dwarf_frame_register.c revision 0ab97839da3c382ab8799ebdbf5eb0a79bf20bdc 
1/* Get register location expression for frame.
2   Copyright (C) 2009-2010 Red Hat, Inc.
3   This file is part of Red Hat elfutils.
4
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6   it under the terms of the GNU General Public License as published by the
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12   General Public License for more details.
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16   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
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40   this file solely under the GPL without exception.
41
42   Red Hat elfutils is an included package of the Open Invention Network.
43   An included package of the Open Invention Network is a package for which
44   Open Invention Network licensees cross-license their patents.  No patent
45   license is granted, either expressly or impliedly, by designation as an
46   included package.  Should you wish to participate in the Open Invention
47   Network licensing program, please visit www.openinventionnetwork.com
48   <http://www.openinventionnetwork.com>.  */
49
50#ifdef HAVE_CONFIG_H
51# include <config.h>
52#endif
53
54#include "cfi.h"
55#include <dwarf.h>
56
57int
58dwarf_frame_register (fs, regno, ops_mem, ops, nops)
59     Dwarf_Frame *fs;
60     int regno;
61     Dwarf_Op ops_mem[3];
62     Dwarf_Op **ops;
63     size_t *nops;
64{
65  /* Maybe there was a previous error.  */
66  if (fs == NULL)
67    return -1;
68
69  if (unlikely (regno < 0))
70    {
71      __libdw_seterrno (DWARF_E_INVALID_ACCESS);
72      return -1;
73    }
74
75  *ops = ops_mem;
76  *nops = 0;
77
78  if (unlikely ((size_t) regno >= fs->nregs))
79    goto default_rule;
80
81  const struct dwarf_frame_register *reg = &fs->regs[regno];
82
83  switch (reg->rule)
84    {
85    case reg_unspecified:
86    default_rule:
87      /* Use the default rule for registers not yet mentioned in CFI.  */
88      if (fs->cache->default_same_value)
89	goto same_value;
90      /*FALLTHROUGH*/
91    case reg_undefined:
92      /* The value is known to be unavailable.  */
93      break;
94
95    case reg_same_value:
96    same_value:
97      /* The location is not known here, but the caller might know it.  */
98      *ops = NULL;
99      break;
100
101    case reg_offset:
102    case reg_val_offset:
103      ops_mem[(*nops)++] = (Dwarf_Op) { .atom = DW_OP_call_frame_cfa };
104      if (reg->value != 0)
105	ops_mem[(*nops)++] = (Dwarf_Op) { .atom = DW_OP_plus_uconst,
106					  .number = reg->value };
107      if (reg->rule == reg_val_offset)
108	/* A value, not a location.  */
109	ops_mem[(*nops)++] = (Dwarf_Op) { .atom = DW_OP_stack_value };
110      *ops = ops_mem;
111      break;
112
113    case reg_register:
114      ops_mem[(*nops)++] = (Dwarf_Op) { .atom = DW_OP_regx,
115					.number = reg->value };
116      break;
117
118    case reg_val_expression:
119    case reg_expression:
120      {
121	unsigned int address_size = (fs->cache->e_ident[EI_CLASS] == ELFCLASS32
122				     ? 4 : 8);
123
124	Dwarf_Block block;
125	const uint8_t *p = fs->cache->data->d.d_buf + reg->value;
126	get_uleb128 (block.length, p);
127	block.data = (void *) p;
128
129	/* Parse the expression into internal form.  */
130	if (__libdw_intern_expression (NULL,
131				       fs->cache->other_byte_order,
132				       address_size,
133				       &fs->cache->expr_tree, &block,
134				       true, reg->rule == reg_val_expression,
135				       ops, nops, IDX_debug_frame) < 0)
136	  return -1;
137	break;
138      }
139    }
140
141  return 0;
142}
143