gdb/displaced-stepping.h

   1 /* Displaced stepping related things.
   2
   3    Copyright (C) 2020-2022 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef DISPLACED_STEPPING_H
  21 #define DISPLACED_STEPPING_H
  22
  23 #include "gdbsupport/array-view.h"
  24 #include "gdbsupport/byte-vector.h"
  25
  26 struct gdbarch;
  27 struct thread_info;
  28
  29 /* True if we are debugging displaced stepping.  */
  30
  31 extern bool debug_displaced;
  32
  33 /* Print a "displaced" debug statement.  */
  34
  35 #define displaced_debug_printf(fmt, ...) \
  36   debug_prefixed_printf_cond (debug_displaced, "displaced",fmt, ##__VA_ARGS__)
  37
  38 enum displaced_step_prepare_status
  39 {
  40   /* A displaced stepping buffer was successfully allocated and prepared.  */
  41   DISPLACED_STEP_PREPARE_STATUS_OK,
  42
  43   /* This particular instruction can't be displaced stepped, GDB should fall
  44      back on in-line stepping.  */
  45   DISPLACED_STEP_PREPARE_STATUS_CANT,
  46
  47   /* Not enough resources are available at this time, try again later.  */
  48   DISPLACED_STEP_PREPARE_STATUS_UNAVAILABLE,
  49 };
  50
  51 enum displaced_step_finish_status
  52 {
  53   /* Either the instruction was stepped and fixed up, or the specified thread
  54      wasn't executing a displaced step (in which case there's nothing to
  55      finish). */
  56   DISPLACED_STEP_FINISH_STATUS_OK,
  57
  58   /* The thread started a displaced step, but didn't complete it.  */
  59   DISPLACED_STEP_FINISH_STATUS_NOT_EXECUTED,
  60 };
  61
  62 /* Data returned by a gdbarch displaced_step_copy_insn method, to be passed to
  63    the matching displaced_step_fixup method.  */
  64
  65 struct displaced_step_copy_insn_closure
  66 {
  67   virtual ~displaced_step_copy_insn_closure () = 0;
  68 };
  69
  70 using displaced_step_copy_insn_closure_up
  71   = std::unique_ptr<displaced_step_copy_insn_closure>;
  72
  73 /* A simple displaced step closure that contains only a byte buffer.  */
  74
  75 struct buf_displaced_step_copy_insn_closure : displaced_step_copy_insn_closure
  76 {
  77   buf_displaced_step_copy_insn_closure (int buf_size)
  78   : buf (buf_size)
  79   {}
  80
  81   /* The content of this buffer is up to the user of the class, but typically
  82      original instruction bytes, used during fixup to determine what needs to
  83      be fixed up.  */
  84   gdb::byte_vector buf;
  85 };
  86
  87 /* Per-inferior displaced stepping state.  */
  88
  89 struct displaced_step_inferior_state
  90 {
  91   displaced_step_inferior_state ()
  92   {
  93     reset ();
  94   }
  95
  96   /* Put this object back in its original state.  */
  97   void reset ()
  98   {
  99     failed_before = false;
 100     in_progress_count = 0;
 101     unavailable = false;
 102   }
 103
 104   /* True if preparing a displaced step ever failed.  If so, we won't
 105      try displaced stepping for this inferior again.  */
 106   bool failed_before;
 107
 108   /* Number of displaced steps in progress for this inferior.  */
 109   unsigned int in_progress_count;
 110
 111   /* If true, this tells GDB that it's not worth asking the gdbarch displaced
 112      stepping implementation to prepare a displaced step, because it would
 113      return UNAVAILABLE.  This is set and reset by the gdbarch in the
 114      displaced_step_prepare and displaced_step_finish methods.  */
 115   bool unavailable;
 116 };
 117
 118 /* Per-thread displaced stepping state.  */
 119
 120 struct displaced_step_thread_state
 121 {
 122   /* Return true if this thread is currently executing a displaced step.  */
 123   bool in_progress () const
 124   {
 125     return m_original_gdbarch != nullptr;
 126   }
 127
 128   /* Return the gdbarch of the thread prior to the step.  */
 129   gdbarch *get_original_gdbarch () const
 130   {
 131     return m_original_gdbarch;
 132   }
 133
 134   /* Mark this thread as currently executing a displaced step.
 135
 136      ORIGINAL_GDBARCH is the current gdbarch of the thread (before the step
 137      is executed).  */
 138   void set (gdbarch *original_gdbarch)
 139   {
 140     m_original_gdbarch = original_gdbarch;
 141   }
 142
 143   /* Mark this thread as no longer executing a displaced step.  */
 144   void reset ()
 145   {
 146     m_original_gdbarch = nullptr;
 147   }
 148
 149 private:
 150   gdbarch *m_original_gdbarch = nullptr;
 151 };
 152
 153 /* Control access to multiple displaced stepping buffers at fixed addresses.  */
 154
 155 struct displaced_step_buffers
 156 {
 157   explicit displaced_step_buffers (gdb::array_view<CORE_ADDR> buffer_addrs)
 158   {
 159     gdb_assert (buffer_addrs.size () > 0);
 160
 161     m_buffers.reserve (buffer_addrs.size ());
 162
 163     for (CORE_ADDR buffer_addr : buffer_addrs)
 164       m_buffers.emplace_back (buffer_addr);
 165   }
 166
 167   displaced_step_prepare_status prepare (thread_info *thread,
 168                                          CORE_ADDR &displaced_pc);
 169
 170   displaced_step_finish_status finish (gdbarch *arch, thread_info *thread,
 171                                        gdb_signal sig);
 172
 173   const displaced_step_copy_insn_closure *
 174     copy_insn_closure_by_addr (CORE_ADDR addr);
 175
 176   void restore_in_ptid (ptid_t ptid);
 177
 178 private:
 179
 180   /* State of a single buffer.  */
 181
 182   struct displaced_step_buffer
 183   {
 184     explicit displaced_step_buffer (CORE_ADDR addr)
 185       : addr (addr)
 186     {}
 187
 188     /* Address of the buffer.  */
 189     const CORE_ADDR addr;
 190
 191     /* The original PC of the instruction currently being stepped.  */
 192     CORE_ADDR original_pc = 0;
 193
 194     /* If set, the thread currently using the buffer.  If unset, the buffer is not
 195        used.  */
 196     thread_info *current_thread = nullptr;
 197
 198     /* Saved copy of the bytes in the displaced buffer, to be restored once the
 199        buffer is no longer used.  */
 200     gdb::byte_vector saved_copy;
 201
 202     /* Closure obtained from gdbarch_displaced_step_copy_insn, to be passed to
 203        gdbarch_displaced_step_fixup_insn.  */
 204     displaced_step_copy_insn_closure_up copy_insn_closure;
 205   };
 206
 207   std::vector<displaced_step_buffer> m_buffers;
 208 };
 209
 210 #endif /* DISPLACED_STEPPING_H */