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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 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