binutils-gdb/gdb/i386fbsd-nat.c

/* Native-dependent code for FreeBSD/i386.
   Copyright 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 "inferior.h"
#include "regcache.h"

#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/sysctl.h>

/* Prevent warning from -Wmissing-prototypes.  */
void _initialize_i386fbsd_nat (void);

/* Resume execution of the inferior process.
   If STEP is nonzero, single-step it.
   If SIGNAL is nonzero, give it that signal.  */

void
child_resume (ptid_t ptid, int step, enum target_signal signal)
{
  pid_t pid = ptid_get_pid (ptid);
  int request = PT_STEP;

  if (pid == -1)
    /* Resume all threads.  This only gets used in the non-threaded
       case, where "resume all threads" and "resume inferior_ptid" are
       the same.  */
    pid = ptid_get_pid (inferior_ptid);

  if (!step)
    {
      unsigned int eflags;

      /* Workaround for a bug in FreeBSD.  Make sure that the trace
 	 flag is off when doing a continue.  There is a code path
 	 through the kernel which leaves the flag set when it should
 	 have been cleared.  If a process has a signal pending (such
 	 as SIGALRM) and we do a PT_STEP, the process never really has
 	 a chance to run because the kernel needs to notify the
 	 debugger that a signal is being sent.  Therefore, the process
 	 never goes through the kernel's trap() function which would
 	 normally clear it.  */

      eflags = read_register (PS_REGNUM);
      if (eflags & 0x0100)
	write_register (PS_REGNUM, eflags & ~0x0100);

      request = PT_CONTINUE;
    }

  /* An addres of (caddr_t) 1 tells ptrace to continue from where it
     was.  (If GDB wanted it to start some other way, we have already
     written a new PC value to the child.)  */
  if (ptrace (request, pid, (caddr_t) 1,
	      target_signal_to_host (signal)) == -1)
    perror_with_name ("ptrace");
}

void
_initialize_i386fbsd_nat (void)
{
  /* FreeBSD provides a kern.ps_strings sysctl that we can use to
     locate the sigtramp.  That way we can still recognize a sigtramp
     if its location is changed in a new kernel.  Of course this is
     still based on the assumption that the sigtramp is placed
     directly under the location where the program arguments and
     environment can be found.  */
#ifdef KERN_PS_STRINGS
  {
    int mib[2];
    int ps_strings;
    size_t len;

    extern CORE_ADDR i386fbsd_sigtramp_start;
    extern CORE_ADDR i386fbsd_sigtramp_end;

    mib[0] = CTL_KERN;
    mib[1] = KERN_PS_STRINGS;
    len = sizeof (ps_strings);
    if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
      {
	i386fbsd_sigtramp_start = ps_strings - 128;
	i386fbsd_sigtramp_end = ps_strings;
      }
  }
#endif
}