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      1 /* Function return value location for S/390 ABI.
      2    Copyright (C) 2006, 2007 Red Hat, Inc.
      3    This file is part of Red Hat elfutils.
      4 
      5    Red Hat elfutils is free software; you can redistribute it and/or modify
      6    it under the terms of the GNU General Public License as published by the
      7    Free Software Foundation; version 2 of the License.
      8 
      9    Red Hat elfutils is distributed in the hope that it will be useful, but
     10    WITHOUT ANY WARRANTY; without even the implied warranty of
     11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     12    General Public License for more details.
     13 
     14    You should have received a copy of the GNU General Public License along
     15    with Red Hat elfutils; if not, write to the Free Software Foundation,
     16    Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
     17 
     18    Red Hat elfutils is an included package of the Open Invention Network.
     19    An included package of the Open Invention Network is a package for which
     20    Open Invention Network licensees cross-license their patents.  No patent
     21    license is granted, either expressly or impliedly, by designation as an
     22    included package.  Should you wish to participate in the Open Invention
     23    Network licensing program, please visit www.openinventionnetwork.com
     24    <http://www.openinventionnetwork.com>.  */
     25 
     26 #ifdef HAVE_CONFIG_H
     27 # include <config.h>
     28 #endif
     29 
     30 #include <assert.h>
     31 #include <dwarf.h>
     32 
     33 #define BACKEND s390_
     34 #include "libebl_CPU.h"
     35 
     36 
     37 /* %r2, or pair %r2, %r3.  */
     38 static const Dwarf_Op loc_intreg[] =
     39   {
     40     { .atom = DW_OP_reg2 }, { .atom = DW_OP_piece, .number = 4 },
     41     { .atom = DW_OP_reg3 }, { .atom = DW_OP_piece, .number = 4 },
     42   };
     43 #define nloc_intreg	1
     44 #define nloc_intregpair	4
     45 
     46 /* %f0.  */
     47 static const Dwarf_Op loc_fpreg[] =
     48   {
     49     { .atom = DW_OP_reg16 },
     50   };
     51 #define nloc_fpreg	1
     52 
     53 /* The return value is a structure and is actually stored in stack space
     54    passed in a hidden argument by the caller.  But, the compiler
     55    helpfully returns the address of that space in %r2.  */
     56 static const Dwarf_Op loc_aggregate[] =
     57   {
     58     { .atom = DW_OP_breg2, .number = 0 }
     59   };
     60 #define nloc_aggregate 1
     61 
     62 
     63 int
     64 s390_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
     65 {
     66   /* Start with the function's type, and get the DW_AT_type attribute,
     67      which is the type of the return value.  */
     68 
     69   Dwarf_Attribute attr_mem;
     70   Dwarf_Attribute *attr = dwarf_attr_integrate (functypedie, DW_AT_type,
     71 						&attr_mem);
     72   if (attr == NULL)
     73     /* The function has no return value, like a `void' function in C.  */
     74     return 0;
     75 
     76   Dwarf_Die die_mem;
     77   Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
     78   int tag = dwarf_tag (typedie);
     79 
     80   /* Follow typedefs and qualifiers to get to the actual type.  */
     81   while (tag == DW_TAG_typedef
     82 	 || tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
     83 	 || tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
     84     {
     85       attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
     86       typedie = dwarf_formref_die (attr, &die_mem);
     87       tag = dwarf_tag (typedie);
     88     }
     89 
     90   Dwarf_Word size;
     91   switch (tag)
     92     {
     93     case -1:
     94       return -1;
     95 
     96     case DW_TAG_subrange_type:
     97       if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
     98 	{
     99 	  attr = dwarf_attr (typedie, DW_AT_type, &attr_mem);
    100 	  typedie = dwarf_formref_die (attr, &die_mem);
    101 	  tag = dwarf_tag (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_Die cudie;
    111 	uint8_t asize;
    112 	if (dwarf_diecu (typedie, &cudie, &asize, NULL) == NULL)
    113 	  return -1;
    114 
    115 	if (dwarf_formudata (dwarf_attr (typedie, DW_AT_byte_size,
    116 					 &attr_mem), &size) != 0)
    117 	  {
    118 	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
    119 	      size = asize;
    120 	    else
    121 	      return -1;
    122 	  }
    123 	if (tag == DW_TAG_base_type)
    124 	  {
    125 	    Dwarf_Word encoding;
    126 	    if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
    127 						       &attr_mem),
    128 				 &encoding) != 0)
    129 	      return -1;
    130 	    if (encoding == DW_ATE_float && size <= 8)
    131 	      {
    132 		*locp = loc_fpreg;
    133 		return nloc_fpreg;
    134 	      }
    135 	  }
    136 	if (size <= 8)
    137 	  {
    138 	    *locp = loc_intreg;
    139 	    return size <= asize ? nloc_intreg : nloc_intregpair;
    140 	  }
    141       }
    142       /* Fall through.  */
    143 
    144     case DW_TAG_structure_type:
    145     case DW_TAG_class_type:
    146     case DW_TAG_union_type:
    147     case DW_TAG_array_type:
    148       *locp = loc_aggregate;
    149       return nloc_aggregate;
    150     }
    151 
    152   /* XXX We don't have a good way to return specific errors from ebl calls.
    153      This value means we do not understand the type, but it is well-formed
    154      DWARF and might be valid.  */
    155   return -2;
    156 }
    157