Sophie: howto-html-en-20080722-2mdv2010.1 noarch

howto-html-en-20080722-2mdv2010.1.noarch.rpm

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><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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