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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
47 : 20 : 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 : 20 : Dwarf_Word sp, newSp, lr, newLr;
54 : :
55 : : /* Stack pointer points to the backchain which contains the previous sp. */
56 [ - + ]: 20 : if (! getfunc (SP_REG, 1, &sp, arg))
57 : 0 : sp = 0;
58 : :
59 : : /* Link register contains previous program counter. */
60 [ + - ]: 20 : if (! getfunc (LR_REG, 1, &lr, arg)
61 [ + + ]: 20 : || lr == 0
62 [ - + ]: 16 : || ! setfunc (-1, 1, &lr, arg))
63 : 4 : return false;
64 : :
65 [ - + ]: 16 : if (! readfunc(sp, &newSp, arg))
66 : 0 : newSp = 0;
67 : :
68 [ - + ]: 16 : if (! readfunc(newSp + LR_OFFSET, &newLr, arg))
69 : 0 : newLr = 0;
70 : :
71 : 16 : setfunc(SP_REG, 1, &newSp, arg);
72 : 16 : setfunc(LR_REG, 1, &newLr, arg);
73 : :
74 : : /* Sanity check the stack grows down. */
75 : 16 : return newSp > sp;
76 : : }
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