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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

   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"

/* 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_unwind_dummy_id.  */

  struct frame_id id;

  /* The caller's regcache.  */

  struct regcache *regcache;

};

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 (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 (current_gdbarch)))

        return 1;

    }

  return 0;

}

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

   dummy-frame stack.  */

void

dummy_frame_push (struct regcache *caller_regcache,

                  const struct frame_id *dummy_id)

{

  struct gdbarch *gdbarch = get_regcache_arch (caller_regcache);

  struct dummy_frame *dummy_frame;

  /* Check to see if there are stale dummy frames, perhaps left over

     from when a longjump took us out of a function that was called by

     the debugger.  */

  dummy_frame = dummy_frame_stack;

  while (dummy_frame)

    /* FIXME: cagney/2004-08-02: Should just test IDs.  */

    if (frame_id_inner (gdbarch, dummy_frame->id, (*dummy_id)))

      /* Stale -- destroy!  */

      {

        dummy_frame_stack = dummy_frame->next;

        regcache_xfree (dummy_frame->regcache);

        xfree (dummy_frame);

        dummy_frame = dummy_frame_stack;

      }

    else

      dummy_frame = dummy_frame->next;

  dummy_frame = XZALLOC (struct dummy_frame);

  dummy_frame->regcache = caller_regcache;

  dummy_frame->id = (*dummy_id);

  dummy_frame->next = dummy_frame_stack;

  dummy_frame_stack = dummy_frame;

}

/* 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;

};

int

dummy_frame_sniffer (const struct frame_unwind *self,

                     struct frame_info *next_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 unles there is at least one dummy frame.  */

  if (dummy_frame_stack != NULL)

    {

      /* Use an architecture specific method to extract the prev's

         dummy ID from the next frame.  Note that this method uses

         frame_register_unwind to obtain the register values needed to

         determine the dummy frame's ID.  */

      this_id = gdbarch_unwind_dummy_id (get_frame_arch (next_frame),

                                         next_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 = dummyframe->regcache;

              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 void

dummy_frame_prev_register (struct frame_info *next_frame,

                           void **this_prologue_cache,

                           int regnum, int *optimized,

                           enum lval_type *lvalp, CORE_ADDR *addrp,

                           int *realnum, gdb_byte *bufferp)

{

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

  struct dummy_frame_cache *cache = (*this_prologue_cache);

  gdb_assert (cache != NULL);

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

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

  *optimized = 0;

  *lvalp = not_lval;

  *addrp = 0;

  *realnum = -1;

  /* If needed, find and return the value of the register.  */

  if (bufferp != NULL)

    {

      /* Return the actual value.  */

      /* 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, bufferp);

    }

}

/* Assuming that THIS frame is a dummy (remember, the NEXT and not

   THIS frame is passed in), return the ID of THIS frame.  That ID is

   determined by examining the NEXT frame's unwound registers using

   the method unwind_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 *next_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 ui_file *file = gdb_fopen (args, "w");

      if (file == NULL)

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

      fprint_dummy_frames (file);

      ui_file_delete (file);

    }

}

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);

}