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coff.h
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1 /* This file is derived from the GAS 2.1.4 assembler control file.
2  The GAS product is under the GNU General Public License, version 2 or later.
3  As such, this file is also under that license.
4 
5  If the file format changes in the COFF object, this file should be
6  subsequently updated to reflect the changes.
7 
8  The actual loader module only uses a few of these structures. The full
9  set is documented here because I received the full set. If you wish
10  more information about COFF, then O'Reilly has a very excellent book.
11 */
12 
13 #define E_SYMNMLEN 8 /* Number of characters in a symbol name */
14 #define E_FILNMLEN 14 /* Number of characters in a file name */
15 #define E_DIMNUM 4 /* Number of array dimensions in auxiliary entry */
16 
17 /*
18  * These defines are byte order independent. There is no alignment of fields
19  * permitted in the structures. Therefore they are declared as characters
20  * and the values loaded from the character positions. It also makes it
21  * nice to have it "endian" independent.
22  */
23 
24 /* Load a short int from the following tables with little-endian formats */
25 #define COFF_SHORT_L(ps) ((short)(((unsigned short)((unsigned char)ps[1])<<8)|\
26  ((unsigned short)((unsigned char)ps[0]))))
27 
28 /* Load a long int from the following tables with little-endian formats */
29 #define COFF_LONG_L(ps) (((long)(((unsigned long)((unsigned char)ps[3])<<24) |\
30  ((unsigned long)((unsigned char)ps[2])<<16) |\
31  ((unsigned long)((unsigned char)ps[1])<<8) |\
32  ((unsigned long)((unsigned char)ps[0])))))
33 
34 /* Load a short int from the following tables with big-endian formats */
35 #define COFF_SHORT_H(ps) ((short)(((unsigned short)((unsigned char)ps[0])<<8)|\
36  ((unsigned short)((unsigned char)ps[1]))))
37 
38 /* Load a long int from the following tables with big-endian formats */
39 #define COFF_LONG_H(ps) (((long)(((unsigned long)((unsigned char)ps[0])<<24) |\
40  ((unsigned long)((unsigned char)ps[1])<<16) |\
41  ((unsigned long)((unsigned char)ps[2])<<8) |\
42  ((unsigned long)((unsigned char)ps[3])))))
43 
44 /* These may be overridden later by brain dead implementations which generate
45  a big-endian header with little-endian data. In that case, generate a
46  replacement macro which tests a flag and uses either of the two above
47  as appropriate. */
48 
49 #define COFF_LONG(v) COFF_LONG_L(v)
50 #define COFF_SHORT(v) COFF_SHORT_L(v)
51 
52 /*** coff information for Intel 386/486. */
53 
54 /********************** FILE HEADER **********************/
55 
56 struct COFF_filehdr {
57  char f_magic[2]; /* magic number */
58  char f_nscns[2]; /* number of sections */
59  char f_timdat[4]; /* time & date stamp */
60  char f_symptr[4]; /* file pointer to symtab */
61  char f_nsyms[4]; /* number of symtab entries */
62  char f_opthdr[2]; /* sizeof(optional hdr) */
63  char f_flags[2]; /* flags */
64 };
65 
66 /*
67  * Bits for f_flags:
68  *
69  * F_RELFLG relocation info stripped from file
70  * F_EXEC file is executable (i.e. no unresolved external
71  * references)
72  * F_LNNO line numbers stripped from file
73  * F_LSYMS local symbols stripped from file
74  * F_MINMAL this is a minimal object file (".m") output of fextract
75  * F_UPDATE this is a fully bound update file, output of ogen
76  * F_SWABD this file has had its bytes swabbed (in names)
77  * F_AR16WR this file has the byte ordering of an AR16WR
78  * (e.g. 11/70) machine
79  * F_AR32WR this file has the byte ordering of an AR32WR machine
80  * (e.g. vax and iNTEL 386)
81  * F_AR32W this file has the byte ordering of an AR32W machine
82  * (e.g. 3b,maxi)
83  * F_PATCH file contains "patch" list in optional header
84  * F_NODF (minimal file only) no decision functions for
85  * replaced functions
86  */
87 
88 #define COFF_F_RELFLG 0000001
89 #define COFF_F_EXEC 0000002
90 #define COFF_F_LNNO 0000004
91 #define COFF_F_LSYMS 0000010
92 #define COFF_F_MINMAL 0000020
93 #define COFF_F_UPDATE 0000040
94 #define COFF_F_SWABD 0000100
95 #define COFF_F_AR16WR 0000200
96 #define COFF_F_AR32WR 0000400
97 #define COFF_F_AR32W 0001000
98 #define COFF_F_PATCH 0002000
99 #define COFF_F_NODF 0002000
100 
101 #define COFF_I386MAGIC 0x14c /* Linux's system */
102 
103 #if 0 /* Perhaps, someday, these formats may be used. */
104 #define COFF_I386PTXMAGIC 0x154
105 #define COFF_I386AIXMAGIC 0x175 /* IBM's AIX system */
106 #define COFF_I386BADMAG(x) ((COFF_SHORT((x).f_magic) != COFF_I386MAGIC) \
107  && COFF_SHORT((x).f_magic) != COFF_I386PTXMAGIC \
108  && COFF_SHORT((x).f_magic) != COFF_I386AIXMAGIC)
109 #else
110 #define COFF_I386BADMAG(x) (COFF_SHORT((x).f_magic) != COFF_I386MAGIC)
111 #endif
112 
113 #define COFF_FILHDR struct COFF_filehdr
114 #define COFF_FILHSZ sizeof(COFF_FILHDR)
115 
116 /********************** AOUT "OPTIONAL HEADER" **********************/
117 
118 /* Linux COFF must have this "optional" header. Standard COFF has no entry
119  location for the "entry" point. They normally would start with the first
120  location of the .text section. This is not a good idea for linux. So,
121  the use of this "optional" header is not optional. It is required.
122 
123  Do not be tempted to assume that the size of the optional header is
124  a constant and simply index the next byte by the size of this structure.
125  Use the 'f_opthdr' field in the main coff header for the size of the
126  structure actually written to the file!!
127 */
128 
129 typedef struct
130 {
131  char magic[2]; /* type of file */
132  char vstamp[2]; /* version stamp */
133  char tsize[4]; /* text size in bytes, padded to FW bdry */
134  char dsize[4]; /* initialized data " " */
135  char bsize[4]; /* uninitialized data " " */
136  char entry[4]; /* entry pt. */
137  char text_start[4]; /* base of text used for this file */
138  char data_start[4]; /* base of data used for this file */
139 }
140 COFF_AOUTHDR;
141 
142 #define COFF_AOUTSZ (sizeof(COFF_AOUTHDR))
143 
144 #define COFF_STMAGIC 0401
145 #define COFF_OMAGIC 0404
146 #define COFF_JMAGIC 0407 /* dirty text and data image, can't share */
147 #define COFF_DMAGIC 0410 /* dirty text segment, data aligned */
148 #define COFF_ZMAGIC 0413 /* The proper magic number for executables */
149 #define COFF_SHMAGIC 0443 /* shared library header */
150 
151 /********************** SECTION HEADER **********************/
152 
153 struct COFF_scnhdr {
154  char s_name[8]; /* section name */
155  char s_paddr[4]; /* physical address, aliased s_nlib */
156  char s_vaddr[4]; /* virtual address */
157  char s_size[4]; /* section size */
158  char s_scnptr[4]; /* file ptr to raw data for section */
159  char s_relptr[4]; /* file ptr to relocation */
160  char s_lnnoptr[4]; /* file ptr to line numbers */
161  char s_nreloc[2]; /* number of relocation entries */
162  char s_nlnno[2]; /* number of line number entries */
163  char s_flags[4]; /* flags */
164 };
165 
166 #define COFF_SCNHDR struct COFF_scnhdr
167 #define COFF_SCNHSZ sizeof(COFF_SCNHDR)
168 
169 /*
170  * names of "special" sections
171  */
172 
173 #define COFF_TEXT ".text"
174 #define COFF_DATA ".data"
175 #define COFF_BSS ".bss"
176 #define COFF_COMMENT ".comment"
177 #define COFF_LIB ".lib"
178 
179 #define COFF_SECT_TEXT 0 /* Section for instruction code */
180 #define COFF_SECT_DATA 1 /* Section for initialized globals */
181 #define COFF_SECT_BSS 2 /* Section for un-initialized globals */
182 #define COFF_SECT_REQD 3 /* Minimum number of sections for good file */
183 
184 #define COFF_STYP_REG 0x00 /* regular segment */
185 #define COFF_STYP_DSECT 0x01 /* dummy segment */
186 #define COFF_STYP_NOLOAD 0x02 /* no-load segment */
187 #define COFF_STYP_GROUP 0x04 /* group segment */
188 #define COFF_STYP_PAD 0x08 /* .pad segment */
189 #define COFF_STYP_COPY 0x10 /* copy section */
190 #define COFF_STYP_TEXT 0x20 /* .text segment */
191 #define COFF_STYP_DATA 0x40 /* .data segment */
192 #define COFF_STYP_BSS 0x80 /* .bss segment */
193 #define COFF_STYP_INFO 0x200 /* .comment section */
194 #define COFF_STYP_OVER 0x400 /* overlay section */
195 #define COFF_STYP_LIB 0x800 /* library section */
196 
197 /*
198  * Shared libraries have the following section header in the data field for
199  * each library.
200  */
201 
202 struct COFF_slib {
203  char sl_entsz[4]; /* Size of this entry */
204  char sl_pathndx[4]; /* size of the header field */
205 };
206 
207 #define COFF_SLIBHD struct COFF_slib
208 #define COFF_SLIBSZ sizeof(COFF_SLIBHD)
209 
210 /********************** LINE NUMBERS **********************/
211 
212 /* 1 line number entry for every "breakpointable" source line in a section.
213  * Line numbers are grouped on a per function basis; first entry in a function
214  * grouping will have l_lnno = 0 and in place of physical address will be the
215  * symbol table index of the function name.
216  */
217 
218 struct COFF_lineno {
219  union {
220  char l_symndx[4]; /* function name symbol index, iff l_lnno == 0*/
221  char l_paddr[4]; /* (physical) address of line number */
222  } l_addr;
223  char l_lnno[2]; /* line number */
224 };
225 
226 #define COFF_LINENO struct COFF_lineno
227 #define COFF_LINESZ 6
228 
229 /********************** SYMBOLS **********************/
230 
231 #define COFF_E_SYMNMLEN 8 /* # characters in a short symbol name */
232 #define COFF_E_FILNMLEN 14 /* # characters in a file name */
233 #define COFF_E_DIMNUM 4 /* # array dimensions in auxiliary entry */
234 
235 /*
236  * All symbols and sections have the following definition
237  */
238 
239 struct COFF_syment
240 {
241  union {
242  char e_name[E_SYMNMLEN]; /* Symbol name (first 8 characters) */
243  struct {
244  char e_zeroes[4]; /* Leading zeros */
245  char e_offset[4]; /* Offset if this is a header section */
246  } e;
247  } e;
248 
249  char e_value[4]; /* Value (address) of the segment */
250  char e_scnum[2]; /* Section number */
251  char e_type[2]; /* Type of section */
252  char e_sclass[1]; /* Loader class */
253  char e_numaux[1]; /* Number of auxiliary entries which follow */
254 };
255 
256 #define COFF_N_BTMASK (0xf) /* Mask for important class bits */
257 #define COFF_N_TMASK (0x30) /* Mask for important type bits */
258 #define COFF_N_BTSHFT (4) /* # bits to shift class field */
259 #define COFF_N_TSHIFT (2) /* # bits to shift type field */
260 
261 /*
262  * Auxiliary entries because the main table is too limiting.
263  */
264 
265 union COFF_auxent {
266 
267 /*
268  * Debugger information
269  */
270 
271  struct {
272  char x_tagndx[4]; /* str, un, or enum tag indx */
273  union {
274  struct {
275  char x_lnno[2]; /* declaration line number */
276  char x_size[2]; /* str/union/array size */
277  } x_lnsz;
278  char x_fsize[4]; /* size of function */
279  } x_misc;
280 
281  union {
282  struct { /* if ISFCN, tag, or .bb */
283  char x_lnnoptr[4]; /* ptr to fcn line # */
284  char x_endndx[4]; /* entry ndx past block end */
285  } x_fcn;
286 
287  struct { /* if ISARY, up to 4 dimen. */
288  char x_dimen[E_DIMNUM][2];
289  } x_ary;
290  } x_fcnary;
291 
292  char x_tvndx[2]; /* tv index */
293  } x_sym;
294 
295 /*
296  * Source file names (debugger information)
297  */
298 
299  union {
300  char x_fname[E_FILNMLEN];
301  struct {
302  char x_zeroes[4];
303  char x_offset[4];
304  } x_n;
305  } x_file;
306 
307 /*
308  * Section information
309  */
310 
311  struct {
312  char x_scnlen[4]; /* section length */
313  char x_nreloc[2]; /* # relocation entries */
314  char x_nlinno[2]; /* # line numbers */
315  } x_scn;
316 
317 /*
318  * Transfer vector (branch table)
319  */
320 
321  struct {
322  char x_tvfill[4]; /* tv fill value */
323  char x_tvlen[2]; /* length of .tv */
324  char x_tvran[2][2]; /* tv range */
325  } x_tv; /* info about .tv section (in auxent of symbol .tv)) */
326 };
327 
328 #define COFF_SYMENT struct COFF_syment
329 #define COFF_SYMESZ 18
330 #define COFF_AUXENT union COFF_auxent
331 #define COFF_AUXESZ 18
332 
333 #define COFF_ETEXT "etext"
334 
335 /********************** RELOCATION DIRECTIVES **********************/
336 
337 struct COFF_reloc {
338  char r_vaddr[4]; /* Virtual address of item */
339  char r_symndx[4]; /* Symbol index in the symtab */
340  char r_type[2]; /* Relocation type */
341 };
342 
343 #define COFF_RELOC struct COFF_reloc
344 #define COFF_RELSZ 10
345 
346 #define COFF_DEF_DATA_SECTION_ALIGNMENT 4
347 #define COFF_DEF_BSS_SECTION_ALIGNMENT 4
348 #define COFF_DEF_TEXT_SECTION_ALIGNMENT 4
349 
350 /* For new sections we haven't heard of before */
351 #define COFF_DEF_SECTION_ALIGNMENT 4
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