gdb/i386fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright (C) 2001, 2002, 2003, 2004, 2007 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 3 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, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "inferior.h"
  22 #include "regcache.h"
  23 #include "target.h"
  24
  25 #include <sys/types.h>
  26 #include <sys/ptrace.h>
  27 #include <sys/sysctl.h>
  28
  29 #include "fbsd-nat.h"
  30 #include "i386-tdep.h"
  31 #include "i386bsd-nat.h"
  32
  33 /* Resume execution of the inferior process.  If STEP is nonzero,
  34    single-step it.  If SIGNAL is nonzero, give it that signal.  */
  35
  36 static void
  37 i386fbsd_resume (ptid_t ptid, int step, enum target_signal signal)
  38 {
  39   pid_t pid = ptid_get_pid (ptid);
  40   int request = PT_STEP;
  41
  42   if (pid == -1)
  43     /* Resume all threads.  This only gets used in the non-threaded
  44        case, where "resume all threads" and "resume inferior_ptid" are
  45        the same.  */
  46     pid = ptid_get_pid (inferior_ptid);
  47
  48   if (!step)
  49     {
  50       struct regcache *regcache = get_current_regcache ();
  51       ULONGEST eflags;
  52
  53       /* Workaround for a bug in FreeBSD.  Make sure that the trace
  54          flag is off when doing a continue.  There is a code path
  55          through the kernel which leaves the flag set when it should
  56          have been cleared.  If a process has a signal pending (such
  57          as SIGALRM) and we do a PT_STEP, the process never really has
  58          a chance to run because the kernel needs to notify the
  59          debugger that a signal is being sent.  Therefore, the process
  60          never goes through the kernel's trap() function which would
  61          normally clear it.  */
  62
  63       regcache_cooked_read_unsigned (regcache, I386_EFLAGS_REGNUM,
  64                                      &eflags);
  65       if (eflags & 0x0100)
  66         regcache_cooked_write_unsigned (regcache, I386_EFLAGS_REGNUM,
  67                                         eflags & ~0x0100);
  68
  69       request = PT_CONTINUE;
  70     }
  71
  72   /* An addres of (caddr_t) 1 tells ptrace to continue from where it
  73      was.  (If GDB wanted it to start some other way, we have already
  74      written a new PC value to the child.)  */
  75   if (ptrace (request, pid, (caddr_t) 1,
  76               target_signal_to_host (signal)) == -1)
  77     perror_with_name (("ptrace"));
  78 }
  79 \f
  80
  81 /* Support for debugging kernel virtual memory images.  */
  82
  83 #include <sys/types.h>
  84 #include <machine/pcb.h>
  85
  86 #include "bsd-kvm.h"
  87
  88 static int
  89 i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  90 {
  91   /* The following is true for FreeBSD 4.7:
  92
  93      The pcb contains %eip, %ebx, %esp, %ebp, %esi, %edi and %gs.
  94      This accounts for all callee-saved registers specified by the
  95      psABI and then some.  Here %esp contains the stack pointer at the
  96      point just after the call to cpu_switch().  From this information
  97      we reconstruct the register state as it would look when we just
  98      returned from cpu_switch().  */
  99
 100   /* The stack pointer shouldn't be zero.  */
 101   if (pcb->pcb_esp == 0)
 102     return 0;
 103
 104   pcb->pcb_esp += 4;
 105   regcache_raw_supply (regcache, I386_EDI_REGNUM, &pcb->pcb_edi);
 106   regcache_raw_supply (regcache, I386_ESI_REGNUM, &pcb->pcb_esi);
 107   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
 108   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
 109   regcache_raw_supply (regcache, I386_EBX_REGNUM, &pcb->pcb_ebx);
 110   regcache_raw_supply (regcache, I386_EIP_REGNUM, &pcb->pcb_eip);
 111   regcache_raw_supply (regcache, I386_GS_REGNUM, &pcb->pcb_gs);
 112
 113   return 1;
 114 }
 115 \f
 116
 117 /* Prevent warning from -Wmissing-prototypes.  */
 118 void _initialize_i386fbsd_nat (void);
 119
 120 void
 121 _initialize_i386fbsd_nat (void)
 122 {
 123   struct target_ops *t;
 124
 125   /* Add some extra features to the common *BSD/i386 target.  */
 126   t = i386bsd_target ();
 127   t->to_resume = i386fbsd_resume;
 128   t->to_pid_to_exec_file = fbsd_pid_to_exec_file;
 129   t->to_find_memory_regions = fbsd_find_memory_regions;
 130   t->to_make_corefile_notes = fbsd_make_corefile_notes;
 131   add_target (t);
 132
 133   /* Support debugging kernel virtual memory images.  */
 134   bsd_kvm_add_target (i386fbsd_supply_pcb);
 135
 136   /* FreeBSD provides a kern.ps_strings sysctl that we can use to
 137      locate the sigtramp.  That way we can still recognize a sigtramp
 138      if its location is changed in a new kernel.  Of course this is
 139      still based on the assumption that the sigtramp is placed
 140      directly under the location where the program arguments and
 141      environment can be found.  */
 142 #ifdef KERN_PS_STRINGS
 143   {
 144     int mib[2];
 145     u_long ps_strings;
 146     size_t len;
 147
 148     mib[0] = CTL_KERN;
 149     mib[1] = KERN_PS_STRINGS;
 150     len = sizeof (ps_strings);
 151     if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
 152       {
 153         i386fbsd_sigtramp_start_addr = ps_strings - 128;
 154         i386fbsd_sigtramp_end_addr = ps_strings;
 155       }
 156   }
 157 #endif
 158 }