1 /* Get previous frame state for an existing frame state.
2 Copyright (C) 2017 Red Hat, Inc.
3 This file is part of elfutils.
4
5 This file is free software; you can redistribute it and/or modify
6 it under the terms of either
7
8 * the GNU Lesser General Public License as published by the Free
9 Software Foundation; either version 3 of the License, or (at
10 your option) any later version
11
12 or
13
14 * the GNU General Public License as published by the Free
15 Software Foundation; either version 2 of the License, or (at
16 your option) any later version
17
18 or both in parallel, as here.
19
20 elfutils is distributed in the hope that it will be useful, but
21 WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 General Public License for more details.
24
25 You should have received copies of the GNU General Public License and
26 the GNU Lesser General Public License along with this program. If
27 not, see <http://www.gnu.org/licenses/>. */
28
29 #ifdef HAVE_CONFIG_H
30 # include <config.h>
31 #endif
32
33 #define BACKEND ppc64_
34
35 #define LR_REG 65 /* Not 108, see ppc_dwarf_to_regno. */
36 #define SP_REG 1
37
38 #define LR_OFFSET 16
39
40 #include "libebl_CPU.h"
41
42 /* Simplistic fallback frame unwinder. SP points to the backchain (contains
43 address of previous stack pointer). At SP offset 16 is the LR save area
44 (contains the value of the previous LR). */
45
46 bool
EBLHOOK(unwind)47 EBLHOOK(unwind) (Ebl *ebl __attribute__ ((unused)),
48 Dwarf_Addr pc __attribute__ ((unused)),
49 ebl_tid_registers_t *setfunc, ebl_tid_registers_get_t *getfunc,
50 ebl_pid_memory_read_t *readfunc, void *arg,
51 bool *signal_framep __attribute__ ((unused)))
52 {
53 Dwarf_Word sp, newSp, lr, newLr;
54
55 /* Stack pointer points to the backchain which contains the previous sp. */
56 if (! getfunc (SP_REG, 1, &sp, arg))
57 sp = 0;
58
59 /* Link register contains previous program counter. */
60 if (! getfunc (LR_REG, 1, &lr, arg)
61 || lr == 0
62 || ! setfunc (-1, 1, &lr, arg))
63 return false;
64
65 if (! readfunc(sp, &newSp, arg))
66 newSp = 0;
67
68 if (! readfunc(newSp + LR_OFFSET, &newLr, arg))
69 newLr = 0;
70
71 setfunc(SP_REG, 1, &newSp, arg);
72 setfunc(LR_REG, 1, &newLr, arg);
73
74 /* Sanity check the stack grows down. */
75 return newSp > sp;
76 }
77