1/* Function return value location for Linux/PPC ABI.
2   Copyright (C) 2005, 2006, 2007, 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 ppc_
37#include "libebl_CPU.h"
38
39
40/* This is the SVR4 ELF ABI convention, but AIX and Linux do not use it.  */
41#define SVR4_STRUCT_RETURN 0
42
43
44/* r3, or pair r3, r4, or quad r3-r6.  */
45static const Dwarf_Op loc_intreg[] =
46  {
47    { .atom = DW_OP_reg3 }, { .atom = DW_OP_piece, .number = 4 },
48    { .atom = DW_OP_reg4 }, { .atom = DW_OP_piece, .number = 4 },
49    { .atom = DW_OP_reg5 }, { .atom = DW_OP_piece, .number = 4 },
50    { .atom = DW_OP_reg6 }, { .atom = DW_OP_piece, .number = 4 },
51  };
52#define nloc_intreg	1
53#define nloc_intregpair	4
54#define nloc_intregquad	8
55
56/* f1.  */
57static const Dwarf_Op loc_fpreg[] =
58  {
59    { .atom = DW_OP_regx, .number = 33 }
60  };
61#define nloc_fpreg	1
62
63/* vr2.  */
64static const Dwarf_Op loc_vmxreg[] =
65  {
66    { .atom = DW_OP_regx, .number = 1124 + 2 }
67  };
68#define nloc_vmxreg	1
69
70/* The return value is a structure and is actually stored in stack space
71   passed in a hidden argument by the caller.  But, the compiler
72   helpfully returns the address of that space in r3.  */
73static const Dwarf_Op loc_aggregate[] =
74  {
75    { .atom = DW_OP_breg3, .number = 0 }
76  };
77#define nloc_aggregate 1
78
79
80/* XXX We should check the SHT_GNU_ATTRIBUTES bits here (or in ppc_init).  */
81static bool
82ppc_altivec_abi (void)
83{
84  return true;
85}
86
87int
88ppc_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
89{
90  /* Start with the function's type, and get the DW_AT_type attribute,
91     which is the type of the return value.  */
92  Dwarf_Die die_mem, *typedie = &die_mem;
93  int tag = dwarf_peeled_die_type (functypedie, typedie);
94  if (tag <= 0)
95    return tag;
96
97  Dwarf_Word size;
98  switch (tag)
99    {
100    case -1:
101      return -1;
102
103    case DW_TAG_subrange_type:
104      if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
105	{
106	  Dwarf_Attribute attr_mem, *attr;
107	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
108	  typedie = dwarf_formref_die (attr, &die_mem);
109	  tag = DWARF_TAG_OR_RETURN (typedie);
110	}
111      /* Fall through.  */
112
113    case DW_TAG_base_type:
114    case DW_TAG_enumeration_type:
115    case DW_TAG_pointer_type:
116    case DW_TAG_ptr_to_member_type:
117      {
118	Dwarf_Attribute attr_mem;
119	if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
120						   &attr_mem), &size) != 0)
121	  {
122	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
123	      size = 4;
124	    else
125	      return -1;
126	  }
127      }
128
129      if (size <= 8)
130	{
131	  if (tag == DW_TAG_base_type)
132	    {
133	      Dwarf_Attribute attr_mem;
134	      Dwarf_Word encoding;
135	      if (dwarf_formudata (dwarf_attr_integrate (typedie,
136							 DW_AT_encoding,
137							 &attr_mem),
138				   &encoding) != 0)
139		return -1;
140	      if (encoding == DW_ATE_float)
141		{
142		  *locp = loc_fpreg;
143		  return nloc_fpreg;
144		}
145	    }
146	intreg:
147	  *locp = loc_intreg;
148	  return size <= 4 ? nloc_intreg : nloc_intregpair;
149	}
150
151    aggregate:
152      *locp = loc_aggregate;
153      return nloc_aggregate;
154
155    case DW_TAG_array_type:
156      {
157	Dwarf_Attribute attr_mem;
158	bool is_vector;
159	if (dwarf_formflag (dwarf_attr_integrate (typedie, DW_AT_GNU_vector,
160						  &attr_mem), &is_vector) == 0
161	    && is_vector
162	    && dwarf_aggregate_size (typedie, &size) == 0)
163	  switch (size)
164	    {
165	    case 16:
166	      if (ppc_altivec_abi ())
167		{
168		  *locp = loc_vmxreg;
169		  return nloc_vmxreg;
170		}
171	      *locp = loc_intreg;
172	      return nloc_intregquad;
173	    }
174      }
175      /* Fall through.  */
176
177    case DW_TAG_structure_type:
178    case DW_TAG_class_type:
179    case DW_TAG_union_type:
180      if (SVR4_STRUCT_RETURN
181	  && dwarf_aggregate_size (typedie, &size) == 0
182	  && size > 0 && size <= 8)
183	goto intreg;
184      goto aggregate;
185    }
186
187  /* XXX We don't have a good way to return specific errors from ebl calls.
188     This value means we do not understand the type, but it is well-formed
189     DWARF and might be valid.  */
190  return -2;
191}
192