1/* libunwind - a platform-independent unwind library
2   Copyright (C) 2006-2007 IBM
3   Contributed by
4     Corey Ashford <cjashfor@us.ibm.com>
5     Jose Flavio Aguilar Paulino <jflavio@br.ibm.com> <joseflavio@gmail.com>
6
7This file is part of libunwind.
8
9Permission is hereby granted, free of charge, to any person obtaining
10a copy of this software and associated documentation files (the
11"Software"), to deal in the Software without restriction, including
12without limitation the rights to use, copy, modify, merge, publish,
13distribute, sublicense, and/or sell copies of the Software, and to
14permit persons to whom the Software is furnished to do so, subject to
15the following conditions:
16
17The above copyright notice and this permission notice shall be
18included in all copies or substantial portions of the Software.
19
20THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
24LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
25OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
26WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
27
28#include <libunwind_i.h>
29
30PROTECTED int
31unw_is_signal_frame (unw_cursor_t * cursor)
32{
33  struct cursor *c = (struct cursor *) cursor;
34  unw_word_t w0, w1, ip;
35  unw_addr_space_t as;
36  unw_accessors_t *a;
37  void *arg;
38  int ret;
39
40  as = c->dwarf.as;
41  as->validate = 1;		/* Don't trust the ip */
42  arg = c->dwarf.as_arg;
43
44  /* Check if return address points at sigreturn sequence.
45     on ppc64 Linux that is (see libc.so):
46     0x38210080  addi r1, r1, 128  // pop the stack
47     0x380000ac  li r0, 172        // invoke system service 172
48     0x44000002  sc
49   */
50
51  ip = c->dwarf.ip;
52  if (ip == 0)
53    return 0;
54
55  /* Read up two 8-byte words at the IP.  We are only looking at 3
56     consecutive 32-bit words, so the second 8-byte word needs to be
57     shifted right by 32 bits (think big-endian) */
58
59  a = unw_get_accessors (as);
60  if ((ret = (*a->access_mem) (as, ip, &w0, 0, arg)) < 0
61      || (ret = (*a->access_mem) (as, ip + 8, &w1, 0, arg)) < 0)
62    return 0;
63  w1 >>= 32;
64  return (w0 == 0x38210080380000ac && w1 == 0x44000002);
65
66}
67