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 /* Fall through. */
104
105 case DW_TAG_base_type:
106 case DW_TAG_enumeration_type:
107 case DW_TAG_pointer_type:
108 case DW_TAG_ptr_to_member_type:
109 {
110 Dwarf_Attribute attr_mem;
111 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
112 &attr_mem), &size) != 0)
113 {
114 if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
115 size = 8;
116 else
117 return -1;
118 }
119 }
120
121 if (tag == DW_TAG_base_type)
122 {
123 Dwarf_Attribute attr_mem;
124 Dwarf_Word encoding;
125 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
126 &attr_mem),
127 &encoding) != 0)
128 return -1;
129
130 switch (encoding)
131 {
132 case DW_ATE_complex_float:
133 switch (size)
134 {
135 case 4 * 2: /* complex float */
136 case 8 * 2: /* complex double */
137 *locp = loc_ssereg;
138 return nloc_sseregpair;
139 case 16 * 2: /* complex long double */
140 *locp = loc_x87reg;
141 return nloc_x87regpair;
142 }
143 return -2;
144
145 case DW_ATE_float:
146 switch (size)
147 {
148 case 4: /* float */
149 case 8: /* double */
150 *locp = loc_ssereg;
151 return nloc_ssereg;
152 case 16: /* long double */
153 /* XXX distinguish __float128, which is sseregpair?? */
154 *locp = loc_x87reg;
155 return nloc_x87reg;
156 }
157 return -2;
158 }
159 }
160
161 intreg:
162 *locp = loc_intreg;
163 if (size <= 8)
164 return nloc_intreg;
165 if (size <= 16)
166 return nloc_intregpair;
167
168 large:
169 *locp = loc_aggregate;
170 return nloc_aggregate;
171
172 case DW_TAG_structure_type:
173 case DW_TAG_class_type:
174 case DW_TAG_union_type:
175 case DW_TAG_array_type:
176 if (dwarf_aggregate_size (typedie, &size) != 0)
177 goto large;
178 if (size > 16)
179 goto large;
180
181 /* XXX
182 Must examine the fields in picayune ways to determine the
183 actual answer. This will be right for small C structs
184 containing integer types and similarly simple cases.
185 */
186
187 goto intreg;
188 }
189
190 /* XXX We don't have a good way to return specific errors from ebl calls.
191 This value means we do not understand the type, but it is well-formed
192 DWARF and might be valid. */
193 return -2;
194 }
195