1 /* Function return value location for Linux/PPC ABI.
2 Copyright (C) 2005, 2006, 2007 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 ppc_
34 #include "libebl_CPU.h"
35
36
37 /* This is the SVR4 ELF ABI convention, but AIX and Linux do not use it. */
38 #define SVR4_STRUCT_RETURN 0
39
40
41 /* r3, or pair r3, r4. */
42 static const Dwarf_Op loc_intreg[] =
43 {
44 { .atom = DW_OP_reg3 }, { .atom = DW_OP_piece, .number = 4 },
45 { .atom = DW_OP_reg4 }, { .atom = DW_OP_piece, .number = 4 },
46 };
47 #define nloc_intreg 1
48 #define nloc_intregpair 4
49
50 /* f1. */
51 static const Dwarf_Op loc_fpreg[] =
52 {
53 { .atom = DW_OP_regx, .number = 33 }
54 };
55 #define nloc_fpreg 1
56
57 /* The return value is a structure and is actually stored in stack space
58 passed in a hidden argument by the caller. But, the compiler
59 helpfully returns the address of that space in r3. */
60 static const Dwarf_Op loc_aggregate[] =
61 {
62 { .atom = DW_OP_breg3, .number = 0 }
63 };
64 #define nloc_aggregate 1
65
66
67 int
ppc_return_value_location(Dwarf_Die * functypedie,const Dwarf_Op ** locp)68 ppc_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
69 {
70 /* Start with the function's type, and get the DW_AT_type attribute,
71 which is the type of the return value. */
72
73 Dwarf_Attribute attr_mem;
74 Dwarf_Attribute *attr = dwarf_attr_integrate (functypedie, DW_AT_type,
75 &attr_mem);
76 if (attr == NULL)
77 /* The function has no return value, like a `void' function in C. */
78 return 0;
79
80 Dwarf_Die die_mem;
81 Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
82 int tag = dwarf_tag (typedie);
83
84 /* Follow typedefs and qualifiers to get to the actual type. */
85 while (tag == DW_TAG_typedef
86 || tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
87 || tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
88 {
89 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
90 typedie = dwarf_formref_die (attr, &die_mem);
91 tag = dwarf_tag (typedie);
92 }
93
94 Dwarf_Word size;
95 switch (tag)
96 {
97 case -1:
98 return -1;
99
100 case DW_TAG_subrange_type:
101 if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
102 {
103 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
104 typedie = dwarf_formref_die (attr, &die_mem);
105 tag = dwarf_tag (typedie);
106 }
107 /* Fall through. */
108
109 case DW_TAG_base_type:
110 case DW_TAG_enumeration_type:
111 case DW_TAG_pointer_type:
112 case DW_TAG_ptr_to_member_type:
113 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
114 &attr_mem), &size) != 0)
115 {
116 if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
117 size = 4;
118 else
119 return -1;
120 }
121 if (size <= 8)
122 {
123 if (tag == DW_TAG_base_type)
124 {
125 Dwarf_Word encoding;
126 if (dwarf_formudata (dwarf_attr_integrate (typedie,
127 DW_AT_encoding,
128 &attr_mem),
129 &encoding) != 0)
130 return -1;
131 if (encoding == DW_ATE_float)
132 {
133 *locp = loc_fpreg;
134 return nloc_fpreg;
135 }
136 }
137 intreg:
138 *locp = loc_intreg;
139 return size <= 4 ? nloc_intreg : nloc_intregpair;
140 }
141
142 aggregate:
143 *locp = loc_aggregate;
144 return nloc_aggregate;
145
146 case DW_TAG_structure_type:
147 case DW_TAG_class_type:
148 case DW_TAG_union_type:
149 case DW_TAG_array_type:
150 if (SVR4_STRUCT_RETURN
151 && dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
152 &attr_mem), &size) == 0
153 && size > 0 && size <= 8)
154 goto intreg;
155 goto aggregate;
156 }
157
158 /* XXX We don't have a good way to return specific errors from ebl calls.
159 This value means we do not understand the type, but it is well-formed
160 DWARF and might be valid. */
161 return -2;
162 }
163