1 /* frags.c - manage frags - 2 Copyright (C) 1987-2016 Free Software Foundation, Inc. 3 4 This file is part of GAS, the GNU Assembler. 5 6 GAS is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3, or (at your option) 9 any later version. 10 11 GAS is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GAS; see the file COPYING. If not, write to the Free 18 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA 19 02110-1301, USA. */ 20 21 #include "as.h" 22 #include "subsegs.h" 23 #include "obstack.h" 24 25 extern fragS zero_address_frag; 26 extern fragS predefined_address_frag; 27 28 static int totalfrags; 29 30 int 31 get_frag_count (void) 32 { 33 return totalfrags; 34 } 35 36 void 37 clear_frag_count (void) 38 { 39 totalfrags = 0; 40 } 41 42 /* Initialization for frag routines. */ 44 45 void 46 frag_init (void) 47 { 48 zero_address_frag.fr_type = rs_fill; 49 predefined_address_frag.fr_type = rs_fill; 50 } 51 52 /* Check that we're not trying to assemble into a section that can't 54 allocate frags (currently, this is only possible in the absolute 55 section), or into an mri common. */ 56 57 static void 58 frag_alloc_check (const struct obstack *ob) 59 { 60 if (ob->chunk_size == 0) 61 { 62 as_bad (_("attempt to allocate data in absolute section")); 63 subseg_set (text_section, 0); 64 } 65 66 if (mri_common_symbol != NULL) 67 { 68 as_bad (_("attempt to allocate data in common section")); 69 mri_common_symbol = NULL; 70 } 71 } 72 73 /* Allocate a frag on the specified obstack. 74 Call this routine from everywhere else, so that all the weird alignment 75 hackery can be done in just one place. */ 76 77 fragS * 78 frag_alloc (struct obstack *ob) 79 { 80 fragS *ptr; 81 int oalign; 82 83 (void) obstack_alloc (ob, 0); 84 oalign = obstack_alignment_mask (ob); 85 obstack_alignment_mask (ob) = 0; 86 ptr = (fragS *) obstack_alloc (ob, SIZEOF_STRUCT_FRAG); 87 obstack_alignment_mask (ob) = oalign; 88 memset (ptr, 0, SIZEOF_STRUCT_FRAG); 89 totalfrags++; 90 return ptr; 91 } 92 93 /* Try to augment current frag by nchars chars. 95 If there is no room, close of the current frag with a ".fill 0" 96 and begin a new frag. Unless the new frag has nchars chars available 97 do not return. Do not set up any fields of *now_frag. */ 98 99 void 100 frag_grow (size_t nchars) 101 { 102 if (obstack_room (&frchain_now->frch_obstack) < nchars) 103 { 104 size_t oldc; 105 size_t newc; 106 107 /* Try to allocate a bit more than needed right now. But don't do 108 this if we would waste too much memory. Especially necessary 109 for extremely big (like 2GB initialized) frags. */ 110 if (nchars < 0x10000) 111 newc = 2 * nchars; 112 else 113 newc = nchars + 0x10000; 114 newc += SIZEOF_STRUCT_FRAG; 115 116 /* Check for possible overflow. */ 117 if (newc < nchars) 118 as_fatal (_("can't extend frag %lu chars"), (unsigned long) nchars); 119 120 /* Force to allocate at least NEWC bytes, but not less than the 121 default. */ 122 oldc = obstack_chunk_size (&frchain_now->frch_obstack); 123 if (newc > oldc) 124 obstack_chunk_size (&frchain_now->frch_obstack) = newc; 125 126 while (obstack_room (&frchain_now->frch_obstack) < nchars) 127 { 128 /* Not enough room in this frag. Close it and start a new one. 129 This must be done in a loop because the created frag may not 130 be big enough if the current obstack chunk is used. */ 131 frag_wane (frag_now); 132 frag_new (0); 133 } 134 135 /* Restore the old chunk size. */ 136 obstack_chunk_size (&frchain_now->frch_obstack) = oldc; 137 } 138 } 139 140 /* Call this to close off a completed frag, and start up a new (empty) 142 frag, in the same subsegment as the old frag. 143 [frchain_now remains the same but frag_now is updated.] 144 Because this calculates the correct value of fr_fix by 145 looking at the obstack 'frags', it needs to know how many 146 characters at the end of the old frag belong to the maximal 147 variable part; The rest must belong to fr_fix. 148 It doesn't actually set up the old frag's fr_var. You may have 149 set fr_var == 1, but allocated 10 chars to the end of the frag; 150 In this case you pass old_frags_var_max_size == 10. 151 In fact, you may use fr_var for something totally unrelated to the 152 size of the variable part of the frag; None of the generic frag 153 handling code makes use of fr_var. 154 155 Make a new frag, initialising some components. Link new frag at end 156 of frchain_now. */ 157 158 void 159 frag_new (size_t old_frags_var_max_size 160 /* Number of chars (already allocated on obstack frags) in 161 variable_length part of frag. */) 162 { 163 fragS *former_last_fragP; 164 frchainS *frchP; 165 166 gas_assert (frchain_now->frch_last == frag_now); 167 168 /* Fix up old frag's fr_fix. */ 169 frag_now->fr_fix = frag_now_fix_octets () - old_frags_var_max_size; 170 /* Make sure its type is valid. */ 171 gas_assert (frag_now->fr_type != 0); 172 173 /* This will align the obstack so the next struct we allocate on it 174 will begin at a correct boundary. */ 175 obstack_finish (&frchain_now->frch_obstack); 176 frchP = frchain_now; 177 know (frchP); 178 former_last_fragP = frchP->frch_last; 179 gas_assert (former_last_fragP != 0); 180 gas_assert (former_last_fragP == frag_now); 181 frag_now = frag_alloc (&frchP->frch_obstack); 182 183 frag_now->fr_file = as_where (&frag_now->fr_line); 184 185 /* Generally, frag_now->points to an address rounded up to next 186 alignment. However, characters will add to obstack frags 187 IMMEDIATELY after the struct frag, even if they are not starting 188 at an alignment address. */ 189 former_last_fragP->fr_next = frag_now; 190 frchP->frch_last = frag_now; 191 192 #ifndef NO_LISTING 193 { 194 extern struct list_info_struct *listing_tail; 195 frag_now->line = listing_tail; 196 } 197 #endif 198 199 gas_assert (frchain_now->frch_last == frag_now); 200 201 frag_now->fr_next = NULL; 202 } 203 204 /* Start a new frag unless we have n more chars of room in the current frag. 206 Close off the old frag with a .fill 0. 207 208 Return the address of the 1st char to write into. Advance 209 frag_now_growth past the new chars. */ 210 211 char * 212 frag_more (size_t nchars) 213 { 214 char *retval; 215 216 frag_alloc_check (&frchain_now->frch_obstack); 217 frag_grow (nchars); 218 retval = obstack_next_free (&frchain_now->frch_obstack); 219 obstack_blank_fast (&frchain_now->frch_obstack, nchars); 220 return retval; 221 } 222 223 /* Close the current frag, setting its fields for a relaxable frag. Start a 225 new frag. */ 226 227 static void 228 frag_var_init (relax_stateT type, size_t max_chars, size_t var, 229 relax_substateT subtype, symbolS *symbol, offsetT offset, 230 char *opcode) 231 { 232 frag_now->fr_var = var; 233 frag_now->fr_type = type; 234 frag_now->fr_subtype = subtype; 235 frag_now->fr_symbol = symbol; 236 frag_now->fr_offset = offset; 237 frag_now->fr_opcode = opcode; 238 #ifdef USING_CGEN 239 frag_now->fr_cgen.insn = 0; 240 frag_now->fr_cgen.opindex = 0; 241 frag_now->fr_cgen.opinfo = 0; 242 #endif 243 #ifdef TC_FRAG_INIT 244 TC_FRAG_INIT (frag_now); 245 #endif 246 frag_now->fr_file = as_where (&frag_now->fr_line); 247 248 frag_new (max_chars); 249 } 250 251 /* Start a new frag unless we have max_chars more chars of room in the 252 current frag. Close off the old frag with a .fill 0. 253 254 Set up a machine_dependent relaxable frag, then start a new frag. 255 Return the address of the 1st char of the var part of the old frag 256 to write into. */ 257 258 char * 259 frag_var (relax_stateT type, size_t max_chars, size_t var, 260 relax_substateT subtype, symbolS *symbol, offsetT offset, 261 char *opcode) 262 { 263 char *retval; 264 265 frag_grow (max_chars); 266 retval = obstack_next_free (&frchain_now->frch_obstack); 267 obstack_blank_fast (&frchain_now->frch_obstack, max_chars); 268 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode); 269 return retval; 270 } 271 272 /* OVE: This variant of frag_var assumes that space for the tail has been 274 allocated by caller. 275 No call to frag_grow is done. */ 276 277 char * 278 frag_variant (relax_stateT type, size_t max_chars, size_t var, 279 relax_substateT subtype, symbolS *symbol, offsetT offset, 280 char *opcode) 281 { 282 char *retval; 283 284 retval = obstack_next_free (&frchain_now->frch_obstack); 285 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode); 286 287 return retval; 288 } 289 290 /* Reduce the variable end of a frag to a harmless state. */ 292 293 void 294 frag_wane (fragS *fragP) 295 { 296 fragP->fr_type = rs_fill; 297 fragP->fr_offset = 0; 298 fragP->fr_var = 0; 299 } 300 301 /* Return the number of bytes by which the current frag can be grown. */ 303 304 size_t 305 frag_room (void) 306 { 307 return obstack_room (&frchain_now->frch_obstack); 308 } 309 310 /* Make an alignment frag. The size of this frag will be adjusted to 312 force the next frag to have the appropriate alignment. ALIGNMENT 313 is the power of two to which to align. FILL_CHARACTER is the 314 character to use to fill in any bytes which are skipped. MAX is 315 the maximum number of characters to skip when doing the alignment, 316 or 0 if there is no maximum. */ 317 318 void 319 frag_align (int alignment, int fill_character, int max) 320 { 321 if (now_seg == absolute_section) 322 { 323 addressT new_off; 324 addressT mask; 325 326 mask = (~(addressT) 0) << alignment; 327 new_off = (abs_section_offset + ~mask) & mask; 328 if (max == 0 || new_off - abs_section_offset <= (addressT) max) 329 abs_section_offset = new_off; 330 } 331 else 332 { 333 char *p; 334 335 p = frag_var (rs_align, 1, 1, (relax_substateT) max, 336 (symbolS *) 0, (offsetT) alignment, (char *) 0); 337 *p = fill_character; 338 } 339 } 340 341 /* Make an alignment frag like frag_align, but fill with a repeating 342 pattern rather than a single byte. ALIGNMENT is the power of two 343 to which to align. FILL_PATTERN is the fill pattern to repeat in 344 the bytes which are skipped. N_FILL is the number of bytes in 345 FILL_PATTERN. MAX is the maximum number of characters to skip when 346 doing the alignment, or 0 if there is no maximum. */ 347 348 void 349 frag_align_pattern (int alignment, const char *fill_pattern, 350 size_t n_fill, int max) 351 { 352 char *p; 353 354 p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) max, 355 (symbolS *) 0, (offsetT) alignment, (char *) 0); 356 memcpy (p, fill_pattern, n_fill); 357 } 358 359 /* The NOP_OPCODE is for the alignment fill value. Fill it with a nop 360 instruction so that the disassembler does not choke on it. */ 361 #ifndef NOP_OPCODE 362 #define NOP_OPCODE 0x00 363 #endif 364 365 /* Use this to restrict the amount of memory allocated for representing 366 the alignment code. Needs to be large enough to hold any fixed sized 367 prologue plus the replicating portion. */ 368 #ifndef MAX_MEM_FOR_RS_ALIGN_CODE 369 /* Assume that if HANDLE_ALIGN is not defined then no special action 370 is required to code fill, which means that we get just repeat the 371 one NOP_OPCODE byte. */ 372 # ifndef HANDLE_ALIGN 373 # define MAX_MEM_FOR_RS_ALIGN_CODE 1 374 # else 375 # define MAX_MEM_FOR_RS_ALIGN_CODE ((1 << alignment) - 1) 376 # endif 377 #endif 378 379 void 380 frag_align_code (int alignment, int max) 381 { 382 char *p; 383 384 p = frag_var (rs_align_code, MAX_MEM_FOR_RS_ALIGN_CODE, 1, 385 (relax_substateT) max, (symbolS *) 0, 386 (offsetT) alignment, (char *) 0); 387 *p = NOP_OPCODE; 388 } 389 390 addressT 391 frag_now_fix_octets (void) 392 { 393 if (now_seg == absolute_section) 394 return abs_section_offset; 395 396 return ((char *) obstack_next_free (&frchain_now->frch_obstack) 397 - frag_now->fr_literal); 398 } 399 400 addressT 401 frag_now_fix (void) 402 { 403 return frag_now_fix_octets () / OCTETS_PER_BYTE; 404 } 405 406 void 407 frag_append_1_char (int datum) 408 { 409 frag_alloc_check (&frchain_now->frch_obstack); 410 if (obstack_room (&frchain_now->frch_obstack) <= 1) 411 { 412 frag_wane (frag_now); 413 frag_new (0); 414 } 415 obstack_1grow (&frchain_now->frch_obstack, datum); 416 } 417 418 /* Return TRUE if FRAG1 and FRAG2 have a fixed relationship between 419 their start addresses. Set OFFSET to the difference in address 420 not already accounted for in the frag FR_ADDRESS. */ 421 422 bfd_boolean 423 frag_offset_fixed_p (const fragS *frag1, const fragS *frag2, offsetT *offset) 424 { 425 const fragS *frag; 426 offsetT off; 427 428 /* Start with offset initialised to difference between the two frags. 429 Prior to assigning frag addresses this will be zero. */ 430 off = frag1->fr_address - frag2->fr_address; 431 if (frag1 == frag2) 432 { 433 *offset = off; 434 return TRUE; 435 } 436 437 /* Maybe frag2 is after frag1. */ 438 frag = frag1; 439 while (frag->fr_type == rs_fill) 440 { 441 off += frag->fr_fix + frag->fr_offset * frag->fr_var; 442 frag = frag->fr_next; 443 if (frag == NULL) 444 break; 445 if (frag == frag2) 446 { 447 *offset = off; 448 return TRUE; 449 } 450 } 451 452 /* Maybe frag1 is after frag2. */ 453 off = frag1->fr_address - frag2->fr_address; 454 frag = frag2; 455 while (frag->fr_type == rs_fill) 456 { 457 off -= frag->fr_fix + frag->fr_offset * frag->fr_var; 458 frag = frag->fr_next; 459 if (frag == NULL) 460 break; 461 if (frag == frag1) 462 { 463 *offset = off; 464 return TRUE; 465 } 466 } 467 468 return FALSE; 469 } 470
