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| <a name="aout"></a> |
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| Next: <a href="coff.html#coff" accesskey="n" rel="next">coff</a>, Previous: <a href="What-to-Put-Where.html#What-to-Put-Where" accesskey="p" rel="prev">What to Put Where</a>, Up: <a href="BFD-back-ends.html#BFD-back-ends" accesskey="u" rel="up">BFD back ends</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> |
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| <hr> |
| <a name="a_002eout-backends"></a> |
| <h3 class="section">3.2 a.out backends</h3> |
| |
| |
| <p><strong>Description</strong><br> |
| BFD supports a number of different flavours of a.out format, |
| though the major differences are only the sizes of the |
| structures on disk, and the shape of the relocation |
| information. |
| </p> |
| <p>The support is split into a basic support file <samp>aoutx.h</samp> |
| and other files which derive functions from the base. One |
| derivation file is <samp>aoutf1.h</samp> (for a.out flavour 1), and |
| adds to the basic a.out functions support for sun3, sun4, 386 |
| and 29k a.out files, to create a target jump vector for a |
| specific target. |
| </p> |
| <p>This information is further split out into more specific files |
| for each machine, including <samp>sunos.c</samp> for sun3 and sun4, |
| <samp>newsos3.c</samp> for the Sony NEWS, and <samp>demo64.c</samp> for a |
| demonstration of a 64 bit a.out format. |
| </p> |
| <p>The base file <samp>aoutx.h</samp> defines general mechanisms for |
| reading and writing records to and from disk and various |
| other methods which BFD requires. It is included by |
| <samp>aout32.c</samp> and <samp>aout64.c</samp> to form the names |
| <code>aout_32_swap_exec_header_in</code>, <code>aout_64_swap_exec_header_in</code>, etc. |
| </p> |
| <p>As an example, this is what goes on to make the back end for a |
| sun4, from <samp>aout32.c</samp>: |
| </p> |
| <div class="example"> |
| <pre class="example"> #define ARCH_SIZE 32 |
| #include "aoutx.h" |
| </pre></div> |
| |
| <p>Which exports names: |
| </p> |
| <div class="example"> |
| <pre class="example"> ... |
| aout_32_canonicalize_reloc |
| aout_32_find_nearest_line |
| aout_32_get_lineno |
| aout_32_get_reloc_upper_bound |
| ... |
| </pre></div> |
| |
| <p>from <samp>sunos.c</samp>: |
| </p> |
| <div class="example"> |
| <pre class="example"> #define TARGET_NAME "a.out-sunos-big" |
| #define VECNAME sparc_aout_sunos_be_vec |
| #include "aoutf1.h" |
| </pre></div> |
| |
| <p>requires all the names from <samp>aout32.c</samp>, and produces the jump vector |
| </p> |
| <div class="example"> |
| <pre class="example"> sparc_aout_sunos_be_vec |
| </pre></div> |
| |
| <p>The file <samp>host-aout.c</samp> is a special case. It is for a large set |
| of hosts that use “more or less standard” a.out files, and |
| for which cross-debugging is not interesting. It uses the |
| standard 32-bit a.out support routines, but determines the |
| file offsets and addresses of the text, data, and BSS |
| sections, the machine architecture and machine type, and the |
| entry point address, in a host-dependent manner. Once these |
| values have been determined, generic code is used to handle |
| the object file. |
| </p> |
| <p>When porting it to run on a new system, you must supply: |
| </p> |
| <div class="example"> |
| <pre class="example"> HOST_PAGE_SIZE |
| HOST_SEGMENT_SIZE |
| HOST_MACHINE_ARCH (optional) |
| HOST_MACHINE_MACHINE (optional) |
| HOST_TEXT_START_ADDR |
| HOST_STACK_END_ADDR |
| </pre></div> |
| |
| <p>in the file <samp>../include/sys/h-<var>XXX</var>.h</samp> (for your host). These |
| values, plus the structures and macros defined in <samp>a.out.h</samp> on |
| your host system, will produce a BFD target that will access |
| ordinary a.out files on your host. To configure a new machine |
| to use <samp>host-aout.c</samp>, specify: |
| </p> |
| <div class="example"> |
| <pre class="example"> TDEFAULTS = -DDEFAULT_VECTOR=host_aout_big_vec |
| TDEPFILES= host-aout.o trad-core.o |
| </pre></div> |
| |
| <p>in the <samp>config/<var>XXX</var>.mt</samp> file, and modify <samp>configure.ac</samp> |
| to use the |
| <samp><var>XXX</var>.mt</samp> file (by setting "<code>bfd_target=XXX</code>") when your |
| configuration is selected. |
| </p> |
| <a name="Relocations-2"></a> |
| <h4 class="subsection">3.2.1 Relocations</h4> |
| |
| |
| <p><strong>Description</strong><br> |
| The file <samp>aoutx.h</samp> provides for both the <em>standard</em> |
| and <em>extended</em> forms of a.out relocation records. |
| </p> |
| <p>The standard records contain only an |
| address, a symbol index, and a type field. The extended records |
| (used on 29ks and sparcs) also have a full integer for an |
| addend. |
| </p> |
| <a name="Internal-entry-points"></a> |
| <h4 class="subsection">3.2.2 Internal entry points</h4> |
| |
| |
| <p><strong>Description</strong><br> |
| <samp>aoutx.h</samp> exports several routines for accessing the |
| contents of an a.out file, which are gathered and exported in |
| turn by various format specific files (eg sunos.c). |
| </p> |
| <a name="index-aout_005fsize_005fswap_005fexec_005fheader_005fin"></a> |
| <a name="aout_005fsize_005fswap_005fexec_005fheader_005fin"></a> |
| <h4 class="subsubsection">3.2.2.1 <code>aout_<var>size</var>_swap_exec_header_in</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">void aout_<var>size</var>_swap_exec_header_in, |
| (bfd *abfd, |
| struct external_exec *bytes, |
| struct internal_exec *execp); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Swap the information in an executable header <var>raw_bytes</var> taken |
| from a raw byte stream memory image into the internal exec header |
| structure <var>execp</var>. |
| </p> |
| <a name="index-aout_005fsize_005fswap_005fexec_005fheader_005fout"></a> |
| <a name="aout_005fsize_005fswap_005fexec_005fheader_005fout"></a> |
| <h4 class="subsubsection">3.2.2.2 <code>aout_<var>size</var>_swap_exec_header_out</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">void aout_<var>size</var>_swap_exec_header_out |
| (bfd *abfd, |
| struct internal_exec *execp, |
| struct external_exec *raw_bytes); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Swap the information in an internal exec header structure |
| <var>execp</var> into the buffer <var>raw_bytes</var> ready for writing to disk. |
| </p> |
| <a name="index-aout_005fsize_005fsome_005faout_005fobject_005fp"></a> |
| <a name="aout_005fsize_005fsome_005faout_005fobject_005fp"></a> |
| <h4 class="subsubsection">3.2.2.3 <code>aout_<var>size</var>_some_aout_object_p</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">const bfd_target *aout_<var>size</var>_some_aout_object_p |
| (bfd *abfd, |
| struct internal_exec *execp, |
| const bfd_target *(*callback_to_real_object_p) (bfd *)); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Some a.out variant thinks that the file open in <var>abfd</var> |
| checking is an a.out file. Do some more checking, and set up |
| for access if it really is. Call back to the calling |
| environment’s "finish up" function just before returning, to |
| handle any last-minute setup. |
| </p> |
| <a name="index-aout_005fsize_005fmkobject"></a> |
| <a name="aout_005fsize_005fmkobject"></a> |
| <h4 class="subsubsection">3.2.2.4 <code>aout_<var>size</var>_mkobject</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">bfd_boolean aout_<var>size</var>_mkobject, (bfd *abfd); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Initialize BFD <var>abfd</var> for use with a.out files. |
| </p> |
| <a name="index-aout_005fsize_005fmachine_005ftype"></a> |
| <a name="aout_005fsize_005fmachine_005ftype"></a> |
| <h4 class="subsubsection">3.2.2.5 <code>aout_<var>size</var>_machine_type</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">enum machine_type aout_<var>size</var>_machine_type |
| (enum bfd_architecture arch, |
| unsigned long machine, |
| bfd_boolean *unknown); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Keep track of machine architecture and machine type for |
| a.out’s. Return the <code>machine_type</code> for a particular |
| architecture and machine, or <code>M_UNKNOWN</code> if that exact architecture |
| and machine can’t be represented in a.out format. |
| </p> |
| <p>If the architecture is understood, machine type 0 (default) |
| is always understood. |
| </p> |
| <a name="index-aout_005fsize_005fset_005farch_005fmach"></a> |
| <a name="aout_005fsize_005fset_005farch_005fmach"></a> |
| <h4 class="subsubsection">3.2.2.6 <code>aout_<var>size</var>_set_arch_mach</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">bfd_boolean aout_<var>size</var>_set_arch_mach, |
| (bfd *, |
| enum bfd_architecture arch, |
| unsigned long machine); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Set the architecture and the machine of the BFD <var>abfd</var> to the |
| values <var>arch</var> and <var>machine</var>. Verify that <var>abfd</var>’s format |
| can support the architecture required. |
| </p> |
| <a name="index-aout_005fsize_005fnew_005fsection_005fhook"></a> |
| <a name="aout_005fsize_005fnew_005fsection_005fhook"></a> |
| <h4 class="subsubsection">3.2.2.7 <code>aout_<var>size</var>_new_section_hook</code></h4> |
| <p><strong>Synopsis</strong> |
| </p><div class="example"> |
| <pre class="example">bfd_boolean aout_<var>size</var>_new_section_hook, |
| (bfd *abfd, |
| asection *newsect); |
| </pre></div> |
| <p><strong>Description</strong><br> |
| Called by the BFD in response to a <code>bfd_make_section</code> |
| request. |
| </p> |
| |
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