* doc/invoke.texi (TC_LARGEST_EXPONENT_IS_NORMAL): Document.

[deliverable/binutils-gdb.git] / gdb / blockframe.c

/* Get info from stack frames; convert between frames, blocks,
   functions and pc values.

   Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
   1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002 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 2 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, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "frame.h"
#include "gdbcore.h"
#include "value.h"              /* for read_register */
#include "target.h"             /* for target_has_stack */
#include "inferior.h"           /* for read_pc */
#include "annotate.h"
#include "regcache.h"

/* Prototypes for exported functions. */

void _initialize_blockframe (void);

/* A default FRAME_CHAIN_VALID, in the form that is suitable for most
   targets.  If FRAME_CHAIN_VALID returns zero it means that the given
   frame is the outermost one and has no caller. */

int
file_frame_chain_valid (CORE_ADDR chain, struct frame_info *thisframe)
{
  return ((chain) != 0
          && !inside_entry_file (FRAME_SAVED_PC (thisframe)));
}

/* Use the alternate method of avoiding running up off the end of the
   frame chain or following frames back into the startup code.  See
   the comments in objfiles.h. */

int
func_frame_chain_valid (CORE_ADDR chain, struct frame_info *thisframe)
{
  return ((chain) != 0
          && !inside_main_func ((thisframe)->pc)
          && !inside_entry_func ((thisframe)->pc));
}

/* A very simple method of determining a valid frame */

int
nonnull_frame_chain_valid (CORE_ADDR chain, struct frame_info *thisframe)
{
  return ((chain) != 0);
}

/* Is ADDR inside the startup file?  Note that if your machine
   has a way to detect the bottom of the stack, there is no need
   to call this function from FRAME_CHAIN_VALID; the reason for
   doing so is that some machines have no way of detecting bottom
   of stack. 

   A PC of zero is always considered to be the bottom of the stack. */

int
inside_entry_file (CORE_ADDR addr)
{
  if (addr == 0)
    return 1;
  if (symfile_objfile == 0)
    return 0;
  if (CALL_DUMMY_LOCATION == AT_ENTRY_POINT)
    {
      /* Do not stop backtracing if the pc is in the call dummy
         at the entry point.  */
      /* FIXME: Won't always work with zeros for the last two arguments */
      if (PC_IN_CALL_DUMMY (addr, 0, 0))
        return 0;
    }
  return (addr >= symfile_objfile->ei.entry_file_lowpc &&
          addr < symfile_objfile->ei.entry_file_highpc);
}

/* Test a specified PC value to see if it is in the range of addresses
   that correspond to the main() function.  See comments above for why
   we might want to do this.

   Typically called from FRAME_CHAIN_VALID.

   A PC of zero is always considered to be the bottom of the stack. */

int
inside_main_func (CORE_ADDR pc)
{
  if (pc == 0)
    return 1;
  if (symfile_objfile == 0)
    return 0;

  /* If the addr range is not set up at symbol reading time, set it up now.
     This is for FRAME_CHAIN_VALID_ALTERNATE. I do this for coff, because
     it is unable to set it up and symbol reading time. */

  if (symfile_objfile->ei.main_func_lowpc == INVALID_ENTRY_LOWPC &&
      symfile_objfile->ei.main_func_highpc == INVALID_ENTRY_HIGHPC)
    {
      struct symbol *mainsym;

      mainsym = lookup_symbol (main_name (), NULL, VAR_NAMESPACE, NULL, NULL);
      if (mainsym && SYMBOL_CLASS (mainsym) == LOC_BLOCK)
        {
          symfile_objfile->ei.main_func_lowpc =
            BLOCK_START (SYMBOL_BLOCK_VALUE (mainsym));
          symfile_objfile->ei.main_func_highpc =
            BLOCK_END (SYMBOL_BLOCK_VALUE (mainsym));
        }
    }
  return (symfile_objfile->ei.main_func_lowpc <= pc &&
          symfile_objfile->ei.main_func_highpc > pc);
}

/* Test a specified PC value to see if it is in the range of addresses
   that correspond to the process entry point function.  See comments
   in objfiles.h for why we might want to do this.

   Typically called from FRAME_CHAIN_VALID.

   A PC of zero is always considered to be the bottom of the stack. */

int
inside_entry_func (CORE_ADDR pc)
{
  if (pc == 0)
    return 1;
  if (symfile_objfile == 0)
    return 0;
  if (CALL_DUMMY_LOCATION == AT_ENTRY_POINT)
    {
      /* Do not stop backtracing if the pc is in the call dummy
         at the entry point.  */
      /* FIXME: Won't always work with zeros for the last two arguments */
      if (PC_IN_CALL_DUMMY (pc, 0, 0))
        return 0;
    }
  return (symfile_objfile->ei.entry_func_lowpc <= pc &&
          symfile_objfile->ei.entry_func_highpc > pc);
}

/* Info about the innermost stack frame (contents of FP register) */

static struct frame_info *current_frame;

/* Cache for frame addresses already read by gdb.  Valid only while
   inferior is stopped.  Control variables for the frame cache should
   be local to this module.  */

static struct obstack frame_cache_obstack;

void *
frame_obstack_alloc (unsigned long size)
{
  return obstack_alloc (&frame_cache_obstack, size);
}

void
frame_saved_regs_zalloc (struct frame_info *fi)
{
  fi->saved_regs = (CORE_ADDR *)
    frame_obstack_alloc (SIZEOF_FRAME_SAVED_REGS);
  memset (fi->saved_regs, 0, SIZEOF_FRAME_SAVED_REGS);
}


/* Return the innermost (currently executing) stack frame.  */

struct frame_info *
get_current_frame (void)
{
  if (current_frame == NULL)
    {
      if (target_has_stack)
        current_frame = create_new_frame (read_fp (), read_pc ());
      else
        error ("No stack.");
    }
  return current_frame;
}

void
set_current_frame (struct frame_info *frame)
{
  current_frame = frame;
}

/* Create an arbitrary (i.e. address specified by user) or innermost frame.
   Always returns a non-NULL value.  */

struct frame_info *
create_new_frame (CORE_ADDR addr, CORE_ADDR pc)
{
  struct frame_info *fi;
  char *name;

  fi = (struct frame_info *)
    obstack_alloc (&frame_cache_obstack,
                   sizeof (struct frame_info));

  /* Zero all fields by default.  */
  memset (fi, 0, sizeof (struct frame_info));

  fi->frame = addr;
  fi->pc = pc;
  find_pc_partial_function (pc, &name, (CORE_ADDR *) NULL, (CORE_ADDR *) NULL);
  fi->signal_handler_caller = IN_SIGTRAMP (fi->pc, name);

  if (INIT_EXTRA_FRAME_INFO_P ())
    INIT_EXTRA_FRAME_INFO (0, fi);

  return fi;
}

/* Return the frame that FRAME calls (NULL if FRAME is the innermost
   frame).  */

struct frame_info *
get_next_frame (struct frame_info *frame)
{
  return frame->next;
}

/* Flush the entire frame cache.  */

void
flush_cached_frames (void)
{
  /* Since we can't really be sure what the first object allocated was */
  obstack_free (&frame_cache_obstack, 0);
  obstack_init (&frame_cache_obstack);

  current_frame = NULL;         /* Invalidate cache */
  select_frame (NULL, -1);
  annotate_frames_invalid ();
}

/* Flush the frame cache, and start a new one if necessary.  */

void
reinit_frame_cache (void)
{
  flush_cached_frames ();

  /* FIXME: The inferior_ptid test is wrong if there is a corefile.  */
  if (PIDGET (inferior_ptid) != 0)
    {
      select_frame (get_current_frame (), 0);
    }
}

/* Return nonzero if the function for this frame lacks a prologue.  Many
   machines can define FRAMELESS_FUNCTION_INVOCATION to just call this
   function.  */

int
frameless_look_for_prologue (struct frame_info *frame)
{
  CORE_ADDR func_start, after_prologue;

  func_start = get_pc_function_start (frame->pc);
  if (func_start)
    {
      func_start += FUNCTION_START_OFFSET;
      /* This is faster, since only care whether there *is* a
         prologue, not how long it is.  */
      return PROLOGUE_FRAMELESS_P (func_start);
    }
  else if (frame->pc == 0)
    /* A frame with a zero PC is usually created by dereferencing a
       NULL function pointer, normally causing an immediate core dump
       of the inferior. Mark function as frameless, as the inferior
       has no chance of setting up a stack frame.  */
    return 1;
  else
    /* If we can't find the start of the function, we don't really
       know whether the function is frameless, but we should be able
       to get a reasonable (i.e. best we can do under the
       circumstances) backtrace by saying that it isn't.  */
    return 0;
}

/* Default a few macros that people seldom redefine.  */

#ifndef FRAME_CHAIN_COMBINE
#define FRAME_CHAIN_COMBINE(chain, thisframe) (chain)
#endif

/* Return a structure containing various interesting information
   about the frame that called NEXT_FRAME.  Returns NULL
   if there is no such frame.  */

struct frame_info *
get_prev_frame (struct frame_info *next_frame)
{
  CORE_ADDR address = 0;
  struct frame_info *prev;
  int fromleaf = 0;
  char *name;

  /* If the requested entry is in the cache, return it.
     Otherwise, figure out what the address should be for the entry
     we're about to add to the cache. */

  if (!next_frame)
    {
#if 0
      /* This screws value_of_variable, which just wants a nice clean
         NULL return from block_innermost_frame if there are no frames.
         I don't think I've ever seen this message happen otherwise.
         And returning NULL here is a perfectly legitimate thing to do.  */
      if (!current_frame)
        {
          error ("You haven't set up a process's stack to examine.");
        }
#endif

      return current_frame;
    }

  /* If we have the prev one, return it */
  if (next_frame->prev)
    return next_frame->prev;

  /* On some machines it is possible to call a function without
     setting up a stack frame for it.  On these machines, we
     define this macro to take two args; a frameinfo pointer
     identifying a frame and a variable to set or clear if it is
     or isn't leafless.  */

  /* Still don't want to worry about this except on the innermost
     frame.  This macro will set FROMLEAF if NEXT_FRAME is a
     frameless function invocation.  */
  if (!(next_frame->next))
    {
      fromleaf = FRAMELESS_FUNCTION_INVOCATION (next_frame);
      if (fromleaf)
        address = FRAME_FP (next_frame);
    }

  if (!fromleaf)
    {
      /* Two macros defined in tm.h specify the machine-dependent
         actions to be performed here.
         First, get the frame's chain-pointer.
         If that is zero, the frame is the outermost frame or a leaf
         called by the outermost frame.  This means that if start
         calls main without a frame, we'll return 0 (which is fine
         anyway).

         Nope; there's a problem.  This also returns when the current
         routine is a leaf of main.  This is unacceptable.  We move
         this to after the ffi test; I'd rather have backtraces from
         start go curfluy than have an abort called from main not show
         main.  */
      address = FRAME_CHAIN (next_frame);
      if (!FRAME_CHAIN_VALID (address, next_frame))
        return 0;
      address = FRAME_CHAIN_COMBINE (address, next_frame);
    }
  if (address == 0)
    return 0;

  prev = (struct frame_info *)
    obstack_alloc (&frame_cache_obstack,
                   sizeof (struct frame_info));

  /* Zero all fields by default.  */
  memset (prev, 0, sizeof (struct frame_info));

  if (next_frame)
    next_frame->prev = prev;
  prev->next = next_frame;
  prev->frame = address;
  prev->level = next_frame->level + 1;

/* This change should not be needed, FIXME!  We should
   determine whether any targets *need* INIT_FRAME_PC to happen
   after INIT_EXTRA_FRAME_INFO and come up with a simple way to
   express what goes on here.

   INIT_EXTRA_FRAME_INFO is called from two places: create_new_frame
   (where the PC is already set up) and here (where it isn't).
   INIT_FRAME_PC is only called from here, always after
   INIT_EXTRA_FRAME_INFO.

   The catch is the MIPS, where INIT_EXTRA_FRAME_INFO requires the PC
   value (which hasn't been set yet).  Some other machines appear to
   require INIT_EXTRA_FRAME_INFO before they can do INIT_FRAME_PC.  Phoo.

   We shouldn't need INIT_FRAME_PC_FIRST to add more complication to
   an already overcomplicated part of GDB.   gnu@cygnus.com, 15Sep92.

   Assuming that some machines need INIT_FRAME_PC after
   INIT_EXTRA_FRAME_INFO, one possible scheme:

   SETUP_INNERMOST_FRAME()
   Default version is just create_new_frame (read_fp ()),
   read_pc ()).  Machines with extra frame info would do that (or the
   local equivalent) and then set the extra fields.
   SETUP_ARBITRARY_FRAME(argc, argv)
   Only change here is that create_new_frame would no longer init extra
   frame info; SETUP_ARBITRARY_FRAME would have to do that.
   INIT_PREV_FRAME(fromleaf, prev)
   Replace INIT_EXTRA_FRAME_INFO and INIT_FRAME_PC.  This should
   also return a flag saying whether to keep the new frame, or
   whether to discard it, because on some machines (e.g.  mips) it
   is really awkward to have FRAME_CHAIN_VALID called *before*
   INIT_EXTRA_FRAME_INFO (there is no good way to get information
   deduced in FRAME_CHAIN_VALID into the extra fields of the new frame).
   std_frame_pc(fromleaf, prev)
   This is the default setting for INIT_PREV_FRAME.  It just does what
   the default INIT_FRAME_PC does.  Some machines will call it from
   INIT_PREV_FRAME (either at the beginning, the end, or in the middle).
   Some machines won't use it.
   kingdon@cygnus.com, 13Apr93, 31Jan94, 14Dec94.  */

  INIT_FRAME_PC_FIRST (fromleaf, prev);

  if (INIT_EXTRA_FRAME_INFO_P ())
    INIT_EXTRA_FRAME_INFO (fromleaf, prev);

  /* This entry is in the frame queue now, which is good since
     FRAME_SAVED_PC may use that queue to figure out its value
     (see tm-sparc.h).  We want the pc saved in the inferior frame. */
  INIT_FRAME_PC (fromleaf, prev);

  /* If ->frame and ->pc are unchanged, we are in the process of getting
     ourselves into an infinite backtrace.  Some architectures check this
     in FRAME_CHAIN or thereabouts, but it seems like there is no reason
     this can't be an architecture-independent check.  */
  if (next_frame != NULL)
    {
      if (prev->frame == next_frame->frame
          && prev->pc == next_frame->pc)
        {
          next_frame->prev = NULL;
          obstack_free (&frame_cache_obstack, prev);
          return NULL;
        }
    }

  find_pc_partial_function (prev->pc, &name,
                            (CORE_ADDR *) NULL, (CORE_ADDR *) NULL);
  if (IN_SIGTRAMP (prev->pc, name))
    prev->signal_handler_caller = 1;

  return prev;
}

CORE_ADDR
get_frame_pc (struct frame_info *frame)
{
  return frame->pc;
}


#ifdef FRAME_FIND_SAVED_REGS
/* XXX - deprecated.  This is a compatibility function for targets
   that do not yet implement FRAME_INIT_SAVED_REGS.  */
/* Find the addresses in which registers are saved in FRAME.  */

void
get_frame_saved_regs (struct frame_info *frame,
                      struct frame_saved_regs *saved_regs_addr)
{
  if (frame->saved_regs == NULL)
    {
      frame->saved_regs = (CORE_ADDR *)
        frame_obstack_alloc (SIZEOF_FRAME_SAVED_REGS);
    }
  if (saved_regs_addr == NULL)
    {
      struct frame_saved_regs saved_regs;
      FRAME_FIND_SAVED_REGS (frame, saved_regs);
      memcpy (frame->saved_regs, &saved_regs, SIZEOF_FRAME_SAVED_REGS);
    }
  else
    {
      FRAME_FIND_SAVED_REGS (frame, *saved_regs_addr);
      memcpy (frame->saved_regs, saved_regs_addr, SIZEOF_FRAME_SAVED_REGS);
    }
}
#endif

/* Return the innermost lexical block in execution
   in a specified stack frame.  The frame address is assumed valid.

   If ADDR_IN_BLOCK is non-zero, set *ADDR_IN_BLOCK to the exact code
   address we used to choose the block.  We use this to find a source
   line, to decide which macro definitions are in scope.

   The value returned in *ADDR_IN_BLOCK isn't necessarily the frame's
   PC, and may not really be a valid PC at all.  For example, in the
   caller of a function declared to never return, the code at the
   return address will never be reached, so the call instruction may
   be the very last instruction in the block.  So the address we use
   to choose the block is actually one byte before the return address
   --- hopefully pointing us at the call instruction, or its delay
   slot instruction.  */

struct block *
get_frame_block (struct frame_info *frame, CORE_ADDR *addr_in_block)
{
  CORE_ADDR pc;

  pc = frame->pc;
  if (frame->next != 0 && frame->next->signal_handler_caller == 0)
    /* We are not in the innermost frame and we were not interrupted
       by a signal.  We need to subtract one to get the correct block,
       in case the call instruction was the last instruction of the block.
       If there are any machines on which the saved pc does not point to
       after the call insn, we probably want to make frame->pc point after
       the call insn anyway.  */
    --pc;

  if (addr_in_block)
    *addr_in_block = pc;

  return block_for_pc (pc);
}

struct block *
get_current_block (CORE_ADDR *addr_in_block)
{
  CORE_ADDR pc = read_pc ();

  if (addr_in_block)
    *addr_in_block = pc;

  return block_for_pc (pc);
}

CORE_ADDR
get_pc_function_start (CORE_ADDR pc)
{
  register struct block *bl;
  register struct symbol *symbol;
  register struct minimal_symbol *msymbol;
  CORE_ADDR fstart;

  if ((bl = block_for_pc (pc)) != NULL &&
      (symbol = block_function (bl)) != NULL)
    {
      bl = SYMBOL_BLOCK_VALUE (symbol);
      fstart = BLOCK_START (bl);
    }
  else if ((msymbol = lookup_minimal_symbol_by_pc (pc)) != NULL)
    {
      fstart = SYMBOL_VALUE_ADDRESS (msymbol);
    }
  else
    {
      fstart = 0;
    }
  return (fstart);
}

/* Return the symbol for the function executing in frame FRAME.  */

struct symbol *
get_frame_function (struct frame_info *frame)
{
  register struct block *bl = get_frame_block (frame, 0);
  if (bl == 0)
    return 0;
  return block_function (bl);
}
\f

/* Return the blockvector immediately containing the innermost lexical block
   containing the specified pc value and section, or 0 if there is none.
   PINDEX is a pointer to the index value of the block.  If PINDEX
   is NULL, we don't pass this information back to the caller.  */

struct blockvector *
blockvector_for_pc_sect (register CORE_ADDR pc, struct sec *section,
                         int *pindex, struct symtab *symtab)
{
  register struct block *b;
  register int bot, top, half;
  struct blockvector *bl;

  if (symtab == 0)              /* if no symtab specified by caller */
    {
      /* First search all symtabs for one whose file contains our pc */
      if ((symtab = find_pc_sect_symtab (pc, section)) == 0)
        return 0;
    }

  bl = BLOCKVECTOR (symtab);
  b = BLOCKVECTOR_BLOCK (bl, 0);

  /* Then search that symtab for the smallest block that wins.  */
  /* Use binary search to find the last block that starts before PC.  */

  bot = 0;
  top = BLOCKVECTOR_NBLOCKS (bl);

  while (top - bot > 1)
    {
      half = (top - bot + 1) >> 1;
      b = BLOCKVECTOR_BLOCK (bl, bot + half);
      if (BLOCK_START (b) <= pc)
        bot += half;
      else
        top = bot + half;
    }

  /* Now search backward for a block that ends after PC.  */

  while (bot >= 0)
    {
      b = BLOCKVECTOR_BLOCK (bl, bot);
      if (BLOCK_END (b) > pc)
        {
          if (pindex)
            *pindex = bot;
          return bl;
        }
      bot--;
    }
  return 0;
}

/* Return the blockvector immediately containing the innermost lexical block
   containing the specified pc value, or 0 if there is none.
   Backward compatibility, no section.  */

struct blockvector *
blockvector_for_pc (register CORE_ADDR pc, int *pindex)
{
  return blockvector_for_pc_sect (pc, find_pc_mapped_section (pc),
                                  pindex, NULL);
}

/* Return the innermost lexical block containing the specified pc value
   in the specified section, or 0 if there is none.  */

struct block *
block_for_pc_sect (register CORE_ADDR pc, struct sec *section)
{
  register struct blockvector *bl;
  int index;

  bl = blockvector_for_pc_sect (pc, section, &index, NULL);
  if (bl)
    return BLOCKVECTOR_BLOCK (bl, index);
  return 0;
}

/* Return the innermost lexical block containing the specified pc value,
   or 0 if there is none.  Backward compatibility, no section.  */

struct block *
block_for_pc (register CORE_ADDR pc)
{
  return block_for_pc_sect (pc, find_pc_mapped_section (pc));
}

/* Return the function containing pc value PC in section SECTION.
   Returns 0 if function is not known.  */

struct symbol *
find_pc_sect_function (CORE_ADDR pc, struct sec *section)
{
  register struct block *b = block_for_pc_sect (pc, section);
  if (b == 0)
    return 0;
  return block_function (b);
}

/* Return the function containing pc value PC.
   Returns 0 if function is not known.  Backward compatibility, no section */

struct symbol *
find_pc_function (CORE_ADDR pc)
{
  return find_pc_sect_function (pc, find_pc_mapped_section (pc));
}

/* These variables are used to cache the most recent result
 * of find_pc_partial_function. */

static CORE_ADDR cache_pc_function_low = 0;
static CORE_ADDR cache_pc_function_high = 0;
static char *cache_pc_function_name = 0;
static struct sec *cache_pc_function_section = NULL;

/* Clear cache, e.g. when symbol table is discarded. */

void
clear_pc_function_cache (void)
{
  cache_pc_function_low = 0;
  cache_pc_function_high = 0;
  cache_pc_function_name = (char *) 0;
  cache_pc_function_section = NULL;
}

/* Finds the "function" (text symbol) that is smaller than PC but
   greatest of all of the potential text symbols in SECTION.  Sets
   *NAME and/or *ADDRESS conditionally if that pointer is non-null.
   If ENDADDR is non-null, then set *ENDADDR to be the end of the
   function (exclusive), but passing ENDADDR as non-null means that
   the function might cause symbols to be read.  This function either
   succeeds or fails (not halfway succeeds).  If it succeeds, it sets
   *NAME, *ADDRESS, and *ENDADDR to real information and returns 1.
   If it fails, it sets *NAME, *ADDRESS, and *ENDADDR to zero and
   returns 0.  */

int
find_pc_sect_partial_function (CORE_ADDR pc, asection *section, char **name,
                               CORE_ADDR *address, CORE_ADDR *endaddr)
{
  struct partial_symtab *pst;
  struct symbol *f;
  struct minimal_symbol *msymbol;
  struct partial_symbol *psb;
  struct obj_section *osect;
  int i;
  CORE_ADDR mapped_pc;

  mapped_pc = overlay_mapped_address (pc, section);

  if (mapped_pc >= cache_pc_function_low &&
      mapped_pc < cache_pc_function_high &&
      section == cache_pc_function_section)
    goto return_cached_value;

  /* If sigtramp is in the u area, it counts as a function (especially
     important for step_1).  */
#if defined SIGTRAMP_START
  if (IN_SIGTRAMP (mapped_pc, (char *) NULL))
    {
      cache_pc_function_low = SIGTRAMP_START (mapped_pc);
      cache_pc_function_high = SIGTRAMP_END (mapped_pc);
      cache_pc_function_name = "<sigtramp>";
      cache_pc_function_section = section;
      goto return_cached_value;
    }
#endif

  msymbol = lookup_minimal_symbol_by_pc_section (mapped_pc, section);
  pst = find_pc_sect_psymtab (mapped_pc, section);
  if (pst)
    {
      /* Need to read the symbols to get a good value for the end address.  */
      if (endaddr != NULL && !pst->readin)
        {
          /* Need to get the terminal in case symbol-reading produces
             output.  */
          target_terminal_ours_for_output ();
          PSYMTAB_TO_SYMTAB (pst);
        }

      if (pst->readin)
        {
          /* Checking whether the msymbol has a larger value is for the
             "pathological" case mentioned in print_frame_info.  */
          f = find_pc_sect_function (mapped_pc, section);
          if (f != NULL
              && (msymbol == NULL
                  || (BLOCK_START (SYMBOL_BLOCK_VALUE (f))
                      >= SYMBOL_VALUE_ADDRESS (msymbol))))
            {
              cache_pc_function_low = BLOCK_START (SYMBOL_BLOCK_VALUE (f));
              cache_pc_function_high = BLOCK_END (SYMBOL_BLOCK_VALUE (f));
              cache_pc_function_name = SYMBOL_NAME (f);
              cache_pc_function_section = section;
              goto return_cached_value;
            }
        }
      else
        {
          /* Now that static symbols go in the minimal symbol table, perhaps
             we could just ignore the partial symbols.  But at least for now
             we use the partial or minimal symbol, whichever is larger.  */
          psb = find_pc_sect_psymbol (pst, mapped_pc, section);

          if (psb
              && (msymbol == NULL ||
                  (SYMBOL_VALUE_ADDRESS (psb)
                   >= SYMBOL_VALUE_ADDRESS (msymbol))))
            {
              /* This case isn't being cached currently. */
              if (address)
                *address = SYMBOL_VALUE_ADDRESS (psb);
              if (name)
                *name = SYMBOL_NAME (psb);
              /* endaddr non-NULL can't happen here.  */
              return 1;
            }
        }
    }

  /* Not in the normal symbol tables, see if the pc is in a known section.
     If it's not, then give up.  This ensures that anything beyond the end
     of the text seg doesn't appear to be part of the last function in the
     text segment.  */

  osect = find_pc_sect_section (mapped_pc, section);

  if (!osect)
    msymbol = NULL;

  /* Must be in the minimal symbol table.  */
  if (msymbol == NULL)
    {
      /* No available symbol.  */
      if (name != NULL)
        *name = 0;
      if (address != NULL)
        *address = 0;
      if (endaddr != NULL)
        *endaddr = 0;
      return 0;
    }

  cache_pc_function_low = SYMBOL_VALUE_ADDRESS (msymbol);
  cache_pc_function_name = SYMBOL_NAME (msymbol);
  cache_pc_function_section = section;

  /* Use the lesser of the next minimal symbol in the same section, or
     the end of the section, as the end of the function.  */

  /* Step over other symbols at this same address, and symbols in
     other sections, to find the next symbol in this section with
     a different address.  */

  for (i = 1; SYMBOL_NAME (msymbol + i) != NULL; i++)
    {
      if (SYMBOL_VALUE_ADDRESS (msymbol + i) != SYMBOL_VALUE_ADDRESS (msymbol)
        && SYMBOL_BFD_SECTION (msymbol + i) == SYMBOL_BFD_SECTION (msymbol))
        break;
    }

  if (SYMBOL_NAME (msymbol + i) != NULL
      && SYMBOL_VALUE_ADDRESS (msymbol + i) < osect->endaddr)
    cache_pc_function_high = SYMBOL_VALUE_ADDRESS (msymbol + i);
  else
    /* We got the start address from the last msymbol in the objfile.
       So the end address is the end of the section.  */
    cache_pc_function_high = osect->endaddr;

return_cached_value:

  if (address)
    {
      if (pc_in_unmapped_range (pc, section))
        *address = overlay_unmapped_address (cache_pc_function_low, section);
      else
        *address = cache_pc_function_low;
    }

  if (name)
    *name = cache_pc_function_name;

  if (endaddr)
    {
      if (pc_in_unmapped_range (pc, section))
        {
          /* Because the high address is actually beyond the end of
             the function (and therefore possibly beyond the end of
             the overlay), we must actually convert (high - 1)
             and then add one to that. */

          *endaddr = 1 + overlay_unmapped_address (cache_pc_function_high - 1,
                                                   section);
        }
      else
        *endaddr = cache_pc_function_high;
    }

  return 1;
}

/* Backward compatibility, no section argument */

int
find_pc_partial_function (CORE_ADDR pc, char **name, CORE_ADDR *address,
                          CORE_ADDR *endaddr)
{
  asection *section;

  section = find_pc_overlay (pc);
  return find_pc_sect_partial_function (pc, section, name, address, endaddr);
}

/* Return the innermost stack frame executing inside of BLOCK,
   or NULL if there is no such frame.  If BLOCK is NULL, just return NULL.  */

struct frame_info *
block_innermost_frame (struct block *block)
{
  struct frame_info *frame;
  register CORE_ADDR start;
  register CORE_ADDR end;

  if (block == NULL)
    return NULL;

  start = BLOCK_START (block);
  end = BLOCK_END (block);

  frame = NULL;
  while (1)
    {
      frame = get_prev_frame (frame);
      if (frame == NULL)
        return NULL;
      if (frame->pc >= start && frame->pc < end)
        return frame;
    }
}

/* Return the full FRAME which corresponds to the given CORE_ADDR
   or NULL if no FRAME on the chain corresponds to CORE_ADDR.  */

struct frame_info *
find_frame_addr_in_frame_chain (CORE_ADDR frame_addr)
{
  struct frame_info *frame = NULL;

  if (frame_addr == (CORE_ADDR) 0)
    return NULL;

  while (1)
    {
      frame = get_prev_frame (frame);
      if (frame == NULL)
        return NULL;
      if (FRAME_FP (frame) == frame_addr)
        return frame;
    }
}

#ifdef SIGCONTEXT_PC_OFFSET
/* Get saved user PC for sigtramp from sigcontext for BSD style sigtramp.  */

CORE_ADDR
sigtramp_saved_pc (struct frame_info *frame)
{
  CORE_ADDR sigcontext_addr;
  char *buf;
  int ptrbytes = TARGET_PTR_BIT / TARGET_CHAR_BIT;
  int sigcontext_offs = (2 * TARGET_INT_BIT) / TARGET_CHAR_BIT;

  buf = alloca (ptrbytes);
  /* Get sigcontext address, it is the third parameter on the stack.  */
  if (frame->next)
    sigcontext_addr = read_memory_integer (FRAME_ARGS_ADDRESS (frame->next)
                                           + FRAME_ARGS_SKIP
                                           + sigcontext_offs,
                                           ptrbytes);
  else
    sigcontext_addr = read_memory_integer (read_register (SP_REGNUM)
                                           + sigcontext_offs,
                                           ptrbytes);

  /* Don't cause a memory_error when accessing sigcontext in case the stack
     layout has changed or the stack is corrupt.  */
  target_read_memory (sigcontext_addr + SIGCONTEXT_PC_OFFSET, buf, ptrbytes);
  return extract_unsigned_integer (buf, ptrbytes);
}
#endif /* SIGCONTEXT_PC_OFFSET */


/* Are we in a call dummy?  The code below which allows DECR_PC_AFTER_BREAK
   below is for infrun.c, which may give the macro a pc without that
   subtracted out.  */

extern CORE_ADDR text_end;

int
pc_in_call_dummy_before_text_end (CORE_ADDR pc, CORE_ADDR sp,
                                  CORE_ADDR frame_address)
{
  return ((pc) >= text_end - CALL_DUMMY_LENGTH
          && (pc) <= text_end + DECR_PC_AFTER_BREAK);
}

int
pc_in_call_dummy_after_text_end (CORE_ADDR pc, CORE_ADDR sp,
                                 CORE_ADDR frame_address)
{
  return ((pc) >= text_end
          && (pc) <= text_end + CALL_DUMMY_LENGTH + DECR_PC_AFTER_BREAK);
}

/* Is the PC in a call dummy?  SP and FRAME_ADDRESS are the bottom and
   top of the stack frame which we are checking, where "bottom" and
   "top" refer to some section of memory which contains the code for
   the call dummy.  Calls to this macro assume that the contents of
   SP_REGNUM and FP_REGNUM (or the saved values thereof), respectively,
   are the things to pass.

   This won't work on the 29k, where SP_REGNUM and FP_REGNUM don't
   have that meaning, but the 29k doesn't use ON_STACK.  This could be
   fixed by generalizing this scheme, perhaps by passing in a frame
   and adding a few fields, at least on machines which need them for
   PC_IN_CALL_DUMMY.

   Something simpler, like checking for the stack segment, doesn't work,
   since various programs (threads implementations, gcc nested function
   stubs, etc) may either allocate stack frames in another segment, or
   allocate other kinds of code on the stack.  */

int
pc_in_call_dummy_on_stack (CORE_ADDR pc, CORE_ADDR sp, CORE_ADDR frame_address)
{
  return (INNER_THAN ((sp), (pc))
          && (frame_address != 0)
          && INNER_THAN ((pc), (frame_address)));
}

int
pc_in_call_dummy_at_entry_point (CORE_ADDR pc, CORE_ADDR sp,
                                 CORE_ADDR frame_address)
{
  return ((pc) >= CALL_DUMMY_ADDRESS ()
          && (pc) <= (CALL_DUMMY_ADDRESS () + DECR_PC_AFTER_BREAK));
}


/*
 * GENERIC DUMMY FRAMES
 * 
 * The following code serves to maintain the dummy stack frames for
 * inferior function calls (ie. when gdb calls into the inferior via
 * call_function_by_hand).  This code saves the machine state before 
 * the call in host memory, so we must maintain an independent stack 
 * and keep it consistant etc.  I am attempting to make this code 
 * generic enough to be used by many targets.
 *
 * The cheapest and most generic way to do CALL_DUMMY on a new target
 * is probably to define CALL_DUMMY to be empty, CALL_DUMMY_LENGTH to
 * zero, and CALL_DUMMY_LOCATION to AT_ENTRY.  Then you must remember
 * to define PUSH_RETURN_ADDRESS, because no call instruction will be
 * being executed by the target.  Also FRAME_CHAIN_VALID as
 * generic_{file,func}_frame_chain_valid and FIX_CALL_DUMMY as
 * generic_fix_call_dummy.  */

/* 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;

  CORE_ADDR pc;
  CORE_ADDR fp;
  CORE_ADDR sp;
  CORE_ADDR top;
  char *registers;
};

static struct dummy_frame *dummy_frame_stack = NULL;

/* Function: find_dummy_frame(pc, fp, sp)
   Search the stack of dummy frames for one matching the given PC, FP and SP.
   This is the work-horse for pc_in_call_dummy and read_register_dummy     */

char *
generic_find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
{
  struct dummy_frame *dummyframe;

  if (pc != entry_point_address ())
    return 0;

  for (dummyframe = dummy_frame_stack; dummyframe != NULL;
       dummyframe = dummyframe->next)
    if (fp == dummyframe->fp
        || fp == dummyframe->sp
        || fp == dummyframe->top)
      /* The frame in question lies between the saved fp and sp, inclusive */
      return dummyframe->registers;

  return 0;
}

/* Function: pc_in_call_dummy (pc, fp)
   Return true if this is a dummy frame created by gdb for an inferior call */

int
generic_pc_in_call_dummy (CORE_ADDR pc, CORE_ADDR sp, CORE_ADDR fp)
{
  /* if find_dummy_frame succeeds, then PC is in a call dummy */
  /* Note: SP and not FP is passed on. */
  return (generic_find_dummy_frame (pc, sp) != 0);
}

/* Function: read_register_dummy 
   Find a saved register from before GDB calls a function in the inferior */

CORE_ADDR
generic_read_register_dummy (CORE_ADDR pc, CORE_ADDR fp, int regno)
{
  char *dummy_regs = generic_find_dummy_frame (pc, fp);

  if (dummy_regs)
    return extract_address (&dummy_regs[REGISTER_BYTE (regno)],
                            REGISTER_RAW_SIZE (regno));
  else
    return 0;
}

/* Save all the registers on the dummy frame stack.  Most ports save the
   registers on the target stack.  This results in lots of unnecessary memory
   references, which are slow when debugging via a serial line.  Instead, we
   save all the registers internally, and never write them to the stack.  The
   registers get restored when the called function returns to the entry point,
   where a breakpoint is laying in wait.  */

void
generic_push_dummy_frame (void)
{
  struct dummy_frame *dummy_frame;
  CORE_ADDR fp = (get_current_frame ())->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)
    if (INNER_THAN (dummy_frame->fp, fp))       /* stale -- destroy! */
      {
        dummy_frame_stack = dummy_frame->next;
        xfree (dummy_frame->registers);
        xfree (dummy_frame);
        dummy_frame = dummy_frame_stack;
      }
    else
      dummy_frame = dummy_frame->next;

  dummy_frame = xmalloc (sizeof (struct dummy_frame));
  dummy_frame->registers = xmalloc (REGISTER_BYTES);

  dummy_frame->pc = read_pc ();
  dummy_frame->sp = read_sp ();
  dummy_frame->top = dummy_frame->sp;
  dummy_frame->fp = fp;
  read_register_bytes (0, dummy_frame->registers, REGISTER_BYTES);
  dummy_frame->next = dummy_frame_stack;
  dummy_frame_stack = dummy_frame;
}

void
generic_save_dummy_frame_tos (CORE_ADDR sp)
{
  dummy_frame_stack->top = sp;
}

/* Restore the machine state from either the saved dummy stack or a
   real stack frame. */

void
generic_pop_current_frame (void (*popper) (struct frame_info * frame))
{
  struct frame_info *frame = get_current_frame ();

  if (PC_IN_CALL_DUMMY (frame->pc, frame->frame, frame->frame))
    generic_pop_dummy_frame ();
  else
    (*popper) (frame);
}

/* Function: pop_dummy_frame
   Restore the machine state from a saved dummy stack frame. */

void
generic_pop_dummy_frame (void)
{
  struct dummy_frame *dummy_frame = dummy_frame_stack;

  /* FIXME: what if the first frame isn't the right one, eg..
     because one call-by-hand function has done a longjmp into another one? */

  if (!dummy_frame)
    error ("Can't pop dummy frame!");
  dummy_frame_stack = dummy_frame->next;
  write_register_bytes (0, dummy_frame->registers, REGISTER_BYTES);
  flush_cached_frames ();

  xfree (dummy_frame->registers);
  xfree (dummy_frame);
}

/* Function: frame_chain_valid 
   Returns true for a user frame or a call_function_by_hand dummy frame,
   and false for the CRT0 start-up frame.  Purpose is to terminate backtrace */

int
generic_file_frame_chain_valid (CORE_ADDR fp, struct frame_info *fi)
{
  if (PC_IN_CALL_DUMMY (FRAME_SAVED_PC (fi), fp, fp))
    return 1;                   /* don't prune CALL_DUMMY frames */
  else                          /* fall back to default algorithm (see frame.h) */
    return (fp != 0
            && (INNER_THAN (fi->frame, fp) || fi->frame == fp)
            && !inside_entry_file (FRAME_SAVED_PC (fi)));
}

int
generic_func_frame_chain_valid (CORE_ADDR fp, struct frame_info *fi)
{
  if (PC_IN_CALL_DUMMY ((fi)->pc, fp, fp))
    return 1;                   /* don't prune CALL_DUMMY frames */
  else                          /* fall back to default algorithm (see frame.h) */
    return (fp != 0
            && (INNER_THAN (fi->frame, fp) || fi->frame == fp)
            && !inside_main_func ((fi)->pc)
            && !inside_entry_func ((fi)->pc));
}

/* Function: fix_call_dummy
   Stub function.  Generic dummy frames typically do not need to fix
   the frame being created */

void
generic_fix_call_dummy (char *dummy, CORE_ADDR pc, CORE_ADDR fun, int nargs,
                        struct value **args, struct type *type, int gcc_p)
{
  return;
}

/* Function: get_saved_register
   Find register number REGNUM relative to FRAME and put its (raw,
   target format) contents in *RAW_BUFFER.  

   Set *OPTIMIZED if the variable was optimized out (and thus can't be
   fetched).  Note that this is never set to anything other than zero
   in this implementation.

   Set *LVAL to lval_memory, lval_register, or not_lval, depending on
   whether the value was fetched from memory, from a register, or in a
   strange and non-modifiable way (e.g. a frame pointer which was
   calculated rather than fetched).  We will use not_lval for values
   fetched from generic dummy frames.

   Set *ADDRP to the address, either in memory or as a REGISTER_BYTE
   offset into the registers array.  If the value is stored in a dummy
   frame, set *ADDRP to zero.

   To use this implementation, define a function called
   "get_saved_register" in your target code, which simply passes all
   of its arguments to this function.

   The argument RAW_BUFFER must point to aligned memory.  */

void
generic_get_saved_register (char *raw_buffer, int *optimized, CORE_ADDR *addrp,
                            struct frame_info *frame, int regnum,
                            enum lval_type *lval)
{
  if (!target_has_registers)
    error ("No registers.");

  /* Normal systems don't optimize out things with register numbers.  */
  if (optimized != NULL)
    *optimized = 0;

  if (addrp)                    /* default assumption: not found in memory */
    *addrp = 0;

  /* Note: since the current frame's registers could only have been
     saved by frames INTERIOR TO the current frame, we skip examining
     the current frame itself: otherwise, we would be getting the
     previous frame's registers which were saved by the current frame.  */

  while (frame && ((frame = frame->next) != NULL))
    {
      if (PC_IN_CALL_DUMMY (frame->pc, frame->frame, frame->frame))
        {
          if (lval)             /* found it in a CALL_DUMMY frame */
            *lval = not_lval;
          if (raw_buffer)
            memcpy (raw_buffer,
                    generic_find_dummy_frame (frame->pc, frame->frame) +
                    REGISTER_BYTE (regnum),
                    REGISTER_RAW_SIZE (regnum));
          return;
        }

      FRAME_INIT_SAVED_REGS (frame);
      if (frame->saved_regs != NULL
          && frame->saved_regs[regnum] != 0)
        {
          if (lval)             /* found it saved on the stack */
            *lval = lval_memory;
          if (regnum == SP_REGNUM)
            {
              if (raw_buffer)   /* SP register treated specially */
                store_address (raw_buffer, REGISTER_RAW_SIZE (regnum),
                               frame->saved_regs[regnum]);
            }
          else
            {
              if (addrp)        /* any other register */
                *addrp = frame->saved_regs[regnum];
              if (raw_buffer)
                read_memory (frame->saved_regs[regnum], raw_buffer,
                             REGISTER_RAW_SIZE (regnum));
            }
          return;
        }
    }

  /* If we get thru the loop to this point, it means the register was
     not saved in any frame.  Return the actual live-register value.  */

  if (lval)                     /* found it in a live register */
    *lval = lval_register;
  if (addrp)
    *addrp = REGISTER_BYTE (regnum);
  if (raw_buffer)
    read_register_gen (regnum, raw_buffer);
}

void
_initialize_blockframe (void)
{
  obstack_init (&frame_cache_obstack);
}