| 1 | /* Intel 386 target-dependent stuff. |
| 2 | Copyright (C) 1988, 1989, 1991 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of GDB. |
| 5 | |
| 6 | This program 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 2 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program 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 this program; if not, write to the Free Software |
| 18 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ |
| 19 | |
| 20 | #include "defs.h" |
| 21 | #include "frame.h" |
| 22 | #include "inferior.h" |
| 23 | #include "gdbcore.h" |
| 24 | #include "target.h" |
| 25 | |
| 26 | static long |
| 27 | i386_get_frame_setup PARAMS ((int)); |
| 28 | |
| 29 | static void |
| 30 | i386_follow_jump PARAMS ((void)); |
| 31 | |
| 32 | static void |
| 33 | codestream_read PARAMS ((unsigned char *, int)); |
| 34 | |
| 35 | static void |
| 36 | codestream_seek PARAMS ((int)); |
| 37 | |
| 38 | static unsigned char |
| 39 | codestream_fill PARAMS ((int)); |
| 40 | |
| 41 | /* helper functions for tm-i386.h */ |
| 42 | |
| 43 | /* Stdio style buffering was used to minimize calls to ptrace, but this |
| 44 | buffering did not take into account that the code section being accessed |
| 45 | may not be an even number of buffers long (even if the buffer is only |
| 46 | sizeof(int) long). In cases where the code section size happened to |
| 47 | be a non-integral number of buffers long, attempting to read the last |
| 48 | buffer would fail. Simply using target_read_memory and ignoring errors, |
| 49 | rather than read_memory, is not the correct solution, since legitimate |
| 50 | access errors would then be totally ignored. To properly handle this |
| 51 | situation and continue to use buffering would require that this code |
| 52 | be able to determine the minimum code section size granularity (not the |
| 53 | alignment of the section itself, since the actual failing case that |
| 54 | pointed out this problem had a section alignment of 4 but was not a |
| 55 | multiple of 4 bytes long), on a target by target basis, and then |
| 56 | adjust it's buffer size accordingly. This is messy, but potentially |
| 57 | feasible. It probably needs the bfd library's help and support. For |
| 58 | now, the buffer size is set to 1. (FIXME -fnf) */ |
| 59 | |
| 60 | #define CODESTREAM_BUFSIZ 1 /* Was sizeof(int), see note above. */ |
| 61 | static CORE_ADDR codestream_next_addr; |
| 62 | static CORE_ADDR codestream_addr; |
| 63 | static unsigned char codestream_buf[CODESTREAM_BUFSIZ]; |
| 64 | static int codestream_off; |
| 65 | static int codestream_cnt; |
| 66 | |
| 67 | #define codestream_tell() (codestream_addr + codestream_off) |
| 68 | #define codestream_peek() (codestream_cnt == 0 ? \ |
| 69 | codestream_fill(1): codestream_buf[codestream_off]) |
| 70 | #define codestream_get() (codestream_cnt-- == 0 ? \ |
| 71 | codestream_fill(0) : codestream_buf[codestream_off++]) |
| 72 | |
| 73 | static unsigned char |
| 74 | codestream_fill (peek_flag) |
| 75 | int peek_flag; |
| 76 | { |
| 77 | codestream_addr = codestream_next_addr; |
| 78 | codestream_next_addr += CODESTREAM_BUFSIZ; |
| 79 | codestream_off = 0; |
| 80 | codestream_cnt = CODESTREAM_BUFSIZ; |
| 81 | read_memory (codestream_addr, (char *) codestream_buf, CODESTREAM_BUFSIZ); |
| 82 | |
| 83 | if (peek_flag) |
| 84 | return (codestream_peek()); |
| 85 | else |
| 86 | return (codestream_get()); |
| 87 | } |
| 88 | |
| 89 | static void |
| 90 | codestream_seek (place) |
| 91 | int place; |
| 92 | { |
| 93 | codestream_next_addr = place / CODESTREAM_BUFSIZ; |
| 94 | codestream_next_addr *= CODESTREAM_BUFSIZ; |
| 95 | codestream_cnt = 0; |
| 96 | codestream_fill (1); |
| 97 | while (codestream_tell() != place) |
| 98 | codestream_get (); |
| 99 | } |
| 100 | |
| 101 | static void |
| 102 | codestream_read (buf, count) |
| 103 | unsigned char *buf; |
| 104 | int count; |
| 105 | { |
| 106 | unsigned char *p; |
| 107 | int i; |
| 108 | p = buf; |
| 109 | for (i = 0; i < count; i++) |
| 110 | *p++ = codestream_get (); |
| 111 | } |
| 112 | |
| 113 | /* next instruction is a jump, move to target */ |
| 114 | |
| 115 | static void |
| 116 | i386_follow_jump () |
| 117 | { |
| 118 | int long_delta; |
| 119 | short short_delta; |
| 120 | char byte_delta; |
| 121 | int data16; |
| 122 | int pos; |
| 123 | |
| 124 | pos = codestream_tell (); |
| 125 | |
| 126 | data16 = 0; |
| 127 | if (codestream_peek () == 0x66) |
| 128 | { |
| 129 | codestream_get (); |
| 130 | data16 = 1; |
| 131 | } |
| 132 | |
| 133 | switch (codestream_get ()) |
| 134 | { |
| 135 | case 0xe9: |
| 136 | /* relative jump: if data16 == 0, disp32, else disp16 */ |
| 137 | if (data16) |
| 138 | { |
| 139 | codestream_read ((unsigned char *)&short_delta, 2); |
| 140 | |
| 141 | /* include size of jmp inst (including the 0x66 prefix). */ |
| 142 | pos += short_delta + 4; |
| 143 | } |
| 144 | else |
| 145 | { |
| 146 | codestream_read ((unsigned char *)&long_delta, 4); |
| 147 | pos += long_delta + 5; |
| 148 | } |
| 149 | break; |
| 150 | case 0xeb: |
| 151 | /* relative jump, disp8 (ignore data16) */ |
| 152 | codestream_read ((unsigned char *)&byte_delta, 1); |
| 153 | pos += byte_delta + 2; |
| 154 | break; |
| 155 | } |
| 156 | codestream_seek (pos); |
| 157 | } |
| 158 | |
| 159 | /* |
| 160 | * find & return amound a local space allocated, and advance codestream to |
| 161 | * first register push (if any) |
| 162 | * |
| 163 | * if entry sequence doesn't make sense, return -1, and leave |
| 164 | * codestream pointer random |
| 165 | */ |
| 166 | |
| 167 | static long |
| 168 | i386_get_frame_setup (pc) |
| 169 | int pc; |
| 170 | { |
| 171 | unsigned char op; |
| 172 | |
| 173 | codestream_seek (pc); |
| 174 | |
| 175 | i386_follow_jump (); |
| 176 | |
| 177 | op = codestream_get (); |
| 178 | |
| 179 | if (op == 0x58) /* popl %eax */ |
| 180 | { |
| 181 | /* |
| 182 | * this function must start with |
| 183 | * |
| 184 | * popl %eax 0x58 |
| 185 | * xchgl %eax, (%esp) 0x87 0x04 0x24 |
| 186 | * or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00 |
| 187 | * |
| 188 | * (the system 5 compiler puts out the second xchg |
| 189 | * inst, and the assembler doesn't try to optimize it, |
| 190 | * so the 'sib' form gets generated) |
| 191 | * |
| 192 | * this sequence is used to get the address of the return |
| 193 | * buffer for a function that returns a structure |
| 194 | */ |
| 195 | int pos; |
| 196 | unsigned char buf[4]; |
| 197 | static unsigned char proto1[3] = { 0x87,0x04,0x24 }; |
| 198 | static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 }; |
| 199 | pos = codestream_tell (); |
| 200 | codestream_read (buf, 4); |
| 201 | if (memcmp (buf, proto1, 3) == 0) |
| 202 | pos += 3; |
| 203 | else if (memcmp (buf, proto2, 4) == 0) |
| 204 | pos += 4; |
| 205 | |
| 206 | codestream_seek (pos); |
| 207 | op = codestream_get (); /* update next opcode */ |
| 208 | } |
| 209 | |
| 210 | if (op == 0x55) /* pushl %ebp */ |
| 211 | { |
| 212 | /* check for movl %esp, %ebp - can be written two ways */ |
| 213 | switch (codestream_get ()) |
| 214 | { |
| 215 | case 0x8b: |
| 216 | if (codestream_get () != 0xec) |
| 217 | return (-1); |
| 218 | break; |
| 219 | case 0x89: |
| 220 | if (codestream_get () != 0xe5) |
| 221 | return (-1); |
| 222 | break; |
| 223 | default: |
| 224 | return (-1); |
| 225 | } |
| 226 | /* check for stack adjustment |
| 227 | * |
| 228 | * subl $XXX, %esp |
| 229 | * |
| 230 | * note: you can't subtract a 16 bit immediate |
| 231 | * from a 32 bit reg, so we don't have to worry |
| 232 | * about a data16 prefix |
| 233 | */ |
| 234 | op = codestream_peek (); |
| 235 | if (op == 0x83) |
| 236 | { |
| 237 | /* subl with 8 bit immed */ |
| 238 | codestream_get (); |
| 239 | if (codestream_get () != 0xec) |
| 240 | /* Some instruction starting with 0x83 other than subl. */ |
| 241 | { |
| 242 | codestream_seek (codestream_tell () - 2); |
| 243 | return 0; |
| 244 | } |
| 245 | /* subl with signed byte immediate |
| 246 | * (though it wouldn't make sense to be negative) |
| 247 | */ |
| 248 | return (codestream_get()); |
| 249 | } |
| 250 | else if (op == 0x81) |
| 251 | { |
| 252 | char buf[4]; |
| 253 | /* Maybe it is subl with 32 bit immedediate. */ |
| 254 | codestream_get(); |
| 255 | if (codestream_get () != 0xec) |
| 256 | /* Some instruction starting with 0x81 other than subl. */ |
| 257 | { |
| 258 | codestream_seek (codestream_tell () - 2); |
| 259 | return 0; |
| 260 | } |
| 261 | /* It is subl with 32 bit immediate. */ |
| 262 | codestream_read ((unsigned char *)buf, 4); |
| 263 | return extract_signed_integer (buf, 4); |
| 264 | } |
| 265 | else |
| 266 | { |
| 267 | return (0); |
| 268 | } |
| 269 | } |
| 270 | else if (op == 0xc8) |
| 271 | { |
| 272 | char buf[2]; |
| 273 | /* enter instruction: arg is 16 bit unsigned immed */ |
| 274 | codestream_read ((unsigned char *)buf, 2); |
| 275 | codestream_get (); /* flush final byte of enter instruction */ |
| 276 | return extract_unsigned_integer (buf, 2); |
| 277 | } |
| 278 | return (-1); |
| 279 | } |
| 280 | |
| 281 | /* Return number of args passed to a frame. |
| 282 | Can return -1, meaning no way to tell. */ |
| 283 | |
| 284 | int |
| 285 | i386_frame_num_args (fi) |
| 286 | struct frame_info *fi; |
| 287 | { |
| 288 | #if 1 |
| 289 | return -1; |
| 290 | #else |
| 291 | /* This loses because not only might the compiler not be popping the |
| 292 | args right after the function call, it might be popping args from both |
| 293 | this call and a previous one, and we would say there are more args |
| 294 | than there really are. */ |
| 295 | |
| 296 | int retpc; |
| 297 | unsigned char op; |
| 298 | struct frame_info *pfi; |
| 299 | |
| 300 | /* on the 386, the instruction following the call could be: |
| 301 | popl %ecx - one arg |
| 302 | addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits |
| 303 | anything else - zero args */ |
| 304 | |
| 305 | int frameless; |
| 306 | |
| 307 | FRAMELESS_FUNCTION_INVOCATION (fi, frameless); |
| 308 | if (frameless) |
| 309 | /* In the absence of a frame pointer, GDB doesn't get correct values |
| 310 | for nameless arguments. Return -1, so it doesn't print any |
| 311 | nameless arguments. */ |
| 312 | return -1; |
| 313 | |
| 314 | pfi = get_prev_frame_info (fi); |
| 315 | if (pfi == 0) |
| 316 | { |
| 317 | /* Note: this can happen if we are looking at the frame for |
| 318 | main, because FRAME_CHAIN_VALID won't let us go into |
| 319 | start. If we have debugging symbols, that's not really |
| 320 | a big deal; it just means it will only show as many arguments |
| 321 | to main as are declared. */ |
| 322 | return -1; |
| 323 | } |
| 324 | else |
| 325 | { |
| 326 | retpc = pfi->pc; |
| 327 | op = read_memory_integer (retpc, 1); |
| 328 | if (op == 0x59) |
| 329 | /* pop %ecx */ |
| 330 | return 1; |
| 331 | else if (op == 0x83) |
| 332 | { |
| 333 | op = read_memory_integer (retpc+1, 1); |
| 334 | if (op == 0xc4) |
| 335 | /* addl $<signed imm 8 bits>, %esp */ |
| 336 | return (read_memory_integer (retpc+2,1)&0xff)/4; |
| 337 | else |
| 338 | return 0; |
| 339 | } |
| 340 | else if (op == 0x81) |
| 341 | { /* add with 32 bit immediate */ |
| 342 | op = read_memory_integer (retpc+1, 1); |
| 343 | if (op == 0xc4) |
| 344 | /* addl $<imm 32>, %esp */ |
| 345 | return read_memory_integer (retpc+2, 4) / 4; |
| 346 | else |
| 347 | return 0; |
| 348 | } |
| 349 | else |
| 350 | { |
| 351 | return 0; |
| 352 | } |
| 353 | } |
| 354 | #endif |
| 355 | } |
| 356 | |
| 357 | /* |
| 358 | * parse the first few instructions of the function to see |
| 359 | * what registers were stored. |
| 360 | * |
| 361 | * We handle these cases: |
| 362 | * |
| 363 | * The startup sequence can be at the start of the function, |
| 364 | * or the function can start with a branch to startup code at the end. |
| 365 | * |
| 366 | * %ebp can be set up with either the 'enter' instruction, or |
| 367 | * 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful, |
| 368 | * but was once used in the sys5 compiler) |
| 369 | * |
| 370 | * Local space is allocated just below the saved %ebp by either the |
| 371 | * 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has |
| 372 | * a 16 bit unsigned argument for space to allocate, and the |
| 373 | * 'addl' instruction could have either a signed byte, or |
| 374 | * 32 bit immediate. |
| 375 | * |
| 376 | * Next, the registers used by this function are pushed. In |
| 377 | * the sys5 compiler they will always be in the order: %edi, %esi, %ebx |
| 378 | * (and sometimes a harmless bug causes it to also save but not restore %eax); |
| 379 | * however, the code below is willing to see the pushes in any order, |
| 380 | * and will handle up to 8 of them. |
| 381 | * |
| 382 | * If the setup sequence is at the end of the function, then the |
| 383 | * next instruction will be a branch back to the start. |
| 384 | */ |
| 385 | |
| 386 | void |
| 387 | i386_frame_find_saved_regs (fip, fsrp) |
| 388 | struct frame_info *fip; |
| 389 | struct frame_saved_regs *fsrp; |
| 390 | { |
| 391 | long locals; |
| 392 | unsigned char op; |
| 393 | CORE_ADDR dummy_bottom; |
| 394 | CORE_ADDR adr; |
| 395 | int i; |
| 396 | |
| 397 | memset (fsrp, 0, sizeof *fsrp); |
| 398 | |
| 399 | /* if frame is the end of a dummy, compute where the |
| 400 | * beginning would be |
| 401 | */ |
| 402 | dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH; |
| 403 | |
| 404 | /* check if the PC is in the stack, in a dummy frame */ |
| 405 | if (dummy_bottom <= fip->pc && fip->pc <= fip->frame) |
| 406 | { |
| 407 | /* all regs were saved by push_call_dummy () */ |
| 408 | adr = fip->frame; |
| 409 | for (i = 0; i < NUM_REGS; i++) |
| 410 | { |
| 411 | adr -= REGISTER_RAW_SIZE (i); |
| 412 | fsrp->regs[i] = adr; |
| 413 | } |
| 414 | return; |
| 415 | } |
| 416 | |
| 417 | locals = i386_get_frame_setup (get_pc_function_start (fip->pc)); |
| 418 | |
| 419 | if (locals >= 0) |
| 420 | { |
| 421 | adr = fip->frame - 4 - locals; |
| 422 | for (i = 0; i < 8; i++) |
| 423 | { |
| 424 | op = codestream_get (); |
| 425 | if (op < 0x50 || op > 0x57) |
| 426 | break; |
| 427 | fsrp->regs[op - 0x50] = adr; |
| 428 | adr -= 4; |
| 429 | } |
| 430 | } |
| 431 | |
| 432 | fsrp->regs[PC_REGNUM] = fip->frame + 4; |
| 433 | fsrp->regs[FP_REGNUM] = fip->frame; |
| 434 | } |
| 435 | |
| 436 | /* return pc of first real instruction */ |
| 437 | |
| 438 | int |
| 439 | i386_skip_prologue (pc) |
| 440 | int pc; |
| 441 | { |
| 442 | unsigned char op; |
| 443 | int i; |
| 444 | |
| 445 | if (i386_get_frame_setup (pc) < 0) |
| 446 | return (pc); |
| 447 | |
| 448 | /* found valid frame setup - codestream now points to |
| 449 | * start of push instructions for saving registers |
| 450 | */ |
| 451 | |
| 452 | /* skip over register saves */ |
| 453 | for (i = 0; i < 8; i++) |
| 454 | { |
| 455 | op = codestream_peek (); |
| 456 | /* break if not pushl inst */ |
| 457 | if (op < 0x50 || op > 0x57) |
| 458 | break; |
| 459 | codestream_get (); |
| 460 | } |
| 461 | |
| 462 | i386_follow_jump (); |
| 463 | |
| 464 | return (codestream_tell ()); |
| 465 | } |
| 466 | |
| 467 | void |
| 468 | i386_push_dummy_frame () |
| 469 | { |
| 470 | CORE_ADDR sp = read_register (SP_REGNUM); |
| 471 | int regnum; |
| 472 | char regbuf[MAX_REGISTER_RAW_SIZE]; |
| 473 | |
| 474 | sp = push_word (sp, read_register (PC_REGNUM)); |
| 475 | sp = push_word (sp, read_register (FP_REGNUM)); |
| 476 | write_register (FP_REGNUM, sp); |
| 477 | for (regnum = 0; regnum < NUM_REGS; regnum++) |
| 478 | { |
| 479 | read_register_gen (regnum, regbuf); |
| 480 | sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum)); |
| 481 | } |
| 482 | write_register (SP_REGNUM, sp); |
| 483 | } |
| 484 | |
| 485 | void |
| 486 | i386_pop_frame () |
| 487 | { |
| 488 | FRAME frame = get_current_frame (); |
| 489 | CORE_ADDR fp; |
| 490 | int regnum; |
| 491 | struct frame_saved_regs fsr; |
| 492 | struct frame_info *fi; |
| 493 | char regbuf[MAX_REGISTER_RAW_SIZE]; |
| 494 | |
| 495 | fi = get_frame_info (frame); |
| 496 | fp = fi->frame; |
| 497 | get_frame_saved_regs (fi, &fsr); |
| 498 | for (regnum = 0; regnum < NUM_REGS; regnum++) |
| 499 | { |
| 500 | CORE_ADDR adr; |
| 501 | adr = fsr.regs[regnum]; |
| 502 | if (adr) |
| 503 | { |
| 504 | read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum)); |
| 505 | write_register_bytes (REGISTER_BYTE (regnum), regbuf, |
| 506 | REGISTER_RAW_SIZE (regnum)); |
| 507 | } |
| 508 | } |
| 509 | write_register (FP_REGNUM, read_memory_integer (fp, 4)); |
| 510 | write_register (PC_REGNUM, read_memory_integer (fp + 4, 4)); |
| 511 | write_register (SP_REGNUM, fp + 8); |
| 512 | flush_cached_frames (); |
| 513 | set_current_frame ( create_new_frame (read_register (FP_REGNUM), |
| 514 | read_pc ())); |
| 515 | } |
| 516 | |
| 517 | #ifdef GET_LONGJMP_TARGET |
| 518 | |
| 519 | /* Figure out where the longjmp will land. Slurp the args out of the stack. |
| 520 | We expect the first arg to be a pointer to the jmp_buf structure from which |
| 521 | we extract the pc (JB_PC) that we will land at. The pc is copied into PC. |
| 522 | This routine returns true on success. */ |
| 523 | |
| 524 | int |
| 525 | get_longjmp_target(pc) |
| 526 | CORE_ADDR *pc; |
| 527 | { |
| 528 | char buf[TARGET_PTR_BIT / TARGET_CHAR_BIT]; |
| 529 | CORE_ADDR sp, jb_addr; |
| 530 | |
| 531 | sp = read_register (SP_REGNUM); |
| 532 | |
| 533 | if (target_read_memory (sp + SP_ARG0, /* Offset of first arg on stack */ |
| 534 | buf, |
| 535 | TARGET_PTR_BIT / TARGET_CHAR_BIT)) |
| 536 | return 0; |
| 537 | |
| 538 | jb_addr = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT); |
| 539 | |
| 540 | if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf, |
| 541 | TARGET_PTR_BIT / TARGET_CHAR_BIT)) |
| 542 | return 0; |
| 543 | |
| 544 | *pc = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT); |
| 545 | |
| 546 | return 1; |
| 547 | } |
| 548 | |
| 549 | #endif /* GET_LONGJMP_TARGET */ |
| 550 | |
| 551 | #ifdef I386_AIX_TARGET |
| 552 | /* On AIX, floating point values are returned in floating point registers. */ |
| 553 | |
| 554 | void |
| 555 | i386_extract_return_value(type, regbuf, valbuf) |
| 556 | struct type *type; |
| 557 | char regbuf[REGISTER_BYTES]; |
| 558 | char *valbuf; |
| 559 | { |
| 560 | if (TYPE_CODE_FLT == TYPE_CODE(type)) |
| 561 | { |
| 562 | extern struct ext_format ext_format_i387; |
| 563 | double d; |
| 564 | /* 387 %st(0), gcc uses this */ |
| 565 | ieee_extended_to_double (&ext_format_i387, |
| 566 | ®buf[REGISTER_BYTE(FP0_REGNUM)], |
| 567 | &d); |
| 568 | switch (TYPE_LENGTH(type)) |
| 569 | { |
| 570 | case 4: /* float */ |
| 571 | { |
| 572 | float f = (float) d; |
| 573 | memcpy (valbuf, &f, 4); |
| 574 | break; |
| 575 | } |
| 576 | case 8: /* double */ |
| 577 | memcpy (valbuf, &d, 8); |
| 578 | break; |
| 579 | default: |
| 580 | error("Unknown floating point size"); |
| 581 | break; |
| 582 | } |
| 583 | } |
| 584 | else |
| 585 | { |
| 586 | memcpy (valbuf, regbuf, TYPE_LENGTH (type)); |
| 587 | } |
| 588 | } |
| 589 | #endif /* I386_AIX_TARGET */ |