001 // This file is part of the program FRYSK.
002 //
003 // Copyright 2007, 2008, Red Hat Inc.
004 //
005 // FRYSK is free software; you can redistribute it and/or modify it
006 // under the terms of the GNU General Public License as published by
007 // the Free Software Foundation; version 2 of the License.
008 //
009 // FRYSK is distributed in the hope that it will be useful, but
010 // WITHOUT ANY WARRANTY; without even the implied warranty of
011 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012 // General Public License for more details.
013 //
014 // You should have received a copy of the GNU General Public License
015 // along with FRYSK; if not, write to the Free Software Foundation,
016 // Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
017 //
018 // In addition, as a special exception, Red Hat, Inc. gives You the
019 // additional right to link the code of FRYSK with code not covered
020 // under the GNU General Public License ("Non-GPL Code") and to
021 // distribute linked combinations including the two, subject to the
022 // limitations in this paragraph. Non-GPL Code permitted under this
023 // exception must only link to the code of FRYSK through those well
024 // defined interfaces identified in the file named EXCEPTION found in
025 // the source code files (the "Approved Interfaces"). The files of
026 // Non-GPL Code may instantiate templates or use macros or inline
027 // functions from the Approved Interfaces without causing the
028 // resulting work to be covered by the GNU General Public
029 // License. Only Red Hat, Inc. may make changes or additions to the
030 // list of Approved Interfaces. You must obey the GNU General Public
031 // License in all respects for all of the FRYSK code and other code
032 // used in conjunction with FRYSK except the Non-GPL Code covered by
033 // this exception. If you modify this file, you may extend this
034 // exception to your version of the file, but you are not obligated to
035 // do so. If you do not wish to provide this exception without
036 // modification, you must delete this exception statement from your
037 // version and license this file solely under the GPL without
038 // exception.
039
040 package frysk.stepping;
041
042 import frysk.dwfl.ElfSectionCache;
043 import frysk.proc.Task;
044 import lib.dwfl.DwflLine;
045 import lib.dwfl.ElfSectionHeader;
046
047 public class InstructionStepState extends State {
048
049 private ElfSectionCache elfCache;
050 private final String PLT_DL_FIXUP = "_dl_fixup";
051
052 /**
053 * Indicates that this is a step (into) line, if true then plt
054 * entries are skipped.
055 */
056 private final boolean isLine;
057
058 public InstructionStepState(Task task, boolean isLine) {
059 this.task = task;
060 this.isLine = isLine;
061 }
062
063 /**
064 * When the instruction observer from SteppingEngine returns, a single
065 * step has been performed. All that is left to do is to reset the State
066 * for this Task back to a StoppedState.
067 *
068 * @param tse
069 * The TaskStepEngine for this State.
070 * @return new StoppedState
071 */
072 public State handleUpdate(TaskStepEngine tse) {
073
074 if (isLine) {
075 long addr = this.task.getPC();
076 this.elfCache = new ElfSectionCache(this.task);
077 ElfSectionHeader header = this.elfCache.getSectionHeader(".plt", addr);
078
079 /* If the user steps into a function call, the following
080 * catches the .plt section of the program, and ensures that
081 * Frysk steps past it, so that the user is landed back into
082 * their own code after the call. */
083 if (header != null
084 && header.addr <= addr
085 && (header.addr + header.offset) >= addr
086 && (header.type == ElfSectionHeader.ELF_SHT_PROGBITS
087 || header.type == ElfSectionHeader.ELF_SHT_NOBITS)) {
088
089 DwflLine line = tse.getDwflLine();
090
091 if (line == null) {
092 tse.getSteppingEngine().continueForStepping(this.task, true);
093 return new InstructionStepThroughState(task, PLT_DL_FIXUP);
094 }
095 }
096 }
097 return new StoppedState(this.task);
098 }
099
100 public boolean isStopped() {
101 return false;
102 }
103
104 public boolean isAlive() {
105 return true;
106 }
107 }