gdb/i386fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright (C) 2001, 2002, 2003, 2004, 2007, 2008, 2009, 2010
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "inferior.h"
  23 #include "regcache.h"
  24 #include "target.h"
  25
  26 #include <sys/types.h>
  27 #include <sys/ptrace.h>
  28 #include <sys/sysctl.h>
  29
  30 #include "fbsd-nat.h"
  31 #include "i386-tdep.h"
  32 #include "i386-nat.h"
  33 #include "i386bsd-nat.h"
  34
  35 /* Resume execution of the inferior process.  If STEP is nonzero,
  36    single-step it.  If SIGNAL is nonzero, give it that signal.  */
  37
  38 static void
  39 i386fbsd_resume (struct target_ops *ops,
  40                  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       struct regcache *regcache = get_current_regcache ();
  54       ULONGEST eflags;
  55
  56       /* Workaround for a bug in FreeBSD.  Make sure that the trace
  57          flag is off when doing a continue.  There is a code path
  58          through the kernel which leaves the flag set when it should
  59          have been cleared.  If a process has a signal pending (such
  60          as SIGALRM) and we do a PT_STEP, the process never really has
  61          a chance to run because the kernel needs to notify the
  62          debugger that a signal is being sent.  Therefore, the process
  63          never goes through the kernel's trap() function which would
  64          normally clear it.  */
  65
  66       regcache_cooked_read_unsigned (regcache, I386_EFLAGS_REGNUM,
  67                                      &eflags);
  68       if (eflags & 0x0100)
  69         regcache_cooked_write_unsigned (regcache, I386_EFLAGS_REGNUM,
  70                                         eflags & ~0x0100);
  71
  72       request = PT_CONTINUE;
  73     }
  74
  75   /* An addres of (caddr_t) 1 tells ptrace to continue from where it
  76      was.  (If GDB wanted it to start some other way, we have already
  77      written a new PC value to the child.)  */
  78   if (ptrace (request, pid, (caddr_t) 1,
  79               target_signal_to_host (signal)) == -1)
  80     perror_with_name (("ptrace"));
  81 }
  82 \f
  83
  84 /* Support for debugging kernel virtual memory images.  */
  85
  86 #include <sys/types.h>
  87 #include <machine/pcb.h>
  88
  89 #include "bsd-kvm.h"
  90
  91 static int
  92 i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  93 {
  94   /* The following is true for FreeBSD 4.7:
  95
  96      The pcb contains %eip, %ebx, %esp, %ebp, %esi, %edi and %gs.
  97      This accounts for all callee-saved registers specified by the
  98      psABI and then some.  Here %esp contains the stack pointer at the
  99      point just after the call to cpu_switch().  From this information
 100      we reconstruct the register state as it would look when we just
 101      returned from cpu_switch().  */
 102
 103   /* The stack pointer shouldn't be zero.  */
 104   if (pcb->pcb_esp == 0)
 105     return 0;
 106
 107   pcb->pcb_esp += 4;
 108   regcache_raw_supply (regcache, I386_EDI_REGNUM, &pcb->pcb_edi);
 109   regcache_raw_supply (regcache, I386_ESI_REGNUM, &pcb->pcb_esi);
 110   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
 111   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
 112   regcache_raw_supply (regcache, I386_EBX_REGNUM, &pcb->pcb_ebx);
 113   regcache_raw_supply (regcache, I386_EIP_REGNUM, &pcb->pcb_eip);
 114   regcache_raw_supply (regcache, I386_GS_REGNUM, &pcb->pcb_gs);
 115
 116   return 1;
 117 }
 118 \f
 119
 120 /* Prevent warning from -Wmissing-prototypes.  */
 121 void _initialize_i386fbsd_nat (void);
 122
 123 void
 124 _initialize_i386fbsd_nat (void)
 125 {
 126   struct target_ops *t;
 127
 128   /* Add some extra features to the common *BSD/i386 target.  */
 129   t = i386bsd_target ();
 130
 131 #ifdef HAVE_PT_GETDBREGS
 132
 133   i386_use_watchpoints (t);
 134
 135   i386_dr_low.set_control = i386bsd_dr_set_control;
 136   i386_dr_low.set_addr = i386bsd_dr_set_addr;
 137   i386_dr_low.reset_addr = i386bsd_dr_reset_addr;
 138   i386_dr_low.get_status = i386bsd_dr_get_status;
 139   i386_set_debug_register_length (4);
 140
 141 #endif /* HAVE_PT_GETDBREGS */
 142
 143
 144   t->to_resume = i386fbsd_resume;
 145   t->to_pid_to_exec_file = fbsd_pid_to_exec_file;
 146   t->to_find_memory_regions = fbsd_find_memory_regions;
 147   t->to_make_corefile_notes = fbsd_make_corefile_notes;
 148   add_target (t);
 149
 150   /* Support debugging kernel virtual memory images.  */
 151   bsd_kvm_add_target (i386fbsd_supply_pcb);
 152
 153   /* FreeBSD provides a kern.ps_strings sysctl that we can use to
 154      locate the sigtramp.  That way we can still recognize a sigtramp
 155      if its location is changed in a new kernel.  Of course this is
 156      still based on the assumption that the sigtramp is placed
 157      directly under the location where the program arguments and
 158      environment can be found.  */
 159 #ifdef KERN_PS_STRINGS
 160   {
 161     int mib[2];
 162     u_long ps_strings;
 163     size_t len;
 164
 165     mib[0] = CTL_KERN;
 166     mib[1] = KERN_PS_STRINGS;
 167     len = sizeof (ps_strings);
 168     if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
 169       {
 170         i386fbsd_sigtramp_start_addr = ps_strings - 128;
 171         i386fbsd_sigtramp_end_addr = ps_strings;
 172       }
 173   }
 174 #endif
 175 }