gdb/i386fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright (C) 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., 51 Franklin Street, Fifth Floor,
  20    Boston, MA 02110-1301, USA.  */
  21
  22 #include "defs.h"
  23 #include "inferior.h"
  24 #include "regcache.h"
  25 #include "target.h"
  26
  27 #include <sys/types.h>
  28 #include <sys/ptrace.h>
  29 #include <sys/sysctl.h>
  30
  31 #include "fbsd-nat.h"
  32 #include "i386-tdep.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 (ptid_t ptid, int step, enum target_signal signal)
  40 {
  41   pid_t pid = ptid_get_pid (ptid);
  42   int request = PT_STEP;
  43
  44   if (pid == -1)
  45     /* Resume all threads.  This only gets used in the non-threaded
  46        case, where "resume all threads" and "resume inferior_ptid" are
  47        the same.  */
  48     pid = ptid_get_pid (inferior_ptid);
  49
  50   if (!step)
  51     {
  52       ULONGEST eflags;
  53
  54       /* Workaround for a bug in FreeBSD.  Make sure that the trace
  55          flag is off when doing a continue.  There is a code path
  56          through the kernel which leaves the flag set when it should
  57          have been cleared.  If a process has a signal pending (such
  58          as SIGALRM) and we do a PT_STEP, the process never really has
  59          a chance to run because the kernel needs to notify the
  60          debugger that a signal is being sent.  Therefore, the process
  61          never goes through the kernel's trap() function which would
  62          normally clear it.  */
  63
  64       regcache_cooked_read_unsigned (current_regcache, I386_EFLAGS_REGNUM,
  65                                      &eflags);
  66       if (eflags & 0x0100)
  67         regcache_cooked_write_unsigned (current_regcache, I386_EFLAGS_REGNUM,
  68                                         eflags & ~0x0100);
  69
  70       request = PT_CONTINUE;
  71     }
  72
  73   /* An addres of (caddr_t) 1 tells ptrace to continue from where it
  74      was.  (If GDB wanted it to start some other way, we have already
  75      written a new PC value to the child.)  */
  76   if (ptrace (request, pid, (caddr_t) 1,
  77               target_signal_to_host (signal)) == -1)
  78     perror_with_name (("ptrace"));
  79 }
  80 \f
  81
  82 /* Support for debugging kernel virtual memory images.  */
  83
  84 #include <sys/types.h>
  85 #include <machine/pcb.h>
  86
  87 #include "bsd-kvm.h"
  88
  89 static int
  90 i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  91 {
  92   /* The following is true for FreeBSD 4.7:
  93
  94      The pcb contains %eip, %ebx, %esp, %ebp, %esi, %edi and %gs.
  95      This accounts for all callee-saved registers specified by the
  96      psABI and then some.  Here %esp contains the stack pointer at the
  97      point just after the call to cpu_switch().  From this information
  98      we reconstruct the register state as it would look when we just
  99      returned from cpu_switch().  */
 100
 101   /* The stack pointer shouldn't be zero.  */
 102   if (pcb->pcb_esp == 0)
 103     return 0;
 104
 105   pcb->pcb_esp += 4;
 106   regcache_raw_supply (regcache, I386_EDI_REGNUM, &pcb->pcb_edi);
 107   regcache_raw_supply (regcache, I386_ESI_REGNUM, &pcb->pcb_esi);
 108   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
 109   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
 110   regcache_raw_supply (regcache, I386_EBX_REGNUM, &pcb->pcb_ebx);
 111   regcache_raw_supply (regcache, I386_EIP_REGNUM, &pcb->pcb_eip);
 112   regcache_raw_supply (regcache, I386_GS_REGNUM, &pcb->pcb_gs);
 113
 114   return 1;
 115 }
 116 \f
 117
 118 /* Prevent warning from -Wmissing-prototypes.  */
 119 void _initialize_i386fbsd_nat (void);
 120
 121 void
 122 _initialize_i386fbsd_nat (void)
 123 {
 124   struct target_ops *t;
 125
 126   /* Add some extra features to the common *BSD/i386 target.  */
 127   t = i386bsd_target ();
 128   t->to_resume = i386fbsd_resume;
 129   t->to_pid_to_exec_file = fbsd_pid_to_exec_file;
 130   t->to_find_memory_regions = fbsd_find_memory_regions;
 131   t->to_make_corefile_notes = fbsd_make_corefile_notes;
 132   add_target (t);
 133
 134   /* Support debugging kernel virtual memory images.  */
 135   bsd_kvm_add_target (i386fbsd_supply_pcb);
 136
 137   /* FreeBSD provides a kern.ps_strings sysctl that we can use to
 138      locate the sigtramp.  That way we can still recognize a sigtramp
 139      if its location is changed in a new kernel.  Of course this is
 140      still based on the assumption that the sigtramp is placed
 141      directly under the location where the program arguments and
 142      environment can be found.  */
 143 #ifdef KERN_PS_STRINGS
 144   {
 145     int mib[2];
 146     u_long ps_strings;
 147     size_t len;
 148
 149     mib[0] = CTL_KERN;
 150     mib[1] = KERN_PS_STRINGS;
 151     len = sizeof (ps_strings);
 152     if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
 153       {
 154         i386fbsd_sigtramp_start_addr = ps_strings - 128;
 155         i386fbsd_sigtramp_end_addr = ps_strings;
 156       }
 157   }
 158 #endif
 159 }