1/* Exception handling and frame unwind runtime interface routines.
2   Copyright (C) 2001-2015 Free Software Foundation, Inc.
3
4   This file is part of GCC.
5
6   GCC is free software; you can redistribute it and/or modify it
7   under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 3, or (at your option)
9   any later version.
10
11   GCC is distributed in the hope that it will be useful, but WITHOUT
12   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
14   License for more details.
15
16   Under Section 7 of GPL version 3, you are granted additional
17   permissions described in the GCC Runtime Library Exception, version
18   3.1, as published by the Free Software Foundation.
19
20   You should have received a copy of the GNU General Public License and
21   a copy of the GCC Runtime Library Exception along with this program;
22   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23   <http://www.gnu.org/licenses/>.  */
24
25/* @@@ Really this should be out of line, but this also causes link
26   compatibility problems with the base ABI.  This is slightly better
27   than duplicating code, however.  */
28
29#ifndef GCC_UNWIND_PE_H
30#define GCC_UNWIND_PE_H
31
32/* If using C++, references to abort have to be qualified with std::.  */
33#if __cplusplus
34#define __gxx_abort std::abort
35#else
36#define __gxx_abort abort
37#endif
38
39/* Pointer encodings, from dwarf2.h.  */
40#define DW_EH_PE_absptr         0x00
41#define DW_EH_PE_omit           0xff
42
43#define DW_EH_PE_uleb128        0x01
44#define DW_EH_PE_udata2         0x02
45#define DW_EH_PE_udata4         0x03
46#define DW_EH_PE_udata8         0x04
47#define DW_EH_PE_sleb128        0x09
48#define DW_EH_PE_sdata2         0x0A
49#define DW_EH_PE_sdata4         0x0B
50#define DW_EH_PE_sdata8         0x0C
51#define DW_EH_PE_signed         0x08
52
53#define DW_EH_PE_pcrel          0x10
54#define DW_EH_PE_textrel        0x20
55#define DW_EH_PE_datarel        0x30
56#define DW_EH_PE_funcrel        0x40
57#define DW_EH_PE_aligned        0x50
58
59#define DW_EH_PE_indirect	0x80
60
61
62#ifndef NO_SIZE_OF_ENCODED_VALUE
63
64/* Given an encoding, return the number of bytes the format occupies.
65   This is only defined for fixed-size encodings, and so does not
66   include leb128.  */
67
68static unsigned int
69size_of_encoded_value (unsigned char encoding) __attribute__ ((unused));
70
71static unsigned int
72size_of_encoded_value (unsigned char encoding)
73{
74  if (encoding == DW_EH_PE_omit)
75    return 0;
76
77  switch (encoding & 0x07)
78    {
79    case DW_EH_PE_absptr:
80      return sizeof (void *);
81    case DW_EH_PE_udata2:
82      return 2;
83    case DW_EH_PE_udata4:
84      return 4;
85    case DW_EH_PE_udata8:
86      return 8;
87    }
88  __gxx_abort ();
89}
90
91#endif
92
93#ifndef NO_BASE_OF_ENCODED_VALUE
94
95/* Given an encoding and an _Unwind_Context, return the base to which
96   the encoding is relative.  This base may then be passed to
97   read_encoded_value_with_base for use when the _Unwind_Context is
98   not available.  */
99
100static _Unwind_Ptr
101base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
102{
103  if (encoding == DW_EH_PE_omit)
104    return 0;
105
106  switch (encoding & 0x70)
107    {
108    case DW_EH_PE_absptr:
109    case DW_EH_PE_pcrel:
110    case DW_EH_PE_aligned:
111      return 0;
112
113    case DW_EH_PE_textrel:
114      return _Unwind_GetTextRelBase (context);
115    case DW_EH_PE_datarel:
116      return _Unwind_GetDataRelBase (context);
117    case DW_EH_PE_funcrel:
118      return _Unwind_GetRegionStart (context);
119    }
120  __gxx_abort ();
121}
122
123#endif
124
125/* Read an unsigned leb128 value from P, store the value in VAL, return
126   P incremented past the value.  We assume that a word is large enough to
127   hold any value so encoded; if it is smaller than a pointer on some target,
128   pointers should not be leb128 encoded on that target.  */
129
130static const unsigned char *
131read_uleb128 (const unsigned char *p, _uleb128_t *val)
132{
133  unsigned int shift = 0;
134  unsigned char byte;
135  _uleb128_t result;
136
137  result = 0;
138  do
139    {
140      byte = *p++;
141      result |= ((_uleb128_t)byte & 0x7f) << shift;
142      shift += 7;
143    }
144  while (byte & 0x80);
145
146  *val = result;
147  return p;
148}
149
150/* Similar, but read a signed leb128 value.  */
151
152static const unsigned char *
153read_sleb128 (const unsigned char *p, _sleb128_t *val)
154{
155  unsigned int shift = 0;
156  unsigned char byte;
157  _uleb128_t result;
158
159  result = 0;
160  do
161    {
162      byte = *p++;
163      result |= ((_uleb128_t)byte & 0x7f) << shift;
164      shift += 7;
165    }
166  while (byte & 0x80);
167
168  /* Sign-extend a negative value.  */
169  if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
170    result |= -(((_uleb128_t)1L) << shift);
171
172  *val = (_sleb128_t) result;
173  return p;
174}
175
176/* Load an encoded value from memory at P.  The value is returned in VAL;
177   The function returns P incremented past the value.  BASE is as given
178   by base_of_encoded_value for this encoding in the appropriate context.  */
179
180static const unsigned char *
181read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
182			      const unsigned char *p, _Unwind_Ptr *val)
183{
184  union unaligned
185    {
186      void *ptr;
187      unsigned u2 __attribute__ ((mode (HI)));
188      unsigned u4 __attribute__ ((mode (SI)));
189      unsigned u8 __attribute__ ((mode (DI)));
190      signed s2 __attribute__ ((mode (HI)));
191      signed s4 __attribute__ ((mode (SI)));
192      signed s8 __attribute__ ((mode (DI)));
193    } __attribute__((__packed__));
194
195  const union unaligned *u = (const union unaligned *) p;
196  _Unwind_Internal_Ptr result;
197
198  if (encoding == DW_EH_PE_aligned)
199    {
200      _Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
201      a = (a + sizeof (void *) - 1) & - sizeof(void *);
202      result = *(_Unwind_Internal_Ptr *) a;
203      p = (const unsigned char *) (_Unwind_Internal_Ptr) (a + sizeof (void *));
204    }
205  else
206    {
207      switch (encoding & 0x0f)
208	{
209	case DW_EH_PE_absptr:
210	  result = (_Unwind_Internal_Ptr) u->ptr;
211	  p += sizeof (void *);
212	  break;
213
214	case DW_EH_PE_uleb128:
215	  {
216	    _uleb128_t tmp;
217	    p = read_uleb128 (p, &tmp);
218	    result = (_Unwind_Internal_Ptr) tmp;
219	  }
220	  break;
221
222	case DW_EH_PE_sleb128:
223	  {
224	    _sleb128_t tmp;
225	    p = read_sleb128 (p, &tmp);
226	    result = (_Unwind_Internal_Ptr) tmp;
227	  }
228	  break;
229
230	case DW_EH_PE_udata2:
231	  result = u->u2;
232	  p += 2;
233	  break;
234	case DW_EH_PE_udata4:
235	  result = u->u4;
236	  p += 4;
237	  break;
238	case DW_EH_PE_udata8:
239	  result = u->u8;
240	  p += 8;
241	  break;
242
243	case DW_EH_PE_sdata2:
244	  result = u->s2;
245	  p += 2;
246	  break;
247	case DW_EH_PE_sdata4:
248	  result = u->s4;
249	  p += 4;
250	  break;
251	case DW_EH_PE_sdata8:
252	  result = u->s8;
253	  p += 8;
254	  break;
255
256	default:
257	  __gxx_abort ();
258	}
259
260      if (result != 0)
261	{
262	  result += ((encoding & 0x70) == DW_EH_PE_pcrel
263		     ? (_Unwind_Internal_Ptr) u : base);
264	  if (encoding & DW_EH_PE_indirect)
265	    result = *(_Unwind_Internal_Ptr *) result;
266	}
267    }
268
269  *val = result;
270  return p;
271}
272
273#ifndef NO_BASE_OF_ENCODED_VALUE
274
275/* Like read_encoded_value_with_base, but get the base from the context
276   rather than providing it directly.  */
277
278static inline const unsigned char *
279read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
280		    const unsigned char *p, _Unwind_Ptr *val)
281{
282  return read_encoded_value_with_base (encoding,
283		base_of_encoded_value (encoding, context),
284		p, val);
285}
286
287#endif
288
289#endif /* unwind-pe.h */
290