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
5 This file is part of libunwind.
6
7 Permission is hereby granted, free of charge, to any person obtaining
8 a copy of this software and associated documentation files (the
9 "Software"), to deal in the Software without restriction, including
10 without limitation the rights to use, copy, modify, merge, publish,
11 distribute, sublicense, and/or sell copies of the Software, and to
12 permit persons to whom the Software is furnished to do so, subject to
13 the following conditions:
14
15 The above copyright notice and this permission notice shall be
16 included in all copies or substantial portions of the Software.
17
18 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
19 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
21 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
22 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
23 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
24 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
25
26 #include "unwind_i.h"
27 #include "offsets.h"
28
29 PROTECTED int
unw_step(unw_cursor_t * cursor)30 unw_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 {
126 Dprintf ("%s: ip and cfa unchanged; stopping here (ip=0x%lx)\n",
127 __FUNCTION__, (long) c->dwarf.ip);
128 return -UNW_EBADFRAME;
129 }
130 c->dwarf.frame++;
131 }
132 /* End of ANDROID update. */
133 ret = (c->dwarf.ip == 0) ? 0 : 1;
134 Debug (2, "returning %d\n", ret);
135 return ret;
136 }
137