1 /* Function return value location for ARM EABI.
2 Copyright (C) 2009-2010 Red Hat, Inc.
3 This file is part of Red Hat elfutils.
4
5 Red Hat elfutils is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by the
7 Free Software Foundation; version 2 of the License.
8
9 Red Hat elfutils is distributed in the hope that it will be useful, but
10 WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 General Public License for more details.
13
14 You should have received a copy of the GNU General Public License along
15 with Red Hat elfutils; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
17
18 Red Hat elfutils is an included package of the Open Invention Network.
19 An included package of the Open Invention Network is a package for which
20 Open Invention Network licensees cross-license their patents. No patent
21 license is granted, either expressly or impliedly, by designation as an
22 included package. Should you wish to participate in the Open Invention
23 Network licensing program, please visit www.openinventionnetwork.com
24 <http://www.openinventionnetwork.com>. */
25
26 #ifdef HAVE_CONFIG_H
27 # include <config.h>
28 #endif
29
30 #include <assert.h>
31 #include <dwarf.h>
32
33 #define BACKEND arm_
34 #include "libebl_CPU.h"
35
36
37 /* r0, or pair r0, r1, or aggregate up to r0-r3. */
38 static const Dwarf_Op loc_intreg[] =
39 {
40 { .atom = DW_OP_reg0 }, { .atom = DW_OP_piece, .number = 4 },
41 { .atom = DW_OP_reg1 }, { .atom = DW_OP_piece, .number = 4 },
42 { .atom = DW_OP_reg2 }, { .atom = DW_OP_piece, .number = 4 },
43 { .atom = DW_OP_reg3 }, { .atom = DW_OP_piece, .number = 4 },
44 };
45 #define nloc_intreg 1
46 #define nloc_intregs(n) (2 * (n))
47
48 /* The return value is a structure and is actually stored in stack space
49 passed in a hidden argument by the caller. But, the compiler
50 helpfully returns the address of that space in r0. */
51 static const Dwarf_Op loc_aggregate[] =
52 {
53 { .atom = DW_OP_breg0, .number = 0 }
54 };
55 #define nloc_aggregate 1
56
57
58 int
arm_return_value_location(Dwarf_Die * functypedie,const Dwarf_Op ** locp)59 arm_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
60 {
61 /* Start with the function's type, and get the DW_AT_type attribute,
62 which is the type of the return value. */
63
64 Dwarf_Attribute attr_mem;
65 Dwarf_Attribute *attr = dwarf_attr_integrate (functypedie, DW_AT_type,
66 &attr_mem);
67 if (attr == NULL)
68 /* The function has no return value, like a `void' function in C. */
69 return 0;
70
71 Dwarf_Die die_mem;
72 Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
73 int tag = dwarf_tag (typedie);
74
75 /* Follow typedefs and qualifiers to get to the actual type. */
76 while (tag == DW_TAG_typedef
77 || tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
78 || tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
79 {
80 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
81 typedie = dwarf_formref_die (attr, &die_mem);
82 tag = dwarf_tag (typedie);
83 }
84
85 Dwarf_Word size;
86 switch (tag)
87 {
88 case -1:
89 return -1;
90
91 case DW_TAG_subrange_type:
92 if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
93 {
94 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
95 typedie = dwarf_formref_die (attr, &die_mem);
96 tag = dwarf_tag (typedie);
97 }
98 /* Fall through. */
99
100 case DW_TAG_base_type:
101 case DW_TAG_enumeration_type:
102 case DW_TAG_pointer_type:
103 case DW_TAG_ptr_to_member_type:
104 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
105 &attr_mem), &size) != 0)
106 {
107 if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
108 size = 4;
109 else
110 return -1;
111 }
112 if (size <= 16)
113 {
114 intreg:
115 *locp = loc_intreg;
116 return size <= 4 ? nloc_intreg : nloc_intregs ((size + 3) / 4);
117 }
118
119 aggregate:
120 *locp = loc_aggregate;
121 return nloc_aggregate;
122
123 case DW_TAG_structure_type:
124 case DW_TAG_class_type:
125 case DW_TAG_union_type:
126 case DW_TAG_array_type:
127 if (dwarf_aggregate_size (typedie, &size) == 0
128 && size > 0 && size <= 4)
129 goto intreg;
130 goto aggregate;
131 }
132
133 /* XXX We don't have a good way to return specific errors from ebl calls.
134 This value means we do not understand the type, but it is well-formed
135 DWARF and might be valid. */
136 return -2;
137 }
138