gdb/i386obsd-nat.c

   1 /* Native-dependent code for OpenBSD/i386.
   2
   3    Copyright (C) 2002, 2003, 2004, 2006, 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 "gdbcore.h"
  22 #include "regcache.h"
  23 #include "target.h"
  24
  25 #include <sys/param.h>
  26 #include <sys/sysctl.h>
  27 #include <machine/frame.h>
  28 #include <machine/pcb.h>
  29
  30 #include "i386-tdep.h"
  31 #include "i386bsd-nat.h"
  32 #include "bsd-kvm.h"
  33
  34 static int
  35 i386obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  36 {
  37   struct switchframe sf;
  38
  39   /* The following is true for OpenBSD 3.6:
  40
  41      The pcb contains %esp and %ebp at the point of the context switch
  42      in cpu_switch().  At that point we have a stack frame as
  43      described by `struct switchframe', which for OpenBSD 3.6 has the
  44      following layout:
  45
  46      interrupt level
  47      %edi
  48      %esi
  49      %ebx
  50      %eip
  51
  52      we reconstruct the register state as it would look when we just
  53      returned from cpu_switch().  */
  54
  55   /* The stack pointer shouldn't be zero.  */
  56   if (pcb->pcb_esp == 0)
  57     return 0;
  58
  59   /* Read the stack frame, and check its validity.  We do this by
  60      checking if the saved interrupt priority level in the stack frame
  61      looks reasonable..  */
  62   read_memory (pcb->pcb_esp, (char *) &sf, sizeof sf);
  63   if ((unsigned int) sf.sf_ppl < 0x100 && (sf.sf_ppl & 0xf) == 0)
  64     {
  65       /* Yes, we have a frame that matches cpu_switch().  */
  66       pcb->pcb_esp += sizeof (struct switchframe);
  67       regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
  68       regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
  69       regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
  70       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
  71     }
  72   else
  73     {
  74       /* No, the pcb must have been last updated by savectx().  */
  75       pcb->pcb_esp += 4;
  76       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf);
  77     }
  78
  79   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
  80   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
  81
  82   return 1;
  83 }
  84 \f
  85
  86 /* Prevent warning from -Wmissing-prototypes.  */
  87 void _initialize_i386obsd_nat (void);
  88
  89 void
  90 _initialize_i386obsd_nat (void)
  91 {
  92   /* We've got nothing to add to the common *BSD/i386 target.  */
  93   add_target (i386bsd_target ());
  94
  95   /* Support debugging kernel virtual memory images.  */
  96   bsd_kvm_add_target (i386obsd_supply_pcb);
  97
  98   /* OpenBSD provides a vm.psstrings sysctl that we can use to locate
  99      the sigtramp.  That way we can still recognize a sigtramp if its
 100      location is changed in a new kernel.  This is especially
 101      important for OpenBSD, since it uses a different memory layout
 102      than NetBSD, yet we cannot distinguish between the two.
 103
 104      Of course this is still based on the assumption that the sigtramp
 105      is placed directly under the location where the program arguments
 106      and environment can be found.  */
 107 #ifdef VM_PSSTRINGS
 108   {
 109     struct _ps_strings _ps;
 110     int mib[2];
 111     size_t len;
 112
 113     mib[0] = CTL_VM;
 114     mib[1] = VM_PSSTRINGS;
 115     len = sizeof (_ps);
 116     if (sysctl (mib, 2, &_ps, &len, NULL, 0) == 0)
 117       {
 118         i386obsd_sigtramp_start_addr = (u_long) _ps.val - 128;
 119         i386obsd_sigtramp_end_addr = (u_long) _ps.val;
 120       }
 121   }
 122 #endif
 123 }