Two pass build for on-demand paging now works

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2896 42af7a65-404d-4744-a932-0658087f49c3

Documentation/NuttxPortingGuide.html

@@ -12,7 +12,7 @@
       <h1><big><font color="#3c34ec">
         <i>NuttX RTOS Porting Guide</i>
       </font></big></h1>
-      <p>Last Updated: August 27, 2010</p>
+      <p>Last Updated: August 29, 2010</p>
     </td>
   </tr>
 </table>
@@ -2178,6 +2178,7 @@ extern void up_ledoff(int led);
     The start address of DRAM (virtual)</li>
 </ul>
 
+<h2>Build Options</h2>
 <p>
   General build options:
 </p>
@@ -2206,9 +2207,9 @@ extern void up_ledoff(int led);
     have been defined in the configurations <code>Make.defs</code> file.
   </li>
 </ul>
-
-<h2>General OS setup</h2>
-
+<p>
+  Building application code:
+</p>
 <ul>
   <li>
     <p>
@@ -2261,6 +2262,38 @@ build
       It can be used, for example, to include makefile fragments (e.g., <code>.config</code> or <code>Make.defs</code>) or to set up include file paths.
     </p>
   </li>
+</ul>
+<p>
+  Two-pass Build Options.
+  If the 2 pass build option is selected, then these options configure the make system build a extra link object.
+  This link object is assumed to be an incremental (relative) link object, but could be a static library (archive)
+  (some modification to this Makefile would be required if CONFIG_PASS1_OBJECT is an archive).
+  Pass 1 1ncremental (relative) link objects should be put into the processor-specific source directory 
+  where other link objects will be created - ff the pass1 obect is an archive, it could	go anywhere.
+</p>
+<ul>
+  <li>
+    <code>CONFIG_BUILD_2PASS</code>:
+      Enables the two pass build options.
+  </li>
+</ul>
+<p>
+  When the two pass build option is enabled, the following also apply:
+</p>
+<ul>
+  <li>
+    <code>CONFIG_PASS1_OBJECT</code>: The name of the first pass object.
+  </li>
+  <li><code>CONFIG_PASS1_BUILDIR</code>:
+  The path, relative to the top NuttX build directory to directory that contains the Makefile to build the first pass object.
+  The Makefile must support the following targets:
+  <ul>
+    <li>The special target <code>arch/$(CONFIG_ARCH)/src/$(CONFIG_PASS1_OBJECT)</code>, and</li>
+    <li>The usual depend, clean, and distclean targets.</li>
+  </ul>
+</ul>
+
+<h2>General OS setup</h2>
   <li>
     <code>CONFIG_DEBUG</code>: enables built-in debug options
   </li>
@@ -2434,7 +2467,8 @@ build
 </ul>
 
 <p>
-  If CONFIG_PAGING is selected, then the following also apply:
+  If CONFIG_PAGING is selected, then you will probabaly need <code>CONFIG_BUILD_2PASS</code> to correctly position
+  the code and the following configuration options also apply:
 </p>
 <ul>
   <li>