495 lines
12 KiB
C
495 lines
12 KiB
C
/* Intel 386 stuff.
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Copyright (C) 1988, 1989 Free Software Foundation, Inc.
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This file is part of GDB.
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GDB is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 1, or (at your option)
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any later version.
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GDB is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GDB; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
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#include <stdio.h>
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#include "defs.h"
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#include "param.h"
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#include "frame.h"
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#include "inferior.h"
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#include "gdbcore.h"
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#ifdef USG
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#include <sys/types.h>
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#endif
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#include <sys/param.h>
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#include <sys/dir.h>
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#include <signal.h>
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#include <sys/user.h>
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#include <sys/ioctl.h>
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#include <fcntl.h>
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#ifndef N_SET_MAGIC
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#ifdef COFF_FORMAT
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#define N_SET_MAGIC(exec, val) ((exec).magic = (val))
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#else
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#define N_SET_MAGIC(exec, val) ((exec).a_magic = (val))
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#endif
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#endif
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#include <sys/file.h>
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#include <sys/stat.h>
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/* I don't know whether this is right for cross-debugging even if you
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do somehow manage to get the right include file. */
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#if defined (USE_MACHINE_REG_H)
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#include <machine/reg.h>
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#else
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#include <sys/reg.h>
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#endif
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/* helper functions for m-i386.h */
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/* stdio style buffering to minimize calls to ptrace */
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static CORE_ADDR codestream_next_addr;
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static CORE_ADDR codestream_addr;
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static unsigned char codestream_buf[sizeof (int)];
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static int codestream_off;
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static int codestream_cnt;
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#define codestream_tell() (codestream_addr + codestream_off)
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#define codestream_peek() (codestream_cnt == 0 ? \
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codestream_fill(1): codestream_buf[codestream_off])
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#define codestream_get() (codestream_cnt-- == 0 ? \
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codestream_fill(0) : codestream_buf[codestream_off++])
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static unsigned char
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codestream_fill (peek_flag)
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{
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codestream_addr = codestream_next_addr;
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codestream_next_addr += sizeof (int);
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codestream_off = 0;
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codestream_cnt = sizeof (int);
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read_memory (codestream_addr,
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(unsigned char *)codestream_buf,
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sizeof (int));
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if (peek_flag)
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return (codestream_peek());
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else
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return (codestream_get());
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}
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static void
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codestream_seek (place)
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{
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codestream_next_addr = place & -sizeof (int);
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codestream_cnt = 0;
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codestream_fill (1);
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while (codestream_tell() != place)
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codestream_get ();
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}
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static void
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codestream_read (buf, count)
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unsigned char *buf;
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{
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unsigned char *p;
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int i;
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p = buf;
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for (i = 0; i < count; i++)
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*p++ = codestream_get ();
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}
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/* next instruction is a jump, move to target */
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static
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i386_follow_jump ()
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{
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int long_delta;
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short short_delta;
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char byte_delta;
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int data16;
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int pos;
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pos = codestream_tell ();
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data16 = 0;
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if (codestream_peek () == 0x66)
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{
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codestream_get ();
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data16 = 1;
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}
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switch (codestream_get ())
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{
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case 0xe9:
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/* relative jump: if data16 == 0, disp32, else disp16 */
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if (data16)
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{
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codestream_read ((unsigned char *)&short_delta, 2);
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pos += short_delta + 3; /* include size of jmp inst */
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}
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else
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{
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codestream_read ((unsigned char *)&long_delta, 4);
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pos += long_delta + 5;
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}
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break;
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case 0xeb:
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/* relative jump, disp8 (ignore data16) */
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codestream_read ((unsigned char *)&byte_delta, 1);
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pos += byte_delta + 2;
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break;
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}
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codestream_seek (pos + data16);
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}
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/*
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* find & return amound a local space allocated, and advance codestream to
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* first register push (if any)
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*
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* if entry sequence doesn't make sense, return -1, and leave
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* codestream pointer random
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*/
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static long
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i386_get_frame_setup (pc)
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{
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unsigned char op;
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codestream_seek (pc);
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i386_follow_jump ();
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op = codestream_get ();
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if (op == 0x58) /* popl %eax */
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{
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/*
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* this function must start with
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*
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* popl %eax 0x58
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* xchgl %eax, (%esp) 0x87 0x04 0x24
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* or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00
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*
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* (the system 5 compiler puts out the second xchg
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* inst, and the assembler doesn't try to optimize it,
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* so the 'sib' form gets generated)
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*
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* this sequence is used to get the address of the return
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* buffer for a function that returns a structure
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*/
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int pos;
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unsigned char buf[4];
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static unsigned char proto1[3] = { 0x87,0x04,0x24 };
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static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 };
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pos = codestream_tell ();
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codestream_read (buf, 4);
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if (bcmp (buf, proto1, 3) == 0)
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pos += 3;
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else if (bcmp (buf, proto2, 4) == 0)
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pos += 4;
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codestream_seek (pos);
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op = codestream_get (); /* update next opcode */
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}
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if (op == 0x55) /* pushl %ebp */
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{
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/* check for movl %esp, %ebp - can be written two ways */
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switch (codestream_get ())
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{
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case 0x8b:
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if (codestream_get () != 0xec)
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return (-1);
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break;
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case 0x89:
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if (codestream_get () != 0xe5)
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return (-1);
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break;
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default:
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return (-1);
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}
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/* check for stack adjustment
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*
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* subl $XXX, %esp
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*
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* note: you can't subtract a 16 bit immediate
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* from a 32 bit reg, so we don't have to worry
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* about a data16 prefix
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*/
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op = codestream_peek ();
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if (op == 0x83)
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{
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/* subl with 8 bit immed */
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codestream_get ();
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if (codestream_get () != 0xec)
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/* Some instruction starting with 0x83 other than subl. */
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{
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codestream_seek (codestream_tell () - 2);
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return 0;
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}
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/* subl with signed byte immediate
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* (though it wouldn't make sense to be negative)
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*/
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return (codestream_get());
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}
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else if (op == 0x81)
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{
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/* subl with 32 bit immed */
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int locals;
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codestream_get();
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if (codestream_get () != 0xec)
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/* Some instruction starting with 0x81 other than subl. */
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{
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codestream_seek (codestream_tell () - 2);
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return 0;
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}
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/* subl with 32 bit immediate */
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codestream_read ((unsigned char *)&locals, 4);
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return (locals);
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}
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else
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{
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return (0);
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}
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}
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else if (op == 0xc8)
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{
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/* enter instruction: arg is 16 bit unsigned immed */
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unsigned short slocals;
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codestream_read ((unsigned char *)&slocals, 2);
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codestream_get (); /* flush final byte of enter instruction */
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return (slocals);
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}
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return (-1);
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}
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/* Return number of args passed to a frame.
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Can return -1, meaning no way to tell. */
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/* on the 386, the instruction following the call could be:
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* popl %ecx - one arg
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* addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits
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* anything else - zero args
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*/
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int
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i386_frame_num_args (fi)
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struct frame_info fi;
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{
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int retpc;
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unsigned char op;
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struct frame_info *pfi;
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int frameless;
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FRAMELESS_FUNCTION_INVOCATION (fi, frameless);
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if (frameless)
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/* In the absence of a frame pointer, GDB doesn't get correct values
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for nameless arguments. Return -1, so it doesn't print any
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nameless arguments. */
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return -1;
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pfi = get_prev_frame_info ((fi));
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if (pfi == 0)
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{
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/* Note: this can happen if we are looking at the frame for
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main, because FRAME_CHAIN_VALID won't let us go into
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start. If we have debugging symbols, that's not really
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a big deal; it just means it will only show as many arguments
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to main as are declared. */
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return -1;
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}
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else
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{
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retpc = pfi->pc;
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op = read_memory_integer (retpc, 1);
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if (op == 0x59)
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/* pop %ecx */
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return 1;
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else if (op == 0x83)
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{
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op = read_memory_integer (retpc+1, 1);
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if (op == 0xc4)
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/* addl $<signed imm 8 bits>, %esp */
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return (read_memory_integer (retpc+2,1)&0xff)/4;
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else
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return 0;
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}
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else if (op == 0x81)
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{ /* add with 32 bit immediate */
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op = read_memory_integer (retpc+1, 1);
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if (op == 0xc4)
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/* addl $<imm 32>, %esp */
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return read_memory_integer (retpc+2, 4) / 4;
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else
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return 0;
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}
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else
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{
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return 0;
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}
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}
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}
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/*
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* parse the first few instructions of the function to see
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* what registers were stored.
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*
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* We handle these cases:
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*
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* The startup sequence can be at the start of the function,
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* or the function can start with a branch to startup code at the end.
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*
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* %ebp can be set up with either the 'enter' instruction, or
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* 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful,
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* but was once used in the sys5 compiler)
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*
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* Local space is allocated just below the saved %ebp by either the
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* 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has
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* a 16 bit unsigned argument for space to allocate, and the
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* 'addl' instruction could have either a signed byte, or
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* 32 bit immediate.
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*
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* Next, the registers used by this function are pushed. In
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* the sys5 compiler they will always be in the order: %edi, %esi, %ebx
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* (and sometimes a harmless bug causes it to also save but not restore %eax);
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* however, the code below is willing to see the pushes in any order,
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* and will handle up to 8 of them.
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*
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* If the setup sequence is at the end of the function, then the
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* next instruction will be a branch back to the start.
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*/
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i386_frame_find_saved_regs (fip, fsrp)
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struct frame_info *fip;
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struct frame_saved_regs *fsrp;
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{
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long locals;
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unsigned char *p;
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unsigned char op;
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CORE_ADDR dummy_bottom;
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CORE_ADDR adr;
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int i;
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bzero (fsrp, sizeof *fsrp);
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/* if frame is the end of a dummy, compute where the
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* beginning would be
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*/
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dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH;
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/* check if the PC is in the stack, in a dummy frame */
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if (dummy_bottom <= fip->pc && fip->pc <= fip->frame)
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{
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/* all regs were saved by push_call_dummy () */
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adr = fip->frame;
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for (i = 0; i < NUM_REGS; i++)
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{
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adr -= REGISTER_RAW_SIZE (i);
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fsrp->regs[i] = adr;
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}
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return;
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}
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locals = i386_get_frame_setup (get_pc_function_start (fip->pc));
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if (locals >= 0)
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{
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adr = fip->frame - 4 - locals;
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for (i = 0; i < 8; i++)
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{
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op = codestream_get ();
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if (op < 0x50 || op > 0x57)
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break;
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fsrp->regs[op - 0x50] = adr;
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adr -= 4;
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}
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}
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fsrp->regs[PC_REGNUM] = fip->frame + 4;
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fsrp->regs[FP_REGNUM] = fip->frame;
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}
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/* return pc of first real instruction */
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i386_skip_prologue (pc)
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{
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unsigned char op;
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int i;
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if (i386_get_frame_setup (pc) < 0)
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return (pc);
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/* found valid frame setup - codestream now points to
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* start of push instructions for saving registers
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*/
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/* skip over register saves */
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for (i = 0; i < 8; i++)
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{
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op = codestream_peek ();
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/* break if not pushl inst */
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if (op < 0x50 || op > 0x57)
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break;
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codestream_get ();
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}
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i386_follow_jump ();
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return (codestream_tell ());
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}
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i386_push_dummy_frame ()
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{
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CORE_ADDR sp = read_register (SP_REGNUM);
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int regnum;
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char regbuf[MAX_REGISTER_RAW_SIZE];
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sp = push_word (sp, read_register (PC_REGNUM));
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sp = push_word (sp, read_register (FP_REGNUM));
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write_register (FP_REGNUM, sp);
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for (regnum = 0; regnum < NUM_REGS; regnum++)
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{
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read_register_gen (regnum, regbuf);
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sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum));
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}
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write_register (SP_REGNUM, sp);
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}
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i386_pop_frame ()
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{
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FRAME frame = get_current_frame ();
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CORE_ADDR fp;
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int regnum;
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struct frame_saved_regs fsr;
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struct frame_info *fi;
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char regbuf[MAX_REGISTER_RAW_SIZE];
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fi = get_frame_info (frame);
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fp = fi->frame;
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get_frame_saved_regs (fi, &fsr);
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for (regnum = 0; regnum < NUM_REGS; regnum++)
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{
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CORE_ADDR adr;
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adr = fsr.regs[regnum];
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if (adr)
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{
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read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum));
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write_register_bytes (REGISTER_BYTE (regnum), regbuf,
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REGISTER_RAW_SIZE (regnum));
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}
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}
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write_register (FP_REGNUM, read_memory_integer (fp, 4));
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write_register (PC_REGNUM, read_memory_integer (fp + 4, 4));
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write_register (SP_REGNUM, fp + 8);
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flush_cached_frames ();
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set_current_frame ( create_new_frame (read_register (FP_REGNUM),
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read_pc ()));
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}
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