<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
<html>
|
<!-- This file documents the BFD library.
|
|
Copyright (C) 1991-2016 Free Software Foundation, Inc.
|
|
Permission is granted to copy, distribute and/or modify this document
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
any later version published by the Free Software Foundation; with the
|
Invariant Sections being "GNU General Public License" and "Funding
|
Free Software", the Front-Cover texts being (a) (see below), and with
|
the Back-Cover Texts being (b) (see below). A copy of the license is
|
included in the section entitled "GNU Free Documentation License".
|
|
(a) The FSF's Front-Cover Text is:
|
|
A GNU Manual
|
|
(b) The FSF's Back-Cover Text is:
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
software. Copies published by the Free Software Foundation raise
|
funds for GNU development. -->
|
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
|
<head>
|
<title>Untitled Document: File layout</title>
|
|
<meta name="description" content="Untitled Document: File layout">
|
<meta name="keywords" content="Untitled Document: File layout">
|
<meta name="resource-type" content="document">
|
<meta name="distribution" content="global">
|
<meta name="Generator" content="makeinfo">
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
<link href="index.html#Top" rel="start" title="Top">
|
<link href="BFD-Index.html#BFD-Index" rel="index" title="BFD Index">
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
<link href="mmo.html#mmo" rel="up" title="mmo">
|
<link href="Symbol_002dtable.html#Symbol_002dtable" rel="next" title="Symbol-table">
|
<link href="mmo.html#mmo" rel="prev" title="mmo">
|
<style type="text/css">
|
<!--
|
a.summary-letter {text-decoration: none}
|
blockquote.smallquotation {font-size: smaller}
|
div.display {margin-left: 3.2em}
|
div.example {margin-left: 3.2em}
|
div.indentedblock {margin-left: 3.2em}
|
div.lisp {margin-left: 3.2em}
|
div.smalldisplay {margin-left: 3.2em}
|
div.smallexample {margin-left: 3.2em}
|
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
|
div.smalllisp {margin-left: 3.2em}
|
kbd {font-style:oblique}
|
pre.display {font-family: inherit}
|
pre.format {font-family: inherit}
|
pre.menu-comment {font-family: serif}
|
pre.menu-preformatted {font-family: serif}
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
pre.smallexample {font-size: smaller}
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
pre.smalllisp {font-size: smaller}
|
span.nocodebreak {white-space:nowrap}
|
span.nolinebreak {white-space:nowrap}
|
span.roman {font-family:serif; font-weight:normal}
|
span.sansserif {font-family:sans-serif; font-weight:normal}
|
ul.no-bullet {list-style: none}
|
-->
|
</style>
|
|
|
</head>
|
|
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
|
<a name="File-layout"></a>
|
<div class="header">
|
<p>
|
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> [<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>
|
</div>
|
<hr>
|
<a name="File-layout-2"></a>
|
<h4 class="subsection">3.5.1 File layout</h4>
|
<p>The mmo file contents is not partitioned into named sections as
|
with e.g. ELF. Memory areas is formed by specifying the
|
location of the data that follows. Only the memory area
|
‘<samp>0x0000…00</samp>’ to ‘<samp>0x01ff…ff</samp>’ is executable, so
|
it is used for code (and constants) and the area
|
‘<samp>0x2000…00</samp>’ to ‘<samp>0x20ff…ff</samp>’ is used for
|
writable data. See <a href="mmo-section-mapping.html#mmo-section-mapping">mmo section mapping</a>.
|
</p>
|
<p>There is provision for specifying “special data” of 65536
|
different types. We use type 80 (decimal), arbitrarily chosen the
|
same as the ELF <code>e_machine</code> number for MMIX, filling it with
|
section information normally found in ELF objects. See <a href="mmo-section-mapping.html#mmo-section-mapping">mmo section mapping</a>.
|
</p>
|
<p>Contents is entered as 32-bit words, xor:ed over previous
|
contents, always zero-initialized. A word that starts with the
|
byte ‘<samp>0x98</samp>’ forms a command called a ‘<samp>lopcode</samp>’, where
|
the next byte distinguished between the thirteen lopcodes. The
|
two remaining bytes, called the ‘<samp>Y</samp>’ and ‘<samp>Z</samp>’ fields, or
|
the ‘<samp>YZ</samp>’ field (a 16-bit big-endian number), are used for
|
various purposes different for each lopcode. As documented in
|
<a href="http://mmix.cs.hm.edu/doc/mmixal.pdf">http://mmix.cs.hm.edu/doc/mmixal.pdf</a>,
|
the lopcodes are:
|
</p>
|
<dl compact="compact">
|
<dt><code>lop_quote</code></dt>
|
<dd><p>0x98000001. The next word is contents, regardless of whether it
|
starts with 0x98 or not.
|
</p>
|
</dd>
|
<dt><code>lop_loc</code></dt>
|
<dd><p>0x9801YYZZ, where ‘<samp>Z</samp>’ is 1 or 2. This is a location
|
directive, setting the location for the next data to the next
|
32-bit word (for <em>Z = 1</em>) or 64-bit word (for <em>Z = 2</em>),
|
plus <em>Y * 2^56</em>. Normally ‘<samp>Y</samp>’ is 0 for the text segment
|
and 2 for the data segment. Beware that the low bits of non-
|
tetrabyte-aligned values are silently discarded when being
|
automatically incremented and when storing contents (in contrast
|
to e.g. its use as current location when followed by lop_fixo
|
et al before the next possibly-quoted tetrabyte contents).
|
</p>
|
</dd>
|
<dt><code>lop_skip</code></dt>
|
<dd><p>0x9802YYZZ. Increase the current location by ‘<samp>YZ</samp>’ bytes.
|
</p>
|
</dd>
|
<dt><code>lop_fixo</code></dt>
|
<dd><p>0x9803YYZZ, where ‘<samp>Z</samp>’ is 1 or 2. Store the current location
|
as 64 bits into the location pointed to by the next 32-bit
|
(<em>Z = 1</em>) or 64-bit (<em>Z = 2</em>) word, plus <em>Y *
|
2^56</em>.
|
</p>
|
</dd>
|
<dt><code>lop_fixr</code></dt>
|
<dd><p>0x9804YYZZ. ‘<samp>YZ</samp>’ is stored into the current location plus
|
<em>2 - 4 * YZ</em>.
|
</p>
|
</dd>
|
<dt><code>lop_fixrx</code></dt>
|
<dd><p>0x980500ZZ. ‘<samp>Z</samp>’ is 16 or 24. A value ‘<samp>L</samp>’ derived from
|
the following 32-bit word are used in a manner similar to
|
‘<samp>YZ</samp>’ in lop_fixr: it is xor:ed into the current location
|
minus <em>4 * L</em>. The first byte of the word is 0 or 1. If it
|
is 1, then <em>L = (<var>lowest 24 bits of word</var>) - 2^Z</em>, if 0,
|
then <em>L = (<var>lowest 24 bits of word</var>)</em>.
|
</p>
|
</dd>
|
<dt><code>lop_file</code></dt>
|
<dd><p>0x9806YYZZ. ‘<samp>Y</samp>’ is the file number, ‘<samp>Z</samp>’ is count of
|
32-bit words. Set the file number to ‘<samp>Y</samp>’ and the line
|
counter to 0. The next <em>Z * 4</em> bytes contain the file name,
|
padded with zeros if the count is not a multiple of four. The
|
same ‘<samp>Y</samp>’ may occur multiple times, but ‘<samp>Z</samp>’ must be 0 for
|
all but the first occurrence.
|
</p>
|
</dd>
|
<dt><code>lop_line</code></dt>
|
<dd><p>0x9807YYZZ. ‘<samp>YZ</samp>’ is the line number. Together with
|
lop_file, it forms the source location for the next 32-bit word.
|
Note that for each non-lopcode 32-bit word, line numbers are
|
assumed incremented by one.
|
</p>
|
</dd>
|
<dt><code>lop_spec</code></dt>
|
<dd><p>0x9808YYZZ. ‘<samp>YZ</samp>’ is the type number. Data until the next
|
lopcode other than lop_quote forms special data of type ‘<samp>YZ</samp>’.
|
See <a href="mmo-section-mapping.html#mmo-section-mapping">mmo section mapping</a>.
|
</p>
|
<p>Other types than 80, (or type 80 with a content that does not
|
parse) is stored in sections named <code>.MMIX.spec_data.<var>n</var></code>
|
where <var>n</var> is the ‘<samp>YZ</samp>’-type. The flags for such a
|
sections say not to allocate or load the data. The vma is 0.
|
Contents of multiple occurrences of special data <var>n</var> is
|
concatenated to the data of the previous lop_spec <var>n</var>s. The
|
location in data or code at which the lop_spec occurred is lost.
|
</p>
|
</dd>
|
<dt><code>lop_pre</code></dt>
|
<dd><p>0x980901ZZ. The first lopcode in a file. The ‘<samp>Z</samp>’ field forms the
|
length of header information in 32-bit words, where the first word
|
tells the time in seconds since ‘<samp>00:00:00 GMT Jan 1 1970</samp>’.
|
</p>
|
</dd>
|
<dt><code>lop_post</code></dt>
|
<dd><p>0x980a00ZZ. <em>Z > 32</em>. This lopcode follows after all
|
content-generating lopcodes in a program. The ‘<samp>Z</samp>’ field
|
denotes the value of ‘<samp>rG</samp>’ at the beginning of the program.
|
The following <em>256 - Z</em> big-endian 64-bit words are loaded
|
into global registers ‘<samp>$G</samp>’ … ‘<samp>$255</samp>’.
|
</p>
|
</dd>
|
<dt><code>lop_stab</code></dt>
|
<dd><p>0x980b0000. The next-to-last lopcode in a program. Must follow
|
immediately after the lop_post lopcode and its data. After this
|
lopcode follows all symbols in a compressed format
|
(see <a href="Symbol_002dtable.html#Symbol_002dtable">Symbol-table</a>).
|
</p>
|
</dd>
|
<dt><code>lop_end</code></dt>
|
<dd><p>0x980cYYZZ. The last lopcode in a program. It must follow the
|
lop_stab lopcode and its data. The ‘<samp>YZ</samp>’ field contains the
|
number of 32-bit words of symbol table information after the
|
preceding lop_stab lopcode.
|
</p></dd>
|
</dl>
|
|
<p>Note that the lopcode "fixups"; <code>lop_fixr</code>, <code>lop_fixrx</code> and
|
<code>lop_fixo</code> are not generated by BFD, but are handled. They are
|
generated by <code>mmixal</code>.
|
</p>
|
<p>This trivial one-label, one-instruction file:
|
</p>
|
<div class="example">
|
<pre class="example"> :Main TRAP 1,2,3
|
</pre></div>
|
|
<p>can be represented this way in mmo:
|
</p>
|
<div class="example">
|
<pre class="example"> 0x98090101 - lop_pre, one 32-bit word with timestamp.
|
<timestamp>
|
0x98010002 - lop_loc, text segment, using a 64-bit address.
|
Note that mmixal does not emit this for the file above.
|
0x00000000 - Address, high 32 bits.
|
0x00000000 - Address, low 32 bits.
|
0x98060002 - lop_file, 2 32-bit words for file-name.
|
0x74657374 - "test"
|
0x2e730000 - ".s\0\0"
|
0x98070001 - lop_line, line 1.
|
0x00010203 - TRAP 1,2,3
|
0x980a00ff - lop_post, setting $255 to 0.
|
0x00000000
|
0x00000000
|
0x980b0000 - lop_stab for ":Main" = 0, serial 1.
|
0x203a4040 See <a href="Symbol_002dtable.html#Symbol_002dtable">Symbol-table</a>.
|
0x10404020
|
0x4d206120
|
0x69016e00
|
0x81000000
|
0x980c0005 - lop_end; symbol table contained five 32-bit words.
|
</pre></div>
|
<hr>
|
<div class="header">
|
<p>
|
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> [<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>
|
</div>
|
|
|
|
</body>
|
</html>
|
