1/* libunwind - a platform-independent unwind library
2   Copyright (C) 2002-2004 Hewlett-Packard Co
3	Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
4
5This file is part of libunwind.
6
7Permission is hereby granted, free of charge, to any person obtaining
8a copy of this software and associated documentation files (the
9"Software"), to deal in the Software without restriction, including
10without limitation the rights to use, copy, modify, merge, publish,
11distribute, sublicense, and/or sell copies of the Software, and to
12permit persons to whom the Software is furnished to do so, subject to
13the following conditions:
14
15The above copyright notice and this permission notice shall be
16included in all copies or substantial portions of the Software.
17
18THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
22LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
23OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
24WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
25
26#include "unwind_i.h"
27#include "offsets.h"
28
29PROTECTED int
30unw_step (unw_cursor_t *cursor)
31{
32  struct cursor *c = (struct cursor *) cursor;
33  int ret, i;
34
35  Debug (1, "(cursor=%p, ip=0x%08x)\n", c, (unsigned) c->dwarf.ip);
36
37  /* ANDROID support update. */
38  /* Save the current ip/cfa to prevent looping if the decode yields
39     the same ip/cfa as before. */
40  unw_word_t old_ip = c->dwarf.ip;
41  unw_word_t old_cfa = c->dwarf.cfa;
42  /* End of ANDROID update. */
43
44  /* Try DWARF-based unwinding... */
45  ret = dwarf_step (&c->dwarf);
46
47  if (ret < 0)
48    {
49      /* DWARF failed, let's see if we can follow the frame-chain
50	 or skip over the signal trampoline.  */
51      struct dwarf_loc ebp_loc, eip_loc;
52
53      /* We could get here because of missing/bad unwind information.
54         Validate all addresses before dereferencing. */
55      c->validate = 1;
56
57      Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
58
59      if (unw_is_signal_frame (cursor))
60        {
61          ret = unw_handle_signal_frame(cursor);
62	  if (ret < 0)
63	    {
64	      Debug (2, "returning 0\n");
65	      return 0;
66	    }
67        }
68      else
69	{
70	  ret = dwarf_get (&c->dwarf, c->dwarf.loc[EBP], &c->dwarf.cfa);
71	  if (ret < 0)
72	    {
73	      Debug (2, "returning %d\n", ret);
74	      return ret;
75	    }
76
77	  Debug (13, "[EBP=0x%x] = 0x%x\n", DWARF_GET_LOC (c->dwarf.loc[EBP]),
78		 c->dwarf.cfa);
79
80	  ebp_loc = DWARF_LOC (c->dwarf.cfa, 0);
81	  eip_loc = DWARF_LOC (c->dwarf.cfa + 4, 0);
82	  c->dwarf.cfa += 8;
83
84	  /* Mark all registers unsaved, since we don't know where
85	     they are saved (if at all), except for the EBP and
86	     EIP.  */
87	  for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
88	    c->dwarf.loc[i] = DWARF_NULL_LOC;
89
90          c->dwarf.loc[EBP] = ebp_loc;
91          c->dwarf.loc[EIP] = eip_loc;
92	}
93      c->dwarf.ret_addr_column = EIP;
94
95      if (!DWARF_IS_NULL_LOC (c->dwarf.loc[EBP]))
96	{
97	  ret = dwarf_get (&c->dwarf, c->dwarf.loc[EIP], &c->dwarf.ip);
98	  if (ret < 0)
99	    {
100	      Debug (13, "dwarf_get([EIP=0x%x]) failed\n", DWARF_GET_LOC (c->dwarf.loc[EIP]));
101	      Debug (2, "returning %d\n", ret);
102	      return ret;
103	    }
104	  else
105	    {
106	      Debug (13, "[EIP=0x%x] = 0x%x\n", DWARF_GET_LOC (c->dwarf.loc[EIP]),
107		c->dwarf.ip);
108	    }
109	}
110      else
111	c->dwarf.ip = 0;
112    }
113
114  /* ANDROID support update. */
115  if (ret >= 0)
116    {
117      if (c->dwarf.ip)
118        {
119          /* Adjust the pc to the instruction before. */
120          c->dwarf.ip--;
121        }
122      /* If the decode yields the exact same ip/cfa as before, then indicate
123         the unwind is complete. */
124      if (old_ip == c->dwarf.ip && old_cfa == c->dwarf.cfa)
125        return 0;
126      c->dwarf.frame++;
127    }
128  /* End of ANDROID update. */
129  ret = (c->dwarf.ip == 0) ? 0 : 1;
130  Debug (2, "returning %d\n", ret);
131  return ret;
132}
133