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/* Displaced stepping related things.
Copyright (C) 2020-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef DISPLACED_STEPPING_H
#define DISPLACED_STEPPING_H
#include "gdbsupport/array-view.h"
#include "gdbsupport/byte-vector.h"
struct gdbarch;
struct thread_info;
/* True if we are debugging displaced stepping. */
extern bool debug_displaced;
/* Print a "displaced" debug statement. */
#define displaced_debug_printf(fmt, ...) \
debug_prefixed_printf_cond (debug_displaced, "displaced",fmt, ##__VA_ARGS__)
enum displaced_step_prepare_status
{
/* A displaced stepping buffer was successfully allocated and prepared. */
DISPLACED_STEP_PREPARE_STATUS_OK,
/* This particular instruction can't be displaced stepped, GDB should fall
back on in-line stepping. */
DISPLACED_STEP_PREPARE_STATUS_CANT,
/* Not enough resources are available at this time, try again later. */
DISPLACED_STEP_PREPARE_STATUS_UNAVAILABLE,
};
enum displaced_step_finish_status
{
/* Either the instruction was stepped and fixed up, or the specified thread
wasn't executing a displaced step (in which case there's nothing to
finish). */
DISPLACED_STEP_FINISH_STATUS_OK,
/* The thread started a displaced step, but didn't complete it. */
DISPLACED_STEP_FINISH_STATUS_NOT_EXECUTED,
};
/* Data returned by a gdbarch displaced_step_copy_insn method, to be passed to
the matching displaced_step_fixup method. */
struct displaced_step_copy_insn_closure
{
virtual ~displaced_step_copy_insn_closure () = 0;
};
using displaced_step_copy_insn_closure_up
= std::unique_ptr<displaced_step_copy_insn_closure>;
/* A simple displaced step closure that contains only a byte buffer. */
struct buf_displaced_step_copy_insn_closure : displaced_step_copy_insn_closure
{
buf_displaced_step_copy_insn_closure (int buf_size)
: buf (buf_size)
{}
/* The content of this buffer is up to the user of the class, but typically
original instruction bytes, used during fixup to determine what needs to
be fixed up. */
gdb::byte_vector buf;
};
/* Per-inferior displaced stepping state. */
struct displaced_step_inferior_state
{
displaced_step_inferior_state ()
{
reset ();
}
/* Put this object back in its original state. */
void reset ()
{
failed_before = false;
in_progress_count = 0;
unavailable = false;
}
/* True if preparing a displaced step ever failed. If so, we won't
try displaced stepping for this inferior again. */
bool failed_before;
/* Number of displaced steps in progress for this inferior. */
unsigned int in_progress_count;
/* If true, this tells GDB that it's not worth asking the gdbarch displaced
stepping implementation to prepare a displaced step, because it would
return UNAVAILABLE. This is set and reset by the gdbarch in the
displaced_step_prepare and displaced_step_finish methods. */
bool unavailable;
};
/* Per-thread displaced stepping state. */
struct displaced_step_thread_state
{
/* Return true if this thread is currently executing a displaced step. */
bool in_progress () const
{
return m_original_gdbarch != nullptr;
}
/* Return the gdbarch of the thread prior to the step. */
gdbarch *get_original_gdbarch () const
{
return m_original_gdbarch;
}
/* Mark this thread as currently executing a displaced step.
ORIGINAL_GDBARCH is the current gdbarch of the thread (before the step
is executed). */
void set (gdbarch *original_gdbarch)
{
m_original_gdbarch = original_gdbarch;
}
/* Mark this thread as no longer executing a displaced step. */
void reset ()
{
m_original_gdbarch = nullptr;
}
private:
gdbarch *m_original_gdbarch = nullptr;
};
/* Control access to multiple displaced stepping buffers at fixed addresses. */
struct displaced_step_buffers
{
explicit displaced_step_buffers (gdb::array_view<CORE_ADDR> buffer_addrs)
{
gdb_assert (buffer_addrs.size () > 0);
m_buffers.reserve (buffer_addrs.size ());
for (CORE_ADDR buffer_addr : buffer_addrs)
m_buffers.emplace_back (buffer_addr);
}
displaced_step_prepare_status prepare (thread_info *thread,
CORE_ADDR &displaced_pc);
displaced_step_finish_status finish (gdbarch *arch, thread_info *thread,
gdb_signal sig);
const displaced_step_copy_insn_closure *
copy_insn_closure_by_addr (CORE_ADDR addr);
void restore_in_ptid (ptid_t ptid);
private:
/* State of a single buffer. */
struct displaced_step_buffer
{
explicit displaced_step_buffer (CORE_ADDR addr)
: addr (addr)
{}
/* Address of the buffer. */
const CORE_ADDR addr;
/* The original PC of the instruction currently being stepped. */
CORE_ADDR original_pc = 0;
/* If set, the thread currently using the buffer. If unset, the buffer is not
used. */
thread_info *current_thread = nullptr;
/* Saved copy of the bytes in the displaced buffer, to be restored once the
buffer is no longer used. */
gdb::byte_vector saved_copy;
/* Closure obtained from gdbarch_displaced_step_copy_insn, to be passed to
gdbarch_displaced_step_fixup_insn. */
displaced_step_copy_insn_closure_up copy_insn_closure;
};
std::vector<displaced_step_buffer> m_buffers;
};
#endif /* DISPLACED_STEPPING_H */
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