1 /* Intel 386 target-dependent stuff. 2 Copyright (C) 1988, 1989, 1991, 1994, 1995, 1996 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ 19 20 #include "defs.h" 21 #include "gdb_string.h" 22 #include "frame.h" 23 #include "inferior.h" 24 #include "gdbcore.h" 25 #include "target.h" 26 #include "floatformat.h" 27 #include "symtab.h" 28 #include "gdbcmd.h" 29 30 static long i386_get_frame_setup PARAMS ((CORE_ADDR)); 31 32 static void i386_follow_jump PARAMS ((void)); 33 34 static void codestream_read PARAMS ((unsigned char *, int)); 35 36 static void codestream_seek PARAMS ((CORE_ADDR)); 37 38 static unsigned char codestream_fill PARAMS ((int)); 39 40 /* Stdio style buffering was used to minimize calls to ptrace, but this 41 buffering did not take into account that the code section being accessed 42 may not be an even number of buffers long (even if the buffer is only 43 sizeof(int) long). In cases where the code section size happened to 44 be a non-integral number of buffers long, attempting to read the last 45 buffer would fail. Simply using target_read_memory and ignoring errors, 46 rather than read_memory, is not the correct solution, since legitimate 47 access errors would then be totally ignored. To properly handle this 48 situation and continue to use buffering would require that this code 49 be able to determine the minimum code section size granularity (not the 50 alignment of the section itself, since the actual failing case that 51 pointed out this problem had a section alignment of 4 but was not a 52 multiple of 4 bytes long), on a target by target basis, and then 53 adjust it's buffer size accordingly. This is messy, but potentially 54 feasible. It probably needs the bfd library's help and support. For 55 now, the buffer size is set to 1. (FIXME -fnf) */ 56 57 #define CODESTREAM_BUFSIZ 1 /* Was sizeof(int), see note above. */ 58 static CORE_ADDR codestream_next_addr; 59 static CORE_ADDR codestream_addr; 60 static unsigned char codestream_buf[CODESTREAM_BUFSIZ]; 61 static int codestream_off; 62 static int codestream_cnt; 63 64 #define codestream_tell() (codestream_addr + codestream_off) 65 #define codestream_peek() (codestream_cnt == 0 ? \ 66 codestream_fill(1): codestream_buf[codestream_off]) 67 #define codestream_get() (codestream_cnt-- == 0 ? \ 68 codestream_fill(0) : codestream_buf[codestream_off++]) 69 70 static unsigned char 71 codestream_fill (peek_flag) 72 int peek_flag; 73 { 74 codestream_addr = codestream_next_addr; 75 codestream_next_addr += CODESTREAM_BUFSIZ; 76 codestream_off = 0; 77 codestream_cnt = CODESTREAM_BUFSIZ; 78 read_memory (codestream_addr, (char *) codestream_buf, CODESTREAM_BUFSIZ); 79 80 if (peek_flag) 81 return (codestream_peek()); 82 else 83 return (codestream_get()); 84 } 85 86 static void 87 codestream_seek (place) 88 CORE_ADDR place; 89 { 90 codestream_next_addr = place / CODESTREAM_BUFSIZ; 91 codestream_next_addr *= CODESTREAM_BUFSIZ; 92 codestream_cnt = 0; 93 codestream_fill (1); 94 while (codestream_tell() != place) 95 codestream_get (); 96 } 97 98 static void 99 codestream_read (buf, count) 100 unsigned char *buf; 101 int count; 102 { 103 unsigned char *p; 104 int i; 105 p = buf; 106 for (i = 0; i < count; i++) 107 *p++ = codestream_get (); 108 } 109 110 /* next instruction is a jump, move to target */ 111 112 static void 113 i386_follow_jump () 114 { 115 unsigned char buf[4]; 116 long delta; 117 118 int data16; 119 CORE_ADDR pos; 120 121 pos = codestream_tell (); 122 123 data16 = 0; 124 if (codestream_peek () == 0x66) 125 { 126 codestream_get (); 127 data16 = 1; 128 } 129 130 switch (codestream_get ()) 131 { 132 case 0xe9: 133 /* relative jump: if data16 == 0, disp32, else disp16 */ 134 if (data16) 135 { 136 codestream_read (buf, 2); 137 delta = extract_signed_integer (buf, 2); 138 139 /* include size of jmp inst (including the 0x66 prefix). */ 140 pos += delta + 4; 141 } 142 else 143 { 144 codestream_read (buf, 4); 145 delta = extract_signed_integer (buf, 4); 146 147 pos += delta + 5; 148 } 149 break; 150 case 0xeb: 151 /* relative jump, disp8 (ignore data16) */ 152 codestream_read (buf, 1); 153 /* Sign-extend it. */ 154 delta = extract_signed_integer (buf, 1); 155 156 pos += delta + 2; 157 break; 158 } 159 codestream_seek (pos); 160 } 161 162 /* 163 * find & return amound a local space allocated, and advance codestream to 164 * first register push (if any) 165 * 166 * if entry sequence doesn't make sense, return -1, and leave 167 * codestream pointer random 168 */ 169 170 static long 171 i386_get_frame_setup (pc) 172 CORE_ADDR pc; 173 { 174 unsigned char op; 175 176 codestream_seek (pc); 177 178 i386_follow_jump (); 179 180 op = codestream_get (); 181 182 if (op == 0x58) /* popl %eax */ 183 { 184 /* 185 * this function must start with 186 * 187 * popl %eax 0x58 188 * xchgl %eax, (%esp) 0x87 0x04 0x24 189 * or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00 190 * 191 * (the system 5 compiler puts out the second xchg 192 * inst, and the assembler doesn't try to optimize it, 193 * so the 'sib' form gets generated) 194 * 195 * this sequence is used to get the address of the return 196 * buffer for a function that returns a structure 197 */ 198 int pos; 199 unsigned char buf[4]; 200 static unsigned char proto1[3] = { 0x87,0x04,0x24 }; 201 static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 }; 202 pos = codestream_tell (); 203 codestream_read (buf, 4); 204 if (memcmp (buf, proto1, 3) == 0) 205 pos += 3; 206 else if (memcmp (buf, proto2, 4) == 0) 207 pos += 4; 208 209 codestream_seek (pos); 210 op = codestream_get (); /* update next opcode */ 211 } 212 213 if (op == 0x55) /* pushl %ebp */ 214 { 215 /* check for movl %esp, %ebp - can be written two ways */ 216 switch (codestream_get ()) 217 { 218 case 0x8b: 219 if (codestream_get () != 0xec) 220 return (-1); 221 break; 222 case 0x89: 223 if (codestream_get () != 0xe5) 224 return (-1); 225 break; 226 default: 227 return (-1); 228 } 229 /* check for stack adjustment 230 * 231 * subl $XXX, %esp 232 * 233 * note: you can't subtract a 16 bit immediate 234 * from a 32 bit reg, so we don't have to worry 235 * about a data16 prefix 236 */ 237 op = codestream_peek (); 238 if (op == 0x83) 239 { 240 /* subl with 8 bit immed */ 241 codestream_get (); 242 if (codestream_get () != 0xec) 243 /* Some instruction starting with 0x83 other than subl. */ 244 { 245 codestream_seek (codestream_tell () - 2); 246 return 0; 247 } 248 /* subl with signed byte immediate 249 * (though it wouldn't make sense to be negative) 250 */ 251 return (codestream_get()); 252 } 253 else if (op == 0x81) 254 { 255 char buf[4]; 256 /* Maybe it is subl with 32 bit immedediate. */ 257 codestream_get(); 258 if (codestream_get () != 0xec) 259 /* Some instruction starting with 0x81 other than subl. */ 260 { 261 codestream_seek (codestream_tell () - 2); 262 return 0; 263 } 264 /* It is subl with 32 bit immediate. */ 265 codestream_read ((unsigned char *)buf, 4); 266 return extract_signed_integer (buf, 4); 267 } 268 else 269 { 270 return (0); 271 } 272 } 273 else if (op == 0xc8) 274 { 275 char buf[2]; 276 /* enter instruction: arg is 16 bit unsigned immed */ 277 codestream_read ((unsigned char *)buf, 2); 278 codestream_get (); /* flush final byte of enter instruction */ 279 return extract_unsigned_integer (buf, 2); 280 } 281 return (-1); 282 } 283 284 /* Return number of args passed to a frame. 285 Can return -1, meaning no way to tell. */ 286 287 int 288 i386_frame_num_args (fi) 289 struct frame_info *fi; 290 { 291 #if 1 292 return -1; 293 #else 294 /* This loses because not only might the compiler not be popping the 295 args right after the function call, it might be popping args from both 296 this call and a previous one, and we would say there are more args 297 than there really are. */ 298 299 int retpc; 300 unsigned char op; 301 struct frame_info *pfi; 302 303 /* on the 386, the instruction following the call could be: 304 popl %ecx - one arg 305 addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits 306 anything else - zero args */ 307 308 int frameless; 309 310 FRAMELESS_FUNCTION_INVOCATION (fi, frameless); 311 if (frameless) 312 /* In the absence of a frame pointer, GDB doesn't get correct values 313 for nameless arguments. Return -1, so it doesn't print any 314 nameless arguments. */ 315 return -1; 316 317 pfi = get_prev_frame_info (fi); 318 if (pfi == 0) 319 { 320 /* Note: this can happen if we are looking at the frame for 321 main, because FRAME_CHAIN_VALID won't let us go into 322 start. If we have debugging symbols, that's not really 323 a big deal; it just means it will only show as many arguments 324 to main as are declared. */ 325 return -1; 326 } 327 else 328 { 329 retpc = pfi->pc; 330 op = read_memory_integer (retpc, 1); 331 if (op == 0x59) 332 /* pop %ecx */ 333 return 1; 334 else if (op == 0x83) 335 { 336 op = read_memory_integer (retpc+1, 1); 337 if (op == 0xc4) 338 /* addl $<signed imm 8 bits>, %esp */ 339 return (read_memory_integer (retpc+2,1)&0xff)/4; 340 else 341 return 0; 342 } 343 else if (op == 0x81) 344 { /* add with 32 bit immediate */ 345 op = read_memory_integer (retpc+1, 1); 346 if (op == 0xc4) 347 /* addl $<imm 32>, %esp */ 348 return read_memory_integer (retpc+2, 4) / 4; 349 else 350 return 0; 351 } 352 else 353 { 354 return 0; 355 } 356 } 357 #endif 358 } 359 360 /* 361 * parse the first few instructions of the function to see 362 * what registers were stored. 363 * 364 * We handle these cases: 365 * 366 * The startup sequence can be at the start of the function, 367 * or the function can start with a branch to startup code at the end. 368 * 369 * %ebp can be set up with either the 'enter' instruction, or 370 * 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful, 371 * but was once used in the sys5 compiler) 372 * 373 * Local space is allocated just below the saved %ebp by either the 374 * 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has 375 * a 16 bit unsigned argument for space to allocate, and the 376 * 'addl' instruction could have either a signed byte, or 377 * 32 bit immediate. 378 * 379 * Next, the registers used by this function are pushed. In 380 * the sys5 compiler they will always be in the order: %edi, %esi, %ebx 381 * (and sometimes a harmless bug causes it to also save but not restore %eax); 382 * however, the code below is willing to see the pushes in any order, 383 * and will handle up to 8 of them. 384 * 385 * If the setup sequence is at the end of the function, then the 386 * next instruction will be a branch back to the start. 387 */ 388 389 void 390 i386_frame_find_saved_regs (fip, fsrp) 391 struct frame_info *fip; 392 struct frame_saved_regs *fsrp; 393 { 394 long locals; 395 unsigned char op; 396 CORE_ADDR dummy_bottom; 397 CORE_ADDR adr; 398 int i; 399 400 memset (fsrp, 0, sizeof *fsrp); 401 402 /* if frame is the end of a dummy, compute where the 403 * beginning would be 404 */ 405 dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH; 406 407 /* check if the PC is in the stack, in a dummy frame */ 408 if (dummy_bottom <= fip->pc && fip->pc <= fip->frame) 409 { 410 /* all regs were saved by push_call_dummy () */ 411 adr = fip->frame; 412 for (i = 0; i < NUM_REGS; i++) 413 { 414 adr -= REGISTER_RAW_SIZE (i); 415 fsrp->regs[i] = adr; 416 } 417 return; 418 } 419 420 locals = i386_get_frame_setup (get_pc_function_start (fip->pc)); 421 422 if (locals >= 0) 423 { 424 adr = fip->frame - 4 - locals; 425 for (i = 0; i < 8; i++) 426 { 427 op = codestream_get (); 428 if (op < 0x50 || op > 0x57) 429 break; 430 #ifdef I386_REGNO_TO_SYMMETRY 431 /* Dynix uses different internal numbering. Ick. */ 432 fsrp->regs[I386_REGNO_TO_SYMMETRY(op - 0x50)] = adr; 433 #else 434 fsrp->regs[op - 0x50] = adr; 435 #endif 436 adr -= 4; 437 } 438 } 439 440 fsrp->regs[PC_REGNUM] = fip->frame + 4; 441 fsrp->regs[FP_REGNUM] = fip->frame; 442 } 443 444 /* return pc of first real instruction */ 445 446 int 447 i386_skip_prologue (pc) 448 int pc; 449 { 450 unsigned char op; 451 int i; 452 static unsigned char pic_pat[6] = { 0xe8, 0, 0, 0, 0, /* call 0x0 */ 453 0x5b, /* popl %ebx */ 454 }; 455 CORE_ADDR pos; 456 457 if (i386_get_frame_setup (pc) < 0) 458 return (pc); 459 460 /* found valid frame setup - codestream now points to 461 * start of push instructions for saving registers 462 */ 463 464 /* skip over register saves */ 465 for (i = 0; i < 8; i++) 466 { 467 op = codestream_peek (); 468 /* break if not pushl inst */ 469 if (op < 0x50 || op > 0x57) 470 break; 471 codestream_get (); 472 } 473 474 /* The native cc on SVR4 in -K PIC mode inserts the following code to get 475 the address of the global offset table (GOT) into register %ebx. 476 call 0x0 477 popl %ebx 478 movl %ebx,x(%ebp) (optional) 479 addl y,%ebx 480 This code is with the rest of the prologue (at the end of the 481 function), so we have to skip it to get to the first real 482 instruction at the start of the function. */ 483 484 pos = codestream_tell (); 485 for (i = 0; i < 6; i++) 486 { 487 op = codestream_get (); 488 if (pic_pat [i] != op) 489 break; 490 } 491 if (i == 6) 492 { 493 unsigned char buf[4]; 494 long delta = 6; 495 496 op = codestream_get (); 497 if (op == 0x89) /* movl %ebx, x(%ebp) */ 498 { 499 op = codestream_get (); 500 if (op == 0x5d) /* one byte offset from %ebp */ 501 { 502 delta += 3; 503 codestream_read (buf, 1); 504 } 505 else if (op == 0x9d) /* four byte offset from %ebp */ 506 { 507 delta += 6; 508 codestream_read (buf, 4); 509 } 510 else /* unexpected instruction */ 511 delta = -1; 512 op = codestream_get (); 513 } 514 /* addl y,%ebx */ 515 if (delta > 0 && op == 0x81 && codestream_get () == 0xc3) 516 { 517 pos += delta + 6; 518 } 519 } 520 codestream_seek (pos); 521 522 i386_follow_jump (); 523 524 return (codestream_tell ()); 525 } 526 527 void 528 i386_push_dummy_frame () 529 { 530 CORE_ADDR sp = read_register (SP_REGNUM); 531 int regnum; 532 char regbuf[MAX_REGISTER_RAW_SIZE]; 533 534 sp = push_word (sp, read_register (PC_REGNUM)); 535 sp = push_word (sp, read_register (FP_REGNUM)); 536 write_register (FP_REGNUM, sp); 537 for (regnum = 0; regnum < NUM_REGS; regnum++) 538 { 539 read_register_gen (regnum, regbuf); 540 sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum)); 541 } 542 write_register (SP_REGNUM, sp); 543 } 544 545 void 546 i386_pop_frame () 547 { 548 struct frame_info *frame = get_current_frame (); 549 CORE_ADDR fp; 550 int regnum; 551 struct frame_saved_regs fsr; 552 char regbuf[MAX_REGISTER_RAW_SIZE]; 553 554 fp = FRAME_FP (frame); 555 get_frame_saved_regs (frame, &fsr); 556 for (regnum = 0; regnum < NUM_REGS; regnum++) 557 { 558 CORE_ADDR adr; 559 adr = fsr.regs[regnum]; 560 if (adr) 561 { 562 read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum)); 563 write_register_bytes (REGISTER_BYTE (regnum), regbuf, 564 REGISTER_RAW_SIZE (regnum)); 565 } 566 } 567 write_register (FP_REGNUM, read_memory_integer (fp, 4)); 568 write_register (PC_REGNUM, read_memory_integer (fp + 4, 4)); 569 write_register (SP_REGNUM, fp + 8); 570 flush_cached_frames (); 571 } 572 573 #ifdef GET_LONGJMP_TARGET 574 575 /* Figure out where the longjmp will land. Slurp the args out of the stack. 576 We expect the first arg to be a pointer to the jmp_buf structure from which 577 we extract the pc (JB_PC) that we will land at. The pc is copied into PC. 578 This routine returns true on success. */ 579 580 int 581 get_longjmp_target(pc) 582 CORE_ADDR *pc; 583 { 584 char buf[TARGET_PTR_BIT / TARGET_CHAR_BIT]; 585 CORE_ADDR sp, jb_addr; 586 587 sp = read_register (SP_REGNUM); 588 589 if (target_read_memory (sp + SP_ARG0, /* Offset of first arg on stack */ 590 buf, 591 TARGET_PTR_BIT / TARGET_CHAR_BIT)) 592 return 0; 593 594 jb_addr = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT); 595 596 if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf, 597 TARGET_PTR_BIT / TARGET_CHAR_BIT)) 598 return 0; 599 600 *pc = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT); 601 602 return 1; 603 } 604 605 #endif /* GET_LONGJMP_TARGET */ 606 607 void 608 i386_extract_return_value(type, regbuf, valbuf) 609 struct type *type; 610 char regbuf[REGISTER_BYTES]; 611 char *valbuf; 612 { 613 /* On AIX, floating point values are returned in floating point registers. */ 614 #ifdef I386_AIX_TARGET 615 if (TYPE_CODE_FLT == TYPE_CODE(type)) 616 { 617 double d; 618 /* 387 %st(0), gcc uses this */ 619 floatformat_to_double (&floatformat_i387_ext, 620 ®buf[REGISTER_BYTE(FP0_REGNUM)], 621 &d); 622 store_floating (valbuf, TYPE_LENGTH (type), d); 623 } 624 else 625 #endif /* I386_AIX_TARGET */ 626 { 627 memcpy (valbuf, regbuf, TYPE_LENGTH (type)); 628 } 629 } 630 631 #ifdef I386V4_SIGTRAMP_SAVED_PC 632 /* Get saved user PC for sigtramp from the pushed ucontext on the stack 633 for all three variants of SVR4 sigtramps. */ 634 635 CORE_ADDR 636 i386v4_sigtramp_saved_pc (frame) 637 struct frame_info *frame; 638 { 639 CORE_ADDR saved_pc_offset = 4; 640 char *name = NULL; 641 642 find_pc_partial_function (frame->pc, &name, NULL, NULL); 643 if (name) 644 { 645 if (STREQ (name, "_sigreturn")) 646 saved_pc_offset = 132 + 14 * 4; 647 else if (STREQ (name, "_sigacthandler")) 648 saved_pc_offset = 80 + 14 * 4; 649 else if (STREQ (name, "sigvechandler")) 650 saved_pc_offset = 120 + 14 * 4; 651 } 652 653 if (frame->next) 654 return read_memory_integer (frame->next->frame + saved_pc_offset, 4); 655 return read_memory_integer (read_register (SP_REGNUM) + saved_pc_offset, 4); 656 } 657 #endif /* I386V4_SIGTRAMP_SAVED_PC */ 658 659 660 661 /* Stuff for WIN32 PE style DLL's but is pretty generic really. */ 662 663 CORE_ADDR 664 skip_trampoline_code (pc, name) 665 CORE_ADDR pc; 666 char *name; 667 { 668 if (pc && read_memory_unsigned_integer (pc, 2) == 0x25ff) /* jmp *(dest) */ 669 { 670 unsigned long indirect = read_memory_unsigned_integer (pc+2, 4); 671 struct minimal_symbol *indsym = 672 indirect ? lookup_minimal_symbol_by_pc (indirect) : 0; 673 char *symname = indsym ? SYMBOL_NAME(indsym) : 0; 674 675 if (symname) 676 { 677 if (strncmp (symname,"__imp_", 6) == 0 678 || strncmp (symname,"_imp_", 5) == 0) 679 return name ? 1 : read_memory_unsigned_integer (indirect, 4); 680 } 681 } 682 return 0; /* not a trampoline */ 683 } 684 685 static char *x86_assembly_types[] = {"i386", "i8086", NULL}; 686 static char *x86_assembly_result = "i386"; 687 688 static void 689 set_assembly_language_command (ignore, from_tty, c) 690 char *ignore; 691 int from_tty; 692 struct cmd_list_element *c; 693 { 694 if (strcmp (x86_assembly_result, "i386") == 0) 695 tm_print_insn_info.mach = bfd_mach_i386_i386; 696 else 697 tm_print_insn_info.mach = bfd_mach_i386_i8086; 698 } 699 700 void 701 _initialize_i386_tdep () 702 { 703 struct cmd_list_element *cmd; 704 705 tm_print_insn = print_insn_i386_att; 706 tm_print_insn_info.mach = bfd_mach_i386_i386; 707 708 cmd = add_set_enum_cmd ("assembly-language", class_obscure, 709 x86_assembly_types, (char *)&x86_assembly_result, 710 "Set x86 instruction set to use for disassembly.\n\ 711 This value can be set to either i386 or i8086 to change how instructions are disassembled.", 712 &setlist); 713 add_show_from_set (cmd, &showlist); 714 715 cmd->function.sfunc = set_assembly_language_command; 716 } 717