1 /* Function return value location for Linux/i386 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 i386_
37 #include "libebl_CPU.h"
38
39
40 /* %eax, or pair %eax, %edx. */
41 static const Dwarf_Op loc_intreg[] =
42 {
43 { .atom = DW_OP_reg0 }, { .atom = DW_OP_piece, .number = 4 },
44 { .atom = DW_OP_reg2 }, { .atom = DW_OP_piece, .number = 4 },
45 };
46 #define nloc_intreg 1
47 #define nloc_intregpair 4
48
49 /* %st(0). */
50 static const Dwarf_Op loc_fpreg[] =
51 {
52 { .atom = DW_OP_reg11 }
53 };
54 #define nloc_fpreg 1
55
56 /* The return value is a structure and is actually stored in stack space
57 passed in a hidden argument by the caller. But, the compiler
58 helpfully returns the address of that space in %eax. */
59 static const Dwarf_Op loc_aggregate[] =
60 {
61 { .atom = DW_OP_breg0, .number = 0 }
62 };
63 #define nloc_aggregate 1
64
65 int
i386_return_value_location(Dwarf_Die * functypedie,const Dwarf_Op ** locp)66 i386_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
67 {
68 /* Start with the function's type, and get the DW_AT_type attribute,
69 which is the type of the return value. */
70 Dwarf_Die die_mem, *typedie = &die_mem;
71 int tag = dwarf_peeled_die_type (functypedie, typedie);
72 if (tag <= 0)
73 return tag;
74
75 switch (tag)
76 {
77 case -1:
78 return -1;
79
80 case DW_TAG_subrange_type:
81 if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
82 {
83 Dwarf_Attribute attr_mem, *attr;
84 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
85 typedie = dwarf_formref_die (attr, &die_mem);
86 tag = DWARF_TAG_OR_RETURN (typedie);
87 }
88 FALLTHROUGH;
89
90 case DW_TAG_base_type:
91 case DW_TAG_enumeration_type:
92 case DW_TAG_pointer_type:
93 case DW_TAG_ptr_to_member_type:
94 {
95 Dwarf_Word size;
96 Dwarf_Attribute attr_mem;
97 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
98 &attr_mem), &size) != 0)
99 {
100 if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
101 size = 4;
102 else
103 return -1;
104 }
105 if (tag == DW_TAG_base_type)
106 {
107 Dwarf_Word encoding;
108 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
109 &attr_mem),
110 &encoding) != 0)
111 return -1;
112 if (encoding == DW_ATE_float)
113 {
114 if (size > 16)
115 return -2;
116 *locp = loc_fpreg;
117 return nloc_fpreg;
118 }
119 }
120 *locp = loc_intreg;
121 if (size <= 4)
122 return nloc_intreg;
123 if (size <= 8)
124 return nloc_intregpair;
125 }
126 FALLTHROUGH;
127
128 case DW_TAG_structure_type:
129 case DW_TAG_class_type:
130 case DW_TAG_union_type:
131 case DW_TAG_array_type:
132 *locp = loc_aggregate;
133 return nloc_aggregate;
134 }
135
136 /* XXX We don't have a good way to return specific errors from ebl calls.
137 This value means we do not understand the type, but it is well-formed
138 DWARF and might be valid. */
139 return -2;
140 }
141