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. */ 43 44 void 45 frag_init (void) 46 { 47 zero_address_frag.fr_type = rs_fill; 48 predefined_address_frag.fr_type = rs_fill; 49 } 50 51 /* Check that we're not trying to assemble into a section that can't 52 allocate frags (currently, this is only possible in the absolute 53 section), or into an mri common. */ 54 55 static void 56 frag_alloc_check (const struct obstack *ob) 57 { 58 if (ob->chunk_size == 0) 59 { 60 as_bad (_("attempt to allocate data in absolute section")); 61 subseg_set (text_section, 0); 62 } 63 64 if (mri_common_symbol != NULL) 65 { 66 as_bad (_("attempt to allocate data in common section")); 67 mri_common_symbol = NULL; 68 } 69 } 70 71 /* Allocate a frag on the specified obstack. 72 Call this routine from everywhere else, so that all the weird alignment 73 hackery can be done in just one place. */ 74 75 fragS * 76 frag_alloc (struct obstack *ob) 77 { 78 fragS *ptr; 79 int oalign; 80 81 (void) obstack_alloc (ob, 0); 82 oalign = obstack_alignment_mask (ob); 83 obstack_alignment_mask (ob) = 0; 84 ptr = (fragS *) obstack_alloc (ob, SIZEOF_STRUCT_FRAG); 85 obstack_alignment_mask (ob) = oalign; 86 memset (ptr, 0, SIZEOF_STRUCT_FRAG); 87 totalfrags++; 88 return ptr; 89 } 90 91 /* Try to augment current frag by nchars chars. 92 If there is no room, close of the current frag with a ".fill 0" 93 and begin a new frag. Unless the new frag has nchars chars available 94 do not return. Do not set up any fields of *now_frag. */ 95 96 void 97 frag_grow (size_t nchars) 98 { 99 if (obstack_room (&frchain_now->frch_obstack) < nchars) 100 { 101 size_t oldc; 102 size_t newc; 103 104 /* Try to allocate a bit more than needed right now. But don't do 105 this if we would waste too much memory. Especially necessary 106 for extremely big (like 2GB initialized) frags. */ 107 if (nchars < 0x10000) 108 newc = 2 * nchars; 109 else 110 newc = nchars + 0x10000; 111 newc += SIZEOF_STRUCT_FRAG; 112 113 /* Check for possible overflow. */ 114 if (newc < nchars) 115 as_fatal (_("can't extend frag %lu chars"), (unsigned long) nchars); 116 117 /* Force to allocate at least NEWC bytes, but not less than the 118 default. */ 119 oldc = obstack_chunk_size (&frchain_now->frch_obstack); 120 if (newc > oldc) 121 obstack_chunk_size (&frchain_now->frch_obstack) = newc; 122 123 while (obstack_room (&frchain_now->frch_obstack) < nchars) 124 { 125 /* Not enough room in this frag. Close it and start a new one. 126 This must be done in a loop because the created frag may not 127 be big enough if the current obstack chunk is used. */ 128 frag_wane (frag_now); 129 frag_new (0); 130 } 131 132 /* Restore the old chunk size. */ 133 obstack_chunk_size (&frchain_now->frch_obstack) = oldc; 134 } 135 } 136 137 /* Call this to close off a completed frag, and start up a new (empty) 138 frag, in the same subsegment as the old frag. 139 [frchain_now remains the same but frag_now is updated.] 140 Because this calculates the correct value of fr_fix by 141 looking at the obstack 'frags', it needs to know how many 142 characters at the end of the old frag belong to the maximal 143 variable part; The rest must belong to fr_fix. 144 It doesn't actually set up the old frag's fr_var. You may have 145 set fr_var == 1, but allocated 10 chars to the end of the frag; 146 In this case you pass old_frags_var_max_size == 10. 147 In fact, you may use fr_var for something totally unrelated to the 148 size of the variable part of the frag; None of the generic frag 149 handling code makes use of fr_var. 150 151 Make a new frag, initialising some components. Link new frag at end 152 of frchain_now. */ 153 154 void 155 frag_new (size_t old_frags_var_max_size 156 /* Number of chars (already allocated on obstack frags) in 157 variable_length part of frag. */) 158 { 159 fragS *former_last_fragP; 160 frchainS *frchP; 161 162 gas_assert (frchain_now->frch_last == frag_now); 163 164 /* Fix up old frag's fr_fix. */ 165 frag_now->fr_fix = frag_now_fix_octets () - old_frags_var_max_size; 166 /* Make sure its type is valid. */ 167 gas_assert (frag_now->fr_type != 0); 168 169 /* This will align the obstack so the next struct we allocate on it 170 will begin at a correct boundary. */ 171 obstack_finish (&frchain_now->frch_obstack); 172 frchP = frchain_now; 173 know (frchP); 174 former_last_fragP = frchP->frch_last; 175 gas_assert (former_last_fragP != 0); 176 gas_assert (former_last_fragP == frag_now); 177 frag_now = frag_alloc (&frchP->frch_obstack); 178 179 frag_now->fr_file = as_where (&frag_now->fr_line); 180 181 /* Generally, frag_now->points to an address rounded up to next 182 alignment. However, characters will add to obstack frags 183 IMMEDIATELY after the struct frag, even if they are not starting 184 at an alignment address. */ 185 former_last_fragP->fr_next = frag_now; 186 frchP->frch_last = frag_now; 187 188 #ifndef NO_LISTING 189 { 190 extern struct list_info_struct *listing_tail; 191 frag_now->line = listing_tail; 192 } 193 #endif 194 195 gas_assert (frchain_now->frch_last == frag_now); 196 197 frag_now->fr_next = NULL; 198 } 199 200 /* Start a new frag unless we have n more chars of room in the current frag. 201 Close off the old frag with a .fill 0. 202 203 Return the address of the 1st char to write into. Advance 204 frag_now_growth past the new chars. */ 205 206 char * 207 frag_more (size_t nchars) 208 { 209 char *retval; 210 211 frag_alloc_check (&frchain_now->frch_obstack); 212 frag_grow (nchars); 213 retval = obstack_next_free (&frchain_now->frch_obstack); 214 obstack_blank_fast (&frchain_now->frch_obstack, nchars); 215 return retval; 216 } 217 218 /* Close the current frag, setting its fields for a relaxable frag. Start a 219 new frag. */ 220 221 static void 222 frag_var_init (relax_stateT type, size_t max_chars, size_t var, 223 relax_substateT subtype, symbolS *symbol, offsetT offset, 224 char *opcode) 225 { 226 frag_now->fr_var = var; 227 frag_now->fr_type = type; 228 frag_now->fr_subtype = subtype; 229 frag_now->fr_symbol = symbol; 230 frag_now->fr_offset = offset; 231 frag_now->fr_opcode = opcode; 232 #ifdef USING_CGEN 233 frag_now->fr_cgen.insn = 0; 234 frag_now->fr_cgen.opindex = 0; 235 frag_now->fr_cgen.opinfo = 0; 236 #endif 237 #ifdef TC_FRAG_INIT 238 TC_FRAG_INIT (frag_now); 239 #endif 240 frag_now->fr_file = as_where (&frag_now->fr_line); 241 242 frag_new (max_chars); 243 } 244 245 /* Start a new frag unless we have max_chars more chars of room in the 246 current frag. Close off the old frag with a .fill 0. 247 248 Set up a machine_dependent relaxable frag, then start a new frag. 249 Return the address of the 1st char of the var part of the old frag 250 to write into. */ 251 252 char * 253 frag_var (relax_stateT type, size_t max_chars, size_t var, 254 relax_substateT subtype, symbolS *symbol, offsetT offset, 255 char *opcode) 256 { 257 char *retval; 258 259 frag_grow (max_chars); 260 retval = obstack_next_free (&frchain_now->frch_obstack); 261 obstack_blank_fast (&frchain_now->frch_obstack, max_chars); 262 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode); 263 return retval; 264 } 265 266 /* OVE: This variant of frag_var assumes that space for the tail has been 267 allocated by caller. 268 No call to frag_grow is done. */ 269 270 char * 271 frag_variant (relax_stateT type, size_t max_chars, size_t var, 272 relax_substateT subtype, symbolS *symbol, offsetT offset, 273 char *opcode) 274 { 275 char *retval; 276 277 retval = obstack_next_free (&frchain_now->frch_obstack); 278 frag_var_init (type, max_chars, var, subtype, symbol, offset, opcode); 279 280 return retval; 281 } 282 283 /* Reduce the variable end of a frag to a harmless state. */ 284 285 void 286 frag_wane (fragS *fragP) 287 { 288 fragP->fr_type = rs_fill; 289 fragP->fr_offset = 0; 290 fragP->fr_var = 0; 291 } 292 293 /* Return the number of bytes by which the current frag can be grown. */ 294 295 size_t 296 frag_room (void) 297 { 298 return obstack_room (&frchain_now->frch_obstack); 299 } 300 301 /* Make an alignment frag. The size of this frag will be adjusted to 302 force the next frag to have the appropriate alignment. ALIGNMENT 303 is the power of two to which to align. FILL_CHARACTER is the 304 character to use to fill in any bytes which are skipped. MAX is 305 the maximum number of characters to skip when doing the alignment, 306 or 0 if there is no maximum. */ 307 308 void 309 frag_align (int alignment, int fill_character, int max) 310 { 311 if (now_seg == absolute_section) 312 { 313 addressT new_off; 314 addressT mask; 315 316 mask = (~(addressT) 0) << alignment; 317 new_off = (abs_section_offset + ~mask) & mask; 318 if (max == 0 || new_off - abs_section_offset <= (addressT) max) 319 abs_section_offset = new_off; 320 } 321 else 322 { 323 char *p; 324 325 p = frag_var (rs_align, 1, 1, (relax_substateT) max, 326 (symbolS *) 0, (offsetT) alignment, (char *) 0); 327 *p = fill_character; 328 } 329 } 330 331 /* Make an alignment frag like frag_align, but fill with a repeating 332 pattern rather than a single byte. ALIGNMENT is the power of two 333 to which to align. FILL_PATTERN is the fill pattern to repeat in 334 the bytes which are skipped. N_FILL is the number of bytes in 335 FILL_PATTERN. MAX is the maximum number of characters to skip when 336 doing the alignment, or 0 if there is no maximum. */ 337 338 void 339 frag_align_pattern (int alignment, const char *fill_pattern, 340 size_t n_fill, int max) 341 { 342 char *p; 343 344 p = frag_var (rs_align, n_fill, n_fill, (relax_substateT) max, 345 (symbolS *) 0, (offsetT) alignment, (char *) 0); 346 memcpy (p, fill_pattern, n_fill); 347 } 348 349 /* The NOP_OPCODE is for the alignment fill value. Fill it with a nop 350 instruction so that the disassembler does not choke on it. */ 351 #ifndef NOP_OPCODE 352 #define NOP_OPCODE 0x00 353 #endif 354 355 /* Use this to restrict the amount of memory allocated for representing 356 the alignment code. Needs to be large enough to hold any fixed sized 357 prologue plus the replicating portion. */ 358 #ifndef MAX_MEM_FOR_RS_ALIGN_CODE 359 /* Assume that if HANDLE_ALIGN is not defined then no special action 360 is required to code fill, which means that we get just repeat the 361 one NOP_OPCODE byte. */ 362 # ifndef HANDLE_ALIGN 363 # define MAX_MEM_FOR_RS_ALIGN_CODE 1 364 # else 365 # define MAX_MEM_FOR_RS_ALIGN_CODE ((1 << alignment) - 1) 366 # endif 367 #endif 368 369 void 370 frag_align_code (int alignment, int max) 371 { 372 char *p; 373 374 p = frag_var (rs_align_code, MAX_MEM_FOR_RS_ALIGN_CODE, 1, 375 (relax_substateT) max, (symbolS *) 0, 376 (offsetT) alignment, (char *) 0); 377 *p = NOP_OPCODE; 378 } 379 380 addressT 381 frag_now_fix_octets (void) 382 { 383 if (now_seg == absolute_section) 384 return abs_section_offset; 385 386 return ((char *) obstack_next_free (&frchain_now->frch_obstack) 387 - frag_now->fr_literal); 388 } 389 390 addressT 391 frag_now_fix (void) 392 { 393 return frag_now_fix_octets () / OCTETS_PER_BYTE; 394 } 395 396 void 397 frag_append_1_char (int datum) 398 { 399 frag_alloc_check (&frchain_now->frch_obstack); 400 if (obstack_room (&frchain_now->frch_obstack) <= 1) 401 { 402 frag_wane (frag_now); 403 frag_new (0); 404 } 405 obstack_1grow (&frchain_now->frch_obstack, datum); 406 } 407 408 /* Return TRUE if FRAG1 and FRAG2 have a fixed relationship between 409 their start addresses. Set OFFSET to the difference in address 410 not already accounted for in the frag FR_ADDRESS. */ 411 412 bfd_boolean 413 frag_offset_fixed_p (const fragS *frag1, const fragS *frag2, offsetT *offset) 414 { 415 const fragS *frag; 416 offsetT off; 417 418 /* Start with offset initialised to difference between the two frags. 419 Prior to assigning frag addresses this will be zero. */ 420 off = frag1->fr_address - frag2->fr_address; 421 if (frag1 == frag2) 422 { 423 *offset = off; 424 return TRUE; 425 } 426 427 /* Maybe frag2 is after frag1. */ 428 frag = frag1; 429 while (frag->fr_type == rs_fill) 430 { 431 off += frag->fr_fix + frag->fr_offset * frag->fr_var; 432 frag = frag->fr_next; 433 if (frag == NULL) 434 break; 435 if (frag == frag2) 436 { 437 *offset = off; 438 return TRUE; 439 } 440 } 441 442 /* Maybe frag1 is after frag2. */ 443 off = frag1->fr_address - frag2->fr_address; 444 frag = frag2; 445 while (frag->fr_type == rs_fill) 446 { 447 off -= frag->fr_fix + frag->fr_offset * frag->fr_var; 448 frag = frag->fr_next; 449 if (frag == NULL) 450 break; 451 if (frag == frag1) 452 { 453 *offset = off; 454 return TRUE; 455 } 456 } 457 458 return FALSE; 459 } 460