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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

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  27. <title>File layout (Untitled Document)</title>

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  70. 

  71. <body lang="en">

  72. <a name="File-layout"></a>

  73. <div class="header">

  74. <p>

  75. Next: <a href="Symbol_002dtable.html#Symbol_002dtable" accesskey="n" rel="next">Symbol-table</a>, Previous: <a href="mmo.html#mmo" accesskey="p" rel="prev">mmo</a>, Up: <a href="mmo.html#mmo" accesskey="u" rel="up">mmo</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-Index" title="Index" rel="index">Index</a>]</p>

  76. </div>

  77. <hr>

  78. <a name="File-layout-2"></a>

  79. <h4 class="subsection">3.5.1 File layout</h4>

  80. <p>The mmo file contents is not partitioned into named sections as

  81. with e.g. ELF.  Memory areas is formed by specifying the

  82. location of the data that follows.  Only the memory area

  83. &lsquo;<samp>0x0000&hellip;00</samp>&rsquo; to &lsquo;<samp>0x01ff&hellip;ff</samp>&rsquo; is executable, so

  84. it is used for code (and constants) and the area

  85. &lsquo;<samp>0x2000&hellip;00</samp>&rsquo; to &lsquo;<samp>0x20ff&hellip;ff</samp>&rsquo; is used for

  86. writable data.  See <a href="mmo-section-mapping.html#mmo-section-mapping">mmo section mapping</a>.

  87. </p>

  88. <p>There is provision for specifying &ldquo;special data&rdquo; of 65536

  89. different types.  We use type 80 (decimal), arbitrarily chosen the

  90. same as the ELF <code>e_machine</code> number for MMIX, filling it with

  91. section information normally found in ELF objects. See <a href="mmo-section-mapping.html#mmo-section-mapping">mmo section mapping</a>.

  92. </p>

  93. <p>Contents is entered as 32-bit words, xor:ed over previous

  94. contents, always zero-initialized.  A word that starts with the

  95. byte &lsquo;<samp>0x98</samp>&rsquo; forms a command called a &lsquo;<samp>lopcode</samp>&rsquo;, where

  96. the next byte distinguished between the thirteen lopcodes.  The

  97. two remaining bytes, called the &lsquo;<samp>Y</samp>&rsquo; and &lsquo;<samp>Z</samp>&rsquo; fields, or

  98. the &lsquo;<samp>YZ</samp>&rsquo; field (a 16-bit big-endian number), are used for

  99. various purposes different for each lopcode.  As documented in

  100. <a href="http://mmix.cs.hm.edu/doc/mmixal.pdf">http://mmix.cs.hm.edu/doc/mmixal.pdf</a>,

  101. the lopcodes are:

  102. </p>

  103. <dl compact="compact">

  104. <dt><code>lop_quote</code></dt>

  105. <dd><p>0x98000001.  The next word is contents, regardless of whether it

  106. starts with 0x98 or not.

  107. </p>

  108. </dd>

  109. <dt><code>lop_loc</code></dt>

  110. <dd><p>0x9801YYZZ, where &lsquo;<samp>Z</samp>&rsquo; is 1 or 2.  This is a location

  111. directive, setting the location for the next data to the next

  112. 32-bit word (for <em>Z = 1</em>) or 64-bit word (for <em>Z = 2</em>),

  113. plus <em>Y * 2^56</em>.  Normally &lsquo;<samp>Y</samp>&rsquo; is 0 for the text segment

  114. and 2 for the data segment.  Beware that the low bits of non-

  115. tetrabyte-aligned values are silently discarded when being

  116. automatically incremented and when storing contents (in contrast

  117. to e.g. its use as current location when followed by lop_fixo

  118. et al before the next possibly-quoted tetrabyte contents).

  119. </p>

  120. </dd>

  121. <dt><code>lop_skip</code></dt>

  122. <dd><p>0x9802YYZZ.  Increase the current location by &lsquo;<samp>YZ</samp>&rsquo; bytes.

  123. </p>

  124. </dd>

  125. <dt><code>lop_fixo</code></dt>

  126. <dd><p>0x9803YYZZ, where &lsquo;<samp>Z</samp>&rsquo; is 1 or 2.  Store the current location

  127. as 64 bits into the location pointed to by the next 32-bit

  128. (<em>Z = 1</em>) or 64-bit (<em>Z = 2</em>) word, plus <em>Y *

  129. 2^56</em>.

  130. </p>

  131. </dd>

  132. <dt><code>lop_fixr</code></dt>

  133. <dd><p>0x9804YYZZ.  &lsquo;<samp>YZ</samp>&rsquo; is stored into the current location plus

  134. <em>2 - 4 * YZ</em>.

  135. </p>

  136. </dd>

  137. <dt><code>lop_fixrx</code></dt>

  138. <dd><p>0x980500ZZ.  &lsquo;<samp>Z</samp>&rsquo; is 16 or 24.  A value &lsquo;<samp>L</samp>&rsquo; derived from

  139. the following 32-bit word are used in a manner similar to

  140. &lsquo;<samp>YZ</samp>&rsquo; in lop_fixr: it is xor:ed into the current location

  141. minus <em>4 * L</em>.  The first byte of the word is 0 or 1.  If it

  142. is 1, then <em>L = (<var>lowest 24 bits of word</var>) - 2^Z</em>, if 0,

  143. then <em>L = (<var>lowest 24 bits of word</var>)</em>.

  144. </p>

  145. </dd>

  146. <dt><code>lop_file</code></dt>

  147. <dd><p>0x9806YYZZ.  &lsquo;<samp>Y</samp>&rsquo; is the file number, &lsquo;<samp>Z</samp>&rsquo; is count of

  148. 32-bit words.  Set the file number to &lsquo;<samp>Y</samp>&rsquo; and the line

  149. counter to 0.  The next <em>Z * 4</em> bytes contain the file name,

  150. padded with zeros if the count is not a multiple of four.  The

  151. same &lsquo;<samp>Y</samp>&rsquo; may occur multiple times, but &lsquo;<samp>Z</samp>&rsquo; must be 0 for

  152. all but the first occurrence.

  153. </p>

  154. </dd>

  155. <dt><code>lop_line</code></dt>

  156. <dd><p>0x9807YYZZ.  &lsquo;<samp>YZ</samp>&rsquo; is the line number.  Together with

  157. lop_file, it forms the source location for the next 32-bit word.

  158. Note that for each non-lopcode 32-bit word, line numbers are

  159. assumed incremented by one.

  160. </p>

  161. </dd>

  162. <dt><code>lop_spec</code></dt>

  163. <dd><p>0x9808YYZZ.  &lsquo;<samp>YZ</samp>&rsquo; is the type number.  Data until the next

  164. lopcode other than lop_quote forms special data of type &lsquo;<samp>YZ</samp>&rsquo;.

  165. See <a href="mmo-section-mapping.html#mmo-section-mapping">mmo section mapping</a>.

  166. </p>

  167. <p>Other types than 80, (or type 80 with a content that does not

  168. parse) is stored in sections named <code>.MMIX.spec_data.<var>n</var></code>

  169. where <var>n</var> is the &lsquo;<samp>YZ</samp>&rsquo;-type.  The flags for such a

  170. sections say not to allocate or load the data.  The vma is 0.

  171. Contents of multiple occurrences of special data <var>n</var> is

  172. concatenated to the data of the previous lop_spec <var>n</var>s.  The

  173. location in data or code at which the lop_spec occurred is lost.

  174. </p>

  175. </dd>

  176. <dt><code>lop_pre</code></dt>

  177. <dd><p>0x980901ZZ.  The first lopcode in a file.  The &lsquo;<samp>Z</samp>&rsquo; field forms the

  178. length of header information in 32-bit words, where the first word

  179. tells the time in seconds since &lsquo;<samp>00:00:00 GMT Jan 1 1970</samp>&rsquo;.

  180. </p>

  181. </dd>

  182. <dt><code>lop_post</code></dt>

  183. <dd><p>0x980a00ZZ.  <em>Z &gt; 32</em>.  This lopcode follows after all

  184. content-generating lopcodes in a program.  The &lsquo;<samp>Z</samp>&rsquo; field

  185. denotes the value of &lsquo;<samp>rG</samp>&rsquo; at the beginning of the program.

  186. The following <em>256 - Z</em> big-endian 64-bit words are loaded

  187. into global registers &lsquo;<samp>$G</samp>&rsquo; &hellip; &lsquo;<samp>$255</samp>&rsquo;.

  188. </p>

  189. </dd>

  190. <dt><code>lop_stab</code></dt>

  191. <dd><p>0x980b0000.  The next-to-last lopcode in a program.  Must follow

  192. immediately after the lop_post lopcode and its data.  After this

  193. lopcode follows all symbols in a compressed format

  194. (see <a href="Symbol_002dtable.html#Symbol_002dtable">Symbol-table</a>).

  195. </p>

  196. </dd>

  197. <dt><code>lop_end</code></dt>

  198. <dd><p>0x980cYYZZ.  The last lopcode in a program.  It must follow the

  199. lop_stab lopcode and its data.  The &lsquo;<samp>YZ</samp>&rsquo; field contains the

  200. number of 32-bit words of symbol table information after the

  201. preceding lop_stab lopcode.

  202. </p></dd>

  203. </dl>

  204. 

  205. <p>Note that the lopcode &quot;fixups&quot;; <code>lop_fixr</code>, <code>lop_fixrx</code> and

  206. <code>lop_fixo</code> are not generated by BFD, but are handled.  They are

  207. generated by <code>mmixal</code>.

  208. </p>

  209. <p>This trivial one-label, one-instruction file:

  210. </p>

  211. <div class="example">

  212. <pre class="example"> :Main TRAP 1,2,3

  213. </pre></div>

  214. 

  215. <p>can be represented this way in mmo:

  216. </p>

  217. <div class="example">

  218. <pre class="example"> 0x98090101 - lop_pre, one 32-bit word with timestamp.

  219.  &lt;timestamp&gt;

  220.  0x98010002 - lop_loc, text segment, using a 64-bit address.

  221.               Note that mmixal does not emit this for the file above.

  222.  0x00000000 - Address, high 32 bits.

  223.  0x00000000 - Address, low 32 bits.

  224.  0x98060002 - lop_file, 2 32-bit words for file-name.

  225.  0x74657374 - &quot;test&quot;

  226.  0x2e730000 - &quot;.s\0\0&quot;

  227.  0x98070001 - lop_line, line 1.

  228.  0x00010203 - TRAP 1,2,3

  229.  0x980a00ff - lop_post, setting $255 to 0.

  230.  0x00000000

  231.  0x00000000

  232.  0x980b0000 - lop_stab for &quot;:Main&quot; = 0, serial 1.

  233.  0x203a4040   See <a href="Symbol_002dtable.html#Symbol_002dtable">Symbol-table</a>.

  234.  0x10404020

  235.  0x4d206120

  236.  0x69016e00

  237.  0x81000000

  238.  0x980c0005 - lop_end; symbol table contained five 32-bit words.

  239. </pre></div>

  240. <hr>

  241. <div class="header">

  242. <p>

  243. Next: <a href="Symbol_002dtable.html#Symbol_002dtable" accesskey="n" rel="next">Symbol-table</a>, Previous: <a href="mmo.html#mmo" accesskey="p" rel="prev">mmo</a>, Up: <a href="mmo.html#mmo" accesskey="u" rel="up">mmo</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="BFD-Index.html#BFD-Index" title="Index" rel="index">Index</a>]</p>

  244. </div>

  245. 

  246. 

  247. 

  248. </body>

  249. </html>