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/* Code dealing with dummy stack frames, for GDB, the GNU debugger.

   Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,

   1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2007, 2008, 2009,

   2010 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/>.  */

#include "defs.h"

#include "dummy-frame.h"

#include "regcache.h"

#include "frame.h"

#include "inferior.h"

#include "gdb_assert.h"

#include "frame-unwind.h"

#include "command.h"

#include "gdbcmd.h"

#include "gdb_string.h"

#include "observer.h"

/* Dummy frame.  This saves the processor state just prior to setting

   up the inferior function call.  Older targets save the registers

   on the target stack (but that really slows down function calls).  */

struct dummy_frame

{

  struct dummy_frame *next;

  /* This frame's ID.  Must match the value returned by

     gdbarch_dummy_id.  */

  struct frame_id id;

  /* The caller's state prior to the call.  */

  struct inferior_thread_state *caller_state;

};

static struct dummy_frame *dummy_frame_stack = NULL;

/* Function: deprecated_pc_in_call_dummy (pc)

   Return non-zero if the PC falls in a dummy frame created by gdb for

   an inferior call.  The code below which allows gdbarch_decr_pc_after_break

   is for infrun.c, which may give the function a PC without that

   subtracted out.

   FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can

   figure out what the real PC (as in the resume address) is BEFORE

   calling this function.

   NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of

   infrun.c:adjust_pc_after_break (thanks), this function is now

   always called with a correctly adjusted PC!

   NOTE: cagney/2004-08-02: Code should not need to call this.  */

int

deprecated_pc_in_call_dummy (struct gdbarch *gdbarch, CORE_ADDR pc)

{

  struct dummy_frame *dummyframe;

  for (dummyframe = dummy_frame_stack;

       dummyframe != NULL;

       dummyframe = dummyframe->next)

    {

      if ((pc >= dummyframe->id.code_addr)

          && (pc <= dummyframe->id.code_addr

                    + gdbarch_decr_pc_after_break (gdbarch)))

        return 1;

    }

  return 0;

}

/* Push the caller's state, along with the dummy frame info, onto the

   dummy-frame stack.  */

void

dummy_frame_push (struct inferior_thread_state *caller_state,

                  const struct frame_id *dummy_id)

{

  struct dummy_frame *dummy_frame;

  dummy_frame = XZALLOC (struct dummy_frame);

  dummy_frame->caller_state = caller_state;

  dummy_frame->id = (*dummy_id);

  dummy_frame->next = dummy_frame_stack;

  dummy_frame_stack = dummy_frame;

}

/* Remove *DUMMY_PTR from the dummy frame stack.  */

static void

remove_dummy_frame (struct dummy_frame **dummy_ptr)

{

  struct dummy_frame *dummy = *dummy_ptr;

  *dummy_ptr = dummy->next;

  discard_inferior_thread_state (dummy->caller_state);

  xfree (dummy);

}

/* Pop *DUMMY_PTR, restoring program state to that before the

   frame was created.  */

static void

pop_dummy_frame (struct dummy_frame **dummy_ptr)

{

  struct dummy_frame *dummy;

  restore_inferior_thread_state ((*dummy_ptr)->caller_state);

  /* restore_inferior_status frees inf_state,

     all that remains is to pop *dummy_ptr */

  dummy = *dummy_ptr;

  *dummy_ptr = dummy->next;

  xfree (dummy);

  /* We've made right mess of GDB's local state, just discard

     everything.  */

  reinit_frame_cache ();

}

/* Look up DUMMY_ID.

   Return NULL if not found.  */

static struct dummy_frame **

lookup_dummy_frame (struct frame_id dummy_id)

{

  struct dummy_frame **dp;

  for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)

    {

      if (frame_id_eq ((*dp)->id, dummy_id))

        return dp;

    }

  return NULL;

}

/* Pop the dummy frame DUMMY_ID, restoring program state to that before the

   frame was created.

   On return reinit_frame_cache has been called.

   If the frame isn't found, flag an internal error.

   NOTE: This can only pop the one frame, even if it is in the middle of the

   stack, because the other frames may be for different threads, and there's

   currently no way to tell which stack frame is for which thread.  */

void

dummy_frame_pop (struct frame_id dummy_id)

{

  struct dummy_frame **dp;

  dp = lookup_dummy_frame (dummy_id);

  gdb_assert (dp != NULL);

  pop_dummy_frame (dp);

}

/* There may be stale dummy frames, perhaps left over from when a longjump took

   us out of a function that was called by the debugger.  Clean them up at

   least once whenever we start a new inferior.  */

static void

cleanup_dummy_frames (struct target_ops *target, int from_tty)

{

  while (dummy_frame_stack != NULL)

    remove_dummy_frame (&dummy_frame_stack);

}

/* Return the dummy frame cache, it contains both the ID, and a

   pointer to the regcache.  */

struct dummy_frame_cache

{

  struct frame_id this_id;

  struct regcache *prev_regcache;

};

static int

dummy_frame_sniffer (const struct frame_unwind *self,

                     struct frame_info *this_frame,

                     void **this_prologue_cache)

{

  struct dummy_frame *dummyframe;

  struct frame_id this_id;

  /* When unwinding a normal frame, the stack structure is determined

     by analyzing the frame's function's code (be it using brute force

     prologue analysis, or the dwarf2 CFI).  In the case of a dummy

     frame, that simply isn't possible.  The PC is either the program

     entry point, or some random address on the stack.  Trying to use

     that PC to apply standard frame ID unwind techniques is just

     asking for trouble.  */

  /* Don't bother unless there is at least one dummy frame.  */

  if (dummy_frame_stack != NULL)

    {

      /* Use an architecture specific method to extract this frame's

         dummy ID, assuming it is a dummy frame.  */

      this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);

      /* Use that ID to find the corresponding cache entry.  */

      for (dummyframe = dummy_frame_stack;

           dummyframe != NULL;

           dummyframe = dummyframe->next)

        {

          if (frame_id_eq (dummyframe->id, this_id))

            {

              struct dummy_frame_cache *cache;

              cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);

              cache->prev_regcache = get_inferior_thread_state_regcache (dummyframe->caller_state);

              cache->this_id = this_id;

              (*this_prologue_cache) = cache;

              return 1;

            }

        }

    }

  return 0;

}

/* Given a call-dummy dummy-frame, return the registers.  Here the

   register value is taken from the local copy of the register buffer.  */

static struct value *

dummy_frame_prev_register (struct frame_info *this_frame,

                           void **this_prologue_cache,

                           int regnum)

{

  struct dummy_frame_cache *cache = (*this_prologue_cache);

  struct gdbarch *gdbarch = get_frame_arch (this_frame);

  struct value *reg_val;

  /* The dummy-frame sniffer always fills in the cache.  */

  gdb_assert (cache != NULL);

  /* Describe the register's location.  Generic dummy frames always

     have the register value in an ``expression''.  */

  reg_val = value_zero (register_type (gdbarch, regnum), not_lval);

  /* Use the regcache_cooked_read() method so that it, on the fly,

     constructs either a raw or pseudo register from the raw

     register cache.  */

  regcache_cooked_read (cache->prev_regcache, regnum,

                        value_contents_writeable (reg_val));

  return reg_val;

}

/* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is

   determined by examining the NEXT frame's unwound registers using

   the method dummy_id().  As a side effect, THIS dummy frame's

   dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */

static void

dummy_frame_this_id (struct frame_info *this_frame,

                     void **this_prologue_cache,

                     struct frame_id *this_id)

{

  /* The dummy-frame sniffer always fills in the cache.  */

  struct dummy_frame_cache *cache = (*this_prologue_cache);

  gdb_assert (cache != NULL);

  (*this_id) = cache->this_id;

}

static const struct frame_unwind dummy_frame_unwinder =

{

  DUMMY_FRAME,

  dummy_frame_this_id,

  dummy_frame_prev_register,

  NULL,

  dummy_frame_sniffer,

};

const struct frame_unwind *const dummy_frame_unwind = {

  &dummy_frame_unwinder

};

static void

fprint_dummy_frames (struct ui_file *file)

{

  struct dummy_frame *s;

  for (s = dummy_frame_stack; s != NULL; s = s->next)

    {

      gdb_print_host_address (s, file);

      fprintf_unfiltered (file, ":");

      fprintf_unfiltered (file, " id=");

      fprint_frame_id (file, s->id);

      fprintf_unfiltered (file, "\n");

    }

}

static void

maintenance_print_dummy_frames (char *args, int from_tty)

{

  if (args == NULL)

    fprint_dummy_frames (gdb_stdout);

  else

    {

      struct cleanup *cleanups;

      struct ui_file *file = gdb_fopen (args, "w");

      if (file == NULL)

        perror_with_name (_("maintenance print dummy-frames"));

      cleanups = make_cleanup_ui_file_delete (file);

      fprint_dummy_frames (file);

      do_cleanups (cleanups);

    }

}

extern void _initialize_dummy_frame (void);

void

_initialize_dummy_frame (void)

{

  add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,

           _("Print the contents of the internal dummy-frame stack."),

           &maintenanceprintlist);

  observer_attach_inferior_created (cleanup_dummy_frames);

}