<EM
>input_len</EM
> is at the beginning of
<TT
CLASS="filename"
>piggy.o</TT
>, and it is equal to the size of
<TT
CLASS="filename"
>piggy.o</TT
> excluding
<EM
>input_len</EM
> itself. Refer to
<A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/html_chapter/ld_3.html#SEC20"
TARGET="_top"
>&#13; Using LD, the GNU linker: Section Data Expressions</A
>
for "LONG(expression)" in <EM
>piggy.o</EM
> linker script.
</P
><P
>&#13; To be exact, it is not <TT
CLASS="filename"
>linux/vmlinux</TT
> itself
(in ELF format) that is gzipped but its binary image,
which is generated by <B
CLASS="command"
>objcopy</B
> command.
Note that $(OBJCOPY) has been redefined by
<TT
CLASS="filename"
>linux/arch/i386/Makefile</TT
> in
<A
HREF="makefiles.html#i386_makefile"
>Section 2.3</A
> to output raw binary
using "-O binary" option.
</P
><P
>&#13; When linking {<EM
>bootsect, setup</EM
>} or
{<EM
>bbootsect, bsetup</EM
>}, $(LD) specifies
"--oformat binary" option to output them in binary format.
When making <EM
>zImage</EM
> (or <EM
>bzImage</EM
>),
$(OBJCOPY) generates an intermediate binary output from
<EM
>compressed/vmlinux</EM
>
(or <EM
>compressed/bvmlinux</EM
>) too.
It is vital that all components in <EM
>zImage</EM
> or
<EM
>bzImage</EM
> are in raw binary format,
so that the image can run by itself without asking a loader
to load and relocate it.
</P
><P
>&#13; Both <EM
>vmlinux</EM
> and <EM
>bvmlinux</EM
>
prepend <TT
CLASS="filename"
>head.o</TT
> and <TT
CLASS="filename"
>misc.o</TT
>
before <TT
CLASS="filename"
>piggy.o</TT
>,
but they are linked against different start addresses (0x1000 vs 0x100000).
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="i386_tools_build.c"
></A
>2.6. linux/arch/i386/tools/build.c</H2
><P
>&#13; <TT
CLASS="filename"
>linux/arch/i386/tools/build.c</TT
> is a host utility to
generate <EM
>zImage</EM
> or <EM
>bzImage</EM
>.
</P
><P
>&#13; In <TT
CLASS="filename"
>linux/arch/i386/boot/Makefile</TT
>:
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="screen"
>tools/build bootsect setup compressed/vmlinux.out $(ROOT_DEV) &#62; zImage
tools/build -b bbootsect bsetup compressed/bvmlinux.out $(ROOT_DEV) &#62; bzImage</PRE
></FONT
></TD
></TR
></TABLE
>
"-b" means is_big_kernel, used to check whether system image is too big.
</P
><P
>&#13; <B
CLASS="command"
>tools/build</B
> outputs the following components
to stdout, which is redirected to <EM
>zImage</EM
>
or <EM
>bzImage</EM
>:
<P
></P
><OL
TYPE="1"
><LI
><P
>bootsect or bbootsect: from
<TT
CLASS="filename"
>linux/arch/i386/boot/bootsect.S</TT
>, 512 bytes;
</P
></LI
><LI
><P
>setup or bsetup: from
<TT
CLASS="filename"
>linux/arch/i386/boot/setup.S</TT
>,
4 sectors or more, sector aligned;
</P
></LI
><LI
><P
>compressed/vmlinux.out or compressed/bvmlinux.out, including:
<P
></P
><OL
TYPE="a"
><LI
><P
>head.o: from
<TT
CLASS="filename"
>linux/arch/i386/boot/compressed/head.S</TT
>;
</P
></LI
><LI
><P
>misc.o: from
<TT
CLASS="filename"
>linux/arch/i386/boot/compressed/misc.c</TT
>;
</P
></LI
><LI
><P
>piggy.o: from <EM
>input_len</EM
>
and gzipped <TT
CLASS="filename"
>linux/vmlinux</TT
>.</P
></LI
></OL
>
</P
></LI
></OL
>
</P
><P
>&#13; <B
CLASS="command"
>tools/build</B
> will change some contents
of <EM
>bootsect</EM
> or <EM
>bbootsect</EM
>
when outputting to stdout:
<DIV
CLASS="table"
><A
NAME="AEN456"
></A
><P
><B
>Table 5. Modification made by tools/build</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Offset</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Byte</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Variable</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Comment</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1F1 (497)</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>setup_sectors</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>number of setup sectors, &#62;=4</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1F4 (500)</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>2</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>sys_size</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>system size in 16-bytes, little-endian</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1FC (508)</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>minor_root</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>root dev minor</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1FD (509)</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>1</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>major_root</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>root dev major</TD
></TR
></TBODY
></TABLE
></DIV
>
</P
><P
>&#13; In the following chapters, compressed/vmlinux will be referred as
<EM
>vmlinux</EM
> and compressed/bvmlinux as
<EM
>bvmlinux</EM
>, if not confusing.
</P
></DIV
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="makefile_ref"
></A
>2.7. Reference</H2
><P
>&#13; <P
></P
><UL
><LI
><P
>Linux Kernel Makefiles:
<TT
CLASS="filename"
>linux/Documentation/kbuild/makefiles.txt</TT
></P
></LI
><LI
><P
><A
HREF="http://tldp.org/HOWTO/Kernel-HOWTO/"
TARGET="_top"
>&#13; The Linux Kernel HOWTO</A
></P
></LI
><LI
><P
><A
HREF="http://www.gnu.org/software/make/manual/"
TARGET="_top"
>&#13; GNU make</A
></P
></LI
><LI
><P
>&#13; <A
HREF="http://www.gnu.org/software/binutils/manual/ld-2.9.1/"
TARGET="_top"
>&#13; Using LD, the GNU linker</A
>
</P
></LI
><LI
><P
>&#13; <A
HREF="http://www.gnu.org/software/binutils/manual/"
TARGET="_top"
>&#13; GNU Binary Utilities</A
>
</P
></LI
><LI
><P
><A
HREF="http://www.gnu.org/software/bash/manual/"
TARGET="_top"
>&#13; GNU Bash</A
></P
></LI
></UL
>
</P
></DIV
></DIV
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