gdb/i386fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include "defs.h"
  23 #include "inferior.h"
  24 #include "regcache.h"
  25
  26 #include <sys/types.h>
  27 #include <sys/ptrace.h>
  28 #include <sys/sysctl.h>
  29
  30 #include "i386-tdep.h"
  31
  32 /* Prevent warning from -Wmissing-prototypes.  */
  33 void _initialize_i386fbsd_nat (void);
  34
  35 /* Resume execution of the inferior process.
  36    If STEP is nonzero, single-step it.
  37    If SIGNAL is nonzero, give it that signal.  */
  38
  39 void
  40 child_resume (ptid_t ptid, int step, enum target_signal signal)
  41 {
  42   pid_t pid = ptid_get_pid (ptid);
  43   int request = PT_STEP;
  44
  45   if (pid == -1)
  46     /* Resume all threads.  This only gets used in the non-threaded
  47        case, where "resume all threads" and "resume inferior_ptid" are
  48        the same.  */
  49     pid = ptid_get_pid (inferior_ptid);
  50
  51   if (!step)
  52     {
  53       ULONGEST eflags;
  54
  55       /* Workaround for a bug in FreeBSD.  Make sure that the trace
  56          flag is off when doing a continue.  There is a code path
  57          through the kernel which leaves the flag set when it should
  58          have been cleared.  If a process has a signal pending (such
  59          as SIGALRM) and we do a PT_STEP, the process never really has
  60          a chance to run because the kernel needs to notify the
  61          debugger that a signal is being sent.  Therefore, the process
  62          never goes through the kernel's trap() function which would
  63          normally clear it.  */
  64
  65       regcache_cooked_read_unsigned (current_regcache, I386_EFLAGS_REGNUM,
  66                                      &eflags);
  67       if (eflags & 0x0100)
  68         regcache_cooked_write_unsigned (current_regcache, I386_EFLAGS_REGNUM,
  69                                         eflags & ~0x0100);
  70
  71       request = PT_CONTINUE;
  72     }
  73
  74   /* An addres of (caddr_t) 1 tells ptrace to continue from where it
  75      was.  (If GDB wanted it to start some other way, we have already
  76      written a new PC value to the child.)  */
  77   if (ptrace (request, pid, (caddr_t) 1,
  78               target_signal_to_host (signal)) == -1)
  79     perror_with_name ("ptrace");
  80 }
  81 \f
  82 void
  83 _initialize_i386fbsd_nat (void)
  84 {
  85   /* FreeBSD provides a kern.ps_strings sysctl that we can use to
  86      locate the sigtramp.  That way we can still recognize a sigtramp
  87      if its location is changed in a new kernel.  Of course this is
  88      still based on the assumption that the sigtramp is placed
  89      directly under the location where the program arguments and
  90      environment can be found.  */
  91 #ifdef KERN_PS_STRINGS
  92   {
  93     int mib[2];
  94     int ps_strings;
  95     size_t len;
  96
  97     mib[0] = CTL_KERN;
  98     mib[1] = KERN_PS_STRINGS;
  99     len = sizeof (ps_strings);
 100     if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
 101       {
 102         i386fbsd_sigtramp_start_addr = ps_strings - 128;
 103         i386fbsd_sigtramp_end_addr = ps_strings;
 104       }
 105   }
 106 #endif
 107 }