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261 lines
11 KiB
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<link rel="up" href="BFD-back-ends.html#BFD-back-ends" title="BFD back ends">
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<link rel="prev" href="What-to-Put-Where.html#What-to-Put-Where" title="What to Put Where">
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<!--
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This file documents the BFD library.
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Copyright (C) 1991, 2000, 2001, 2003, 2006, 2007 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.1 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``GNU General Public License'' and ``Funding
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Free Software'', the Front-Cover texts being (a) (see below), and with
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the Back-Cover Texts being (b) (see below). A copy of the license is
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included in the section entitled ``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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</head>
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<body>
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<div class="node">
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<p>
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<a name="aout"></a>Next: <a rel="next" accesskey="n" href="coff.html#coff">coff</a>,
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Previous: <a rel="previous" accesskey="p" href="What-to-Put-Where.html#What-to-Put-Where">What to Put Where</a>,
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Up: <a rel="up" accesskey="u" href="BFD-back-ends.html#BFD-back-ends">BFD back ends</a>
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<hr><br>
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</div>
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<h3 class="section">3.2 a.out backends</h3>
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<p><strong>Description</strong><br>
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BFD supports a number of different flavours of a.out format,
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though the major differences are only the sizes of the
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structures on disk, and the shape of the relocation
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information.
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<p>The support is split into a basic support file <span class="file">aoutx.h</span>
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and other files which derive functions from the base. One
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derivation file is <span class="file">aoutf1.h</span> (for a.out flavour 1), and
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adds to the basic a.out functions support for sun3, sun4, 386
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and 29k a.out files, to create a target jump vector for a
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specific target.
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<p>This information is further split out into more specific files
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for each machine, including <span class="file">sunos.c</span> for sun3 and sun4,
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<span class="file">newsos3.c</span> for the Sony NEWS, and <span class="file">demo64.c</span> for a
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demonstration of a 64 bit a.out format.
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<p>The base file <span class="file">aoutx.h</span> defines general mechanisms for
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reading and writing records to and from disk and various
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other methods which BFD requires. It is included by
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<span class="file">aout32.c</span> and <span class="file">aout64.c</span> to form the names
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<code>aout_32_swap_exec_header_in</code>, <code>aout_64_swap_exec_header_in</code>, etc.
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<p>As an example, this is what goes on to make the back end for a
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sun4, from <span class="file">aout32.c</span>:
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<pre class="example"> #define ARCH_SIZE 32
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#include "aoutx.h"
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</pre>
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<p>Which exports names:
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<pre class="example"> ...
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aout_32_canonicalize_reloc
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aout_32_find_nearest_line
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aout_32_get_lineno
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aout_32_get_reloc_upper_bound
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...
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</pre>
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<p>from <span class="file">sunos.c</span>:
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<pre class="example"> #define TARGET_NAME "a.out-sunos-big"
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#define VECNAME sunos_big_vec
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#include "aoutf1.h"
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</pre>
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<p>requires all the names from <span class="file">aout32.c</span>, and produces the jump vector
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<pre class="example"> sunos_big_vec
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</pre>
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<p>The file <span class="file">host-aout.c</span> is a special case. It is for a large set
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of hosts that use “more or less standard” a.out files, and
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for which cross-debugging is not interesting. It uses the
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standard 32-bit a.out support routines, but determines the
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file offsets and addresses of the text, data, and BSS
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sections, the machine architecture and machine type, and the
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entry point address, in a host-dependent manner. Once these
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values have been determined, generic code is used to handle
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the object file.
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<p>When porting it to run on a new system, you must supply:
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<pre class="example"> HOST_PAGE_SIZE
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HOST_SEGMENT_SIZE
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HOST_MACHINE_ARCH (optional)
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HOST_MACHINE_MACHINE (optional)
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HOST_TEXT_START_ADDR
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HOST_STACK_END_ADDR
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</pre>
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<p>in the file <span class="file">../include/sys/h-</span><var>XXX</var><span class="file">.h</span> (for your host). These
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values, plus the structures and macros defined in <span class="file">a.out.h</span> on
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your host system, will produce a BFD target that will access
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ordinary a.out files on your host. To configure a new machine
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to use <span class="file">host-aout.c</span>, specify:
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<pre class="example"> TDEFAULTS = -DDEFAULT_VECTOR=host_aout_big_vec
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TDEPFILES= host-aout.o trad-core.o
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</pre>
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<p>in the <span class="file">config/</span><var>XXX</var><span class="file">.mt</span> file, and modify <span class="file">configure.in</span>
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to use the
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<var>XXX</var><span class="file">.mt</span> file (by setting "<code>bfd_target=XXX</code>") when your
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configuration is selected.
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<h4 class="subsection">3.2.1 Relocations</h4>
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<p><strong>Description</strong><br>
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The file <span class="file">aoutx.h</span> provides for both the <em>standard</em>
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and <em>extended</em> forms of a.out relocation records.
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<p>The standard records contain only an
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address, a symbol index, and a type field. The extended records
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(used on 29ks and sparcs) also have a full integer for an
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addend.
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<h4 class="subsection">3.2.2 Internal entry points</h4>
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<p><strong>Description</strong><br>
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<span class="file">aoutx.h</span> exports several routines for accessing the
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contents of an a.out file, which are gathered and exported in
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turn by various format specific files (eg sunos.c).
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fswap_005fexec_005fheader_005fin-1390"></a>
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<h5 class="subsubsection">3.2.2.1 <code>aout_</code><var>size</var><code>_swap_exec_header_in</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> void aout_<var>size</var>_swap_exec_header_in,
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(bfd *abfd,
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struct external_exec *bytes,
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struct internal_exec *execp);
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</pre>
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<p><strong>Description</strong><br>
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Swap the information in an executable header <var>raw_bytes</var> taken
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from a raw byte stream memory image into the internal exec header
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structure <var>execp</var>.
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fswap_005fexec_005fheader_005fout-1391"></a>
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<h5 class="subsubsection">3.2.2.2 <code>aout_</code><var>size</var><code>_swap_exec_header_out</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> void aout_<var>size</var>_swap_exec_header_out
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(bfd *abfd,
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struct internal_exec *execp,
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struct external_exec *raw_bytes);
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</pre>
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<p><strong>Description</strong><br>
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Swap the information in an internal exec header structure
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<var>execp</var> into the buffer <var>raw_bytes</var> ready for writing to disk.
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fsome_005faout_005fobject_005fp-1392"></a>
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<h5 class="subsubsection">3.2.2.3 <code>aout_</code><var>size</var><code>_some_aout_object_p</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> const bfd_target *aout_<var>size</var>_some_aout_object_p
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(bfd *abfd,
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struct internal_exec *execp,
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const bfd_target *(*callback_to_real_object_p) (bfd *));
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</pre>
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<p><strong>Description</strong><br>
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Some a.out variant thinks that the file open in <var>abfd</var>
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checking is an a.out file. Do some more checking, and set up
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for access if it really is. Call back to the calling
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environment's "finish up" function just before returning, to
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handle any last-minute setup.
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fmkobject-1393"></a>
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<h5 class="subsubsection">3.2.2.4 <code>aout_</code><var>size</var><code>_mkobject</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> bfd_boolean aout_<var>size</var>_mkobject, (bfd *abfd);
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</pre>
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<p><strong>Description</strong><br>
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Initialize BFD <var>abfd</var> for use with a.out files.
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fmachine_005ftype-1394"></a>
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<h5 class="subsubsection">3.2.2.5 <code>aout_</code><var>size</var><code>_machine_type</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> enum machine_type aout_<var>size</var>_machine_type
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(enum bfd_architecture arch,
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unsigned long machine,
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bfd_boolean *unknown);
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</pre>
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<p><strong>Description</strong><br>
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Keep track of machine architecture and machine type for
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a.out's. Return the <code>machine_type</code> for a particular
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architecture and machine, or <code>M_UNKNOWN</code> if that exact architecture
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and machine can't be represented in a.out format.
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<p>If the architecture is understood, machine type 0 (default)
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is always understood.
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fset_005farch_005fmach-1395"></a>
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<h5 class="subsubsection">3.2.2.6 <code>aout_</code><var>size</var><code>_set_arch_mach</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> bfd_boolean aout_<var>size</var>_set_arch_mach,
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(bfd *,
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enum bfd_architecture arch,
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unsigned long machine);
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</pre>
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<p><strong>Description</strong><br>
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Set the architecture and the machine of the BFD <var>abfd</var> to the
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values <var>arch</var> and <var>machine</var>. Verify that <var>abfd</var>'s format
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can support the architecture required.
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<p><a name="index-aout_005f_0040var_007bsize_007d_005fnew_005fsection_005fhook-1396"></a>
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<h5 class="subsubsection">3.2.2.7 <code>aout_</code><var>size</var><code>_new_section_hook</code></h5>
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<p><strong>Synopsis</strong>
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<pre class="example"> bfd_boolean aout_<var>size</var>_new_section_hook,
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(bfd *abfd,
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asection *newsect);
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</pre>
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<p><strong>Description</strong><br>
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Called by the BFD in response to a <code>bfd_make_section</code>
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request.
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</body></html>
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