1 /* Exception handling and frame unwind runtime interface routines.
2 Copyright (C) 2001-2021 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
68 static unsigned int
69 size_of_encoded_value (unsigned char encoding) __attribute__ ((unused));
70
71 static unsigned int
size_of_encoded_value(unsigned char encoding)72 size_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
100 static _Unwind_Ptr
base_of_encoded_value(unsigned char encoding,struct _Unwind_Context * context)101 base_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
130 static const unsigned char *
read_uleb128(const unsigned char * p,_uleb128_t * val)131 read_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
152 static const unsigned char *
read_sleb128(const unsigned char * p,_sleb128_t * val)153 read_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
180 #pragma GCC diagnostic push
181 #pragma GCC diagnostic ignored "-Waddress-of-packed-member"
182
183 static const unsigned char *
read_encoded_value_with_base(unsigned char encoding,_Unwind_Ptr base,const unsigned char * p,_Unwind_Ptr * val)184 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
185 const unsigned char *p, _Unwind_Ptr *val)
186 {
187 union unaligned
188 {
189 void *ptr;
190 unsigned u2 __attribute__ ((mode (HI)));
191 unsigned u4 __attribute__ ((mode (SI)));
192 unsigned u8 __attribute__ ((mode (DI)));
193 signed s2 __attribute__ ((mode (HI)));
194 signed s4 __attribute__ ((mode (SI)));
195 signed s8 __attribute__ ((mode (DI)));
196 } __attribute__((__packed__));
197
198 const union unaligned *u = (const union unaligned *) p;
199 _Unwind_Internal_Ptr result;
200
201 if (encoding == DW_EH_PE_aligned)
202 {
203 _Unwind_Internal_Ptr a = (_Unwind_Internal_Ptr) p;
204 a = (a + sizeof (void *) - 1) & - sizeof(void *);
205 result = *(_Unwind_Internal_Ptr *) a;
206 p = (const unsigned char *) (_Unwind_Internal_Ptr) (a + sizeof (void *));
207 }
208 else
209 {
210 switch (encoding & 0x0f)
211 {
212 case DW_EH_PE_absptr:
213 result = (_Unwind_Internal_Ptr) u->ptr;
214 p += sizeof (void *);
215 break;
216
217 case DW_EH_PE_uleb128:
218 {
219 _uleb128_t tmp;
220 p = read_uleb128 (p, &tmp);
221 result = (_Unwind_Internal_Ptr) tmp;
222 }
223 break;
224
225 case DW_EH_PE_sleb128:
226 {
227 _sleb128_t tmp;
228 p = read_sleb128 (p, &tmp);
229 result = (_Unwind_Internal_Ptr) tmp;
230 }
231 break;
232
233 case DW_EH_PE_udata2:
234 result = u->u2;
235 p += 2;
236 break;
237 case DW_EH_PE_udata4:
238 result = u->u4;
239 p += 4;
240 break;
241 case DW_EH_PE_udata8:
242 result = u->u8;
243 p += 8;
244 break;
245
246 case DW_EH_PE_sdata2:
247 result = u->s2;
248 p += 2;
249 break;
250 case DW_EH_PE_sdata4:
251 result = u->s4;
252 p += 4;
253 break;
254 case DW_EH_PE_sdata8:
255 result = u->s8;
256 p += 8;
257 break;
258
259 default:
260 __gxx_abort ();
261 }
262
263 if (result != 0)
264 {
265 #if __FDPIC__
266 /* FDPIC relative addresses imply taking the GOT address
267 into account. */
268 if ((encoding & DW_EH_PE_pcrel) && (encoding & DW_EH_PE_indirect))
269 {
270 result += _Unwind_gnu_Find_got ((_Unwind_Ptr) u);
271 result = *(_Unwind_Internal_Ptr *) result;
272 }
273 else
274 {
275 result += ((encoding & 0x70) == DW_EH_PE_pcrel
276 ? (_Unwind_Internal_Ptr) u : base);
277 if (encoding & DW_EH_PE_indirect)
278 result = *(_Unwind_Internal_Ptr *) result;
279 }
280 #else
281 result += ((encoding & 0x70) == DW_EH_PE_pcrel
282 ? (_Unwind_Internal_Ptr) u : base);
283 if (encoding & DW_EH_PE_indirect)
284 result = *(_Unwind_Internal_Ptr *) result;
285 #endif
286 }
287 }
288
289 *val = result;
290 return p;
291 }
292
293 #pragma GCC diagnostic pop
294
295 #ifndef NO_BASE_OF_ENCODED_VALUE
296
297 /* Like read_encoded_value_with_base, but get the base from the context
298 rather than providing it directly. */
299
300 static inline const unsigned char *
read_encoded_value(struct _Unwind_Context * context,unsigned char encoding,const unsigned char * p,_Unwind_Ptr * val)301 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
302 const unsigned char *p, _Unwind_Ptr *val)
303 {
304 return read_encoded_value_with_base (encoding,
305 base_of_encoded_value (encoding, context),
306 p, val);
307 }
308
309 #endif
310
311 #endif /* unwind-pe.h */
312