binutils-gdb/gdb/hppah-nat.c

/* Native support code for HPUX PA-RISC.
   Copyright 1986, 1987, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
   1998, 1999, 2000, 2001
   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., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */


#include "defs.h"
#include "inferior.h"
#include "target.h"
#include <sys/ptrace.h>
#include "gdbcore.h"
#include "gdb_wait.h"
#include "regcache.h"
#include <signal.h>

extern CORE_ADDR text_end;

static void fetch_register (int);

void
fetch_inferior_registers (int regno)
{
  if (regno == -1)
    for (regno = 0; regno < NUM_REGS; regno++)
      fetch_register (regno);
  else
    fetch_register (regno);
}

/* Our own version of the offsetof macro, since we can't assume ANSI C.  */
#define HPPAH_OFFSETOF(type, member) ((int) (&((type *) 0)->member))

/* Store our register values back into the inferior.
   If REGNO is -1, do this for all registers.
   Otherwise, REGNO specifies which register (so we can save time).  */

void
store_inferior_registers (int regno)
{
  register unsigned int regaddr;
  char buf[80];
  register int i;
  unsigned int offset = U_REGS_OFFSET;
  int scratch;

  if (regno >= 0)
    {
      unsigned int addr, len, offset;

      if (CANNOT_STORE_REGISTER (regno))
	return;

      offset = 0;
      len = REGISTER_RAW_SIZE (regno);

      /* Requests for register zero actually want the save_state's
	 ss_flags member.  As RM says: "Oh, what a hack!"  */
      if (regno == 0)
	{
	  save_state_t ss;
	  addr = HPPAH_OFFSETOF (save_state_t, ss_flags);
	  len = sizeof (ss.ss_flags);

	  /* Note that ss_flags is always an int, no matter what
	     REGISTER_RAW_SIZE(0) says.  Assuming all HP-UX PA machines
	     are big-endian, put it at the least significant end of the
	     value, and zap the rest of the buffer.  */
	  offset = REGISTER_RAW_SIZE (0) - len;
	}

      /* Floating-point registers come from the ss_fpblock area.  */
      else if (regno >= FP0_REGNUM)
	addr = (HPPAH_OFFSETOF (save_state_t, ss_fpblock) 
		+ (REGISTER_BYTE (regno) - REGISTER_BYTE (FP0_REGNUM)));

      /* Wide registers come from the ss_wide area.
	 I think it's more PC to test (ss_flags & SS_WIDEREGS) to select
	 between ss_wide and ss_narrow than to use the raw register size.
	 But checking ss_flags would require an extra ptrace call for
	 every register reference.  Bleah.  */
      else if (len == 8)
	addr = (HPPAH_OFFSETOF (save_state_t, ss_wide) 
		+ REGISTER_BYTE (regno));

      /* Narrow registers come from the ss_narrow area.  Note that
	 ss_narrow starts with gr1, not gr0.  */
      else if (len == 4)
	addr = (HPPAH_OFFSETOF (save_state_t, ss_narrow)
		+ (REGISTER_BYTE (regno) - REGISTER_BYTE (1)));
      else
	internal_error (__FILE__, __LINE__,
			"hppah-nat.c (write_register): unexpected register size");

#ifdef GDB_TARGET_IS_HPPA_20W
      /* Unbelieveable.  The PC head and tail must be written in 64bit hunks
	 or we will get an error.  Worse yet, the oddball ptrace/ttrace
	 layering will not allow us to perform a 64bit register store.

	 What a crock.  */
      if (regno == PCOQ_HEAD_REGNUM || regno == PCOQ_TAIL_REGNUM && len == 8)
	{
	  CORE_ADDR temp;

	  temp = *(CORE_ADDR *)&registers[REGISTER_BYTE (regno)];

	  /* Set the priv level (stored in the low two bits of the PC.  */
	  temp |= 0x3;

	  ttrace_write_reg_64 (PIDGET (inferior_ptid), (CORE_ADDR)addr,
	                       (CORE_ADDR)&temp);

	  /* If we fail to write the PC, give a true error instead of
	     just a warning.  */
	  if (errno != 0)
	    {
	      char *err = safe_strerror (errno);
	      char *msg = alloca (strlen (err) + 128);
	      sprintf (msg, "writing `%s' register: %s",
		        REGISTER_NAME (regno), err);
	      perror_with_name (msg);
	    }
	  return;
	}

      /* Another crock.  HPUX complains if you write a nonzero value to
	 the high part of IPSW.  What will it take for HP to catch a
	 clue about building sensible interfaces?  */
     if (regno == IPSW_REGNUM && len == 8)
	*(int *)&registers[REGISTER_BYTE (regno)] = 0;
#endif

      for (i = 0; i < len; i += sizeof (int))
	{
	  errno = 0;
	  call_ptrace (PT_WUREGS, PIDGET (inferior_ptid),
	               (PTRACE_ARG3_TYPE) addr + i,
		       *(int *) &registers[REGISTER_BYTE (regno) + i]);
	  if (errno != 0)
	    {
	      /* Warning, not error, in case we are attached; sometimes
		 the kernel doesn't let us at the registers. */
	      char *err = safe_strerror (errno);
	      char *msg = alloca (strlen (err) + 128);
	      sprintf (msg, "writing `%s' register: %s",
		        REGISTER_NAME (regno), err);
	      /* If we fail to write the PC, give a true error instead of
		 just a warning.  */
	      if (regno == PCOQ_HEAD_REGNUM || regno == PCOQ_TAIL_REGNUM)
		perror_with_name (msg);
	      else
		warning (msg);
	      return;
	    }
	}
    }
  else
    for (regno = 0; regno < NUM_REGS; regno++)
      store_inferior_registers (regno);
}


/* Fetch a register's value from the process's U area.  */
static void
fetch_register (int regno)
{
  char buf[MAX_REGISTER_RAW_SIZE];
  unsigned int addr, len, offset;
  int i;

  offset = 0;
  len = REGISTER_RAW_SIZE (regno);

  /* Requests for register zero actually want the save_state's
     ss_flags member.  As RM says: "Oh, what a hack!"  */
  if (regno == 0)
    {
      save_state_t ss;
      addr = HPPAH_OFFSETOF (save_state_t, ss_flags);
      len = sizeof (ss.ss_flags);

      /* Note that ss_flags is always an int, no matter what
	 REGISTER_RAW_SIZE(0) says.  Assuming all HP-UX PA machines
	 are big-endian, put it at the least significant end of the
	 value, and zap the rest of the buffer.  */
      offset = REGISTER_RAW_SIZE (0) - len;
      memset (buf, 0, sizeof (buf));
    }

  /* Floating-point registers come from the ss_fpblock area.  */
  else if (regno >= FP0_REGNUM)
    addr = (HPPAH_OFFSETOF (save_state_t, ss_fpblock) 
	    + (REGISTER_BYTE (regno) - REGISTER_BYTE (FP0_REGNUM)));

  /* Wide registers come from the ss_wide area.
     I think it's more PC to test (ss_flags & SS_WIDEREGS) to select
     between ss_wide and ss_narrow than to use the raw register size.
     But checking ss_flags would require an extra ptrace call for
     every register reference.  Bleah.  */
  else if (len == 8)
    addr = (HPPAH_OFFSETOF (save_state_t, ss_wide) 
	    + REGISTER_BYTE (regno));

  /* Narrow registers come from the ss_narrow area.  Note that
     ss_narrow starts with gr1, not gr0.  */
  else if (len == 4)
    addr = (HPPAH_OFFSETOF (save_state_t, ss_narrow)
	    + (REGISTER_BYTE (regno) - REGISTER_BYTE (1)));

  else
    internal_error (__FILE__, __LINE__,
		    "hppa-nat.c (fetch_register): unexpected register size");

  for (i = 0; i < len; i += sizeof (int))
    {
      errno = 0;
      /* Copy an int from the U area to buf.  Fill the least
         significant end if len != raw_size.  */
      * (int *) &buf[offset + i] =
	  call_ptrace (PT_RUREGS, PIDGET (inferior_ptid),
		       (PTRACE_ARG3_TYPE) addr + i, 0);
      if (errno != 0)
	{
	  /* Warning, not error, in case we are attached; sometimes
	     the kernel doesn't let us at the registers. */
	  char *err = safe_strerror (errno);
	  char *msg = alloca (strlen (err) + 128);
	  sprintf (msg, "reading `%s' register: %s",
		   REGISTER_NAME (regno), err);
	  warning (msg);
	  return;
	}
    }

  /* If we're reading an address from the instruction address queue,
     mask out the bottom two bits --- they contain the privilege
     level.  */
  if (regno == PCOQ_HEAD_REGNUM || regno == PCOQ_TAIL_REGNUM)
    buf[len - 1] &= ~0x3;

  supply_register (regno, buf);
}


/* Copy LEN bytes to or from inferior's memory starting at MEMADDR
   to debugger memory starting at MYADDR.   Copy to inferior if
   WRITE is nonzero.

   Returns the length copied, which is either the LEN argument or zero.
   This xfer function does not do partial moves, since child_ops
   doesn't allow memory operations to cross below us in the target stack
   anyway.  TARGET is ignored.  */

int
child_xfer_memory (CORE_ADDR memaddr, char *myaddr, int len, int write,
		   struct mem_attrib *mem,
		   struct target_ops *target)
{
  register int i;
  /* Round starting address down to longword boundary.  */
  register CORE_ADDR addr = memaddr & - (CORE_ADDR)(sizeof (int));
  /* Round ending address up; get number of longwords that makes.  */
  register int count
  = (((memaddr + len) - addr) + sizeof (int) - 1) / sizeof (int);

  /* Allocate buffer of that many longwords.
     Note -- do not use alloca to allocate this buffer since there is no
     guarantee of when the buffer will actually be deallocated.

     This routine can be called over and over with the same call chain;
     this (in effect) would pile up all those alloca requests until a call
     to alloca was made from a point higher than this routine in the
     call chain.  */
  register int *buffer = (int *) xmalloc (count * sizeof (int));

  if (write)
    {
      /* Fill start and end extra bytes of buffer with existing memory data.  */
      if (addr != memaddr || len < (int) sizeof (int))
	{
	  /* Need part of initial word -- fetch it.  */
	  buffer[0] = call_ptrace (addr < text_end ? PT_RIUSER : PT_RDUSER,
				   PIDGET (inferior_ptid),
				   (PTRACE_ARG3_TYPE) addr, 0);
	}

      if (count > 1)		/* FIXME, avoid if even boundary */
	{
	  buffer[count - 1]
	    = call_ptrace (addr < text_end ? PT_RIUSER : PT_RDUSER,
			   PIDGET (inferior_ptid),
			   (PTRACE_ARG3_TYPE) (addr
					       + (count - 1) * sizeof (int)),
			   0);
	}

      /* Copy data to be written over corresponding part of buffer */
      memcpy ((char *) buffer + (memaddr & (sizeof (int) - 1)), myaddr, len);

      /* Write the entire buffer.  */
      for (i = 0; i < count; i++, addr += sizeof (int))
	{
	  int pt_status;
	  int pt_request;
	  /* The HP-UX kernel crashes if you use PT_WDUSER to write into the
	     text segment.  FIXME -- does it work to write into the data
	     segment using WIUSER, or do these idiots really expect us to
	     figure out which segment the address is in, so we can use a
	     separate system call for it??!  */
	  errno = 0;
	  pt_request = (addr < text_end) ? PT_WIUSER : PT_WDUSER;
	  pt_status = call_ptrace (pt_request,
				   PIDGET (inferior_ptid),
				   (PTRACE_ARG3_TYPE) addr,
				   buffer[i]);

	  /* Did we fail?  Might we've guessed wrong about which
	     segment this address resides in?  Try the other request,
	     and see if that works...  */
	  if ((pt_status == -1) && errno)
	    {
	      errno = 0;
	      pt_request = (pt_request == PT_WIUSER) ? PT_WDUSER : PT_WIUSER;
	      pt_status = call_ptrace (pt_request,
				       PIDGET (inferior_ptid),
				       (PTRACE_ARG3_TYPE) addr,
				       buffer[i]);

	      /* No, we still fail.  Okay, time to punt. */
	      if ((pt_status == -1) && errno)
		{
		  xfree (buffer);
		  return 0;
		}
	    }
	}
    }
  else
    {
      /* Read all the longwords */
      for (i = 0; i < count; i++, addr += sizeof (int))
	{
	  errno = 0;
	  buffer[i] = call_ptrace (addr < text_end ? PT_RIUSER : PT_RDUSER,
				   PIDGET (inferior_ptid),
				   (PTRACE_ARG3_TYPE) addr, 0);
	  if (errno)
	    {
	      xfree (buffer);
	      return 0;
	    }
	  QUIT;
	}

      /* Copy appropriate bytes out of the buffer.  */
      memcpy (myaddr, (char *) buffer + (memaddr & (sizeof (int) - 1)), len);
    }
  xfree (buffer);
  return len;
}


void
child_post_follow_inferior_by_clone (void)
{
  int status;

  /* This function is used when following both the parent and child
     of a fork.  In this case, the debugger clones itself.  The original
     debugger follows the parent, the clone follows the child.  The
     original detaches from the child, delivering a SIGSTOP to it to
     keep it from running away until the clone can attach itself.

     At this point, the clone has attached to the child.  Because of
     the SIGSTOP, we must now deliver a SIGCONT to the child, or it
     won't behave properly. */
  status = kill (PIDGET (inferior_ptid), SIGCONT);
}


void
child_post_follow_vfork (int parent_pid, int followed_parent, int child_pid,
			 int followed_child)
{
  /* Are we a debugger that followed the parent of a vfork?  If so,
     then recall that the child's vfork event was delivered to us
     first.  And, that the parent was suspended by the OS until the
     child's exec or exit events were received.

     Upon receiving that child vfork, then, we were forced to remove
     all breakpoints in the child and continue it so that it could
     reach the exec or exit point.

     But also recall that the parent and child of a vfork share the
     same address space.  Thus, removing bp's in the child also
     removed them from the parent.

     Now that the child has safely exec'd or exited, we must restore
     the parent's breakpoints before we continue it.  Else, we may
     cause it run past expected stopping points. */
  if (followed_parent)
    {
      reattach_breakpoints (parent_pid);
    }

  /* Are we a debugger that followed the child of a vfork?  If so,
     then recall that we don't actually acquire control of the child
     until after it has exec'd or exited.  */
  if (followed_child)
    {
      /* If the child has exited, then there's nothing for us to do.
         In the case of an exec event, we'll let that be handled by
         the normal mechanism that notices and handles exec events, in
         resume(). */
    }
}

/* Format a process id, given PID.  Be sure to terminate
   this with a null--it's going to be printed via a "%s".  */
char *
child_pid_to_str (ptid_t ptid)
{
  /* Static because address returned */
  static char buf[30];
  pid_t pid = PIDGET (ptid);

  /* Extra NUL for paranoia's sake */
  sprintf (buf, "process %d%c", pid, '\0');

  return buf;
}

/* Format a thread id, given TID.  Be sure to terminate
   this with a null--it's going to be printed via a "%s".

   Note: This is a core-gdb tid, not the actual system tid.
   See infttrace.c for details.  */
char *
hppa_tid_to_str (ptid_t ptid)
{
  /* Static because address returned */
  static char buf[30];
  /* This seems strange, but when I did the ptid conversion, it looked
     as though a pid was always being passed.  - Kevin Buettner  */
  pid_t tid = PIDGET (ptid);

  /* Extra NULLs for paranoia's sake */
  sprintf (buf, "system thread %d%c", tid, '\0');

  return buf;
}

#if !defined (GDB_NATIVE_HPUX_11)

/* The following code is a substitute for the infttrace.c versions used
   with ttrace() in HPUX 11.  */

/* This value is an arbitrary integer. */
#define PT_VERSION 123456

/* This semaphore is used to coordinate the child and parent processes
   after a fork(), and before an exec() by the child.  See
   parent_attach_all for details.  */

typedef struct
{
  int parent_channel[2];	/* Parent "talks" to [1], child "listens" to [0] */
  int child_channel[2];		/* Child "talks" to [1], parent "listens" to [0] */
}
startup_semaphore_t;

#define SEM_TALK (1)
#define SEM_LISTEN (0)

static startup_semaphore_t startup_semaphore;

extern int parent_attach_all (int, PTRACE_ARG3_TYPE, int);

#ifdef PT_SETTRC
/* This function causes the caller's process to be traced by its
   parent.  This is intended to be called after GDB forks itself,
   and before the child execs the target.

   Note that HP-UX ptrace is rather funky in how this is done.
   If the parent wants to get the initial exec event of a child,
   it must set the ptrace event mask of the child to include execs.
   (The child cannot do this itself.)  This must be done after the
   child is forked, but before it execs.

   To coordinate the parent and child, we implement a semaphore using
   pipes.  After SETTRC'ing itself, the child tells the parent that
   it is now traceable by the parent, and waits for the parent's
   acknowledgement.  The parent can then set the child's event mask,
   and notify the child that it can now exec.

   (The acknowledgement by parent happens as a result of a call to
   child_acknowledge_created_inferior.)  */

int
parent_attach_all (int pid, PTRACE_ARG3_TYPE addr, int data)
{
  int pt_status = 0;

  /* We need a memory home for a constant.  */
  int tc_magic_child = PT_VERSION;
  int tc_magic_parent = 0;

  /* The remainder of this function is only useful for HPUX 10.0 and
     later, as it depends upon the ability to request notification
     of specific kinds of events by the kernel.  */
#if defined(PT_SET_EVENT_MASK)

  /* Notify the parent that we're potentially ready to exec(). */
  write (startup_semaphore.child_channel[SEM_TALK],
	 &tc_magic_child,
	 sizeof (tc_magic_child));

  /* Wait for acknowledgement from the parent. */
  read (startup_semaphore.parent_channel[SEM_LISTEN],
	&tc_magic_parent,
	sizeof (tc_magic_parent));
  if (tc_magic_child != tc_magic_parent)
    warning ("mismatched semaphore magic");

  /* Discard our copy of the semaphore. */
  (void) close (startup_semaphore.parent_channel[SEM_LISTEN]);
  (void) close (startup_semaphore.parent_channel[SEM_TALK]);
  (void) close (startup_semaphore.child_channel[SEM_LISTEN]);
  (void) close (startup_semaphore.child_channel[SEM_TALK]);
#endif

  return 0;
}
#endif

int
hppa_require_attach (int pid)
{
  int pt_status;
  CORE_ADDR pc;
  CORE_ADDR pc_addr;
  unsigned int regs_offset;

  /* Are we already attached?  There appears to be no explicit way to
     answer this via ptrace, so we try something which should be
     innocuous if we are attached.  If that fails, then we assume
     we're not attached, and so attempt to make it so. */

  errno = 0;
  regs_offset = U_REGS_OFFSET;
  pc_addr = register_addr (PC_REGNUM, regs_offset);
  pc = call_ptrace (PT_READ_U, pid, (PTRACE_ARG3_TYPE) pc_addr, 0);

  if (errno)
    {
      errno = 0;
      pt_status = call_ptrace (PT_ATTACH, pid, (PTRACE_ARG3_TYPE) 0, 0);

      if (errno)
	return -1;

      /* Now we really are attached. */
      errno = 0;
    }
  attach_flag = 1;
  return pid;
}

int
hppa_require_detach (int pid, int signal)
{
  errno = 0;
  call_ptrace (PT_DETACH, pid, (PTRACE_ARG3_TYPE) 1, signal);
  errno = 0;			/* Ignore any errors. */
  return pid;
}

/* Since ptrace doesn't support memory page-protection events, which
   are used to implement "hardware" watchpoints on HP-UX, these are
   dummy versions, which perform no useful work.  */

void
hppa_enable_page_protection_events (int pid)
{
}

void
hppa_disable_page_protection_events (int pid)
{
}

int
hppa_insert_hw_watchpoint (int pid, CORE_ADDR start, LONGEST len, int type)
{
  error ("Hardware watchpoints not implemented on this platform.");
}

int
hppa_remove_hw_watchpoint (int pid, CORE_ADDR start, LONGEST len,
			   enum bptype type)
{
  error ("Hardware watchpoints not implemented on this platform.");
}

int
hppa_can_use_hw_watchpoint (enum bptype type, int cnt, enum bptype ot)
{
  return 0;
}

int
hppa_range_profitable_for_hw_watchpoint (int pid, CORE_ADDR start, LONGEST len)
{
  error ("Hardware watchpoints not implemented on this platform.");
}

char *
hppa_pid_or_tid_to_str (ptid_t id)
{
  /* In the ptrace world, there are only processes. */
  return child_pid_to_str (id);
}

/* This function has no meaning in a non-threaded world.  Thus, we
   return 0 (FALSE).  See the use of "hppa_prepare_to_proceed" in
   hppa-tdep.c. */

pid_t
hppa_switched_threads (pid_t pid)
{
  return (pid_t) 0;
}

void
hppa_ensure_vforking_parent_remains_stopped (int pid)
{
  /* This assumes that the vforked parent is presently stopped, and
     that the vforked child has just delivered its first exec event.
     Calling kill() this way will cause the SIGTRAP to be delivered as
     soon as the parent is resumed, which happens as soon as the
     vforked child is resumed.  See wait_for_inferior for the use of
     this function.  */
  kill (pid, SIGTRAP);
}

int
hppa_resume_execd_vforking_child_to_get_parent_vfork (void)
{
  return 1;			/* Yes, the child must be resumed. */
}

void
require_notification_of_events (int pid)
{
#if defined(PT_SET_EVENT_MASK)
  int pt_status;
  ptrace_event_t ptrace_events;
  int nsigs;
  int signum;

  /* Instruct the kernel as to the set of events we wish to be
     informed of.  (This support does not exist before HPUX 10.0.
     We'll assume if PT_SET_EVENT_MASK has not been defined by
     <sys/ptrace.h>, then we're being built on pre-10.0.)  */
  memset (&ptrace_events, 0, sizeof (ptrace_events));

  /* Note: By default, all signals are visible to us.  If we wish
     the kernel to keep certain signals hidden from us, we do it
     by calling sigdelset (ptrace_events.pe_signals, signal) for
     each such signal here, before doing PT_SET_EVENT_MASK.  */
  /* RM: The above comment is no longer true. We start with ignoring
     all signals, and then add the ones we are interested in. We could
     do it the other way: start by looking at all signals and then
     deleting the ones that we aren't interested in, except that
     multiple gdb signals may be mapped to the same host signal
     (eg. TARGET_SIGNAL_IO and TARGET_SIGNAL_POLL both get mapped to
     signal 22 on HPUX 10.20) We want to be notified if we are
     interested in either signal.  */
  sigfillset (&ptrace_events.pe_signals);

  /* RM: Let's not bother with signals we don't care about */
  nsigs = (int) TARGET_SIGNAL_LAST;
  for (signum = nsigs; signum > 0; signum--)
    {
      if ((signal_stop_state (signum)) ||
	  (signal_print_state (signum)) ||
	  (!signal_pass_state (signum)))
	{
	  if (target_signal_to_host_p (signum))
	    sigdelset (&ptrace_events.pe_signals,
		       target_signal_to_host (signum));
	}
    }

  ptrace_events.pe_set_event = 0;

  ptrace_events.pe_set_event |= PTRACE_SIGNAL;
  ptrace_events.pe_set_event |= PTRACE_EXEC;
  ptrace_events.pe_set_event |= PTRACE_FORK;
  ptrace_events.pe_set_event |= PTRACE_VFORK;
  /* ??rehrauer: Add this one when we're prepared to catch it...
     ptrace_events.pe_set_event |= PTRACE_EXIT;
   */

  errno = 0;
  pt_status = call_ptrace (PT_SET_EVENT_MASK,
			   pid,
			   (PTRACE_ARG3_TYPE) & ptrace_events,
			   sizeof (ptrace_events));
  if (errno)
    perror_with_name ("ptrace");
  if (pt_status < 0)
    return;
#endif
}

void
require_notification_of_exec_events (int pid)
{
#if defined(PT_SET_EVENT_MASK)
  int pt_status;
  ptrace_event_t ptrace_events;

  /* Instruct the kernel as to the set of events we wish to be
     informed of.  (This support does not exist before HPUX 10.0.
     We'll assume if PT_SET_EVENT_MASK has not been defined by
     <sys/ptrace.h>, then we're being built on pre-10.0.)  */
  memset (&ptrace_events, 0, sizeof (ptrace_events));

  /* Note: By default, all signals are visible to us.  If we wish
     the kernel to keep certain signals hidden from us, we do it
     by calling sigdelset (ptrace_events.pe_signals, signal) for
     each such signal here, before doing PT_SET_EVENT_MASK.  */
  sigemptyset (&ptrace_events.pe_signals);

  ptrace_events.pe_set_event = 0;

  ptrace_events.pe_set_event |= PTRACE_EXEC;
  /* ??rehrauer: Add this one when we're prepared to catch it...
     ptrace_events.pe_set_event |= PTRACE_EXIT;
   */

  errno = 0;
  pt_status = call_ptrace (PT_SET_EVENT_MASK,
			   pid,
			   (PTRACE_ARG3_TYPE) & ptrace_events,
			   sizeof (ptrace_events));
  if (errno)
    perror_with_name ("ptrace");
  if (pt_status < 0)
    return;
#endif
}

/* This function is called by the parent process, with pid being the
   ID of the child process, after the debugger has forked.  */

void
child_acknowledge_created_inferior (int pid)
{
  /* We need a memory home for a constant.  */
  int tc_magic_parent = PT_VERSION;
  int tc_magic_child = 0;

  /* The remainder of this function is only useful for HPUX 10.0 and
     later, as it depends upon the ability to request notification
     of specific kinds of events by the kernel.  */
#if defined(PT_SET_EVENT_MASK)
  /* Wait for the child to tell us that it has forked. */
  read (startup_semaphore.child_channel[SEM_LISTEN],
	&tc_magic_child,
	sizeof (tc_magic_child));

  /* Notify the child that it can exec.

     In the infttrace.c variant of this function, we set the child's
     event mask after the fork but before the exec.  In the ptrace
     world, it seems we can't set the event mask until after the exec.  */
  write (startup_semaphore.parent_channel[SEM_TALK],
	 &tc_magic_parent,
	 sizeof (tc_magic_parent));

  /* We'd better pause a bit before trying to set the event mask,
     though, to ensure that the exec has happened.  We don't want to
     wait() on the child, because that'll screw up the upper layers
     of gdb's execution control that expect to see the exec event.

     After an exec, the child is no longer executing gdb code.  Hence,
     we can't have yet another synchronization via the pipes.  We'll
     just sleep for a second, and hope that's enough delay...  */
  sleep (1);

  /* Instruct the kernel as to the set of events we wish to be
     informed of.  */
  require_notification_of_exec_events (pid);

  /* Discard our copy of the semaphore. */
  (void) close (startup_semaphore.parent_channel[SEM_LISTEN]);
  (void) close (startup_semaphore.parent_channel[SEM_TALK]);
  (void) close (startup_semaphore.child_channel[SEM_LISTEN]);
  (void) close (startup_semaphore.child_channel[SEM_TALK]);
#endif
}

void
child_post_startup_inferior (ptid_t ptid)
{
  require_notification_of_events (PIDGET (ptid));
}

void
child_post_attach (int pid)
{
  require_notification_of_events (pid);
}

int
child_insert_fork_catchpoint (int pid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_SET_EVENT_MASK)
  error ("Unable to catch forks prior to HPUX 10.0");
#else
  /* Enable reporting of fork events from the kernel. */
  /* ??rehrauer: For the moment, we're always enabling these events,
     and just ignoring them if there's no catchpoint to catch them.  */
  return 0;
#endif
}

int
child_remove_fork_catchpoint (int pid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_SET_EVENT_MASK)
  error ("Unable to catch forks prior to HPUX 10.0");
#else
  /* Disable reporting of fork events from the kernel. */
  /* ??rehrauer: For the moment, we're always enabling these events,
     and just ignoring them if there's no catchpoint to catch them.  */
  return 0;
#endif
}

int
child_insert_vfork_catchpoint (int pid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_SET_EVENT_MASK)
  error ("Unable to catch vforks prior to HPUX 10.0");
#else
  /* Enable reporting of vfork events from the kernel. */
  /* ??rehrauer: For the moment, we're always enabling these events,
     and just ignoring them if there's no catchpoint to catch them.  */
  return 0;
#endif
}

int
child_remove_vfork_catchpoint (int pid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_SET_EVENT_MASK)
  error ("Unable to catch vforks prior to HPUX 10.0");
#else
  /* Disable reporting of vfork events from the kernel. */
  /* ??rehrauer: For the moment, we're always enabling these events,
     and just ignoring them if there's no catchpoint to catch them.  */
  return 0;
#endif
}

int
child_has_forked (int pid, int *childpid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_GET_PROCESS_STATE)
  *childpid = 0;
  return 0;
#else
  int pt_status;
  ptrace_state_t ptrace_state;

  errno = 0;
  pt_status = call_ptrace (PT_GET_PROCESS_STATE,
			   pid,
			   (PTRACE_ARG3_TYPE) & ptrace_state,
			   sizeof (ptrace_state));
  if (errno)
    perror_with_name ("ptrace");
  if (pt_status < 0)
    return 0;

  if (ptrace_state.pe_report_event & PTRACE_FORK)
    {
      *childpid = ptrace_state.pe_other_pid;
      return 1;
    }

  return 0;
#endif
}

int
child_has_vforked (int pid, int *childpid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_GET_PROCESS_STATE)
  *childpid = 0;
  return 0;

#else
  int pt_status;
  ptrace_state_t ptrace_state;

  errno = 0;
  pt_status = call_ptrace (PT_GET_PROCESS_STATE,
			   pid,
			   (PTRACE_ARG3_TYPE) & ptrace_state,
			   sizeof (ptrace_state));
  if (errno)
    perror_with_name ("ptrace");
  if (pt_status < 0)
    return 0;

  if (ptrace_state.pe_report_event & PTRACE_VFORK)
    {
      *childpid = ptrace_state.pe_other_pid;
      return 1;
    }

  return 0;
#endif
}

int
child_can_follow_vfork_prior_to_exec (void)
{
  /* ptrace doesn't allow this. */
  return 0;
}

int
child_insert_exec_catchpoint (int pid)
{
  /* This request is only available on HPUX 10.0 and later.   */
#if !defined(PT_SET_EVENT_MASK)
  error ("Unable to catch execs prior to HPUX 10.0");

#else
  /* Enable reporting of exec events from the kernel.  */
  /* ??rehrauer: For the moment, we're always enabling these events,
     and just ignoring them if there's no catchpoint to catch them.  */
  return 0;
#endif
}

int
child_remove_exec_catchpoint (int pid)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_SET_EVENT_MASK)
  error ("Unable to catch execs prior to HPUX 10.0");

#else
  /* Disable reporting of exec events from the kernel. */
  /* ??rehrauer: For the moment, we're always enabling these events,
     and just ignoring them if there's no catchpoint to catch them.  */
  return 0;
#endif
}

int
child_has_execd (int pid, char **execd_pathname)
{
  /* This request is only available on HPUX 10.0 and later.  */
#if !defined(PT_GET_PROCESS_STATE)
  *execd_pathname = NULL;
  return 0;

#else
  int pt_status;
  ptrace_state_t ptrace_state;

  errno = 0;
  pt_status = call_ptrace (PT_GET_PROCESS_STATE,
			   pid,
			   (PTRACE_ARG3_TYPE) & ptrace_state,
			   sizeof (ptrace_state));
  if (errno)
    perror_with_name ("ptrace");
  if (pt_status < 0)
    return 0;

  if (ptrace_state.pe_report_event & PTRACE_EXEC)
    {
      char *exec_file = target_pid_to_exec_file (pid);
      *execd_pathname = savestring (exec_file, strlen (exec_file));
      return 1;
    }

  return 0;
#endif
}

int
child_reported_exec_events_per_exec_call (void)
{
  return 2;			/* ptrace reports the event twice per call. */
}

int
child_has_syscall_event (int pid, enum target_waitkind *kind, int *syscall_id)
{
  /* This request is only available on HPUX 10.30 and later, via
     the ttrace interface.  */

  *kind = TARGET_WAITKIND_SPURIOUS;
  *syscall_id = -1;
  return 0;
}

char *
child_pid_to_exec_file (int pid)
{
  static char exec_file_buffer[1024];
  int pt_status;
  CORE_ADDR top_of_stack;
  char four_chars[4];
  int name_index;
  int i;
  ptid_t saved_inferior_ptid;
  boolean done;

#ifdef PT_GET_PROCESS_PATHNAME
  /* As of 10.x HP-UX, there's an explicit request to get the pathname. */
  pt_status = call_ptrace (PT_GET_PROCESS_PATHNAME,
			   pid,
			   (PTRACE_ARG3_TYPE) exec_file_buffer,
			   sizeof (exec_file_buffer) - 1);
  if (pt_status == 0)
    return exec_file_buffer;
#endif

  /* It appears that this request is broken prior to 10.30.
     If it fails, try a really, truly amazingly gross hack
     that DDE uses, of pawing through the process' data
     segment to find the pathname.  */

  top_of_stack = 0x7b03a000;
  name_index = 0;
  done = 0;

  /* On the chance that pid != inferior_ptid, set inferior_ptid
     to pid, so that (grrrr!) implicit uses of inferior_ptid get
     the right id.  */

  saved_inferior_ptid = inferior_ptid;
  inferior_ptid = pid_to_ptid (pid);

  /* Try to grab a null-terminated string. */
  while (!done)
    {
      if (target_read_memory (top_of_stack, four_chars, 4) != 0)
	{
	  inferior_ptid = saved_inferior_ptid;
	  return NULL;
	}
      for (i = 0; i < 4; i++)
	{
	  exec_file_buffer[name_index++] = four_chars[i];
	  done = (four_chars[i] == '\0');
	  if (done)
	    break;
	}
      top_of_stack += 4;
    }

  if (exec_file_buffer[0] == '\0')
    {
      inferior_ptid = saved_inferior_ptid;
      return NULL;
    }

  inferior_ptid = saved_inferior_ptid;
  return exec_file_buffer;
}

void
pre_fork_inferior (void)
{
  int status;

  status = pipe (startup_semaphore.parent_channel);
  if (status < 0)
    {
      warning ("error getting parent pipe for startup semaphore");
      return;
    }

  status = pipe (startup_semaphore.child_channel);
  if (status < 0)
    {
      warning ("error getting child pipe for startup semaphore");
      return;
    }
}


/* Check to see if the given thread is alive.

   This is a no-op, as ptrace doesn't support threads, so we just
   return "TRUE".  */

int
child_thread_alive (ptid_t ptid)
{
  return 1;
}

#endif /* ! GDB_NATIVE_HPUX_11 */