gdb/i386-fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright (C) 2001-2017 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 "x86-xstate.h"
  34 #include "x86-bsd-nat.h"
  35 #include "i386-bsd-nat.h"
  36
  37 /* Resume execution of the inferior process.  If STEP is nonzero,
  38    single-step it.  If SIGNAL is nonzero, give it that signal.  */
  39
  40 static void
  41 i386fbsd_resume (struct target_ops *ops,
  42                  ptid_t ptid, int step, enum gdb_signal signal)
  43 {
  44   pid_t pid = ptid_get_pid (ptid);
  45   int request = PT_STEP;
  46
  47   if (pid == -1)
  48     /* Resume all threads.  This only gets used in the non-threaded
  49        case, where "resume all threads" and "resume inferior_ptid" are
  50        the same.  */
  51     pid = ptid_get_pid (inferior_ptid);
  52
  53   if (!step)
  54     {
  55       struct regcache *regcache = get_current_regcache ();
  56       ULONGEST eflags;
  57
  58       /* Workaround for a bug in FreeBSD.  Make sure that the trace
  59          flag is off when doing a continue.  There is a code path
  60          through the kernel which leaves the flag set when it should
  61          have been cleared.  If a process has a signal pending (such
  62          as SIGALRM) and we do a PT_STEP, the process never really has
  63          a chance to run because the kernel needs to notify the
  64          debugger that a signal is being sent.  Therefore, the process
  65          never goes through the kernel's trap() function which would
  66          normally clear it.  */
  67
  68       regcache_cooked_read_unsigned (regcache, I386_EFLAGS_REGNUM,
  69                                      &eflags);
  70       if (eflags & 0x0100)
  71         regcache_cooked_write_unsigned (regcache, I386_EFLAGS_REGNUM,
  72                                         eflags & ~0x0100);
  73
  74       request = PT_CONTINUE;
  75     }
  76
  77   /* An addres of (caddr_t) 1 tells ptrace to continue from where it
  78      was.  (If GDB wanted it to start some other way, we have already
  79      written a new PC value to the child.)  */
  80   if (ptrace (request, pid, (caddr_t) 1,
  81               gdb_signal_to_host (signal)) == -1)
  82     perror_with_name (("ptrace"));
  83 }
  84 \f
  85
  86 /* Support for debugging kernel virtual memory images.  */
  87
  88 #include <machine/pcb.h>
  89
  90 #include "bsd-kvm.h"
  91
  92 static int
  93 i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  94 {
  95   /* The following is true for FreeBSD 4.7:
  96
  97      The pcb contains %eip, %ebx, %esp, %ebp, %esi, %edi and %gs.
  98      This accounts for all callee-saved registers specified by the
  99      psABI and then some.  Here %esp contains the stack pointer at the
 100      point just after the call to cpu_switch().  From this information
 101      we reconstruct the register state as it would look when we just
 102      returned from cpu_switch().  */
 103
 104   /* The stack pointer shouldn't be zero.  */
 105   if (pcb->pcb_esp == 0)
 106     return 0;
 107
 108   pcb->pcb_esp += 4;
 109   regcache_raw_supply (regcache, I386_EDI_REGNUM, &pcb->pcb_edi);
 110   regcache_raw_supply (regcache, I386_ESI_REGNUM, &pcb->pcb_esi);
 111   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
 112   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
 113   regcache_raw_supply (regcache, I386_EBX_REGNUM, &pcb->pcb_ebx);
 114   regcache_raw_supply (regcache, I386_EIP_REGNUM, &pcb->pcb_eip);
 115   regcache_raw_supply (regcache, I386_GS_REGNUM, &pcb->pcb_gs);
 116
 117   return 1;
 118 }
 119 \f
 120
 121 #ifdef PT_GETXSTATE_INFO
 122 /* Implement the to_read_description method.  */
 123
 124 static const struct target_desc *
 125 i386fbsd_read_description (struct target_ops *ops)
 126 {
 127   static int xsave_probed;
 128   static uint64_t xcr0;
 129
 130   if (!xsave_probed)
 131     {
 132       struct ptrace_xstate_info info;
 133
 134       if (ptrace (PT_GETXSTATE_INFO, ptid_get_pid (inferior_ptid),
 135                   (PTRACE_TYPE_ARG3) &info, sizeof (info)) == 0)
 136         {
 137           x86bsd_xsave_len = info.xsave_len;
 138           xcr0 = info.xsave_mask;
 139         }
 140       xsave_probed = 1;
 141     }
 142
 143   if (x86bsd_xsave_len == 0)
 144     xcr0 = X86_XSTATE_SSE_MASK;
 145
 146   return i386_target_description (xcr0);
 147 }
 148 #endif
 149
 150 void
 151 _initialize_i386fbsd_nat (void)
 152 {
 153   struct target_ops *t;
 154
 155   /* Add some extra features to the common *BSD/i386 target.  */
 156   t = i386bsd_target ();
 157
 158 #ifdef PT_GETXSTATE_INFO
 159   t->to_read_description = i386fbsd_read_description;
 160 #endif
 161
 162   t->to_resume = i386fbsd_resume;
 163   fbsd_nat_add_target (t);
 164
 165   /* Support debugging kernel virtual memory images.  */
 166   bsd_kvm_add_target (i386fbsd_supply_pcb);
 167
 168 #ifdef KERN_PROC_SIGTRAMP
 169   /* Normally signal frames are detected via i386fbsd_sigtramp_p.
 170      However, FreeBSD 9.2 through 10.1 do not include the page holding
 171      the signal code in core dumps.  These releases do provide a
 172      kern.proc.sigtramp.<pid> sysctl that returns the location of the
 173      signal trampoline for a running process.  We fetch the location
 174      of the current (gdb) process and use this to identify signal
 175      frames in core dumps from these releases.  */
 176   {
 177     int mib[4];
 178     struct kinfo_sigtramp kst;
 179     size_t len;
 180
 181     mib[0] = CTL_KERN;
 182     mib[1] = KERN_PROC;
 183     mib[2] = KERN_PROC_SIGTRAMP;
 184     mib[3] = getpid ();
 185     len = sizeof (kst);
 186     if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
 187       {
 188         i386fbsd_sigtramp_start_addr = (uintptr_t) kst.ksigtramp_start;
 189         i386fbsd_sigtramp_end_addr = (uintptr_t) kst.ksigtramp_end;
 190       }
 191   }
 192 #endif
 193 }