1 /* Native-dependent code for OpenBSD/i386.
2 
3    Copyright 2002, 2003, 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 "obsd-nat.h"
29 #include "i386bsd-nat.h"
30 
31 #include <sys/param.h>
32 #include <sys/sysctl.h>
33 
34 /* Support for debugging kernel virtual memory images.  */
35 
36 #include <machine/frame.h>
37 #include <machine/pcb.h>
38 
39 #include "bsd-kvm.h"
40 
41 static int
42 i386obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
43 {
44   struct switchframe sf;
45 
46   /* The following is true for OpenBSD 4.3:
47 
48      The pcb contains %esp and %ebp at the point of the context switch
49      in cpu_switchto().  At that point we have a stack frame as
50      described by `struct switchframe', which for OpenBSD 4.3 has the
51      following layout:
52 
53      %edi
54      %esi
55      %ebx
56      %eip
57 
58      we reconstruct the register state as it would look when we just
59      returned from cpu_switchto().
60 
61      For crash dumps, the state is saved by savectx().  In that case
62      we just reconstruct the register state as if we just returned
63      from dumsys().  */
64 
65   /* The stack pointer shouldn't be zero.  */
66   if (pcb->pcb_esp == 0)
67     return 0;
68 
69   if ((pcb->pcb_flags & PCB_SAVECTX) == 0)
70     {
71       /* Yes, we have a frame that matches cpu_switchto().  */
72       read_memory (pcb->pcb_esp, (char *) &sf, sizeof sf);
73       pcb->pcb_esp += sizeof (struct switchframe);
74       regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
75       regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
76       regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
77       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
78     }
79   else
80     {
81       /* No, the pcb must have been last updated by savectx().  */
82       pcb->pcb_esp = pcb->pcb_ebp;
83       pcb->pcb_ebp = read_memory_integer(pcb->pcb_esp, 4);
84       sf.sf_eip = read_memory_integer(pcb->pcb_esp + 4, 4);
85       regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
86     }
87 
88   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
89   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
90 
91   return 1;
92 }
93 
94 
95 /* Prevent warning from -Wmissing-prototypes.  */
96 void _initialize_i386obsd_nat (void);
97 
98 void
99 _initialize_i386obsd_nat (void)
100 {
101   struct target_ops *t;
102 
103   /* OpenBSD provides a vm.psstrings sysctl that we can use to locate
104      the sigtramp.  That way we can still recognize a sigtramp if its
105      location is changed in a new kernel.  This is especially
106      important for OpenBSD, since it uses a different memory layout
107      than NetBSD, yet we cannot distinguish between the two.
108 
109      Of course this is still based on the assumption that the sigtramp
110      is placed directly under the location where the program arguments
111      and environment can be found.  */
112 #ifdef VM_PSSTRINGS
113   {
114     struct _ps_strings _ps;
115     int mib[2];
116     size_t len;
117 
118     mib[0] = CTL_VM;
119     mib[1] = VM_PSSTRINGS;
120     len = sizeof (_ps);
121     if (sysctl (mib, 2, &_ps, &len, NULL, 0) == 0)
122       {
123 	i386obsd_sigtramp_start_addr = (CORE_ADDR)_ps.val - 128;
124 	i386obsd_sigtramp_end_addr = (CORE_ADDR)_ps.val;
125       }
126   }
127 #endif
128 
129   /* Add some extra features to the common *BSD/i386 target.  */
130   t = i386bsd_target ();
131   t->to_pid_to_str = obsd_pid_to_str;
132   t->to_find_new_threads = obsd_find_new_threads;
133   t->to_wait = obsd_wait;
134   add_target (t);
135 
136   /* Support debugging kernel virtual memory images.  */
137   bsd_kvm_add_target (i386obsd_supply_pcb);
138 }
139