1 /* Function return value location for Linux/x86-64 ABI.
2 Copyright (C) 2005-2010, 2014 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 #include <assert.h>
34 #include <dwarf.h>
35
36 #define BACKEND x86_64_
37 #include "libebl_CPU.h"
38
39
40 /* %rax, or pair %rax, %rdx. */
41 static const Dwarf_Op loc_intreg[] =
42 {
43 { .atom = DW_OP_reg0 }, { .atom = DW_OP_piece, .number = 8 },
44 { .atom = DW_OP_reg1 }, { .atom = DW_OP_piece, .number = 8 },
45 };
46 #define nloc_intreg 1
47 #define nloc_intregpair 4
48
49 /* %st(0), or pair %st(0), %st(1). */
50 static const Dwarf_Op loc_x87reg[] =
51 {
52 { .atom = DW_OP_regx, .number = 33 },
53 { .atom = DW_OP_piece, .number = 10 },
54 { .atom = DW_OP_regx, .number = 34 },
55 { .atom = DW_OP_piece, .number = 10 },
56 };
57 #define nloc_x87reg 1
58 #define nloc_x87regpair 4
59
60 /* %xmm0, or pair %xmm0, %xmm1. */
61 static const Dwarf_Op loc_ssereg[] =
62 {
63 { .atom = DW_OP_reg17 }, { .atom = DW_OP_piece, .number = 16 },
64 { .atom = DW_OP_reg18 }, { .atom = DW_OP_piece, .number = 16 },
65 };
66 #define nloc_ssereg 1
67 #define nloc_sseregpair 4
68
69 /* The return value is a structure and is actually stored in stack space
70 passed in a hidden argument by the caller. But, the compiler
71 helpfully returns the address of that space in %rax. */
72 static const Dwarf_Op loc_aggregate[] =
73 {
74 { .atom = DW_OP_breg0, .number = 0 }
75 };
76 #define nloc_aggregate 1
77
78
79 int
x86_64_return_value_location(Dwarf_Die * functypedie,const Dwarf_Op ** locp)80 x86_64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
81 {
82 /* Start with the function's type, and get the DW_AT_type attribute,
83 which is the type of the return value. */
84 Dwarf_Die die_mem, *typedie = &die_mem;
85 int tag = dwarf_peeled_die_type (functypedie, typedie);
86 if (tag <= 0)
87 return tag;
88
89 Dwarf_Word size;
90 switch (tag)
91 {
92 case -1:
93 return -1;
94
95 case DW_TAG_subrange_type:
96 if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
97 {
98 Dwarf_Attribute attr_mem, *attr;
99 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
100 typedie = dwarf_formref_die (attr, &die_mem);
101 tag = DWARF_TAG_OR_RETURN (typedie);
102 }
103 FALLTHROUGH;
104
105 case DW_TAG_base_type:
106 case DW_TAG_enumeration_type:
107 CASE_POINTER:
108 {
109 Dwarf_Attribute attr_mem;
110 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
111 &attr_mem), &size) != 0)
112 {
113 if (dwarf_is_pointer (tag))
114 size = 8;
115 else
116 return -1;
117 }
118 }
119
120 if (tag == DW_TAG_base_type)
121 {
122 Dwarf_Attribute attr_mem;
123 Dwarf_Word encoding;
124 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
125 &attr_mem),
126 &encoding) != 0)
127 return -1;
128
129 switch (encoding)
130 {
131 case DW_ATE_complex_float:
132 switch (size)
133 {
134 case 4 * 2: /* complex float */
135 case 8 * 2: /* complex double */
136 *locp = loc_ssereg;
137 return nloc_sseregpair;
138 case 16 * 2: /* complex long double */
139 *locp = loc_x87reg;
140 return nloc_x87regpair;
141 }
142 return -2;
143
144 case DW_ATE_float:
145 switch (size)
146 {
147 case 4: /* float */
148 case 8: /* double */
149 *locp = loc_ssereg;
150 return nloc_ssereg;
151 case 16: /* long double */
152 /* XXX distinguish __float128, which is sseregpair?? */
153 *locp = loc_x87reg;
154 return nloc_x87reg;
155 }
156 return -2;
157 }
158 }
159
160 intreg:
161 *locp = loc_intreg;
162 if (size <= 8)
163 return nloc_intreg;
164 if (size <= 16)
165 return nloc_intregpair;
166
167 large:
168 *locp = loc_aggregate;
169 return nloc_aggregate;
170
171 case DW_TAG_structure_type:
172 case DW_TAG_class_type:
173 case DW_TAG_union_type:
174 case DW_TAG_array_type:
175 if (dwarf_aggregate_size (typedie, &size) != 0)
176 goto large;
177 if (size > 16)
178 goto large;
179
180 /* XXX
181 Must examine the fields in picayune ways to determine the
182 actual answer. This will be right for small C structs
183 containing integer types and similarly simple cases.
184 */
185
186 goto intreg;
187 }
188
189 /* XXX We don't have a good way to return specific errors from ebl calls.
190 This value means we do not understand the type, but it is well-formed
191 DWARF and might be valid. */
192 return -2;
193 }
194