gdb/i386fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright (C) 2001-2015 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 #include <sys/user.h>
  29
  30 #include "fbsd-nat.h"
  31 #include "i386-tdep.h"
  32 #include "x86-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 gdb_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               gdb_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 <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
 130 #ifdef HAVE_PT_GETDBREGS
 131
 132   x86_use_watchpoints (t);
 133
 134   x86_dr_low.set_control = i386bsd_dr_set_control;
 135   x86_dr_low.set_addr = i386bsd_dr_set_addr;
 136   x86_dr_low.get_addr = i386bsd_dr_get_addr;
 137   x86_dr_low.get_status = i386bsd_dr_get_status;
 138   x86_dr_low.get_control = i386bsd_dr_get_control;
 139   x86_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   add_target (t);
 148
 149   /* Support debugging kernel virtual memory images.  */
 150   bsd_kvm_add_target (i386fbsd_supply_pcb);
 151
 152 #ifdef KERN_PROC_SIGTRAMP
 153   /* Normally signal frames are detected via i386fbsd_sigtramp_p.
 154      However, FreeBSD 9.2 through 10.1 do not include the page holding
 155      the signal code in core dumps.  These releases do provide a
 156      kern.proc.sigtramp.<pid> sysctl that returns the location of the
 157      signal trampoline for a running process.  We fetch the location
 158      of the current (gdb) process and use this to identify signal
 159      frames in core dumps from these releases.  */
 160   {
 161     int mib[4];
 162     struct kinfo_sigtramp kst;
 163     size_t len;
 164
 165     mib[0] = CTL_KERN;
 166     mib[1] = KERN_PROC;
 167     mib[2] = KERN_PROC_SIGTRAMP;
 168     mib[3] = getpid ();
 169     len = sizeof (kst);
 170     if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
 171       {
 172         i386fbsd_sigtramp_start_addr = (uintptr_t) kst.ksigtramp_start;
 173         i386fbsd_sigtramp_end_addr = (uintptr_t) kst.ksigtramp_end;
 174       }
 175   }
 176 #endif
 177 }