| 1 | /* frags.c - manage frags - |
| 2 | Copyright 1987, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, |
| 3 | 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007 |
| 4 | Free Software Foundation, Inc. |
| 5 | |
| 6 | This file is part of GAS, the GNU Assembler. |
| 7 | |
| 8 | GAS is free software; you can redistribute it and/or modify |
| 9 | it under the terms of the GNU General Public License as published by |
| 10 | the Free Software Foundation; either version 3, or (at your option) |
| 11 | any later version. |
| 12 | |
| 13 | GAS is distributed in the hope that it will be useful, |
| 14 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | GNU General Public License for more details. |
| 17 | |
| 18 | You should have received a copy of the GNU General Public License |
| 19 | along with GAS; see the file COPYING. If not, write to the Free |
| 20 | Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA |
| 21 | 02110-1301, USA. */ |
| 22 | |
| 23 | #include "as.h" |
| 24 | #include "subsegs.h" |
| 25 | #include "obstack.h" |
| 26 | |
| 27 | extern fragS zero_address_frag; |
| 28 | extern fragS bss_address_frag; |
| 29 | \f |
| 30 | /* Initialization for frag routines. */ |
| 31 | |
| 32 | void |
| 33 | frag_init (void) |
| 34 | { |
| 35 | zero_address_frag.fr_type = rs_fill; |
| 36 | bss_address_frag.fr_type = rs_fill; |
| 37 | } |
| 38 | \f |
| 39 | /* Check that we're not trying to assemble into a section that can't |
| 40 | allocate frags (currently, this is only possible in the absolute |
| 41 | section), or into an mri common. */ |
| 42 | |
| 43 | static void |
| 44 | frag_alloc_check (const struct obstack *ob) |
| 45 | { |
| 46 | if (ob->chunk_size == 0) |
| 47 | { |
| 48 | as_bad (_("attempt to allocate data in absolute section")); |
| 49 | subseg_set (text_section, 0); |
| 50 | } |
| 51 | |
| 52 | if (mri_common_symbol != NULL) |
| 53 | { |
| 54 | as_bad (_("attempt to allocate data in common section")); |
| 55 | mri_common_symbol = NULL; |
| 56 | } |
| 57 | } |
| 58 | |
| 59 | /* Allocate a frag on the specified obstack. |
| 60 | Call this routine from everywhere else, so that all the weird alignment |
| 61 | hackery can be done in just one place. */ |
| 62 | |
| 63 | fragS * |
| 64 | frag_alloc (struct obstack *ob) |
| 65 | { |
| 66 | fragS *ptr; |
| 67 | int oalign; |
| 68 | |
| 69 | (void) obstack_alloc (ob, 0); |
| 70 | oalign = obstack_alignment_mask (ob); |
| 71 | obstack_alignment_mask (ob) = 0; |
| 72 | ptr = (fragS *) obstack_alloc (ob, SIZEOF_STRUCT_FRAG); |
| 73 | obstack_alignment_mask (ob) = oalign; |
| 74 | memset (ptr, 0, SIZEOF_STRUCT_FRAG); |
| 75 | return ptr; |
| 76 | } |
| 77 | \f |
| 78 | /* Try to augment current frag by nchars chars. |
| 79 | If there is no room, close of the current frag with a ".fill 0" |
| 80 | and begin a new frag. Unless the new frag has nchars chars available |
| 81 | do not return. Do not set up any fields of *now_frag. */ |
| 82 | |
| 83 | void |
| 84 | frag_grow (unsigned int nchars) |
| 85 | { |
| 86 | if (obstack_room (&frchain_now->frch_obstack) < nchars) |
| 87 | { |
| 88 | unsigned int n; |
| 89 | long oldc; |
| 90 | |
| 91 | frag_wane (frag_now); |
| 92 | frag_new (0); |
| 93 | oldc = frchain_now->frch_obstack.chunk_size; |
| 94 | /* Try to allocate a bit more than needed right now. But don't do |
| 95 | this if we would waste too much memory. Especially necessary |
| 96 | for extremely big (like 2GB initialized) frags. */ |
| 97 | if (nchars < 0x10000) |
| 98 | frchain_now->frch_obstack.chunk_size = 2 * nchars; |
| 99 | else |
| 100 | frchain_now->frch_obstack.chunk_size = nchars + 0x10000; |
| 101 | frchain_now->frch_obstack.chunk_size += SIZEOF_STRUCT_FRAG; |
| 102 | if (frchain_now->frch_obstack.chunk_size > 0) |
| 103 | while ((n = obstack_room (&frchain_now->frch_obstack)) < nchars |
| 104 | && (unsigned long) frchain_now->frch_obstack.chunk_size > nchars) |
| 105 | { |
| 106 | frag_wane (frag_now); |
| 107 | frag_new (0); |
| 108 | } |
| 109 | frchain_now->frch_obstack.chunk_size = oldc; |
| 110 | } |
| 111 | if (obstack_room (&frchain_now->frch_obstack) < nchars) |
| 112 | as_fatal (_("can't extend frag %u chars"), nchars); |
| 113 | } |
| 114 | \f |
| 115 | /* Call this to close off a completed frag, and start up a new (empty) |
| 116 | frag, in the same subsegment as the old frag. |
| 117 | [frchain_now remains the same but frag_now is updated.] |
| 118 | Because this calculates the correct value of fr_fix by |
| 119 | looking at the obstack 'frags', it needs to know how many |
| 120 | characters at the end of the old frag belong to the maximal |
| 121 | variable part; The rest must belong to fr_fix. |
| 122 | It doesn't actually set up the old frag's fr_var. You may have |
| 123 | set fr_var == 1, but allocated 10 chars to the end of the frag; |
| 124 | In this case you pass old_frags_var_max_size == 10. |
| 125 | In fact, you may use fr_var for something totally unrelated to the |
| 126 | size of the variable part of the frag; None of the generic frag |
| 127 | handling code makes use of fr_var. |
| 128 | |
| 129 | Make a new frag, initialising some components. Link new frag at end |
| 130 | of frchain_now. */ |
| 131 | |
| 132 | void |
| 133 | frag_new (int old_frags_var_max_size |
| 134 | /* Number of chars (already allocated on obstack frags) in |
| 135 | variable_length part of frag. */) |
| 136 | { |
| 137 | fragS *former_last_fragP; |
| 138 | frchainS *frchP; |
| 139 | |
| 140 | assert (frchain_now->frch_last == frag_now); |
| 141 | |
| 142 | /* Fix up old frag's fr_fix. */ |
| 143 | frag_now->fr_fix = frag_now_fix_octets () - old_frags_var_max_size; |
| 144 | /* Make sure its type is valid. */ |
| 145 | assert (frag_now->fr_type != 0); |
| 146 | |
| 147 | /* This will align the obstack so the next struct we allocate on it |
| 148 | will begin at a correct boundary. */ |
| 149 | obstack_finish (&frchain_now->frch_obstack); |
| 150 | frchP = frchain_now; |
| 151 | know (frchP); |
| 152 | former_last_fragP = frchP->frch_last; |
| 153 | assert (former_last_fragP != 0); |
| 154 | assert (former_last_fragP == frag_now); |
| 155 | frag_now = frag_alloc (&frchP->frch_obstack); |
| 156 | |
| 157 | as_where (&frag_now->fr_file, &frag_now->fr_line); |
| 158 | |
| 159 | /* Generally, frag_now->points to an address rounded up to next |
| 160 | alignment. However, characters will add to obstack frags |
| 161 | IMMEDIATELY after the struct frag, even if they are not starting |
| 162 | at an alignment address. */ |
| 163 | former_last_fragP->fr_next = frag_now; |
| 164 | frchP->frch_last = frag_now; |
| 165 | |
| 166 | #ifndef NO_LISTING |
| 167 | { |
| 168 | extern struct list_info_struct *listing_tail; |
| 169 | frag_now->line = listing_tail; |
| 170 | } |
| 171 | #endif |
| 172 | |
| 173 | assert (frchain_now->frch_last == frag_now); |
| 174 | |
| 175 | frag_now->fr_next = NULL; |
| 176 | } |
| 177 | \f |
| 178 | /* Start a new frag unless we have n more chars of room in the current frag. |
| 179 | Close off the old frag with a .fill 0. |
| 180 | |
| 181 | Return the address of the 1st char to write into. Advance |
| 182 | frag_now_growth past the new chars. */ |
| 183 | |
| 184 | char * |
| 185 | frag_more (int nchars) |
| 186 | { |
| 187 | register char *retval; |
| 188 | |
| 189 | frag_alloc_check (&frchain_now->frch_obstack); |
| 190 | frag_grow (nchars); |
| 191 | retval = obstack_next_free (&frchain_now->frch_obstack); |
| 192 | obstack_blank_fast (&frchain_now->frch_obstack, nchars); |
| 193 | return (retval); |
| 194 | } |
| 195 | \f |
| 196 | /* Start a new frag unless we have max_chars more chars of room in the |
| 197 | current frag. Close off the old frag with a .fill 0. |
| 198 | |
| 199 | Set up a machine_dependent relaxable frag, then start a new frag. |
| 200 | Return the address of the 1st char of the var part of the old frag |
| 201 | to write into. */ |
| 202 | |
| 203 | char * |
| 204 | frag_var (relax_stateT type, int max_chars, int var, relax_substateT subtype, |
| 205 | symbolS *symbol, offsetT offset, char *opcode) |
| 206 | { |
| 207 | register char *retval; |
| 208 | |
| 209 | frag_grow (max_chars); |
| 210 | retval = obstack_next_free (&frchain_now->frch_obstack); |
| 211 | obstack_blank_fast (&frchain_now->frch_obstack, max_chars); |
| 212 | frag_now->fr_var = var; |
| 213 | frag_now->fr_type = type; |
| 214 | frag_now->fr_subtype = subtype; |
| 215 | frag_now->fr_symbol = symbol; |
| 216 | frag_now->fr_offset = offset; |
| 217 | frag_now->fr_opcode = opcode; |
| 218 | #ifdef USING_CGEN |
| 219 | frag_now->fr_cgen.insn = 0; |
| 220 | frag_now->fr_cgen.opindex = 0; |
| 221 | frag_now->fr_cgen.opinfo = 0; |
| 222 | #endif |
| 223 | #ifdef TC_FRAG_INIT |
| 224 | TC_FRAG_INIT (frag_now); |
| 225 | #endif |
| 226 | as_where (&frag_now->fr_file, &frag_now->fr_line); |
| 227 | frag_new (max_chars); |
| 228 | return (retval); |
| 229 | } |
| 230 | \f |
| 231 | /* OVE: This variant of frag_var assumes that space for the tail has been |
| 232 | allocated by caller. |
| 233 | No call to frag_grow is done. */ |
| 234 | |
| 235 | char * |
| 236 | frag_variant (relax_stateT type, int max_chars, int var, |
| 237 | relax_substateT subtype, symbolS *symbol, offsetT offset, |
| 238 | char *opcode) |
| 239 | { |
| 240 | register char *retval; |
| 241 | |
| 242 | retval = obstack_next_free (&frchain_now->frch_obstack); |
| 243 | frag_now->fr_var = var; |
| 244 | frag_now->fr_type = type; |
| 245 | frag_now->fr_subtype = subtype; |
| 246 | frag_now->fr_symbol = symbol; |
| 247 | frag_now->fr_offset = offset; |
| 248 | frag_now->fr_opcode = opcode; |
| 249 | #ifdef USING_CGEN |
| 250 | frag_now->fr_cgen.insn = 0; |
| 251 | frag_now->fr_cgen.opindex = 0; |
| 252 | frag_now->fr_cgen.opinfo = 0; |
| 253 | #endif |
| 254 | #ifdef TC_FRAG_INIT |
| 255 | TC_FRAG_INIT (frag_now); |
| 256 | #endif |
| 257 | as_where (&frag_now->fr_file, &frag_now->fr_line); |
| 258 | frag_new (max_chars); |
| 259 | return (retval); |
| 260 | } |
| 261 | \f |
| 262 | /* Reduce the variable end of a frag to a harmless state. */ |
| 263 | |
| 264 | void |
| 265 | frag_wane (register fragS *fragP) |
| 266 | { |
| 267 | fragP->fr_type = rs_fill; |
| 268 | fragP->fr_offset = 0; |
| 269 | fragP->fr_var = 0; |
| 270 | } |
| 271 | \f |
| 272 | /* Return the number of bytes by which the current frag can be grown. */ |
| 273 | |
| 274 | int |
| 275 | frag_room (void) |
| 276 | { |
| 277 | return obstack_room (&frchain_now->frch_obstack); |
| 278 | } |
| 279 | \f |
| 280 | /* Make an alignment frag. The size of this frag will be adjusted to |
| 281 | force the next frag to have the appropriate alignment. ALIGNMENT |
| 282 | is the power of two to which to align. FILL_CHARACTER is the |
| 283 | character to use to fill in any bytes which are skipped. MAX is |
| 284 | the maximum number of characters to skip when doing the alignment, |
| 285 | or 0 if there is no maximum. */ |
| 286 | |
| 287 | void |
| 288 | frag_align (int alignment, int fill_character, int max) |
| 289 | { |
| 290 | if (now_seg == absolute_section) |
| 291 | { |
| 292 | addressT new_off; |
| 293 | addressT mask; |
| 294 | |
| 295 | mask = (~(addressT) 0) << alignment; |
| 296 | new_off = (abs_section_offset + ~mask) & mask; |
| 297 | if (max == 0 || new_off - abs_section_offset <= (addressT) max) |
| 298 | abs_section_offset = new_off; |
| 299 | } |
| 300 | else |
| 301 | { |
| 302 | char *p; |
| 303 | |
| 304 | p = frag_var (rs_align, 1, 1, (relax_substateT) max, |
| 305 | (symbolS *) 0, (offsetT) alignment, (char *) 0); |
| 306 | *p = fill_character; |
| 307 | } |
| 308 | } |
| 309 | |
| 310 | /* Make an alignment frag like frag_align, but fill with a repeating |
| 311 | pattern rather than a single byte. ALIGNMENT is the power of two |
| 312 | to which to align. FILL_PATTERN is the fill pattern to repeat in |
| 313 | the bytes which are skipped. N_FILL is the number of bytes in |
| 314 | FILL_PATTERN. MAX is the maximum number of characters to skip when |
| 315 | doing the alignment, or 0 if there is no maximum. */ |
| 316 | |
| 317 | void |
| 318 | frag_align_pattern (int alignment, const char *fill_pattern, |
| 319 | int n_fill, int max) |
| 320 | { |
| 321 | char *p; |
| 322 | |
| 323 | p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) max, |
| 324 | (symbolS *) 0, (offsetT) alignment, (char *) 0); |
| 325 | memcpy (p, fill_pattern, n_fill); |
| 326 | } |
| 327 | |
| 328 | /* The NOP_OPCODE is for the alignment fill value. Fill it with a nop |
| 329 | instruction so that the disassembler does not choke on it. */ |
| 330 | #ifndef NOP_OPCODE |
| 331 | #define NOP_OPCODE 0x00 |
| 332 | #endif |
| 333 | |
| 334 | /* Use this to restrict the amount of memory allocated for representing |
| 335 | the alignment code. Needs to be large enough to hold any fixed sized |
| 336 | prologue plus the replicating portion. */ |
| 337 | #ifndef MAX_MEM_FOR_RS_ALIGN_CODE |
| 338 | /* Assume that if HANDLE_ALIGN is not defined then no special action |
| 339 | is required to code fill, which means that we get just repeat the |
| 340 | one NOP_OPCODE byte. */ |
| 341 | # ifndef HANDLE_ALIGN |
| 342 | # define MAX_MEM_FOR_RS_ALIGN_CODE 1 |
| 343 | # else |
| 344 | # define MAX_MEM_FOR_RS_ALIGN_CODE ((1 << alignment) - 1) |
| 345 | # endif |
| 346 | #endif |
| 347 | |
| 348 | void |
| 349 | frag_align_code (int alignment, int max) |
| 350 | { |
| 351 | char *p; |
| 352 | |
| 353 | p = frag_var (rs_align_code, MAX_MEM_FOR_RS_ALIGN_CODE, 1, |
| 354 | (relax_substateT) max, (symbolS *) 0, |
| 355 | (offsetT) alignment, (char *) 0); |
| 356 | *p = NOP_OPCODE; |
| 357 | } |
| 358 | |
| 359 | addressT |
| 360 | frag_now_fix_octets (void) |
| 361 | { |
| 362 | if (now_seg == absolute_section) |
| 363 | return abs_section_offset; |
| 364 | |
| 365 | return ((char *) obstack_next_free (&frchain_now->frch_obstack) |
| 366 | - frag_now->fr_literal); |
| 367 | } |
| 368 | |
| 369 | addressT |
| 370 | frag_now_fix (void) |
| 371 | { |
| 372 | return frag_now_fix_octets () / OCTETS_PER_BYTE; |
| 373 | } |
| 374 | |
| 375 | void |
| 376 | frag_append_1_char (int datum) |
| 377 | { |
| 378 | frag_alloc_check (&frchain_now->frch_obstack); |
| 379 | if (obstack_room (&frchain_now->frch_obstack) <= 1) |
| 380 | { |
| 381 | frag_wane (frag_now); |
| 382 | frag_new (0); |
| 383 | } |
| 384 | obstack_1grow (&frchain_now->frch_obstack, datum); |
| 385 | } |
| 386 | |
| 387 | /* Return TRUE if FRAG1 and FRAG2 have a fixed relationship between |
| 388 | their start addresses. Set OFFSET to the difference in address |
| 389 | not already accounted for in the frag FR_ADDRESS. */ |
| 390 | |
| 391 | bfd_boolean |
| 392 | frag_offset_fixed_p (const fragS *frag1, const fragS *frag2, bfd_vma *offset) |
| 393 | { |
| 394 | const fragS *frag; |
| 395 | bfd_vma off; |
| 396 | |
| 397 | /* Start with offset initialised to difference between the two frags. |
| 398 | Prior to assigning frag addresses this will be zero. */ |
| 399 | off = frag1->fr_address - frag2->fr_address; |
| 400 | if (frag1 == frag2) |
| 401 | { |
| 402 | *offset = off; |
| 403 | return TRUE; |
| 404 | } |
| 405 | |
| 406 | /* Maybe frag2 is after frag1. */ |
| 407 | frag = frag1; |
| 408 | while (frag->fr_type == rs_fill) |
| 409 | { |
| 410 | off += frag->fr_fix + frag->fr_offset * frag->fr_var; |
| 411 | frag = frag->fr_next; |
| 412 | if (frag == NULL) |
| 413 | break; |
| 414 | if (frag == frag2) |
| 415 | { |
| 416 | *offset = off; |
| 417 | return TRUE; |
| 418 | } |
| 419 | } |
| 420 | |
| 421 | /* Maybe frag1 is after frag2. */ |
| 422 | off = frag1->fr_address - frag2->fr_address; |
| 423 | frag = frag2; |
| 424 | while (frag->fr_type == rs_fill) |
| 425 | { |
| 426 | off -= frag->fr_fix + frag->fr_offset * frag->fr_var; |
| 427 | frag = frag->fr_next; |
| 428 | if (frag == NULL) |
| 429 | break; |
| 430 | if (frag == frag1) |
| 431 | { |
| 432 | *offset = off; |
| 433 | return TRUE; |
| 434 | } |
| 435 | } |
| 436 | |
| 437 | return FALSE; |
| 438 | } |