1 /* Native-dependent code for NetBSD/i386.
2 
3    Copyright 2004 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., 59 Temple Place - Suite 330,
20    Boston, MA 02111-1307, 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 "bsd-kvm.h"
37 
38 static int
39 i386nbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
40 {
41   struct switchframe sf;
42 
43   /* The following is true for NetBSD 1.6.2:
44 
45      The pcb contains %esp and %ebp at the point of the context switch
46      in cpu_switch().  At that point we have a stack frame as
47      described by `struct switchframe', which for NetBSD 1.6.2 has the
48      following layout:
49 
50      interrupt level
51      %edi
52      %esi
53      %ebx
54      %eip
55 
56      we reconstruct the register state as it would look when we just
57      returned from cpu_switch().  */
58 
59   /* The stack pointer shouldn't be zero.  */
60   if (pcb->pcb_esp == 0)
61     return 0;
62 
63   /* Read the stack frame, and check its validity.  We do this by
64      checking if the saved interrupt priority level in the stack frame
65      looks reasonable..  */
66   read_memory (pcb->pcb_esp, (char *) &sf, sizeof sf);
67   if ((unsigned int) sf.sf_ppl < 0x100 && (sf.sf_ppl & 0xf) == 0)
68     {
69       /* Yes, we have a frame that matches cpu_switch().  */
70       pcb->pcb_esp += sizeof (struct switchframe);
71       regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
72       regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
73       regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
74       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
75     }
76   else
77     {
78       /* No, the pcb must have been last updated by savectx().  */
79       pcb->pcb_esp += 4;
80       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf);
81     }
82 
83   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
84   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
85 
86   return 1;
87 }
88 
89 
90 /* Provide a prototype to silence -Wmissing-prototypes.  */
91 void _initialize_i386nbsd_nat (void);
92 
93 void
94 _initialize_i386nbsd_nat (void)
95 {
96   /* We've got nothing to add to the common *BSD/i386 target.  */
97   add_target (i386bsd_target ());
98 
99   /* Support debugging kernel virtual memory images.  */
100   bsd_kvm_add_target (i386nbsd_supply_pcb);
101 }
102