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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Modifying the Memory Layout</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos User Guide" HREF="ecos-user-guide.html"><LINK REL="UP" TITLE="Manual Configuration" HREF="manual-configuration.html"><LINK REL="PREVIOUS" TITLE="Editing the Sources" HREF="editing-the-sources.html"><LINK REL="NEXT" TITLE="Managing the Package Repository" HREF="managing-package-repository.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >eCos User Guide</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="editing-the-sources.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 28. Manual Configuration</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="managing-package-repository.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="MODIFYING-THE-MEMORY-LAYOUT">Modifying the Memory Layout</H1 ><P >Each <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > platform package is supplied with linker script fragments which describe the location of memory regions on the evaluation board and the location of memory sections within these regions. The correct linker script fragment is selected and included in the <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > linker script <TT CLASS="FILENAME" >target.ld</TT > when <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > is built.</P ><P >It is not necessary to modify the default memory layouts in order to start development with <SPAN CLASS="PRODUCTNAME" >eCos</SPAN >. However, it will be necessary to edit a linker script fragment when the memory map of the evaluation board is changed. For example, if additional memory is added, the linker must be notified that the new memory is available for use. As a minimum, this would involve modifying the length of the corresponding memory region. Where the available memory is non-contiguous, it may be necessary to declare a new memory region and reassign certain linker output sections to the new region.</P ><P >Linker script fragments and memory layout header files should be edited within the <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > install tree. They are located at <TT CLASS="FILENAME" >include/pkgconf/mlt_*.*</TT >. Where multiple start-up types are in use, it will be necessary to edit multiple linker script fragments and header files. The information provided in the header file and the corresponding linker script fragment must always match. A typical linker script fragment is shown below:</P ><DIV CLASS="EXAMPLE" ><A NAME="AEN2992"><P ><B >Example 28-1. <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > linker script fragment</B ></P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" >MEMORY { rom : ORIGIN = 0x40000000, LENGTH = 0x80000 ram : ORIGIN = 0x48000000, LENGTH = 0x200000 } SECTIONS { SECTIONS_BEGIN SECTION_rom_vectors (rom, 0x40000000, LMA_EQ_VMA) SECTION_text (rom, ALIGN (0x1), LMA_EQ_VMA) SECTION_fini (rom, ALIGN (0x1), LMA_EQ_VMA) SECTION_rodata (rom, ALIGN (0x1), LMA_EQ_VMA) SECTION_rodata1 (rom, ALIGN (0x1), LMA_EQ_VMA) SECTION_fixup (rom, ALIGN (0x1), LMA_EQ_VMA) SECTION_gcc_except_table (rom, ALIGN (0x1), LMA_EQ_VMA) SECTION_data (ram, 0x48000000, FOLLOWING (.gcc_except_table)) SECTION_bss (ram, ALIGN (0x4), LMA_EQ_VMA) SECTIONS_END }</PRE ></TD ></TR ></TABLE ></DIV ><P >The file consists of two blocks, the <TT CLASS="LITERAL" >MEMORY</TT > block contains lines describing the address (<TT CLASS="LITERAL" >ORIGIN</TT >) and the size (<TT CLASS="LITERAL" >LENGTH</TT >) of each memory region. The <TT CLASS="LITERAL" >MEMORY</TT > block is followed by the <TT CLASS="LITERAL" >SECTIONS</TT > block which contains lines describing each of the linker output sections. Each section is represented by a macro call. The arguments of these macros are ordered as follows: </P ><P ></P ><OL TYPE="1" ><LI ><P >The memory region in which the section will finally reside.</P ></LI ><LI ><P >The final address ( <TT CLASS="LITERAL" >VMA</TT > ) of the section. This is expressed using one of the following forms:</P ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT ><SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >n</I ></SPAN ></DT ><DD ><P >at the absolute address specified by the unsigned integer <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >n</I ></SPAN ></P ></DD ><DT >ALIGN (<SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >n</I ></SPAN >)</DT ><DD ><P >following the final location of the previous section with alignment to the next <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >n</I ></SPAN >-byte boundary</P ></DD ></DL ></DIV ></LI ><LI ><P >The initial address (<TT CLASS="LITERAL" >LMA</TT >) of the section. This is expressed using one of the following forms:</P ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT >LMA_EQ_VMA</DT ><DD ><P >the <TT CLASS="LITERAL" >LMA</TT > equals the <TT CLASS="LITERAL" >VMA</TT > (no relocation)</P ></DD ><DT >AT (<SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >n</I ></SPAN >)</DT ><DD ><P >at the absolute address specified by the unsigned integer <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >n</I ></SPAN ></P ></DD ><DT >FOLLOWING (.<SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >name</I ></SPAN >)</DT ><DD ><P >following the initial location of section <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >name</I ></SPAN ></P ></DD ></DL ></DIV ></LI ></OL ><P >In order to maintain compatibility with linker script fragments and header files exported by the <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > <SPAN CLASS="APPLICATION" >Configuration Tool</SPAN >, the use of other expressions within these files is not recommended.</P ><P >Note that the names of the linker output sections will vary between target architectures. A description of these sections can be found in the specific <SPAN CLASS="PRODUCTNAME" >GCC</SPAN > documentation for your architecture.</P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="editing-the-sources.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-user-guide.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="managing-package-repository.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Editing the Sources</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="manual-configuration.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Managing the Package Repository</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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