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

  2. <html>

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  70. 

  71. <body lang="en">

  72. <a name="coff"></a>

  73. <div class="header">

  74. <p>

  75. Next: <a href="elf.html#elf" accesskey="n" rel="next">elf</a>, Previous: <a href="aout.html#aout" accesskey="p" rel="prev">aout</a>, Up: <a href="BFD-back-ends.html#BFD-back-ends" accesskey="u" rel="up">BFD back ends</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="coff-backends"></a>

  79. <h3 class="section">3.3 coff backends</h3>

  80. <p>BFD supports a number of different flavours of coff format.

  81. The major differences between formats are the sizes and

  82. alignments of fields in structures on disk, and the occasional

  83. extra field.

  84. </p>

  85. <p>Coff in all its varieties is implemented with a few common

  86. files and a number of implementation specific files. For

  87. example, the i386 coff format is implemented in the file

  88. <samp>coff-i386.c</samp>.  This file <code>#include</code>s

  89. <samp>coff/i386.h</samp> which defines the external structure of the

  90. coff format for the i386, and <samp>coff/internal.h</samp> which

  91. defines the internal structure. <samp>coff-i386.c</samp> also

  92. defines the relocations used by the i386 coff format

  93. See <a href="Relocations.html#Relocations">Relocations</a>.

  94. </p>

  95. <a name="Porting-to-a-new-version-of-coff"></a>

  96. <h4 class="subsection">3.3.1 Porting to a new version of coff</h4>

  97. <p>The recommended method is to select from the existing

  98. implementations the version of coff which is most like the one

  99. you want to use.  For example, we&rsquo;ll say that i386 coff is

  100. the one you select, and that your coff flavour is called foo.

  101. Copy <samp>i386coff.c</samp> to <samp>foocoff.c</samp>, copy

  102. <samp>../include/coff/i386.h</samp> to <samp>../include/coff/foo.h</samp>,

  103. and add the lines to <samp>targets.c</samp> and <samp>Makefile.in</samp>

  104. so that your new back end is used. Alter the shapes of the

  105. structures in <samp>../include/coff/foo.h</samp> so that they match

  106. what you need. You will probably also have to add

  107. <code>#ifdef</code>s to the code in <samp>coff/internal.h</samp> and

  108. <samp>coffcode.h</samp> if your version of coff is too wild.

  109. </p>

  110. <p>You can verify that your new BFD backend works quite simply by

  111. building <samp>objdump</samp> from the <samp>binutils</samp> directory,

  112. and making sure that its version of what&rsquo;s going on and your

  113. host system&rsquo;s idea (assuming it has the pretty standard coff

  114. dump utility, usually called <code>att-dump</code> or just

  115. <code>dump</code>) are the same.  Then clean up your code, and send

  116. what you&rsquo;ve done to Cygnus. Then your stuff will be in the

  117. next release, and you won&rsquo;t have to keep integrating it.

  118. </p>

  119. <a name="How-the-coff-backend-works"></a>

  120. <h4 class="subsection">3.3.2 How the coff backend works</h4>

  121. 

  122. 

  123. <a name="File-layout-1"></a>

  124. <h4 class="subsubsection">3.3.2.1 File layout</h4>

  125. <p>The Coff backend is split into generic routines that are

  126. applicable to any Coff target and routines that are specific

  127. to a particular target.  The target-specific routines are

  128. further split into ones which are basically the same for all

  129. Coff targets except that they use the external symbol format

  130. or use different values for certain constants.

  131. </p>

  132. <p>The generic routines are in <samp>coffgen.c</samp>.  These routines

  133. work for any Coff target.  They use some hooks into the target

  134. specific code; the hooks are in a <code>bfd_coff_backend_data</code>

  135. structure, one of which exists for each target.

  136. </p>

  137. <p>The essentially similar target-specific routines are in

  138. <samp>coffcode.h</samp>.  This header file includes executable C code.

  139. The various Coff targets first include the appropriate Coff

  140. header file, make any special defines that are needed, and

  141. then include <samp>coffcode.h</samp>.

  142. </p>

  143. <p>Some of the Coff targets then also have additional routines in

  144. the target source file itself.

  145. </p>

  146. <a name="Coff-long-section-names"></a>

  147. <h4 class="subsubsection">3.3.2.2 Coff long section names</h4>

  148. <p>In the standard Coff object format, section names are limited to

  149. the eight bytes available in the <code>s_name</code> field of the

  150. <code>SCNHDR</code> section header structure.  The format requires the

  151. field to be NUL-padded, but not necessarily NUL-terminated, so

  152. the longest section names permitted are a full eight characters.

  153. </p>

  154. <p>The Microsoft PE variants of the Coff object file format add

  155. an extension to support the use of long section names.  This

  156. extension is defined in section 4 of the Microsoft PE/COFF

  157. specification (rev 8.1).  If a section name is too long to fit

  158. into the section header&rsquo;s <code>s_name</code> field, it is instead

  159. placed into the string table, and the <code>s_name</code> field is

  160. filled with a slash (&quot;/&quot;) followed by the ASCII decimal

  161. representation of the offset of the full name relative to the

  162. string table base.

  163. </p>

  164. <p>Note that this implies that the extension can only be used in object

  165. files, as executables do not contain a string table.  The standard

  166. specifies that long section names from objects emitted into executable

  167. images are to be truncated.

  168. </p>

  169. <p>However, as a GNU extension, BFD can generate executable images

  170. that contain a string table and long section names.  This

  171. would appear to be technically valid, as the standard only says

  172. that Coff debugging information is deprecated, not forbidden,

  173. and in practice it works, although some tools that parse PE files

  174. expecting the MS standard format may become confused; <samp>PEview</samp> is

  175. one known example.

  176. </p>

  177. <p>The functionality is supported in BFD by code implemented under

  178. the control of the macro <code>COFF_LONG_SECTION_NAMES</code>.  If not

  179. defined, the format does not support long section names in any way.

  180. If defined, it is used to initialise a flag,

  181. <code>_bfd_coff_long_section_names</code>, and a hook function pointer,

  182. <code>_bfd_coff_set_long_section_names</code>, in the Coff backend data

  183. structure.  The flag controls the generation of long section names

  184. in output BFDs at runtime; if it is false, as it will be by default

  185. when generating an executable image, long section names are truncated;

  186. if true, the long section names extension is employed.  The hook

  187. points to a function that allows the value of the flag to be altered

  188. at runtime, on formats that support long section names at all; on

  189. other formats it points to a stub that returns an error indication.

  190. </p>

  191. <p>With input BFDs, the flag is set according to whether any long section

  192. names are detected while reading the section headers.  For a completely

  193. new BFD, the flag is set to the default for the target format.  This

  194. information can be used by a client of the BFD library when deciding

  195. what output format to generate, and means that a BFD that is opened

  196. for read and subsequently converted to a writeable BFD and modified

  197. in-place will retain whatever format it had on input.

  198. </p>

  199. <p>If <code>COFF_LONG_SECTION_NAMES</code> is simply defined (blank), or is

  200. defined to the value &quot;1&quot;, then long section names are enabled by

  201. default; if it is defined to the value zero, they are disabled by

  202. default (but still accepted in input BFDs).  The header <samp>coffcode.h</samp>

  203. defines a macro, <code>COFF_DEFAULT_LONG_SECTION_NAMES</code>, which is

  204. used in the backends to initialise the backend data structure fields

  205. appropriately; see the comments for further detail.

  206. </p>

  207. <a name="Bit-twiddling"></a>

  208. <h4 class="subsubsection">3.3.2.3 Bit twiddling</h4>

  209. <p>Each flavour of coff supported in BFD has its own header file

  210. describing the external layout of the structures. There is also

  211. an internal description of the coff layout, in

  212. <samp>coff/internal.h</samp>. A major function of the

  213. coff backend is swapping the bytes and twiddling the bits to

  214. translate the external form of the structures into the normal

  215. internal form. This is all performed in the

  216. <code>bfd_swap</code>_<i>thing</i>_<i>direction</i> routines. Some

  217. elements are different sizes between different versions of

  218. coff; it is the duty of the coff version specific include file

  219. to override the definitions of various packing routines in

  220. <samp>coffcode.h</samp>. E.g., the size of line number entry in coff is

  221. sometimes 16 bits, and sometimes 32 bits. <code>#define</code>ing

  222. <code>PUT_LNSZ_LNNO</code> and <code>GET_LNSZ_LNNO</code> will select the

  223. correct one. No doubt, some day someone will find a version of

  224. coff which has a varying field size not catered to at the

  225. moment. To port BFD, that person will have to add more <code>#defines</code>.

  226. Three of the bit twiddling routines are exported to

  227. <code>gdb</code>; <code>coff_swap_aux_in</code>, <code>coff_swap_sym_in</code>

  228. and <code>coff_swap_lineno_in</code>. <code>GDB</code> reads the symbol

  229. table on its own, but uses BFD to fix things up.  More of the

  230. bit twiddlers are exported for <code>gas</code>;

  231. <code>coff_swap_aux_out</code>, <code>coff_swap_sym_out</code>,

  232. <code>coff_swap_lineno_out</code>, <code>coff_swap_reloc_out</code>,

  233. <code>coff_swap_filehdr_out</code>, <code>coff_swap_aouthdr_out</code>,

  234. <code>coff_swap_scnhdr_out</code>. <code>Gas</code> currently keeps track

  235. of all the symbol table and reloc drudgery itself, thereby

  236. saving the internal BFD overhead, but uses BFD to swap things

  237. on the way out, making cross ports much safer.  Doing so also

  238. allows BFD (and thus the linker) to use the same header files

  239. as <code>gas</code>, which makes one avenue to disaster disappear.

  240. </p>

  241. <a name="Symbol-reading"></a>

  242. <h4 class="subsubsection">3.3.2.4 Symbol reading</h4>

  243. <p>The simple canonical form for symbols used by BFD is not rich

  244. enough to keep all the information available in a coff symbol

  245. table. The back end gets around this problem by keeping the original

  246. symbol table around, &quot;behind the scenes&quot;.

  247. </p>

  248. <p>When a symbol table is requested (through a call to

  249. <code>bfd_canonicalize_symtab</code>), a request gets through to

  250. <code>coff_get_normalized_symtab</code>. This reads the symbol table from

  251. the coff file and swaps all the structures inside into the

  252. internal form. It also fixes up all the pointers in the table

  253. (represented in the file by offsets from the first symbol in

  254. the table) into physical pointers to elements in the new

  255. internal table. This involves some work since the meanings of

  256. fields change depending upon context: a field that is a

  257. pointer to another structure in the symbol table at one moment

  258. may be the size in bytes of a structure at the next.  Another

  259. pass is made over the table. All symbols which mark file names

  260. (<code>C_FILE</code> symbols) are modified so that the internal

  261. string points to the value in the auxent (the real filename)

  262. rather than the normal text associated with the symbol

  263. (<code>&quot;.file&quot;</code>).

  264. </p>

  265. <p>At this time the symbol names are moved around. Coff stores

  266. all symbols less than nine characters long physically

  267. within the symbol table; longer strings are kept at the end of

  268. the file in the string table. This pass moves all strings

  269. into memory and replaces them with pointers to the strings.

  270. </p>

  271. <p>The symbol table is massaged once again, this time to create

  272. the canonical table used by the BFD application. Each symbol

  273. is inspected in turn, and a decision made (using the

  274. <code>sclass</code> field) about the various flags to set in the

  275. <code>asymbol</code>.  See <a href="Symbols.html#Symbols">Symbols</a>. The generated canonical table

  276. shares strings with the hidden internal symbol table.

  277. </p>

  278. <p>Any linenumbers are read from the coff file too, and attached

  279. to the symbols which own the functions the linenumbers belong to.

  280. </p>

  281. <a name="Symbol-writing"></a>

  282. <h4 class="subsubsection">3.3.2.5 Symbol writing</h4>

  283. <p>Writing a symbol to a coff file which didn&rsquo;t come from a coff

  284. file will lose any debugging information. The <code>asymbol</code>

  285. structure remembers the BFD from which the symbol was taken, and on

  286. output the back end makes sure that the same destination target as

  287. source target is present.

  288. </p>

  289. <p>When the symbols have come from a coff file then all the

  290. debugging information is preserved.

  291. </p>

  292. <p>Symbol tables are provided for writing to the back end in a

  293. vector of pointers to pointers. This allows applications like

  294. the linker to accumulate and output large symbol tables

  295. without having to do too much byte copying.

  296. </p>

  297. <p>This function runs through the provided symbol table and

  298. patches each symbol marked as a file place holder

  299. (<code>C_FILE</code>) to point to the next file place holder in the

  300. list. It also marks each <code>offset</code> field in the list with

  301. the offset from the first symbol of the current symbol.

  302. </p>

  303. <p>Another function of this procedure is to turn the canonical

  304. value form of BFD into the form used by coff. Internally, BFD

  305. expects symbol values to be offsets from a section base; so a

  306. symbol physically at 0x120, but in a section starting at

  307. 0x100, would have the value 0x20. Coff expects symbols to

  308. contain their final value, so symbols have their values

  309. changed at this point to reflect their sum with their owning

  310. section.  This transformation uses the

  311. <code>output_section</code> field of the <code>asymbol</code>&rsquo;s

  312. <code>asection</code> See <a href="Sections.html#Sections">Sections</a>.

  313. </p>

  314. <ul>

  315. <li> <code>coff_mangle_symbols</code>

  316. </li></ul>

  317. <p>This routine runs though the provided symbol table and uses

  318. the offsets generated by the previous pass and the pointers

  319. generated when the symbol table was read in to create the

  320. structured hierarchy required by coff. It changes each pointer

  321. to a symbol into the index into the symbol table of the asymbol.

  322. </p>

  323. <ul>

  324. <li> <code>coff_write_symbols</code>

  325. </li></ul>

  326. <p>This routine runs through the symbol table and patches up the

  327. symbols from their internal form into the coff way, calls the

  328. bit twiddlers, and writes out the table to the file.

  329. </p>

  330. <a name="index-coff_005fsymbol_005ftype"></a>

  331. <a name="coff_005fsymbol_005ftype"></a>

  332. <h4 class="subsubsection">3.3.2.6 <code>coff_symbol_type</code></h4>

  333. <p><strong>Description</strong><br>

  334. The hidden information for an <code>asymbol</code> is described in a

  335. <code>combined_entry_type</code>:

  336. </p>

  337. 

  338. <div class="example">

  339. <pre class="example">

  340. 

  341. typedef struct coff_ptr_struct

  342. {

  343.   /* Remembers the offset from the first symbol in the file for

  344.      this symbol. Generated by coff_renumber_symbols.  */

  345.   unsigned int offset;

  346. 

  347.   /* Should the value of this symbol be renumbered.  Used for

  348.      XCOFF C_BSTAT symbols.  Set by coff_slurp_symbol_table.  */

  349.   unsigned int fix_value : 1;

  350. 

  351.   /* Should the tag field of this symbol be renumbered.

  352.      Created by coff_pointerize_aux.  */

  353.   unsigned int fix_tag : 1;

  354. 

  355.   /* Should the endidx field of this symbol be renumbered.

  356.      Created by coff_pointerize_aux.  */

  357.   unsigned int fix_end : 1;

  358. 

  359.   /* Should the x_csect.x_scnlen field be renumbered.

  360.      Created by coff_pointerize_aux.  */

  361.   unsigned int fix_scnlen : 1;

  362. 

  363.   /* Fix up an XCOFF C_BINCL/C_EINCL symbol.  The value is the

  364.      index into the line number entries.  Set by coff_slurp_symbol_table.  */

  365.   unsigned int fix_line : 1;

  366. 

  367.   /* The container for the symbol structure as read and translated

  368.      from the file.  */

  369.   union

  370.   {

  371.     union internal_auxent auxent;

  372.     struct internal_syment syment;

  373.   } u;

  374. 

  375.  /* Selector for the union above.  */

  376.  bfd_boolean is_sym;

  377. } combined_entry_type;

  378. 

  379. 

  380. /* Each canonical asymbol really looks like this: */

  381. 

  382. typedef struct coff_symbol_struct

  383. {

  384.   /* The actual symbol which the rest of BFD works with */

  385.   asymbol symbol;

  386. 

  387.   /* A pointer to the hidden information for this symbol */

  388.   combined_entry_type *native;

  389. 

  390.   /* A pointer to the linenumber information for this symbol */

  391.   struct lineno_cache_entry *lineno;

  392. 

  393.   /* Have the line numbers been relocated yet ? */

  394.   bfd_boolean done_lineno;

  395. } coff_symbol_type;

  396. </pre></div>

  397. <a name="index-bfd_005fcoff_005fbackend_005fdata"></a>

  398. <a name="bfd_005fcoff_005fbackend_005fdata"></a>

  399. <h4 class="subsubsection">3.3.2.7 <code>bfd_coff_backend_data</code></h4>

  400. 

  401. <div class="example">

  402. <pre class="example">/* COFF symbol classifications.  */

  403. 

  404. enum coff_symbol_classification

  405. {

  406.   /* Global symbol.  */

  407.   COFF_SYMBOL_GLOBAL,

  408.   /* Common symbol.  */

  409.   COFF_SYMBOL_COMMON,

  410.   /* Undefined symbol.  */

  411.   COFF_SYMBOL_UNDEFINED,

  412.   /* Local symbol.  */

  413.   COFF_SYMBOL_LOCAL,

  414.   /* PE section symbol.  */

  415.   COFF_SYMBOL_PE_SECTION

  416. };

  417. 

  418. typedef asection * (*coff_gc_mark_hook_fn)

  419.   (asection *, struct bfd_link_info *, struct internal_reloc *,

  420.    struct coff_link_hash_entry *, struct internal_syment *);

  421. 

  422. </pre></div>

  423. <p>Special entry points for gdb to swap in coff symbol table parts:

  424. </p><div class="example">

  425. <pre class="example">typedef struct

  426. {

  427.   void (*_bfd_coff_swap_aux_in)

  428.     (bfd *, void *, int, int, int, int, void *);

  429. 

  430.   void (*_bfd_coff_swap_sym_in)

  431.     (bfd *, void *, void *);

  432. 

  433.   void (*_bfd_coff_swap_lineno_in)

  434.     (bfd *, void *, void *);

  435. 

  436.   unsigned int (*_bfd_coff_swap_aux_out)

  437.     (bfd *, void *, int, int, int, int, void *);

  438. 

  439.   unsigned int (*_bfd_coff_swap_sym_out)

  440.     (bfd *, void *, void *);

  441. 

  442.   unsigned int (*_bfd_coff_swap_lineno_out)

  443.     (bfd *, void *, void *);

  444. 

  445.   unsigned int (*_bfd_coff_swap_reloc_out)

  446.     (bfd *, void *, void *);

  447. 

  448.   unsigned int (*_bfd_coff_swap_filehdr_out)

  449.     (bfd *, void *, void *);

  450. 

  451.   unsigned int (*_bfd_coff_swap_aouthdr_out)

  452.     (bfd *, void *, void *);

  453. 

  454.   unsigned int (*_bfd_coff_swap_scnhdr_out)

  455.     (bfd *, void *, void *);

  456. 

  457.   unsigned int _bfd_filhsz;

  458.   unsigned int _bfd_aoutsz;

  459.   unsigned int _bfd_scnhsz;

  460.   unsigned int _bfd_symesz;

  461.   unsigned int _bfd_auxesz;

  462.   unsigned int _bfd_relsz;

  463.   unsigned int _bfd_linesz;

  464.   unsigned int _bfd_filnmlen;

  465.   bfd_boolean _bfd_coff_long_filenames;

  466. 

  467.   bfd_boolean _bfd_coff_long_section_names;

  468.   bfd_boolean (*_bfd_coff_set_long_section_names)

  469.     (bfd *, int);

  470. 

  471.   unsigned int _bfd_coff_default_section_alignment_power;

  472.   bfd_boolean _bfd_coff_force_symnames_in_strings;

  473.   unsigned int _bfd_coff_debug_string_prefix_length;

  474.   unsigned int _bfd_coff_max_nscns;

  475. 

  476.   void (*_bfd_coff_swap_filehdr_in)

  477.     (bfd *, void *, void *);

  478. 

  479.   void (*_bfd_coff_swap_aouthdr_in)

  480.     (bfd *, void *, void *);

  481. 

  482.   void (*_bfd_coff_swap_scnhdr_in)

  483.     (bfd *, void *, void *);

  484. 

  485.   void (*_bfd_coff_swap_reloc_in)

  486.     (bfd *abfd, void *, void *);

  487. 

  488.   bfd_boolean (*_bfd_coff_bad_format_hook)

  489.     (bfd *, void *);

  490. 

  491.   bfd_boolean (*_bfd_coff_set_arch_mach_hook)

  492.     (bfd *, void *);

  493. 

  494.   void * (*_bfd_coff_mkobject_hook)

  495.     (bfd *, void *, void *);

  496. 

  497.   bfd_boolean (*_bfd_styp_to_sec_flags_hook)

  498.     (bfd *, void *, const char *, asection *, flagword *);

  499. 

  500.   void (*_bfd_set_alignment_hook)

  501.     (bfd *, asection *, void *);

  502. 

  503.   bfd_boolean (*_bfd_coff_slurp_symbol_table)

  504.     (bfd *);

  505. 

  506.   bfd_boolean (*_bfd_coff_symname_in_debug)

  507.     (bfd *, struct internal_syment *);

  508. 

  509.   bfd_boolean (*_bfd_coff_pointerize_aux_hook)

  510.     (bfd *, combined_entry_type *, combined_entry_type *,

  511.      unsigned int, combined_entry_type *);

  512. 

  513.   bfd_boolean (*_bfd_coff_print_aux)

  514.     (bfd *, FILE *, combined_entry_type *, combined_entry_type *,

  515.      combined_entry_type *, unsigned int);

  516. 

  517.   void (*_bfd_coff_reloc16_extra_cases)

  518.     (bfd *, struct bfd_link_info *, struct bfd_link_order *, arelent *,

  519.      bfd_byte *, unsigned int *, unsigned int *);

  520. 

  521.   int (*_bfd_coff_reloc16_estimate)

  522.     (bfd *, asection *, arelent *, unsigned int,

  523.      struct bfd_link_info *);

  524. 

  525.   enum coff_symbol_classification (*_bfd_coff_classify_symbol)

  526.     (bfd *, struct internal_syment *);

  527. 

  528.   bfd_boolean (*_bfd_coff_compute_section_file_positions)

  529.     (bfd *);

  530. 

  531.   bfd_boolean (*_bfd_coff_start_final_link)

  532.     (bfd *, struct bfd_link_info *);

  533. 

  534.   bfd_boolean (*_bfd_coff_relocate_section)

  535.     (bfd *, struct bfd_link_info *, bfd *, asection *, bfd_byte *,

  536.      struct internal_reloc *, struct internal_syment *, asection **);

  537. 

  538.   reloc_howto_type *(*_bfd_coff_rtype_to_howto)

  539.     (bfd *, asection *, struct internal_reloc *,

  540.      struct coff_link_hash_entry *, struct internal_syment *, bfd_vma *);

  541. 

  542.   bfd_boolean (*_bfd_coff_adjust_symndx)

  543.     (bfd *, struct bfd_link_info *, bfd *, asection *,

  544.      struct internal_reloc *, bfd_boolean *);

  545. 

  546.   bfd_boolean (*_bfd_coff_link_add_one_symbol)

  547.     (struct bfd_link_info *, bfd *, const char *, flagword,

  548.      asection *, bfd_vma, const char *, bfd_boolean, bfd_boolean,

  549.      struct bfd_link_hash_entry **);

  550. 

  551.   bfd_boolean (*_bfd_coff_link_output_has_begun)

  552.     (bfd *, struct coff_final_link_info *);

  553. 

  554.   bfd_boolean (*_bfd_coff_final_link_postscript)

  555.     (bfd *, struct coff_final_link_info *);

  556. 

  557.   bfd_boolean (*_bfd_coff_print_pdata)

  558.     (bfd *, void *);

  559. 

  560. } bfd_coff_backend_data;

  561. 

  562. #define coff_backend_info(abfd) \

  563.   ((bfd_coff_backend_data *) (abfd)-&gt;xvec-&gt;backend_data)

  564. 

  565. #define bfd_coff_swap_aux_in(a,e,t,c,ind,num,i) \

  566.   ((coff_backend_info (a)-&gt;_bfd_coff_swap_aux_in) (a,e,t,c,ind,num,i))

  567. 

  568. #define bfd_coff_swap_sym_in(a,e,i) \

  569.   ((coff_backend_info (a)-&gt;_bfd_coff_swap_sym_in) (a,e,i))

  570. 

  571. #define bfd_coff_swap_lineno_in(a,e,i) \

  572.   ((coff_backend_info ( a)-&gt;_bfd_coff_swap_lineno_in) (a,e,i))

  573. 

  574. #define bfd_coff_swap_reloc_out(abfd, i, o) \

  575.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_reloc_out) (abfd, i, o))

  576. 

  577. #define bfd_coff_swap_lineno_out(abfd, i, o) \

  578.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_lineno_out) (abfd, i, o))

  579. 

  580. #define bfd_coff_swap_aux_out(a,i,t,c,ind,num,o) \

  581.   ((coff_backend_info (a)-&gt;_bfd_coff_swap_aux_out) (a,i,t,c,ind,num,o))

  582. 

  583. #define bfd_coff_swap_sym_out(abfd, i,o) \

  584.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_sym_out) (abfd, i, o))

  585. 

  586. #define bfd_coff_swap_scnhdr_out(abfd, i,o) \

  587.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_scnhdr_out) (abfd, i, o))

  588. 

  589. #define bfd_coff_swap_filehdr_out(abfd, i,o) \

  590.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_filehdr_out) (abfd, i, o))

  591. 

  592. #define bfd_coff_swap_aouthdr_out(abfd, i,o) \

  593.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_aouthdr_out) (abfd, i, o))

  594. 

  595. #define bfd_coff_filhsz(abfd) (coff_backend_info (abfd)-&gt;_bfd_filhsz)

  596. #define bfd_coff_aoutsz(abfd) (coff_backend_info (abfd)-&gt;_bfd_aoutsz)

  597. #define bfd_coff_scnhsz(abfd) (coff_backend_info (abfd)-&gt;_bfd_scnhsz)

  598. #define bfd_coff_symesz(abfd) (coff_backend_info (abfd)-&gt;_bfd_symesz)

  599. #define bfd_coff_auxesz(abfd) (coff_backend_info (abfd)-&gt;_bfd_auxesz)

  600. #define bfd_coff_relsz(abfd)  (coff_backend_info (abfd)-&gt;_bfd_relsz)

  601. #define bfd_coff_linesz(abfd) (coff_backend_info (abfd)-&gt;_bfd_linesz)

  602. #define bfd_coff_filnmlen(abfd) (coff_backend_info (abfd)-&gt;_bfd_filnmlen)

  603. #define bfd_coff_long_filenames(abfd) \

  604.   (coff_backend_info (abfd)-&gt;_bfd_coff_long_filenames)

  605. #define bfd_coff_long_section_names(abfd) \

  606.   (coff_backend_info (abfd)-&gt;_bfd_coff_long_section_names)

  607. #define bfd_coff_set_long_section_names(abfd, enable) \

  608.   ((coff_backend_info (abfd)-&gt;_bfd_coff_set_long_section_names) (abfd, enable))

  609. #define bfd_coff_default_section_alignment_power(abfd) \

  610.   (coff_backend_info (abfd)-&gt;_bfd_coff_default_section_alignment_power)

  611. #define bfd_coff_max_nscns(abfd) \

  612.   (coff_backend_info (abfd)-&gt;_bfd_coff_max_nscns)

  613. 

  614. #define bfd_coff_swap_filehdr_in(abfd, i,o) \

  615.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_filehdr_in) (abfd, i, o))

  616. 

  617. #define bfd_coff_swap_aouthdr_in(abfd, i,o) \

  618.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_aouthdr_in) (abfd, i, o))

  619. 

  620. #define bfd_coff_swap_scnhdr_in(abfd, i,o) \

  621.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_scnhdr_in) (abfd, i, o))

  622. 

  623. #define bfd_coff_swap_reloc_in(abfd, i, o) \

  624.   ((coff_backend_info (abfd)-&gt;_bfd_coff_swap_reloc_in) (abfd, i, o))

  625. 

  626. #define bfd_coff_bad_format_hook(abfd, filehdr) \

  627.   ((coff_backend_info (abfd)-&gt;_bfd_coff_bad_format_hook) (abfd, filehdr))

  628. 

  629. #define bfd_coff_set_arch_mach_hook(abfd, filehdr)\

  630.   ((coff_backend_info (abfd)-&gt;_bfd_coff_set_arch_mach_hook) (abfd, filehdr))

  631. #define bfd_coff_mkobject_hook(abfd, filehdr, aouthdr)\

  632.   ((coff_backend_info (abfd)-&gt;_bfd_coff_mkobject_hook)\

  633.    (abfd, filehdr, aouthdr))

  634. 

  635. #define bfd_coff_styp_to_sec_flags_hook(abfd, scnhdr, name, section, flags_ptr)\

  636.   ((coff_backend_info (abfd)-&gt;_bfd_styp_to_sec_flags_hook)\

  637.    (abfd, scnhdr, name, section, flags_ptr))

  638. 

  639. #define bfd_coff_set_alignment_hook(abfd, sec, scnhdr)\

  640.   ((coff_backend_info (abfd)-&gt;_bfd_set_alignment_hook) (abfd, sec, scnhdr))

  641. 

  642. #define bfd_coff_slurp_symbol_table(abfd)\

  643.   ((coff_backend_info (abfd)-&gt;_bfd_coff_slurp_symbol_table) (abfd))

  644. 

  645. #define bfd_coff_symname_in_debug(abfd, sym)\

  646.   ((coff_backend_info (abfd)-&gt;_bfd_coff_symname_in_debug) (abfd, sym))

  647. 

  648. #define bfd_coff_force_symnames_in_strings(abfd)\

  649.   (coff_backend_info (abfd)-&gt;_bfd_coff_force_symnames_in_strings)

  650. 

  651. #define bfd_coff_debug_string_prefix_length(abfd)\

  652.   (coff_backend_info (abfd)-&gt;_bfd_coff_debug_string_prefix_length)

  653. 

  654. #define bfd_coff_print_aux(abfd, file, base, symbol, aux, indaux)\

  655.   ((coff_backend_info (abfd)-&gt;_bfd_coff_print_aux)\

  656.    (abfd, file, base, symbol, aux, indaux))

  657. 

  658. #define bfd_coff_reloc16_extra_cases(abfd, link_info, link_order,\

  659.                                      reloc, data, src_ptr, dst_ptr)\

  660.   ((coff_backend_info (abfd)-&gt;_bfd_coff_reloc16_extra_cases)\

  661.    (abfd, link_info, link_order, reloc, data, src_ptr, dst_ptr))

  662. 

  663. #define bfd_coff_reloc16_estimate(abfd, section, reloc, shrink, link_info)\

  664.   ((coff_backend_info (abfd)-&gt;_bfd_coff_reloc16_estimate)\

  665.    (abfd, section, reloc, shrink, link_info))

  666. 

  667. #define bfd_coff_classify_symbol(abfd, sym)\

  668.   ((coff_backend_info (abfd)-&gt;_bfd_coff_classify_symbol)\

  669.    (abfd, sym))

  670. 

  671. #define bfd_coff_compute_section_file_positions(abfd)\

  672.   ((coff_backend_info (abfd)-&gt;_bfd_coff_compute_section_file_positions)\

  673.    (abfd))

  674. 

  675. #define bfd_coff_start_final_link(obfd, info)\

  676.   ((coff_backend_info (obfd)-&gt;_bfd_coff_start_final_link)\

  677.    (obfd, info))

  678. #define bfd_coff_relocate_section(obfd,info,ibfd,o,con,rel,isyms,secs)\

  679.   ((coff_backend_info (ibfd)-&gt;_bfd_coff_relocate_section)\

  680.    (obfd, info, ibfd, o, con, rel, isyms, secs))

  681. #define bfd_coff_rtype_to_howto(abfd, sec, rel, h, sym, addendp)\

  682.   ((coff_backend_info (abfd)-&gt;_bfd_coff_rtype_to_howto)\

  683.    (abfd, sec, rel, h, sym, addendp))

  684. #define bfd_coff_adjust_symndx(obfd, info, ibfd, sec, rel, adjustedp)\

  685.   ((coff_backend_info (abfd)-&gt;_bfd_coff_adjust_symndx)\

  686.    (obfd, info, ibfd, sec, rel, adjustedp))

  687. #define bfd_coff_link_add_one_symbol(info, abfd, name, flags, section,\

  688.                                      value, string, cp, coll, hashp)\

  689.   ((coff_backend_info (abfd)-&gt;_bfd_coff_link_add_one_symbol)\

  690.    (info, abfd, name, flags, section, value, string, cp, coll, hashp))

  691. 

  692. #define bfd_coff_link_output_has_begun(a,p) \

  693.   ((coff_backend_info (a)-&gt;_bfd_coff_link_output_has_begun) (a, p))

  694. #define bfd_coff_final_link_postscript(a,p) \

  695.   ((coff_backend_info (a)-&gt;_bfd_coff_final_link_postscript) (a, p))

  696. 

  697. #define bfd_coff_have_print_pdata(a) \

  698.   (coff_backend_info (a)-&gt;_bfd_coff_print_pdata)

  699. #define bfd_coff_print_pdata(a,p) \

  700.   ((coff_backend_info (a)-&gt;_bfd_coff_print_pdata) (a, p))

  701. 

  702. /* Macro: Returns true if the bfd is a PE executable as opposed to a

  703.    PE object file.  */

  704. #define bfd_pei_p(abfd) \

  705.   (CONST_STRNEQ ((abfd)-&gt;xvec-&gt;name, &quot;pei-&quot;))

  706. </pre></div>

  707. <a name="Writing-relocations"></a>

  708. <h4 class="subsubsection">3.3.2.8 Writing relocations</h4>

  709. <p>To write relocations, the back end steps though the

  710. canonical relocation table and create an

  711. <code>internal_reloc</code>. The symbol index to use is removed from

  712. the <code>offset</code> field in the symbol table supplied.  The

  713. address comes directly from the sum of the section base

  714. address and the relocation offset; the type is dug directly

  715. from the howto field.  Then the <code>internal_reloc</code> is

  716. swapped into the shape of an <code>external_reloc</code> and written

  717. out to disk.

  718. </p>

  719. <a name="Reading-linenumbers"></a>

  720. <h4 class="subsubsection">3.3.2.9 Reading linenumbers</h4>

  721. <p>Creating the linenumber table is done by reading in the entire

  722. coff linenumber table, and creating another table for internal use.

  723. </p>

  724. <p>A coff linenumber table is structured so that each function

  725. is marked as having a line number of 0. Each line within the

  726. function is an offset from the first line in the function. The

  727. base of the line number information for the table is stored in

  728. the symbol associated with the function.

  729. </p>

  730. <p>Note: The PE format uses line number 0 for a flag indicating a

  731. new source file.

  732. </p>

  733. <p>The information is copied from the external to the internal

  734. table, and each symbol which marks a function is marked by

  735. pointing its...

  736. </p>

  737. <p>How does this work ?

  738. </p>

  739. <a name="Reading-relocations"></a>

  740. <h4 class="subsubsection">3.3.2.10 Reading relocations</h4>

  741. <p>Coff relocations are easily transformed into the internal BFD form

  742. (<code>arelent</code>).

  743. </p>

  744. <p>Reading a coff relocation table is done in the following stages:

  745. </p>

  746. <ul>

  747. <li> Read the entire coff relocation table into memory.

  748. 

  749. </li><li> Process each relocation in turn; first swap it from the

  750. external to the internal form.

  751. 

  752. </li><li> Turn the symbol referenced in the relocation&rsquo;s symbol index

  753. into a pointer into the canonical symbol table.

  754. This table is the same as the one returned by a call to

  755. <code>bfd_canonicalize_symtab</code>. The back end will call that

  756. routine and save the result if a canonicalization hasn&rsquo;t been done.

  757. 

  758. </li><li> The reloc index is turned into a pointer to a howto

  759. structure, in a back end specific way. For instance, the 386

  760. uses the <code>r_type</code> to directly produce an index

  761. into a howto table vector.

  762. </li></ul>

  763. 

  764. 

  765. <hr>

  766. <div class="header">

  767. <p>

  768. Next: <a href="elf.html#elf" accesskey="n" rel="next">elf</a>, Previous: <a href="aout.html#aout" accesskey="p" rel="prev">aout</a>, Up: <a href="BFD-back-ends.html#BFD-back-ends" accesskey="u" rel="up">BFD back ends</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>

  769. </div>

  770. 

  771. 

  772. 

  773. </body>

  774. </html>