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3379287a JT |
1 | /* Target-dependent code for GNU/Linux on Alpha. |
2 | Copyright 2002 Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GDB. | |
5 | ||
6 | This program is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
8 | the Free Software Foundation; either version 2 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | This program is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with this program; if not, write to the Free Software | |
18 | Foundation, Inc., 59 Temple Place - Suite 330, | |
19 | Boston, MA 02111-1307, USA. */ | |
20 | ||
21 | #include "defs.h" | |
22 | #include "value.h" | |
23 | ||
24 | #include "alpha-tdep.h" | |
25 | ||
26 | /* Under GNU/Linux, signal handler invocations can be identified by the | |
27 | designated code sequence that is used to return from a signal | |
28 | handler. In particular, the return address of a signal handler | |
29 | points to the following sequence (the first instruction is quadword | |
30 | aligned): | |
31 | ||
32 | bis $30,$30,$16 | |
33 | addq $31,0x67,$0 | |
34 | call_pal callsys | |
35 | ||
36 | Each instruction has a unique encoding, so we simply attempt to | |
37 | match the instruction the pc is pointing to with any of the above | |
38 | instructions. If there is a hit, we know the offset to the start | |
39 | of the designated sequence and can then check whether we really are | |
40 | executing in a designated sequence. If not, -1 is returned, | |
41 | otherwise the offset from the start of the desingated sequence is | |
42 | returned. | |
43 | ||
44 | There is a slight chance of false hits: code could jump into the | |
45 | middle of the designated sequence, in which case there is no | |
46 | guarantee that we are in the middle of a sigreturn syscall. Don't | |
47 | think this will be a problem in praxis, though. */ | |
48 | long | |
49 | alpha_linux_sigtramp_offset (CORE_ADDR pc) | |
50 | { | |
51 | unsigned int i[3], w; | |
52 | long off; | |
53 | ||
54 | if (read_memory_nobpt (pc, (char *) &w, 4) != 0) | |
55 | return -1; | |
56 | ||
57 | off = -1; | |
58 | switch (w) | |
59 | { | |
60 | case 0x47de0410: | |
61 | off = 0; | |
62 | break; /* bis $30,$30,$16 */ | |
63 | case 0x43ecf400: | |
64 | off = 4; | |
65 | break; /* addq $31,0x67,$0 */ | |
66 | case 0x00000083: | |
67 | off = 8; | |
68 | break; /* call_pal callsys */ | |
69 | default: | |
70 | return -1; | |
71 | } | |
72 | pc -= off; | |
73 | if (pc & 0x7) | |
74 | { | |
75 | /* designated sequence is not quadword aligned */ | |
76 | return -1; | |
77 | } | |
78 | if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0) | |
79 | return -1; | |
80 | ||
81 | if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083) | |
82 | return off; | |
83 | ||
84 | return -1; | |
85 | } | |
86 | ||
87 | static void | |
88 | alpha_linux_init_abi (struct gdbarch_info info, | |
89 | struct gdbarch *gdbarch) | |
90 | { | |
91 | /* Place holder. */ | |
92 | } | |
93 | ||
94 | void | |
95 | _initialize_alpha_linux_tdep (void) | |
96 | { | |
97 | alpha_gdbarch_register_os_abi (ALPHA_ABI_LINUX, alpha_linux_init_abi); | |
98 | } |