1 /* Intel 386 target-dependent stuff.
2 Copyright (C) 1988, 1989, 1991, 1994, 1995, 1996 Free Software Foundation, Inc.
4 This file is part of GDB.
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.
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.
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. */
21 #include "gdb_string.h"
26 #include "floatformat.h"
29 static long i386_get_frame_setup PARAMS ((CORE_ADDR));
31 static void i386_follow_jump PARAMS ((void));
33 static void codestream_read PARAMS ((unsigned char *, int));
35 static void codestream_seek PARAMS ((CORE_ADDR));
37 static unsigned char codestream_fill PARAMS ((int));
39 /* Stdio style buffering was used to minimize calls to ptrace, but this
40 buffering did not take into account that the code section being accessed
41 may not be an even number of buffers long (even if the buffer is only
42 sizeof(int) long). In cases where the code section size happened to
43 be a non-integral number of buffers long, attempting to read the last
44 buffer would fail. Simply using target_read_memory and ignoring errors,
45 rather than read_memory, is not the correct solution, since legitimate
46 access errors would then be totally ignored. To properly handle this
47 situation and continue to use buffering would require that this code
48 be able to determine the minimum code section size granularity (not the
49 alignment of the section itself, since the actual failing case that
50 pointed out this problem had a section alignment of 4 but was not a
51 multiple of 4 bytes long), on a target by target basis, and then
52 adjust it's buffer size accordingly. This is messy, but potentially
53 feasible. It probably needs the bfd library's help and support. For
54 now, the buffer size is set to 1. (FIXME -fnf) */
56 #define CODESTREAM_BUFSIZ 1 /* Was sizeof(int), see note above. */
57 static CORE_ADDR codestream_next_addr;
58 static CORE_ADDR codestream_addr;
59 static unsigned char codestream_buf[CODESTREAM_BUFSIZ];
60 static int codestream_off;
61 static int codestream_cnt;
63 #define codestream_tell() (codestream_addr + codestream_off)
64 #define codestream_peek() (codestream_cnt == 0 ? \
65 codestream_fill(1): codestream_buf[codestream_off])
66 #define codestream_get() (codestream_cnt-- == 0 ? \
67 codestream_fill(0) : codestream_buf[codestream_off++])
70 codestream_fill (peek_flag)
73 codestream_addr = codestream_next_addr;
74 codestream_next_addr += CODESTREAM_BUFSIZ;
76 codestream_cnt = CODESTREAM_BUFSIZ;
77 read_memory (codestream_addr, (char *) codestream_buf, CODESTREAM_BUFSIZ);
80 return (codestream_peek());
82 return (codestream_get());
86 codestream_seek (place)
89 codestream_next_addr = place / CODESTREAM_BUFSIZ;
90 codestream_next_addr *= CODESTREAM_BUFSIZ;
93 while (codestream_tell() != place)
98 codestream_read (buf, count)
105 for (i = 0; i < count; i++)
106 *p++ = codestream_get ();
109 /* next instruction is a jump, move to target */
114 unsigned char buf[4];
120 pos = codestream_tell ();
123 if (codestream_peek () == 0x66)
129 switch (codestream_get ())
132 /* relative jump: if data16 == 0, disp32, else disp16 */
135 codestream_read (buf, 2);
136 delta = extract_signed_integer (buf, 2);
138 /* include size of jmp inst (including the 0x66 prefix). */
143 codestream_read (buf, 4);
144 delta = extract_signed_integer (buf, 4);
150 /* relative jump, disp8 (ignore data16) */
151 codestream_read (buf, 1);
152 /* Sign-extend it. */
153 delta = extract_signed_integer (buf, 1);
158 codestream_seek (pos);
162 * find & return amound a local space allocated, and advance codestream to
163 * first register push (if any)
165 * if entry sequence doesn't make sense, return -1, and leave
166 * codestream pointer random
170 i386_get_frame_setup (pc)
175 codestream_seek (pc);
179 op = codestream_get ();
181 if (op == 0x58) /* popl %eax */
184 * this function must start with
187 * xchgl %eax, (%esp) 0x87 0x04 0x24
188 * or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00
190 * (the system 5 compiler puts out the second xchg
191 * inst, and the assembler doesn't try to optimize it,
192 * so the 'sib' form gets generated)
194 * this sequence is used to get the address of the return
195 * buffer for a function that returns a structure
198 unsigned char buf[4];
199 static unsigned char proto1[3] = { 0x87,0x04,0x24 };
200 static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 };
201 pos = codestream_tell ();
202 codestream_read (buf, 4);
203 if (memcmp (buf, proto1, 3) == 0)
205 else if (memcmp (buf, proto2, 4) == 0)
208 codestream_seek (pos);
209 op = codestream_get (); /* update next opcode */
212 if (op == 0x55) /* pushl %ebp */
214 /* check for movl %esp, %ebp - can be written two ways */
215 switch (codestream_get ())
218 if (codestream_get () != 0xec)
222 if (codestream_get () != 0xe5)
228 /* check for stack adjustment
232 * note: you can't subtract a 16 bit immediate
233 * from a 32 bit reg, so we don't have to worry
234 * about a data16 prefix
236 op = codestream_peek ();
239 /* subl with 8 bit immed */
241 if (codestream_get () != 0xec)
242 /* Some instruction starting with 0x83 other than subl. */
244 codestream_seek (codestream_tell () - 2);
247 /* subl with signed byte immediate
248 * (though it wouldn't make sense to be negative)
250 return (codestream_get());
255 /* Maybe it is subl with 32 bit immedediate. */
257 if (codestream_get () != 0xec)
258 /* Some instruction starting with 0x81 other than subl. */
260 codestream_seek (codestream_tell () - 2);
263 /* It is subl with 32 bit immediate. */
264 codestream_read ((unsigned char *)buf, 4);
265 return extract_signed_integer (buf, 4);
275 /* enter instruction: arg is 16 bit unsigned immed */
276 codestream_read ((unsigned char *)buf, 2);
277 codestream_get (); /* flush final byte of enter instruction */
278 return extract_unsigned_integer (buf, 2);
283 /* Return number of args passed to a frame.
284 Can return -1, meaning no way to tell. */
287 i386_frame_num_args (fi)
288 struct frame_info *fi;
293 /* This loses because not only might the compiler not be popping the
294 args right after the function call, it might be popping args from both
295 this call and a previous one, and we would say there are more args
296 than there really are. */
300 struct frame_info *pfi;
302 /* on the 386, the instruction following the call could be:
304 addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits
305 anything else - zero args */
309 FRAMELESS_FUNCTION_INVOCATION (fi, frameless);
311 /* In the absence of a frame pointer, GDB doesn't get correct values
312 for nameless arguments. Return -1, so it doesn't print any
313 nameless arguments. */
316 pfi = get_prev_frame_info (fi);
319 /* Note: this can happen if we are looking at the frame for
320 main, because FRAME_CHAIN_VALID won't let us go into
321 start. If we have debugging symbols, that's not really
322 a big deal; it just means it will only show as many arguments
323 to main as are declared. */
329 op = read_memory_integer (retpc, 1);
335 op = read_memory_integer (retpc+1, 1);
337 /* addl $<signed imm 8 bits>, %esp */
338 return (read_memory_integer (retpc+2,1)&0xff)/4;
343 { /* add with 32 bit immediate */
344 op = read_memory_integer (retpc+1, 1);
346 /* addl $<imm 32>, %esp */
347 return read_memory_integer (retpc+2, 4) / 4;
360 * parse the first few instructions of the function to see
361 * what registers were stored.
363 * We handle these cases:
365 * The startup sequence can be at the start of the function,
366 * or the function can start with a branch to startup code at the end.
368 * %ebp can be set up with either the 'enter' instruction, or
369 * 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful,
370 * but was once used in the sys5 compiler)
372 * Local space is allocated just below the saved %ebp by either the
373 * 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has
374 * a 16 bit unsigned argument for space to allocate, and the
375 * 'addl' instruction could have either a signed byte, or
378 * Next, the registers used by this function are pushed. In
379 * the sys5 compiler they will always be in the order: %edi, %esi, %ebx
380 * (and sometimes a harmless bug causes it to also save but not restore %eax);
381 * however, the code below is willing to see the pushes in any order,
382 * and will handle up to 8 of them.
384 * If the setup sequence is at the end of the function, then the
385 * next instruction will be a branch back to the start.
389 i386_frame_find_saved_regs (fip, fsrp)
390 struct frame_info *fip;
391 struct frame_saved_regs *fsrp;
395 CORE_ADDR dummy_bottom;
399 memset (fsrp, 0, sizeof *fsrp);
401 /* if frame is the end of a dummy, compute where the
404 dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH;
406 /* check if the PC is in the stack, in a dummy frame */
407 if (dummy_bottom <= fip->pc && fip->pc <= fip->frame)
409 /* all regs were saved by push_call_dummy () */
411 for (i = 0; i < NUM_REGS; i++)
413 adr -= REGISTER_RAW_SIZE (i);
419 locals = i386_get_frame_setup (get_pc_function_start (fip->pc));
423 adr = fip->frame - 4 - locals;
424 for (i = 0; i < 8; i++)
426 op = codestream_get ();
427 if (op < 0x50 || op > 0x57)
429 #ifdef I386_REGNO_TO_SYMMETRY
430 /* Dynix uses different internal numbering. Ick. */
431 fsrp->regs[I386_REGNO_TO_SYMMETRY(op - 0x50)] = adr;
433 fsrp->regs[op - 0x50] = adr;
439 fsrp->regs[PC_REGNUM] = fip->frame + 4;
440 fsrp->regs[FP_REGNUM] = fip->frame;
443 /* return pc of first real instruction */
446 i386_skip_prologue (pc)
451 static unsigned char pic_pat[6] = { 0xe8, 0, 0, 0, 0, /* call 0x0 */
452 0x5b, /* popl %ebx */
456 if (i386_get_frame_setup (pc) < 0)
459 /* found valid frame setup - codestream now points to
460 * start of push instructions for saving registers
463 /* skip over register saves */
464 for (i = 0; i < 8; i++)
466 op = codestream_peek ();
467 /* break if not pushl inst */
468 if (op < 0x50 || op > 0x57)
473 /* The native cc on SVR4 in -K PIC mode inserts the following code to get
474 the address of the global offset table (GOT) into register %ebx.
477 movl %ebx,x(%ebp) (optional)
479 This code is with the rest of the prologue (at the end of the
480 function), so we have to skip it to get to the first real
481 instruction at the start of the function. */
483 pos = codestream_tell ();
484 for (i = 0; i < 6; i++)
486 op = codestream_get ();
487 if (pic_pat [i] != op)
492 unsigned char buf[4];
495 op = codestream_get ();
496 if (op == 0x89) /* movl %ebx, x(%ebp) */
498 op = codestream_get ();
499 if (op == 0x5d) /* one byte offset from %ebp */
502 codestream_read (buf, 1);
504 else if (op == 0x9d) /* four byte offset from %ebp */
507 codestream_read (buf, 4);
509 else /* unexpected instruction */
511 op = codestream_get ();
514 if (delta > 0 && op == 0x81 && codestream_get () == 0xc3)
519 codestream_seek (pos);
523 return (codestream_tell ());
527 i386_push_dummy_frame ()
529 CORE_ADDR sp = read_register (SP_REGNUM);
531 char regbuf[MAX_REGISTER_RAW_SIZE];
533 sp = push_word (sp, read_register (PC_REGNUM));
534 sp = push_word (sp, read_register (FP_REGNUM));
535 write_register (FP_REGNUM, sp);
536 for (regnum = 0; regnum < NUM_REGS; regnum++)
538 read_register_gen (regnum, regbuf);
539 sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum));
541 write_register (SP_REGNUM, sp);
547 struct frame_info *frame = get_current_frame ();
550 struct frame_saved_regs fsr;
551 char regbuf[MAX_REGISTER_RAW_SIZE];
553 fp = FRAME_FP (frame);
554 get_frame_saved_regs (frame, &fsr);
555 for (regnum = 0; regnum < NUM_REGS; regnum++)
558 adr = fsr.regs[regnum];
561 read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum));
562 write_register_bytes (REGISTER_BYTE (regnum), regbuf,
563 REGISTER_RAW_SIZE (regnum));
566 write_register (FP_REGNUM, read_memory_integer (fp, 4));
567 write_register (PC_REGNUM, read_memory_integer (fp + 4, 4));
568 write_register (SP_REGNUM, fp + 8);
569 flush_cached_frames ();
572 #ifdef GET_LONGJMP_TARGET
574 /* Figure out where the longjmp will land. Slurp the args out of the stack.
575 We expect the first arg to be a pointer to the jmp_buf structure from which
576 we extract the pc (JB_PC) that we will land at. The pc is copied into PC.
577 This routine returns true on success. */
580 get_longjmp_target(pc)
583 char buf[TARGET_PTR_BIT / TARGET_CHAR_BIT];
584 CORE_ADDR sp, jb_addr;
586 sp = read_register (SP_REGNUM);
588 if (target_read_memory (sp + SP_ARG0, /* Offset of first arg on stack */
590 TARGET_PTR_BIT / TARGET_CHAR_BIT))
593 jb_addr = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);
595 if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf,
596 TARGET_PTR_BIT / TARGET_CHAR_BIT))
599 *pc = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);
604 #endif /* GET_LONGJMP_TARGET */
607 i386_extract_return_value(type, regbuf, valbuf)
609 char regbuf[REGISTER_BYTES];
612 /* On AIX, floating point values are returned in floating point registers. */
613 #ifdef I386_AIX_TARGET
614 if (TYPE_CODE_FLT == TYPE_CODE(type))
617 /* 387 %st(0), gcc uses this */
618 floatformat_to_double (&floatformat_i387_ext,
619 ®buf[REGISTER_BYTE(FP0_REGNUM)],
621 store_floating (valbuf, TYPE_LENGTH (type), d);
624 #endif /* I386_AIX_TARGET */
626 memcpy (valbuf, regbuf, TYPE_LENGTH (type));
630 #ifdef I386V4_SIGTRAMP_SAVED_PC
631 /* Get saved user PC for sigtramp from the pushed ucontext on the stack
632 for all three variants of SVR4 sigtramps. */
635 i386v4_sigtramp_saved_pc (frame)
636 struct frame_info *frame;
638 CORE_ADDR saved_pc_offset = 4;
641 find_pc_partial_function (frame->pc, &name, NULL, NULL);
644 if (STREQ (name, "_sigreturn"))
645 saved_pc_offset = 132 + 14 * 4;
646 else if (STREQ (name, "_sigacthandler"))
647 saved_pc_offset = 80 + 14 * 4;
648 else if (STREQ (name, "sigvechandler"))
649 saved_pc_offset = 120 + 14 * 4;
653 return read_memory_integer (frame->next->frame + saved_pc_offset, 4);
654 return read_memory_integer (read_register (SP_REGNUM) + saved_pc_offset, 4);
656 #endif /* I386V4_SIGTRAMP_SAVED_PC */
660 /* Stuff for WIN32 PE style DLL's but is pretty generic really. */
663 skip_trampoline_code (pc, name)
667 if (pc && read_memory_unsigned_integer (pc, 2) == 0x25ff) /* jmp *(dest) */
669 unsigned long indirect = read_memory_unsigned_integer (pc+2, 4);
670 struct minimal_symbol *indsym =
671 indirect ? lookup_minimal_symbol_by_pc (indirect) : 0;
672 char *symname = indsym ? SYMBOL_NAME(indsym) : 0;
676 if (strncmp (symname,"__imp_", 6) == 0
677 || strncmp (symname,"_imp_", 5) == 0)
678 return name ? 1 : read_memory_unsigned_integer (indirect, 4);
681 return 0; /* not a trampoline */
685 _initialize_i386_tdep ()
687 tm_print_insn = print_insn_i386;