binutils-gdb/gdb/hppa-tdep.c

/* Machine-dependent code which would otherwise be in inflow.c and core.c,
   for GDB, the GNU debugger.  This code is for the HP PA-RISC cpu.
   Copyright 1986, 1987, 1989, 1990, 1991, 1992, 1993 Free Software Foundation, Inc.

   Contributed by the Center for Software Science at the
   University of Utah (pa-gdb-bugs@cs.utah.edu).

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., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "value.h"

/* For argument passing to the inferior */
#include "symtab.h"

#ifdef USG
#include <sys/types.h>
#endif

#include <sys/param.h>
#include <sys/dir.h>
#include <signal.h>
#include <sys/ioctl.h>

#ifdef COFF_ENCAPSULATE
#include "a.out.encap.h"
#else
#include <a.out.h>
#endif
#ifndef N_SET_MAGIC
#define N_SET_MAGIC(exec, val) ((exec).a_magic = (val))
#endif

/*#include <sys/user.h>		After a.out.h  */
#include <sys/file.h>
#include <sys/stat.h>
#include <machine/psl.h>
#include "wait.h"

#include "gdbcore.h"
#include "gdbcmd.h"
#include "target.h"
#include "symfile.h"
#include "objfiles.h"

static int restore_pc_queue PARAMS ((struct frame_saved_regs *fsr));
static int hppa_alignof PARAMS ((struct type *arg));
CORE_ADDR frame_saved_pc PARAMS ((FRAME frame));
static int prologue_inst_adjust_sp PARAMS ((unsigned long));
static int is_branch PARAMS ((unsigned long));
static int inst_saves_gr PARAMS ((unsigned long));
static int inst_saves_fr PARAMS ((unsigned long));


/* Routines to extract various sized constants out of hppa 
   instructions. */

/* This assumes that no garbage lies outside of the lower bits of 
   value. */

int
sign_extend (val, bits)
     unsigned val, bits;
{
  return (int)(val >> bits - 1 ? (-1 << bits) | val : val);
}

/* For many immediate values the sign bit is the low bit! */

int
low_sign_extend (val, bits)
     unsigned val, bits;
{
  return (int)((val & 0x1 ? (-1 << (bits - 1)) : 0) | val >> 1);
}
/* extract the immediate field from a ld{bhw}s instruction */

unsigned
get_field (val, from, to)
     unsigned val, from, to;
{
  val = val >> 31 - to;
  return val & ((1 << 32 - from) - 1);
}

unsigned
set_field (val, from, to, new_val)
     unsigned *val, from, to;
{
  unsigned mask = ~((1 << (to - from + 1)) << (31 - from));
  return *val = *val & mask | (new_val << (31 - from));
}

/* extract a 3-bit space register number from a be, ble, mtsp or mfsp */

extract_3 (word)
     unsigned word;
{
  return GET_FIELD (word, 18, 18) << 2 | GET_FIELD (word, 16, 17);
}
       
extract_5_load (word)
     unsigned word;
{
  return low_sign_extend (word >> 16 & MASK_5, 5);
}

/* extract the immediate field from a st{bhw}s instruction */

int
extract_5_store (word)
     unsigned word;
{
  return low_sign_extend (word & MASK_5, 5);
}

/* extract the immediate field from a break instruction */

unsigned
extract_5r_store (word)
     unsigned word;
{
  return (word & MASK_5);
}

/* extract the immediate field from a {sr}sm instruction */

unsigned
extract_5R_store (word)
     unsigned word;
{
  return (word >> 16 & MASK_5);
}

/* extract an 11 bit immediate field */

int
extract_11 (word)
     unsigned word;
{
  return low_sign_extend (word & MASK_11, 11);
}

/* extract a 14 bit immediate field */

int
extract_14 (word)
     unsigned word;
{
  return low_sign_extend (word & MASK_14, 14);
}

/* deposit a 14 bit constant in a word */

unsigned
deposit_14 (opnd, word)
     int opnd;
     unsigned word;
{
  unsigned sign = (opnd < 0 ? 1 : 0);

  return word | ((unsigned)opnd << 1 & MASK_14)  | sign;
}

/* extract a 21 bit constant */

int
extract_21 (word)
     unsigned word;
{
  int val;

  word &= MASK_21;
  word <<= 11;
  val = GET_FIELD (word, 20, 20);
  val <<= 11;
  val |= GET_FIELD (word, 9, 19);
  val <<= 2;
  val |= GET_FIELD (word, 5, 6);
  val <<= 5;
  val |= GET_FIELD (word, 0, 4);
  val <<= 2;
  val |= GET_FIELD (word, 7, 8);
  return sign_extend (val, 21) << 11;
}

/* deposit a 21 bit constant in a word. Although 21 bit constants are
   usually the top 21 bits of a 32 bit constant, we assume that only
   the low 21 bits of opnd are relevant */

unsigned
deposit_21 (opnd, word)
     unsigned opnd, word;
{
  unsigned val = 0;

  val |= GET_FIELD (opnd, 11 + 14, 11 + 18);
  val <<= 2;
  val |= GET_FIELD (opnd, 11 + 12, 11 + 13);
  val <<= 2;
  val |= GET_FIELD (opnd, 11 + 19, 11 + 20);
  val <<= 11;
  val |= GET_FIELD (opnd, 11 + 1, 11 + 11);
  val <<= 1;
  val |= GET_FIELD (opnd, 11 + 0, 11 + 0);
  return word | val;
}

/* extract a 12 bit constant from branch instructions */

int
extract_12 (word)
     unsigned word;
{
  return sign_extend (GET_FIELD (word, 19, 28) |
		      GET_FIELD (word, 29, 29) << 10 |
		      (word & 0x1) << 11, 12) << 2;
}

/* extract a 17 bit constant from branch instructions, returning the
   19 bit signed value. */

int
extract_17 (word)
     unsigned word;
{
  return sign_extend (GET_FIELD (word, 19, 28) |
		      GET_FIELD (word, 29, 29) << 10 |
		      GET_FIELD (word, 11, 15) << 11 |
		      (word & 0x1) << 16, 17) << 2;
}

/* Lookup the unwind (stack backtrace) info for the given PC.  We search all
   of the objfiles seeking the unwind table entry for this PC.  Each objfile
   contains a sorted list of struct unwind_table_entry.  Since we do a binary
   search of the unwind tables, we depend upon them to be sorted.  */

static struct unwind_table_entry *
find_unwind_entry(pc)
     CORE_ADDR pc;
{
  int first, middle, last;
  struct objfile *objfile;

  ALL_OBJFILES (objfile)
    {
      struct obj_unwind_info *ui;

      ui = OBJ_UNWIND_INFO (objfile);

      if (!ui)
	continue;

      /* First, check the cache */

      if (ui->cache
	  && pc >= ui->cache->region_start
	  && pc <= ui->cache->region_end)
	return ui->cache;

      /* Not in the cache, do a binary search */

      first = 0;
      last = ui->last;

      while (first <= last)
	{
	  middle = (first + last) / 2;
	  if (pc >= ui->table[middle].region_start
	      && pc <= ui->table[middle].region_end)
	    {
	      ui->cache = &ui->table[middle];
	      return &ui->table[middle];
	    }

	  if (pc < ui->table[middle].region_start)
	    last = middle - 1;
	  else
	    first = middle + 1;
	}
    }				/* ALL_OBJFILES() */
  return NULL;
}

/* Called when no unwind descriptor was found for PC.  Returns 1 if it
   appears that PC is in a linker stub.  */
static int pc_in_linker_stub PARAMS ((CORE_ADDR));

static int
pc_in_linker_stub (pc)
     CORE_ADDR pc;
{
  int found_magic_instruction = 0;
  int i;
  char buf[4];

  /* If unable to read memory, assume pc is not in a linker stub.  */
  if (target_read_memory (pc, buf, 4) != 0)
    return 0;

  /* We are looking for something like

     ; $$dyncall jams RP into this special spot in the frame (RP')
     ; before calling the "call stub"
     ldw     -18(sp),rp

     ldsid   (rp),r1         ; Get space associated with RP into r1
     mtsp    r1,sp           ; Move it into space register 0
     be,n    0(sr0),rp)      ; back to your regularly scheduled program
     */

  /* Maximum known linker stub size is 4 instructions.  Search forward
     from the given PC, then backward.  */
  for (i = 0; i < 4; i++)
    {
      /* If we hit something with an unwind, stop searching this direction.  */

      if (find_unwind_entry (pc + i * 4) != 0)
	break;

      /* Check for ldsid (rp),r1 which is the magic instruction for a 
	 return from a cross-space function call.  */
      if (read_memory_integer (pc + i * 4, 4) == 0x004010a1)
	{
	  found_magic_instruction = 1;
	  break;
	}
      /* Add code to handle long call/branch and argument relocation stubs
	 here.  */
    }

  if (found_magic_instruction != 0)
    return 1;

  /* Now look backward.  */
  for (i = 0; i < 4; i++)
    {
      /* If we hit something with an unwind, stop searching this direction.  */

      if (find_unwind_entry (pc - i * 4) != 0)
	break;

      /* Check for ldsid (rp),r1 which is the magic instruction for a 
	 return from a cross-space function call.  */
      if (read_memory_integer (pc - i * 4, 4) == 0x004010a1)
	{
	  found_magic_instruction = 1;
	  break;
	}
      /* Add code to handle long call/branch and argument relocation stubs
	 here.  */
    }
  return found_magic_instruction;
}

static int
find_return_regnum(pc)
     CORE_ADDR pc;
{
  struct unwind_table_entry *u;

  u = find_unwind_entry (pc);

  if (!u)
    return RP_REGNUM;

  if (u->Millicode)
    return 31;

  return RP_REGNUM;
}

/* Return size of frame, or -1 if we should use a frame pointer.  */
int
find_proc_framesize(pc)
     CORE_ADDR pc;
{
  struct unwind_table_entry *u;

  u = find_unwind_entry (pc);

  if (!u)
    {
      if (pc_in_linker_stub (pc))
	/* Linker stubs have a zero size frame.  */
	return 0;
      else
	return -1;
    }

  if (u->Save_SP)
    /* If this bit is set, it means there is a frame pointer and we should
       use it.  */
    return -1;

  return u->Total_frame_size << 3;
}

/* Return offset from sp at which rp is saved, or 0 if not saved.  */
static int rp_saved PARAMS ((CORE_ADDR));

static int
rp_saved (pc)
     CORE_ADDR pc;
{
  struct unwind_table_entry *u;

  u = find_unwind_entry (pc);

  if (!u)
    {
      if (pc_in_linker_stub (pc))
	/* This is the so-called RP'.  */
	return -24;
      else
	return 0;
    }

  if (u->Save_RP)
    return -20;
  else if (u->stub_type != 0)
    {
      switch (u->stub_type)
	{
	case EXPORT:
	  return -24;
	case PARAMETER_RELOCATION:
	  return -8;
	default:
	  return 0;
	}
    }
  else
    return 0;
}

int
frameless_function_invocation (frame)
     FRAME frame;
{
  struct unwind_table_entry *u;

  u = find_unwind_entry (frame->pc);

  if (u == 0)
    return frameless_look_for_prologue (frame);

  return (u->Total_frame_size == 0 && u->stub_type == 0);
}

CORE_ADDR
saved_pc_after_call (frame)
     FRAME frame;
{
  int ret_regnum;

  ret_regnum = find_return_regnum (get_frame_pc (frame));

  return read_register (ret_regnum) & ~0x3;
}

CORE_ADDR
frame_saved_pc (frame)
     FRAME frame;
{
  CORE_ADDR pc = get_frame_pc (frame);

  if (frameless_function_invocation (frame))
    {
      int ret_regnum;

      ret_regnum = find_return_regnum (pc);

      return read_register (ret_regnum) & ~0x3;
    }
  else
    {
      int rp_offset = rp_saved (pc);

      if (rp_offset == 0)
	return read_register (RP_REGNUM) & ~0x3;
      else
	return read_memory_integer (frame->frame + rp_offset, 4) & ~0x3;
    }
}

/* We need to correct the PC and the FP for the outermost frame when we are
   in a system call.  */

void
init_extra_frame_info (fromleaf, frame)
     int fromleaf;
     struct frame_info *frame;
{
  int flags;
  int framesize;

  if (frame->next && !fromleaf)
    return;

  /* If the next frame represents a frameless function invocation
     then we have to do some adjustments that are normally done by
     FRAME_CHAIN.  (FRAME_CHAIN is not called in this case.)  */
  if (fromleaf)
    {
      /* Find the framesize of *this* frame without peeking at the PC
	 in the current frame structure (it isn't set yet).  */
      framesize = find_proc_framesize (FRAME_SAVED_PC (get_next_frame (frame)));

      /* Now adjust our base frame accordingly.  If we have a frame pointer
	 use it, else subtract the size of this frame from the current
	 frame.  (we always want frame->frame to point at the lowest address
	 in the frame).  */
      if (framesize == -1)
	frame->frame = read_register (FP_REGNUM);
      else
	frame->frame -= framesize;
      return;
    }

  flags = read_register (FLAGS_REGNUM);
  if (flags & 2)	/* In system call? */
    frame->pc = read_register (31) & ~0x3;

  /* The outermost frame is always derived from PC-framesize

     One might think frameless innermost frames should have
     a frame->frame that is the same as the parent's frame->frame.
     That is wrong; frame->frame in that case should be the *high*
     address of the parent's frame.  It's complicated as hell to
     explain, but the parent *always* creates some stack space for
     the child.  So the child actually does have a frame of some
     sorts, and its base is the high address in its parent's frame.  */
  framesize = find_proc_framesize(frame->pc);
  if (framesize == -1)
    frame->frame = read_register (FP_REGNUM);
  else
    frame->frame = read_register (SP_REGNUM) - framesize;
}

/* Given a GDB frame, determine the address of the calling function's frame.
   This will be used to create a new GDB frame struct, and then
   INIT_EXTRA_FRAME_INFO and INIT_FRAME_PC will be called for the new frame.

   This may involve searching through prologues for several functions
   at boundaries where GCC calls HP C code, or where code which has
   a frame pointer calls code without a frame pointer.  */
  

FRAME_ADDR
frame_chain (frame)
     struct frame_info *frame;
{
  int my_framesize, caller_framesize;
  struct unwind_table_entry *u;

  /* Get frame sizes for the current frame and the frame of the 
     caller.  */
  my_framesize = find_proc_framesize (frame->pc);
  caller_framesize = find_proc_framesize (FRAME_SAVED_PC(frame));

  /* If caller does not have a frame pointer, then its frame
     can be found at current_frame - caller_framesize.  */
  if (caller_framesize != -1)
    return frame->frame - caller_framesize;

  /* Both caller and callee have frame pointers and are GCC compiled
     (SAVE_SP bit in unwind descriptor is on for both functions.
     The previous frame pointer is found at the top of the current frame.  */
  if (caller_framesize == -1 && my_framesize == -1)
    return read_memory_integer (frame->frame, 4);

  /* Caller has a frame pointer, but callee does not.  This is a little
     more difficult as GCC and HP C lay out locals and callee register save
     areas very differently.

     The previous frame pointer could be in a register, or in one of 
     several areas on the stack.

     Walk from the current frame to the innermost frame examining 
     unwind descriptors to determine if %r3 ever gets saved into the
     stack.  If so return whatever value got saved into the stack.
     If it was never saved in the stack, then the value in %r3 is still
     valid, so use it. 

     We use information from unwind descriptors to determine if %r3
     is saved into the stack (Entry_GR field has this information).  */

  while (frame)
    {
      u = find_unwind_entry (frame->pc);

      if (!u)
	{
	  /* We could find this information by examining prologues.  I don't
	     think anyone has actually written any tools (not even "strip")
	     which leave them out of an executable, so maybe this is a moot
	     point.  */
	  warning ("Unable to find unwind for PC 0x%x -- Help!", frame->pc);
	  return 0;
	}

      /* Entry_GR specifies the number of callee-saved general registers
	 saved in the stack.  It starts at %r3, so %r3 would be 1.  */
      if (u->Entry_GR >= 1 || u->Save_SP)
	break;
      else
	frame = frame->next;
    }

  if (frame)
    {
      /* We may have walked down the chain into a function with a frame
	 pointer.  */
      if (u->Save_SP)
	return read_memory_integer (frame->frame, 4);
      /* %r3 was saved somewhere in the stack.  Dig it out.  */
      else 
	{
	  struct frame_info *fi;
	  struct frame_saved_regs saved_regs;

	  fi = get_frame_info (frame);
	  get_frame_saved_regs (fi, &saved_regs);
	  return read_memory_integer (saved_regs.regs[FP_REGNUM], 4);
	}
    }
  else
    {
      /* The value in %r3 was never saved into the stack (thus %r3 still
	 holds the value of the previous frame pointer).  */
      return read_register (FP_REGNUM);
    }
}


/* To see if a frame chain is valid, see if the caller looks like it
   was compiled with gcc. */

int
frame_chain_valid (chain, thisframe)
     FRAME_ADDR chain;
     FRAME thisframe;
{
  struct minimal_symbol *msym_us;
  struct minimal_symbol *msym_start;
  struct unwind_table_entry *u;

  if (!chain)
    return 0;

  u = find_unwind_entry (thisframe->pc);

  /* We can't just check that the same of msym_us is "_start", because
     someone idiotically decided that they were going to make a Ltext_end
     symbol with the same address.  This Ltext_end symbol is totally
     indistinguishable (as nearly as I can tell) from the symbol for a function
     which is (legitimately, since it is in the user's namespace)
     named Ltext_end, so we can't just ignore it.  */
  msym_us = lookup_minimal_symbol_by_pc (FRAME_SAVED_PC (thisframe));
  msym_start = lookup_minimal_symbol ("_start", NULL);
  if (msym_us
      && msym_start
      && SYMBOL_VALUE_ADDRESS (msym_us) == SYMBOL_VALUE_ADDRESS (msym_start))
    return 0;

  if (u == NULL)
    return 1;

  if (u->Save_SP || u->Total_frame_size || u->stub_type != 0)
    return 1;

  if (pc_in_linker_stub (thisframe->pc))
    return 1;

  return 0;
}

/*
 * These functions deal with saving and restoring register state
 * around a function call in the inferior. They keep the stack
 * double-word aligned; eventually, on an hp700, the stack will have
 * to be aligned to a 64-byte boundary.
 */

int
push_dummy_frame ()
{
  register CORE_ADDR sp;
  register int regnum;
  int int_buffer;
  double freg_buffer;

  /* Space for "arguments"; the RP goes in here. */
  sp = read_register (SP_REGNUM) + 48;
  int_buffer = read_register (RP_REGNUM) | 0x3;
  write_memory (sp - 20, (char *)&int_buffer, 4);

  int_buffer = read_register (FP_REGNUM);
  write_memory (sp, (char *)&int_buffer, 4);

  write_register (FP_REGNUM, sp);

  sp += 8;

  for (regnum = 1; regnum < 32; regnum++)
    if (regnum != RP_REGNUM && regnum != FP_REGNUM)
      sp = push_word (sp, read_register (regnum));

  sp += 4;

  for (regnum = FP0_REGNUM; regnum < NUM_REGS; regnum++)
    {
      read_register_bytes (REGISTER_BYTE (regnum), (char *)&freg_buffer, 8);
      sp = push_bytes (sp, (char *)&freg_buffer, 8);
    }
  sp = push_word (sp, read_register (IPSW_REGNUM));
  sp = push_word (sp, read_register (SAR_REGNUM));
  sp = push_word (sp, read_register (PCOQ_HEAD_REGNUM));
  sp = push_word (sp, read_register (PCSQ_HEAD_REGNUM));
  sp = push_word (sp, read_register (PCOQ_TAIL_REGNUM));
  sp = push_word (sp, read_register (PCSQ_TAIL_REGNUM));
  write_register (SP_REGNUM, sp);
}

find_dummy_frame_regs (frame, frame_saved_regs)
     struct frame_info *frame;
     struct frame_saved_regs *frame_saved_regs;
{
  CORE_ADDR fp = frame->frame;
  int i;

  frame_saved_regs->regs[RP_REGNUM] = fp - 20 & ~0x3;
  frame_saved_regs->regs[FP_REGNUM] = fp;
  frame_saved_regs->regs[1] = fp + 8;

  for (fp += 12, i = 3; i < 32; i++)
    {
      if (i != FP_REGNUM)
	{
	  frame_saved_regs->regs[i] = fp;
	  fp += 4;
	}
    }

  fp += 4;
  for (i = FP0_REGNUM; i < NUM_REGS; i++, fp += 8)
    frame_saved_regs->regs[i] = fp;

  frame_saved_regs->regs[IPSW_REGNUM] = fp;
  frame_saved_regs->regs[SAR_REGNUM] = fp + 4;
  frame_saved_regs->regs[PCOQ_HEAD_REGNUM] = fp + 8;
  frame_saved_regs->regs[PCSQ_HEAD_REGNUM] = fp + 12;
  frame_saved_regs->regs[PCOQ_TAIL_REGNUM] = fp + 16;
  frame_saved_regs->regs[PCSQ_TAIL_REGNUM] = fp + 20;
}

int
hppa_pop_frame ()
{
  register FRAME frame = get_current_frame ();
  register CORE_ADDR fp;
  register int regnum;
  struct frame_saved_regs fsr;
  struct frame_info *fi;
  double freg_buffer;

  fi = get_frame_info (frame);
  fp = fi->frame;
  get_frame_saved_regs (fi, &fsr);

  if (fsr.regs[IPSW_REGNUM])    /* Restoring a call dummy frame */
    restore_pc_queue (&fsr);

  for (regnum = 31; regnum > 0; regnum--)
    if (fsr.regs[regnum])
      write_register (regnum, read_memory_integer (fsr.regs[regnum], 4));

  for (regnum = NUM_REGS - 1; regnum >= FP0_REGNUM ; regnum--)
    if (fsr.regs[regnum])
      {
	read_memory (fsr.regs[regnum], (char *)&freg_buffer, 8);
        write_register_bytes (REGISTER_BYTE (regnum), (char *)&freg_buffer, 8);
      }

  if (fsr.regs[IPSW_REGNUM])
    write_register (IPSW_REGNUM,
                    read_memory_integer (fsr.regs[IPSW_REGNUM], 4));

  if (fsr.regs[SAR_REGNUM])
    write_register (SAR_REGNUM,
                    read_memory_integer (fsr.regs[SAR_REGNUM], 4));

  /* If the PC was explicitly saved, then just restore it.  */
  if (fsr.regs[PCOQ_TAIL_REGNUM])
    write_register (PCOQ_TAIL_REGNUM,
                    read_memory_integer (fsr.regs[PCOQ_TAIL_REGNUM], 4));

  /* Else use the value in %rp to set the new PC.  */
  else 
    target_write_pc (read_register (RP_REGNUM));

  write_register (FP_REGNUM, read_memory_integer (fp, 4));

  if (fsr.regs[IPSW_REGNUM])    /* call dummy */
    write_register (SP_REGNUM, fp - 48);
  else
    write_register (SP_REGNUM, fp);

  flush_cached_frames ();
  set_current_frame (create_new_frame (read_register (FP_REGNUM),
                                       read_pc ()));
}

/*
 * After returning to a dummy on the stack, restore the instruction
 * queue space registers. */

static int
restore_pc_queue (fsr)
     struct frame_saved_regs *fsr;
{
  CORE_ADDR pc = read_pc ();
  CORE_ADDR new_pc = read_memory_integer (fsr->regs[PCOQ_HEAD_REGNUM], 4);
  int pid;
  struct target_waitstatus w;
  int insn_count;

  /* Advance past break instruction in the call dummy. */
  write_register (PCOQ_HEAD_REGNUM, pc + 4);
  write_register (PCOQ_TAIL_REGNUM, pc + 8);

  /*
   * HPUX doesn't let us set the space registers or the space
   * registers of the PC queue through ptrace. Boo, hiss.
   * Conveniently, the call dummy has this sequence of instructions
   * after the break:
   *    mtsp r21, sr0
   *    ble,n 0(sr0, r22)
   *
   * So, load up the registers and single step until we are in the
   * right place.
   */

  write_register (21, read_memory_integer (fsr->regs[PCSQ_HEAD_REGNUM], 4));
  write_register (22, new_pc);

  for (insn_count = 0; insn_count < 3; insn_count++)
    {
      /* FIXME: What if the inferior gets a signal right now?  Want to
	 merge this into wait_for_inferior (as a special kind of
	 watchpoint?  By setting a breakpoint at the end?  Is there
	 any other choice?  Is there *any* way to do this stuff with
	 ptrace() or some equivalent?).  */
      resume (1, 0);
      target_wait (inferior_pid, &w);

      if (w.kind == TARGET_WAITKIND_SIGNALLED)
        {
          stop_signal = w.value.sig;
          terminal_ours_for_output ();
          printf_unfiltered ("\nProgram terminated with signal %s, %s.\n",
			     target_signal_to_name (stop_signal),
			     target_signal_to_string (stop_signal));
          gdb_flush (gdb_stdout);
          return 0;
        }
    }
  target_terminal_ours ();
  fetch_inferior_registers (-1);
  return 1;
}

CORE_ADDR
hppa_push_arguments (nargs, args, sp, struct_return, struct_addr)
     int nargs;
     value *args;
     CORE_ADDR sp;
     int struct_return;
     CORE_ADDR struct_addr;
{
  /* array of arguments' offsets */
  int *offset = (int *)alloca(nargs * sizeof (int));
  int cum = 0;
  int i, alignment;
  
  for (i = 0; i < nargs; i++)
    {
      /* Coerce chars to int & float to double if necessary */
      args[i] = value_arg_coerce (args[i]);

      cum += TYPE_LENGTH (VALUE_TYPE (args[i]));

    /* value must go at proper alignment. Assume alignment is a
	 power of two.*/
      alignment = hppa_alignof (VALUE_TYPE (args[i]));
      if (cum % alignment)
	cum = (cum + alignment) & -alignment;
      offset[i] = -cum;
    }
  sp += max ((cum + 7) & -8, 16);

  for (i = 0; i < nargs; i++)
    write_memory (sp + offset[i], VALUE_CONTENTS (args[i]),
		  TYPE_LENGTH (VALUE_TYPE (args[i])));

  if (struct_return)
    write_register (28, struct_addr);
  return sp + 32;
}

/*
 * Insert the specified number of args and function address
 * into a call sequence of the above form stored at DUMMYNAME.
 *
 * On the hppa we need to call the stack dummy through $$dyncall.
 * Therefore our version of FIX_CALL_DUMMY takes an extra argument,
 * real_pc, which is the location where gdb should start up the
 * inferior to do the function call.
 */

CORE_ADDR
hppa_fix_call_dummy (dummy, pc, fun, nargs, args, type, gcc_p)
     char *dummy;
     CORE_ADDR pc;
     CORE_ADDR fun;
     int nargs;
     value *args;
     struct type *type;
     int gcc_p;
{
  CORE_ADDR dyncall_addr, sr4export_addr;
  struct minimal_symbol *msymbol;
  int flags = read_register (FLAGS_REGNUM);

  msymbol = lookup_minimal_symbol ("$$dyncall", (struct objfile *) NULL);
  if (msymbol == NULL)
    error ("Can't find an address for $$dyncall trampoline");

  dyncall_addr = SYMBOL_VALUE_ADDRESS (msymbol);

  msymbol = lookup_minimal_symbol ("_sr4export", (struct objfile *) NULL);
  if (msymbol == NULL)
    error ("Can't find an address for _sr4export trampoline");

  sr4export_addr = SYMBOL_VALUE_ADDRESS (msymbol);

  store_unsigned_integer
    (&dummy[9*REGISTER_SIZE],
     REGISTER_SIZE,
     deposit_21 (fun >> 11,
		 extract_unsigned_integer (&dummy[9*REGISTER_SIZE],
					   REGISTER_SIZE)));
  store_unsigned_integer
    (&dummy[10*REGISTER_SIZE],
     REGISTER_SIZE,
     deposit_14 (fun & MASK_11,
		 extract_unsigned_integer (&dummy[10*REGISTER_SIZE],
					   REGISTER_SIZE)));
  store_unsigned_integer
    (&dummy[12*REGISTER_SIZE],
     REGISTER_SIZE,
     deposit_21 (sr4export_addr >> 11,
		 extract_unsigned_integer (&dummy[12*REGISTER_SIZE],
					   REGISTER_SIZE)));
  store_unsigned_integer
    (&dummy[13*REGISTER_SIZE],
     REGISTER_SIZE,
     deposit_14 (sr4export_addr & MASK_11,
		 extract_unsigned_integer (&dummy[13*REGISTER_SIZE],
					   REGISTER_SIZE)));

  write_register (22, pc);

  /* If we are in a syscall, then we should call the stack dummy
     directly.  $$dyncall is not needed as the kernel sets up the
     space id registers properly based on the value in %r31.  In
     fact calling $$dyncall will not work because the value in %r22
     will be clobbered on the syscall exit path.  */
  if (flags & 2)
    return pc;
  else
    return dyncall_addr;

}

/* Get the PC from %r31 if currently in a syscall.  Also mask out privilege
   bits.  */
CORE_ADDR
target_read_pc ()
{
  int flags = read_register (FLAGS_REGNUM);

  if (flags & 2)
    return read_register (31) & ~0x3;
  return read_register (PC_REGNUM) & ~0x3;
}

/* Write out the PC.  If currently in a syscall, then also write the new
   PC value into %r31.  */
void
target_write_pc (v)
     CORE_ADDR v;
{
  int flags = read_register (FLAGS_REGNUM);

  /* If in a syscall, then set %r31.  Also make sure to get the 
     privilege bits set correctly.  */
  if (flags & 2)
    write_register (31, (long) (v | 0x3));

  write_register (PC_REGNUM, (long) v);
  write_register (NPC_REGNUM, (long) v + 4);
}

/* return the alignment of a type in bytes. Structures have the maximum
   alignment required by their fields. */

static int
hppa_alignof (arg)
     struct type *arg;
{
  int max_align, align, i;
  switch (TYPE_CODE (arg))
    {
    case TYPE_CODE_PTR:
    case TYPE_CODE_INT:
    case TYPE_CODE_FLT:
      return TYPE_LENGTH (arg);
    case TYPE_CODE_ARRAY:
      return hppa_alignof (TYPE_FIELD_TYPE (arg, 0));
    case TYPE_CODE_STRUCT:
    case TYPE_CODE_UNION:
      max_align = 2;
      for (i = 0; i < TYPE_NFIELDS (arg); i++)
	{
	  /* Bit fields have no real alignment. */
	  if (!TYPE_FIELD_BITPOS (arg, i))
	    {
	      align = hppa_alignof (TYPE_FIELD_TYPE (arg, i));
	      max_align = max (max_align, align);
	    }
	}
      return max_align;
    default:
      return 4;
    }
}

/* Print the register regnum, or all registers if regnum is -1 */

pa_do_registers_info (regnum, fpregs)
     int regnum;
     int fpregs;
{
  char raw_regs [REGISTER_BYTES];
  int i;
  
  for (i = 0; i < NUM_REGS; i++)
    read_relative_register_raw_bytes (i, raw_regs + REGISTER_BYTE (i));
  if (regnum == -1)
    pa_print_registers (raw_regs, regnum, fpregs);
  else if (regnum < FP0_REGNUM)
    printf_unfiltered ("%s %x\n", reg_names[regnum], *(long *)(raw_regs +
						    REGISTER_BYTE (regnum)));
  else
    pa_print_fp_reg (regnum);
}

pa_print_registers (raw_regs, regnum, fpregs)
     char *raw_regs;
     int regnum;
     int fpregs;
{
  int i;

  for (i = 0; i < 18; i++)
    printf_unfiltered ("%8.8s: %8x  %8.8s: %8x  %8.8s: %8x  %8.8s: %8x\n",
	    reg_names[i],
	    *(int *)(raw_regs + REGISTER_BYTE (i)),
	    reg_names[i + 18],
	    *(int *)(raw_regs + REGISTER_BYTE (i + 18)),
	    reg_names[i + 36],
	    *(int *)(raw_regs + REGISTER_BYTE (i + 36)),
	    reg_names[i + 54],
	    *(int *)(raw_regs + REGISTER_BYTE (i + 54)));

  if (fpregs)
    for (i = 72; i < NUM_REGS; i++)
      pa_print_fp_reg (i);
}

pa_print_fp_reg (i)
     int i;
{
  unsigned char raw_buffer[MAX_REGISTER_RAW_SIZE];
  unsigned char virtual_buffer[MAX_REGISTER_VIRTUAL_SIZE];

  /* Get the data in raw format.  */
  read_relative_register_raw_bytes (i, raw_buffer);

  /* Convert raw data to virtual format if necessary.  */
#ifdef REGISTER_CONVERTIBLE
  if (REGISTER_CONVERTIBLE (i))
    {
      REGISTER_CONVERT_TO_VIRTUAL (i, REGISTER_VIRTUAL_TYPE (i),
				   raw_buffer, virtual_buffer);
    }
  else
#endif
    memcpy (virtual_buffer, raw_buffer,
	    REGISTER_VIRTUAL_SIZE (i));

  fputs_filtered (reg_names[i], gdb_stdout);
  print_spaces_filtered (15 - strlen (reg_names[i]), gdb_stdout);

  val_print (REGISTER_VIRTUAL_TYPE (i), virtual_buffer, 0, gdb_stdout, 0,
	     1, 0, Val_pretty_default);
  printf_filtered ("\n");
}

/* Function calls that pass into a new compilation unit must pass through a
   small piece of code that does long format (`external' in HPPA parlance)
   jumps.  We figure out where the trampoline is going to end up, and return
   the PC of the final destination.  If we aren't in a trampoline, we just
   return NULL. 

   For computed calls, we just extract the new PC from r22.  */

CORE_ADDR
skip_trampoline_code (pc, name)
     CORE_ADDR pc;
     char *name;
{
  long inst0, inst1;
  static CORE_ADDR dyncall = 0;
  struct minimal_symbol *msym;

/* FIXME XXX - dyncall must be initialized whenever we get a new exec file */

  if (!dyncall)
    {
      msym = lookup_minimal_symbol ("$$dyncall", NULL);
      if (msym)
	dyncall = SYMBOL_VALUE_ADDRESS (msym);
      else
	dyncall = -1;
    }

  if (pc == dyncall)
    return (CORE_ADDR)(read_register (22) & ~0x3);

  inst0 = read_memory_integer (pc, 4);
  inst1 = read_memory_integer (pc+4, 4);

  if (   (inst0 & 0xffe00000) == 0x20200000 /* ldil xxx, r1 */
      && (inst1 & 0xffe0e002) == 0xe0202002) /* be,n yyy(sr4, r1) */
    pc = extract_21 (inst0) + extract_17 (inst1);
  else
    pc = (CORE_ADDR)NULL;

  return pc;
}

/* For the given instruction (INST), return any adjustment it makes
   to the stack pointer or zero for no adjustment. 

   This only handles instructions commonly found in prologues.  */

static int
prologue_inst_adjust_sp (inst)
     unsigned long inst;
{
  /* This must persist across calls.  */
  static int save_high21;

  /* The most common way to perform a stack adjustment ldo X(sp),sp */
  if ((inst & 0xffffc000) == 0x37de0000)
    return extract_14 (inst);

  /* stwm X,D(sp) */
  if ((inst & 0xffe00000) == 0x6fc00000)
    return extract_14 (inst);

  /* addil high21,%r1; ldo low11,(%r1),%r30)
     save high bits in save_high21 for later use.  */
  if ((inst & 0xffe00000) == 0x28200000)
    {
      save_high21 = extract_21 (inst);
      return 0;
    }

  if ((inst & 0xffff0000) == 0x343e0000)
    return save_high21 + extract_14 (inst);

  /* fstws as used by the HP compilers.  */
  if ((inst & 0xffffffe0) == 0x2fd01220)
    return extract_5_load (inst);

  /* No adjustment.  */
  return 0;
}

/* Return nonzero if INST is a branch of some kind, else return zero.  */

static int
is_branch (inst)
     unsigned long inst;
{
  switch (inst >> 26)
    {
    case 0x20:
    case 0x21:
    case 0x22:
    case 0x23:
    case 0x28:
    case 0x29:
    case 0x2a:
    case 0x2b:
    case 0x30:
    case 0x31:
    case 0x32:
    case 0x33:
    case 0x38:
    case 0x39:
    case 0x3a:
      return 1;

    default:
      return 0;
    }
}

/* Return the register number for a GR which is saved by INST or
   zero it INST does not save a GR.

   Note we only care about full 32bit register stores (that's the only
   kind of stores the prologue will use).  */

static int
inst_saves_gr (inst)
     unsigned long inst;
{
  /* Does it look like a stw?  */
  if ((inst >> 26) == 0x1a)
    return extract_5R_store (inst);

  /* Does it look like a stwm?  */
  if ((inst >> 26) == 0x1b)
    return extract_5R_store (inst);

  return 0;
}

/* Return the register number for a FR which is saved by INST or
   zero it INST does not save a FR.

   Note we only care about full 64bit register stores (that's the only
   kind of stores the prologue will use).  */

static int
inst_saves_fr (inst)
     unsigned long inst;
{
  if ((inst & 0xfc1fffe0) == 0x2c101220)
    return extract_5r_store (inst);
  return 0;
}

/* Advance PC across any function entry prologue instructions
   to reach some "real" code. 

   Use information in the unwind table to determine what exactly should
   be in the prologue.  */

CORE_ADDR
skip_prologue(pc)
     CORE_ADDR pc;
{
  char buf[4];
  unsigned long inst, stack_remaining, save_gr, save_fr, save_rp, save_sp;
  int status, i;
  struct unwind_table_entry *u;

  u = find_unwind_entry (pc);
  if (!u)
    return 0;

  /* This is how much of a frame adjustment we need to account for.  */
  stack_remaining = u->Total_frame_size << 3;

  /* Magic register saves we want to know about.  */
  save_rp = u->Save_RP;
  save_sp = u->Save_SP;

  /* Turn the Entry_GR field into a bitmask.  */
  save_gr = 0;
  for (i = 3; i < u->Entry_GR + 3; i++)
    {
      /* Frame pointer gets saved into a special location.  */
      if (u->Save_SP && i == FP_REGNUM)
	continue;

      save_gr |= (1 << i);
    }

  /* Turn the Entry_FR field into a bitmask too.  */
  save_fr = 0;
  for (i = 12; i < u->Entry_FR + 12; i++)
    save_fr |= (1 << i);

  /* Loop until we find everything of interest or hit a branch.

     For unoptimized GCC code and for any HP CC code this will never ever
     examine any user instructions.

     For optimzied GCC code we're faced with problems.  GCC will schedule
     its prologue and make prologue instructions available for delay slot
     filling.  The end result is user code gets mixed in with the prologue
     and a prologue instruction may be in the delay slot of the first branch
     or call.

     Some unexpected things are expected with debugging optimized code, so
     we allow this routine to walk past user instructions in optimized
     GCC code.  */
  while (save_gr || save_fr || save_rp || save_sp || stack_remaining > 0)
    {
      status = target_read_memory (pc, buf, 4);
      inst = extract_unsigned_integer (buf, 4);

      /* Yow! */
      if (status != 0)
	return pc;

      /* Note the interesting effects of this instruction.  */
      stack_remaining -= prologue_inst_adjust_sp (inst);

      /* There is only one instruction used for saving RP into the stack.  */
      if (inst == 0x6bc23fd9)
	save_rp = 0;

      /* This is the only way we save SP into the stack.  At this time
	 the HP compilers never bother to save SP into the stack.  */
      if ((inst & 0xffffc000) == 0x6fc10000)
	save_sp = 0;

      /* Account for general and floating-point register saves.  */
      save_gr &= ~(1 << inst_saves_gr (inst));
      save_fr &= ~(1 << inst_saves_fr (inst));

      /* Quit if we hit any kind of branch.  This can happen if a prologue
	 instruction is in the delay slot of the first call/branch.  */
      if (is_branch (inst))
	break;

      /* Bump the PC.  */
      pc += 4;
    }

  return pc;
}

/* Put here the code to store, into a struct frame_saved_regs,
   the addresses of the saved registers of frame described by FRAME_INFO.
   This includes special registers such as pc and fp saved in special
   ways in the stack frame.  sp is even more special:
   the address we return for it IS the sp for the next frame.  */

void
hppa_frame_find_saved_regs (frame_info, frame_saved_regs)
     struct frame_info *frame_info;
     struct frame_saved_regs *frame_saved_regs;
{
  CORE_ADDR pc;
  struct unwind_table_entry *u;
  unsigned long inst, stack_remaining, save_gr, save_fr, save_rp, save_sp;
  int status, i, reg;
  char buf[4];
  int fp_loc = -1;

  /* Zero out everything.  */
  memset (frame_saved_regs, '\0', sizeof (struct frame_saved_regs));

  /* Call dummy frames always look the same, so there's no need to
     examine the dummy code to determine locations of saved registers;
     instead, let find_dummy_frame_regs fill in the correct offsets
     for the saved registers.  */
  if ((frame_info->pc >= frame_info->frame
       && frame_info->pc <= (frame_info->frame + CALL_DUMMY_LENGTH
			     + 32 * 4 + (NUM_REGS - FP0_REGNUM) * 8
			     + 6 * 4)))
    find_dummy_frame_regs (frame_info, frame_saved_regs);

  /* Get the starting address of the function referred to by the PC
     saved in frame_info.  */
  pc = get_pc_function_start (frame_info->pc);

  /* Yow! */
  u = find_unwind_entry (pc);
  if (!u)
    return;

  /* This is how much of a frame adjustment we need to account for.  */
  stack_remaining = u->Total_frame_size << 3;

  /* Magic register saves we want to know about.  */
  save_rp = u->Save_RP;
  save_sp = u->Save_SP;

  /* Turn the Entry_GR field into a bitmask.  */
  save_gr = 0;
  for (i = 3; i < u->Entry_GR + 3; i++)
    {
      /* Frame pointer gets saved into a special location.  */
      if (u->Save_SP && i == FP_REGNUM)
	continue;

      save_gr |= (1 << i);
    }

  /* Turn the Entry_FR field into a bitmask too.  */
  save_fr = 0;
  for (i = 12; i < u->Entry_FR + 12; i++)
    save_fr |= (1 << i);

  /* Loop until we find everything of interest or hit a branch.

     For unoptimized GCC code and for any HP CC code this will never ever
     examine any user instructions.

     For optimzied GCC code we're faced with problems.  GCC will schedule
     its prologue and make prologue instructions available for delay slot
     filling.  The end result is user code gets mixed in with the prologue
     and a prologue instruction may be in the delay slot of the first branch
     or call.

     Some unexpected things are expected with debugging optimized code, so
     we allow this routine to walk past user instructions in optimized
     GCC code.  */
  while (save_gr || save_fr || save_rp || save_sp || stack_remaining > 0)
    {
      status = target_read_memory (pc, buf, 4);
      inst = extract_unsigned_integer (buf, 4);

      /* Yow! */
      if (status != 0)
	return;

      /* Note the interesting effects of this instruction.  */
      stack_remaining -= prologue_inst_adjust_sp (inst);

      /* There is only one instruction used for saving RP into the stack.  */
      if (inst == 0x6bc23fd9)
	{
	  save_rp = 0;
	  frame_saved_regs->regs[RP_REGNUM] = frame_info->frame - 20;
	}

      /* This is the only way we save SP into the stack.  At this time
	 the HP compilers never bother to save SP into the stack.  */
      if ((inst & 0xffffc000) == 0x6fc10000)
	{
	  save_sp = 0;
	  frame_saved_regs->regs[SP_REGNUM] = frame_info->frame;
	}

      /* Account for general and floating-point register saves.  */
      reg = inst_saves_gr (inst);
      if (reg >= 3 && reg <= 18
	  && (!u->Save_SP || reg != FP_REGNUM))
	{
	  save_gr &= ~(1 << reg);

	  /* stwm with a positive displacement is a *post modify*.  */
	  if ((inst >> 26) == 0x1b
	      && extract_14 (inst) >= 0)
	    frame_saved_regs->regs[reg] = frame_info->frame;
	  else
	    {
	      /* Handle code with and without frame pointers.  */
	      if (u->Save_SP)
		frame_saved_regs->regs[reg]
		  = frame_info->frame + extract_14 (inst);
	      else
		frame_saved_regs->regs[reg]
		  = frame_info->frame + (u->Total_frame_size << 3)
		    + extract_14 (inst);
	    }
	}


      /* GCC handles callee saved FP regs a little differently.  

	 It emits an instruction to put the value of the start of
	 the FP store area into %r1.  It then uses fstds,ma with
	 a basereg of %r1 for the stores.

	 HP CC emits them at the current stack pointer modifying
	 the stack pointer as it stores each register.  */

      /* ldo X(%r3),%r1 or ldo X(%r30),%r1.  */
      if ((inst & 0xffffc000) == 0x34610000
	  || (inst & 0xffffc000) == 0x37c10000)
	fp_loc = extract_14 (inst);
	
      reg = inst_saves_fr (inst);
      if (reg >= 12 && reg <= 21)
	{
	  /* Note +4 braindamage below is necessary because the FP status
	     registers are internally 8 registers rather than the expected
	     4 registers.  */
	  save_fr &= ~(1 << reg);
	  if (fp_loc == -1)
	    {
	      /* 1st HP CC FP register store.  After this instruction
		 we've set enough state that the GCC and HPCC code are
		 both handled in the same manner.  */
	      frame_saved_regs->regs[reg + FP4_REGNUM + 4] = frame_info->frame;
	      fp_loc = 8;
	    }
	  else
	    {
	      frame_saved_regs->regs[reg + FP0_REGNUM + 4]
		= frame_info->frame + fp_loc;
	      fp_loc += 8;
	    }
	}

      /* Quit if we hit any kind of branch.  This can happen if a prologue
	 instruction is in the delay slot of the first call/branch.  */
      if (is_branch (inst))
	break;

      /* Bump the PC.  */
      pc += 4;
    }
}

#ifdef MAINTENANCE_CMDS

static void
unwind_command (exp, from_tty)
     char *exp;
     int from_tty;
{
  CORE_ADDR address;
  union
    {
      int *foo;
      struct unwind_table_entry *u;
    } xxx;

  /* If we have an expression, evaluate it and use it as the address.  */

  if (exp != 0 && *exp != 0)
    address = parse_and_eval_address (exp);
  else
    return;

  xxx.u = find_unwind_entry (address);

  if (!xxx.u)
    {
      printf_unfiltered ("Can't find unwind table entry for PC 0x%x\n", address);
      return;
    }

  printf_unfiltered ("%08x\n%08X\n%08X\n%08X\n", xxx.foo[0], xxx.foo[1], xxx.foo[2],
	  xxx.foo[3]);
}
#endif /* MAINTENANCE_CMDS */

void
_initialize_hppa_tdep ()
{
#ifdef MAINTENANCE_CMDS
  add_cmd ("unwind", class_maintenance, unwind_command,
	   "Print unwind table entry at given address.",
	   &maintenanceprintlist);
#endif /* MAINTENANCE_CMDS */
}