gnu/dist/gdb6/gdb/i386nbsd-nat.c

   1 /* Native-dependent code for NetBSD/i386.
   2
   3    Copyright (C) 2004, 2005 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 "gdbcore.h"
  24 #include "regcache.h"
  25 #include "target.h"
  26
  27 #include "i386-tdep.h"
  28 #include "i386bsd-nat.h"
  29
  30 /* Support for debugging kernel virtual memory images.  */
  31
  32 #include <sys/types.h>
  33 #include <machine/frame.h>
  34 #include <machine/pcb.h>
  35
  36 #include "nbsd-nat.h"
  37 #include "bsd-kvm.h"
  38
  39 static int
  40 i386nbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
  41 {
  42   struct switchframe sf;
  43
  44   /* The following is true for NetBSD 1.6.2 and after:
  45
  46      The pcb contains %esp and %ebp at the point of the context switch
  47      in cpu_switch()/cpu_switchto().  At that point we have a stack frame as
  48      described by `struct switchframe', which for NetBSD (2.0 and later) has
  49      the following layout:
  50
  51      %edi
  52      %esi
  53      %ebx
  54      return address
  55
  56      we reconstruct the register state as it would look when we just
  57      returned from cpu_switch()/cpu_switchto().
  58
  59      For core dumps the pcb is saved by savectx()/dumpsys() and contains the
  60      stack pointer and frame pointer.  A new dumpsys() fakes a switchframe
  61      whereas older code isn't reliable so use an iffy heuristic to detect this
  62      and use the frame pointer to recover enough state.  */
  63
  64   /* The stack pointer shouldn't be zero.  */
  65   if (pcb->pcb_esp == 0)
  66     return 0;
  67
  68   read_memory (pcb->pcb_esp, (gdb_byte *) &sf, sizeof sf);
  69
  70   if ( (unsigned long)sf.sf_eip >= (unsigned long)0xc0100000 )
  71     {
  72       /* Yes, we have a switchframe that matches cpu_switchto() or
  73          the new dumpsys().  */
  74
  75       pcb->pcb_esp += sizeof (struct switchframe);
  76       regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
  77       regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
  78       regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
  79       regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
  80       regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
  81       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
  82     }
  83   else
  84     {
  85       CORE_ADDR pc, fp;
  86
  87       /* No, the pcb must have been last updated by savectx() in old
  88          dumpsys(). Use the frame pointer to recover enough state.  */
  89
  90       read_memory (pcb->pcb_ebp, (gdb_byte *) &fp, sizeof(fp));
  91       read_memory (pcb->pcb_ebp + 4, (gdb_byte *) &pc, sizeof(pc));
  92
  93       regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_ebp);
  94       regcache_raw_supply (regcache, I386_EBP_REGNUM, &fp);
  95       regcache_raw_supply (regcache, I386_EIP_REGNUM, &pc);
  96     }
  97
  98   return 1;
  99 }
 100 \f
 101
 102 /* Provide a prototype to silence -Wmissing-prototypes.  */
 103 void _initialize_i386nbsd_nat (void);
 104
 105 void
 106 _initialize_i386nbsd_nat (void)
 107 {
 108   struct target_ops *t;
 109
 110   /* Add some extra features to the common *BSD/i386 target.  */
 111   t = i386bsd_target ();
 112   t->to_pid_to_exec_file = nbsd_pid_to_exec_file;
 113   add_target (t);
 114
 115   /* Support debugging kernel virtual memory images.  */
 116   bsd_kvm_add_target (i386nbsd_supply_pcb);
 117 }