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 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       struct regcache *regcache = get_current_regcache ();
  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 (regcache, I386_EFLAGS_REGNUM,
  66                                      &eflags);
  67       if (eflags & 0x0100)
  68         regcache_cooked_write_unsigned (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
  83 /* Support for debugging kernel virtual memory images.  */
  84
  85 #include <sys/types.h>
  86 #include <machine/pcb.h>
  87
  88 #include "bsd-kvm.h"
  89
  90 static int
  91 i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  92 {
  93   /* The following is true for FreeBSD 4.7:
  94
  95      The pcb contains %eip, %ebx, %esp, %ebp, %esi, %edi and %gs.
  96      This accounts for all callee-saved registers specified by the
  97      psABI and then some.  Here %esp contains the stack pointer at the
  98      point just after the call to cpu_switch().  From this information
  99      we reconstruct the register state as it would look when we just
 100      returned from cpu_switch().  */
 101
 102   /* The stack pointer shouldn't be zero.  */
 103   if (pcb->pcb_esp == 0)
 104     return 0;
 105
 106   pcb->pcb_esp += 4;
 107   regcache_raw_supply (regcache, I386_EDI_REGNUM, &pcb->pcb_edi);
 108   regcache_raw_supply (regcache, I386_ESI_REGNUM, &pcb->pcb_esi);
 109   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
 110   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
 111   regcache_raw_supply (regcache, I386_EBX_REGNUM, &pcb->pcb_ebx);
 112   regcache_raw_supply (regcache, I386_EIP_REGNUM, &pcb->pcb_eip);
 113   regcache_raw_supply (regcache, I386_GS_REGNUM, &pcb->pcb_gs);
 114
 115   return 1;
 116 }
 117 \f
 118
 119 /* Prevent warning from -Wmissing-prototypes.  */
 120 void _initialize_i386fbsd_nat (void);
 121
 122 void
 123 _initialize_i386fbsd_nat (void)
 124 {
 125   struct target_ops *t;
 126
 127   /* Add some extra features to the common *BSD/i386 target.  */
 128   t = i386bsd_target ();
 129   t->to_resume = i386fbsd_resume;
 130   t->to_pid_to_exec_file = fbsd_pid_to_exec_file;
 131   t->to_find_memory_regions = fbsd_find_memory_regions;
 132   t->to_make_corefile_notes = fbsd_make_corefile_notes;
 133   add_target (t);
 134
 135   /* Support debugging kernel virtual memory images.  */
 136   bsd_kvm_add_target (i386fbsd_supply_pcb);
 137
 138   /* FreeBSD provides a kern.ps_strings sysctl that we can use to
 139      locate the sigtramp.  That way we can still recognize a sigtramp
 140      if its location is changed in a new kernel.  Of course this is
 141      still based on the assumption that the sigtramp is placed
 142      directly under the location where the program arguments and
 143      environment can be found.  */
 144 #ifdef KERN_PS_STRINGS
 145   {
 146     int mib[2];
 147     u_long ps_strings;
 148     size_t len;
 149
 150     mib[0] = CTL_KERN;
 151     mib[1] = KERN_PS_STRINGS;
 152     len = sizeof (ps_strings);
 153     if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
 154       {
 155         i386fbsd_sigtramp_start_addr = ps_strings - 128;
 156         i386fbsd_sigtramp_end_addr = ps_strings;
 157       }
 158   }
 159 #endif
 160 }