| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | \f |
| 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 | } |