1/* DW_EH_PE_* support for libdw unwinder.
2   Copyright (C) 2009-2010 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   In addition, as a special exception, Red Hat, Inc. gives You the
19   additional right to link the code of Red Hat elfutils with code licensed
20   under any Open Source Initiative certified open source license
21   (http://www.opensource.org/licenses/index.php) which requires the
22   distribution of source code with any binary distribution and to
23   distribute linked combinations of the two.  Non-GPL Code permitted under
24   this exception must only link to the code of Red Hat elfutils through
25   those well defined interfaces identified in the file named EXCEPTION
26   found in the source code files (the "Approved Interfaces").  The files
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30   Inc. may make changes or additions to the list of Approved Interfaces.
31   Red Hat's grant of this exception is conditioned upon your not adding
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33   exception, please contact Red Hat.  You must obey the GNU General Public
34   License in all respects for all of the Red Hat elfutils code and other
35   code used in conjunction with Red Hat elfutils except the Non-GPL Code
36   covered by this exception.  If you modify this file, you may extend this
37   exception to your version of the file, but you are not obligated to do
38   so.  If you do not wish to provide this exception without modification,
39   you must delete this exception statement from your version and license
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
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48   <http://www.openinventionnetwork.com>.  */
49
50#ifndef _ENCODED_VALUE_H
51#define _ENCODED_VALUE_H 1
52
53#include <dwarf.h>
54#include <stdlib.h>
55#include "libdwP.h"
56
57
58static size_t __attribute__ ((unused))
59encoded_value_size (const Elf_Data *data, const unsigned char e_ident[],
60		    uint8_t encoding, const uint8_t *p)
61{
62  if (encoding == DW_EH_PE_omit)
63    return 0;
64
65  switch (encoding & 0x07)
66    {
67    case DW_EH_PE_udata2:
68      return 2;
69    case DW_EH_PE_udata4:
70      return 4;
71    case DW_EH_PE_udata8:
72      return 8;
73
74    case DW_EH_PE_absptr:
75      return e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
76
77    case DW_EH_PE_uleb128:
78      if (p != NULL)
79	{
80	  const uint8_t *end = p;
81	  while (end < (uint8_t *) data->d_buf + data->d_size)
82	    if (*end++ & 0x80u)
83	      return end - p;
84	}
85
86    default:
87      abort ();
88      return 0;
89    }
90}
91
92static inline int __attribute__ ((unused))
93__libdw_cfi_read_address_inc (const Dwarf_CFI *cache,
94			      const unsigned char **addrp,
95			      int width, Dwarf_Addr *ret)
96{
97  width = width ?: cache->e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
98
99  if (cache->dbg != NULL)
100    return __libdw_read_address_inc (cache->dbg, IDX_debug_frame,
101				     addrp, width, ret);
102
103  /* Only .debug_frame might have relocation to consider.
104     Read plain values from .eh_frame data.  */
105
106  if (width == 4)
107    *ret = read_4ubyte_unaligned_inc (cache, *addrp);
108  else
109    *ret = read_8ubyte_unaligned_inc (cache, *addrp);
110  return 0;
111}
112
113static bool __attribute__ ((unused))
114read_encoded_value (const Dwarf_CFI *cache, uint8_t encoding, const uint8_t **p,
115		    Dwarf_Addr *result)
116{
117  *result = 0;
118  switch (encoding & 0x70)
119    {
120    case DW_EH_PE_absptr:
121      break;
122    case DW_EH_PE_pcrel:
123      *result = (cache->frame_vaddr
124		 + (*p - (const uint8_t *) cache->data->d.d_buf));
125      break;
126    case DW_EH_PE_textrel:
127      // ia64: segrel
128      *result = cache->textrel;
129      break;
130    case DW_EH_PE_datarel:
131      // i386: GOTOFF
132      // ia64: gprel
133      *result = cache->datarel;
134      break;
135    case DW_EH_PE_funcrel:	/* XXX */
136      break;
137    case DW_EH_PE_aligned:
138      {
139	const size_t size = encoded_value_size (&cache->data->d, cache->e_ident,
140						encoding, *p);
141	size_t align = ((cache->frame_vaddr
142			 + (*p - (const uint8_t *) cache->data->d.d_buf))
143			& (size - 1));
144	if (align != 0)
145	  *p += size - align;
146	break;
147      }
148
149    default:
150      abort ();
151    }
152
153  Dwarf_Addr value;
154  switch (encoding & 0x0f)
155    {
156    case DW_EH_PE_udata2:
157      value = read_2ubyte_unaligned_inc (cache, *p);
158      break;
159
160    case DW_EH_PE_sdata2:
161      value = read_2sbyte_unaligned_inc (cache, *p);
162      break;
163
164    case DW_EH_PE_udata4:
165      if (__libdw_cfi_read_address_inc (cache, p, 4, &value))
166	return true;
167      break;
168
169    case DW_EH_PE_sdata4:
170      if (__libdw_cfi_read_address_inc (cache, p, 4, &value))
171	return true;
172      value = (Dwarf_Sword) (Elf32_Sword) value; /* Sign-extend.  */
173      break;
174
175    case DW_EH_PE_udata8:
176    case DW_EH_PE_sdata8:
177      if (__libdw_cfi_read_address_inc (cache, p, 8, &value))
178	return true;
179      break;
180
181    case DW_EH_PE_absptr:
182      if (__libdw_cfi_read_address_inc (cache, p, 0, &value))
183	return true;
184      break;
185
186    case DW_EH_PE_uleb128:
187      get_uleb128 (value, *p);
188      break;
189
190    case DW_EH_PE_sleb128:
191      get_sleb128 (value, *p);
192      break;
193
194    default:
195      abort ();
196    }
197
198  *result += value;
199
200  if (encoding & DW_EH_PE_indirect)
201    {
202      if (unlikely (*result < cache->frame_vaddr))
203	return true;
204      *result -= cache->frame_vaddr;
205      if (unlikely (*result > (cache->data->d.d_size
206			       - encoded_value_size (NULL, cache->e_ident,
207						     DW_EH_PE_absptr, NULL))))
208	return true;
209      const uint8_t *ptr = cache->data->d.d_buf + *result;
210      return __libdw_cfi_read_address_inc (cache, &ptr, 0, result);
211    }
212
213  return false;
214}
215
216#endif	/* encoded-value.h */
217