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1 /* Function return value location for Linux/PPC64 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 ppc64_
37 #include "libebl_CPU.h"
38 
39 
40 /* r3.  */
41 static const Dwarf_Op loc_intreg[] =
42   {
43     { .atom = DW_OP_reg3 }
44   };
45 #define nloc_intreg	1
46 
47 /* f1, or f1:f2, or f1:f4.  */
48 static const Dwarf_Op loc_fpreg[] =
49   {
50     { .atom = DW_OP_regx, .number = 33 }, { .atom = DW_OP_piece, .number = 8 },
51     { .atom = DW_OP_regx, .number = 34 }, { .atom = DW_OP_piece, .number = 8 },
52     { .atom = DW_OP_regx, .number = 35 }, { .atom = DW_OP_piece, .number = 8 },
53     { .atom = DW_OP_regx, .number = 36 }, { .atom = DW_OP_piece, .number = 8 },
54   };
55 #define nloc_fpreg	1
56 #define nloc_fp2regs	4
57 #define nloc_fp4regs	8
58 
59 /* vr2.  */
60 static const Dwarf_Op loc_vmxreg[] =
61   {
62     { .atom = DW_OP_regx, .number = 1124 + 2 }
63   };
64 #define nloc_vmxreg	1
65 
66 /* The return value is a structure and is actually stored in stack space
67    passed in a hidden argument by the caller.  But, the compiler
68    helpfully returns the address of that space in r3.  */
69 static const Dwarf_Op loc_aggregate[] =
70   {
71     { .atom = DW_OP_breg3, .number = 0 }
72   };
73 #define nloc_aggregate 1
74 
75 int
ppc64_return_value_location(Dwarf_Die * functypedie,const Dwarf_Op ** locp)76 ppc64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
77 {
78   /* Start with the function's type, and get the DW_AT_type attribute,
79      which is the type of the return value.  */
80   Dwarf_Die die_mem, *typedie = &die_mem;
81   int tag = dwarf_peeled_die_type (functypedie, typedie);
82   if (tag <= 0)
83     return tag;
84 
85   Dwarf_Word size;
86   switch (tag)
87     {
88     case -1:
89       return -1;
90 
91     case DW_TAG_subrange_type:
92       if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
93 	{
94 	  Dwarf_Attribute attr_mem, *attr;
95 	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
96 	  typedie = dwarf_formref_die (attr, &die_mem);
97 	  tag = DWARF_TAG_OR_RETURN (typedie);
98 	}
99       /* Fall through.  */
100 
101     case DW_TAG_base_type:
102     case DW_TAG_enumeration_type:
103     case DW_TAG_pointer_type:
104     case DW_TAG_ptr_to_member_type:
105       {
106 	Dwarf_Attribute attr_mem;
107 	if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
108 						   &attr_mem), &size) != 0)
109 	  {
110 	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
111 	      size = 8;
112 	    else
113 	      return -1;
114 	}
115       }
116 
117       if (tag == DW_TAG_base_type)
118 	{
119 	  Dwarf_Attribute attr_mem;
120 	  Dwarf_Word encoding;
121 	  if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
122 						     &attr_mem),
123 			       &encoding) != 0)
124 	    return -1;
125 
126 	  if (encoding == DW_ATE_float || encoding == DW_ATE_complex_float)
127 	    {
128 	      *locp = loc_fpreg;
129 	      if (size <= 8)
130 		return nloc_fpreg;
131 	      if (size <= 16)
132 		return nloc_fp2regs;
133 	      if (size <= 32)
134 		return nloc_fp4regs;
135 	    }
136 	}
137       if (size <= 8)
138 	{
139 	intreg:
140 	  *locp = loc_intreg;
141 	  return nloc_intreg;
142 	}
143 
144       /* Else fall through.  */
145     case DW_TAG_structure_type:
146     case DW_TAG_class_type:
147     case DW_TAG_union_type:
148     aggregate:
149       *locp = loc_aggregate;
150       return nloc_aggregate;
151 
152     case DW_TAG_array_type:
153       {
154 	Dwarf_Attribute attr_mem;
155 	bool is_vector;
156 	if (dwarf_formflag (dwarf_attr_integrate (typedie, DW_AT_GNU_vector,
157 						  &attr_mem), &is_vector) == 0
158 	    && is_vector)
159 	  {
160 	    *locp = loc_vmxreg;
161 	    return nloc_vmxreg;
162 	  }
163       }
164       /* Fall through.  */
165 
166     case DW_TAG_string_type:
167       if (dwarf_aggregate_size (typedie, &size) == 0 && size <= 8)
168 	{
169 	  if (tag == DW_TAG_array_type)
170 	    {
171 	      /* Check if it's a character array.  */
172 	      Dwarf_Attribute attr_mem, *attr;
173 	      attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
174 	      typedie = dwarf_formref_die (attr, &die_mem);
175 	      tag = DWARF_TAG_OR_RETURN (typedie);
176 	      if (tag != DW_TAG_base_type)
177 		goto aggregate;
178 	      if (dwarf_formudata (dwarf_attr_integrate (typedie,
179 							 DW_AT_byte_size,
180 							 &attr_mem),
181 				   &size) != 0)
182 		return -1;
183 	      if (size != 1)
184 		goto aggregate;
185 	    }
186 	  goto intreg;
187 	}
188       goto aggregate;
189     }
190 
191   /* XXX We don't have a good way to return specific errors from ebl calls.
192      This value means we do not understand the type, but it is well-formed
193      DWARF and might be valid.  */
194   return -2;
195 }
196