1 /* Unaligned memory access functionality.
2 Copyright (C) 2000-2014, 2018 Red Hat, Inc.
3 This file is part of elfutils.
4
5 This file is free software; you can redistribute it and/or modify
6 it under the terms of either
7
8 * the GNU Lesser General Public License as published by the Free
9 Software Foundation; either version 3 of the License, or (at
10 your option) any later version
11
12 or
13
14 * the GNU General Public License as published by the Free
15 Software Foundation; either version 2 of the License, or (at
16 your option) any later version
17
18 or both in parallel, as here.
19
20 elfutils is distributed in the hope that it will be useful, but
21 WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 General Public License for more details.
24
25 You should have received copies of the GNU General Public License and
26 the GNU Lesser General Public License along with this program. If
27 not, see <http://www.gnu.org/licenses/>. */
28
29 #ifndef _MEMORY_ACCESS_H
30 #define _MEMORY_ACCESS_H 1
31
32 #include <byteswap.h>
33 #include <endian.h>
34 #include <limits.h>
35 #include <stdint.h>
36
37
38 /* Number decoding macros. See 7.6 Variable Length Data. */
39
40 #define len_leb128(var) ((8 * sizeof (var) + 6) / 7)
41
42 static inline size_t
__libdw_max_len_leb128(const size_t type_len,const unsigned char * addr,const unsigned char * end)43 __libdw_max_len_leb128 (const size_t type_len,
44 const unsigned char *addr, const unsigned char *end)
45 {
46 const size_t pointer_len = likely (addr < end) ? end - addr : 0;
47 return likely (type_len <= pointer_len) ? type_len : pointer_len;
48 }
49
50 static inline size_t
__libdw_max_len_uleb128(const unsigned char * addr,const unsigned char * end)51 __libdw_max_len_uleb128 (const unsigned char *addr, const unsigned char *end)
52 {
53 const size_t type_len = len_leb128 (uint64_t);
54 return __libdw_max_len_leb128 (type_len, addr, end);
55 }
56
57 static inline size_t
__libdw_max_len_sleb128(const unsigned char * addr,const unsigned char * end)58 __libdw_max_len_sleb128 (const unsigned char *addr, const unsigned char *end)
59 {
60 /* Subtract one step, so we don't shift into sign bit. */
61 const size_t type_len = len_leb128 (int64_t) - 1;
62 return __libdw_max_len_leb128 (type_len, addr, end);
63 }
64
65 #define get_uleb128_step(var, addr, nth) \
66 do { \
67 unsigned char __b = *(addr)++; \
68 (var) |= (typeof (var)) (__b & 0x7f) << ((nth) * 7); \
69 if (likely ((__b & 0x80) == 0)) \
70 return (var); \
71 } while (0)
72
73 static inline uint64_t
__libdw_get_uleb128(const unsigned char ** addrp,const unsigned char * end)74 __libdw_get_uleb128 (const unsigned char **addrp, const unsigned char *end)
75 {
76 uint64_t acc = 0;
77
78 /* Unroll the first step to help the compiler optimize
79 for the common single-byte case. */
80 get_uleb128_step (acc, *addrp, 0);
81
82 const size_t max = __libdw_max_len_uleb128 (*addrp - 1, end);
83 for (size_t i = 1; i < max; ++i)
84 get_uleb128_step (acc, *addrp, i);
85 /* Other implementations set VALUE to UINT_MAX in this
86 case. So we better do this as well. */
87 return UINT64_MAX;
88 }
89
90 static inline uint64_t
__libdw_get_uleb128_unchecked(const unsigned char ** addrp)91 __libdw_get_uleb128_unchecked (const unsigned char **addrp)
92 {
93 uint64_t acc = 0;
94
95 /* Unroll the first step to help the compiler optimize
96 for the common single-byte case. */
97 get_uleb128_step (acc, *addrp, 0);
98
99 const size_t max = len_leb128 (uint64_t);
100 for (size_t i = 1; i < max; ++i)
101 get_uleb128_step (acc, *addrp, i);
102 /* Other implementations set VALUE to UINT_MAX in this
103 case. So we better do this as well. */
104 return UINT64_MAX;
105 }
106
107 /* Note, addr needs to me smaller than end. */
108 #define get_uleb128(var, addr, end) ((var) = __libdw_get_uleb128 (&(addr), end))
109 #define get_uleb128_unchecked(var, addr) ((var) = __libdw_get_uleb128_unchecked (&(addr)))
110
111 /* The signed case is similar, but we sign-extend the result. */
112
113 #define get_sleb128_step(var, addr, nth) \
114 do { \
115 unsigned char __b = *(addr)++; \
116 (var) |= (typeof (var)) (__b & 0x7f) << ((nth) * 7); \
117 if (likely ((__b & 0x80) == 0)) \
118 { \
119 if ((__b & 0x40) != 0) \
120 (var) |= - ((typeof (var)) 1 << (((nth) + 1) * 7)); \
121 return (var); \
122 } \
123 } while (0)
124
125 static inline int64_t
__libdw_get_sleb128(const unsigned char ** addrp,const unsigned char * end)126 __libdw_get_sleb128 (const unsigned char **addrp, const unsigned char *end)
127 {
128 /* Do the work in an unsigned type, but use implementation-defined
129 behavior to cast to signed on return. This avoids some undefined
130 behavior when shifting. */
131 uint64_t acc = 0;
132
133 /* Unroll the first step to help the compiler optimize
134 for the common single-byte case. */
135 get_sleb128_step (acc, *addrp, 0);
136
137 const size_t max = __libdw_max_len_sleb128 (*addrp - 1, end);
138 for (size_t i = 1; i < max; ++i)
139 get_sleb128_step (acc, *addrp, i);
140 if (*addrp == end)
141 return INT64_MAX;
142
143 /* There might be one extra byte. */
144 unsigned char b = **addrp;
145 ++*addrp;
146 if (likely ((b & 0x80) == 0))
147 {
148 /* We only need the low bit of the final byte, and as it is the
149 sign bit, we don't need to do anything else here. */
150 acc |= ((typeof (acc)) b) << 7 * max;
151 return acc;
152 }
153
154 /* Other implementations set VALUE to INT_MAX in this
155 case. So we better do this as well. */
156 return INT64_MAX;
157 }
158
159 static inline int64_t
__libdw_get_sleb128_unchecked(const unsigned char ** addrp)160 __libdw_get_sleb128_unchecked (const unsigned char **addrp)
161 {
162 /* Do the work in an unsigned type, but use implementation-defined
163 behavior to cast to signed on return. This avoids some undefined
164 behavior when shifting. */
165 uint64_t acc = 0;
166
167 /* Unroll the first step to help the compiler optimize
168 for the common single-byte case. */
169 get_sleb128_step (acc, *addrp, 0);
170
171 /* Subtract one step, so we don't shift into sign bit. */
172 const size_t max = len_leb128 (int64_t) - 1;
173 for (size_t i = 1; i < max; ++i)
174 get_sleb128_step (acc, *addrp, i);
175
176 /* There might be one extra byte. */
177 unsigned char b = **addrp;
178 ++*addrp;
179 if (likely ((b & 0x80) == 0))
180 {
181 /* We only need the low bit of the final byte, and as it is the
182 sign bit, we don't need to do anything else here. */
183 acc |= ((typeof (acc)) b) << 7 * max;
184 return acc;
185 }
186
187 /* Other implementations set VALUE to INT_MAX in this
188 case. So we better do this as well. */
189 return INT64_MAX;
190 }
191
192 #define get_sleb128(var, addr, end) ((var) = __libdw_get_sleb128 (&(addr), end))
193 #define get_sleb128_unchecked(var, addr) ((var) = __libdw_get_sleb128_unchecked (&(addr)))
194
195
196 /* We use simple memory access functions in case the hardware allows it.
197 The caller has to make sure we don't have alias problems. */
198 #if ALLOW_UNALIGNED
199
200 # define read_2ubyte_unaligned(Dbg, Addr) \
201 (unlikely ((Dbg)->other_byte_order) \
202 ? bswap_16 (*((const uint16_t *) (Addr))) \
203 : *((const uint16_t *) (Addr)))
204 # define read_2sbyte_unaligned(Dbg, Addr) \
205 (unlikely ((Dbg)->other_byte_order) \
206 ? (int16_t) bswap_16 (*((const int16_t *) (Addr))) \
207 : *((const int16_t *) (Addr)))
208
209 # define read_4ubyte_unaligned_noncvt(Addr) \
210 *((const uint32_t *) (Addr))
211 # define read_4ubyte_unaligned(Dbg, Addr) \
212 (unlikely ((Dbg)->other_byte_order) \
213 ? bswap_32 (*((const uint32_t *) (Addr))) \
214 : *((const uint32_t *) (Addr)))
215 # define read_4sbyte_unaligned(Dbg, Addr) \
216 (unlikely ((Dbg)->other_byte_order) \
217 ? (int32_t) bswap_32 (*((const int32_t *) (Addr))) \
218 : *((const int32_t *) (Addr)))
219
220 # define read_8ubyte_unaligned_noncvt(Addr) \
221 *((const uint64_t *) (Addr))
222 # define read_8ubyte_unaligned(Dbg, Addr) \
223 (unlikely ((Dbg)->other_byte_order) \
224 ? bswap_64 (*((const uint64_t *) (Addr))) \
225 : *((const uint64_t *) (Addr)))
226 # define read_8sbyte_unaligned(Dbg, Addr) \
227 (unlikely ((Dbg)->other_byte_order) \
228 ? (int64_t) bswap_64 (*((const int64_t *) (Addr))) \
229 : *((const int64_t *) (Addr)))
230
231 #else
232
233 union unaligned
234 {
235 void *p;
236 uint16_t u2;
237 uint32_t u4;
238 uint64_t u8;
239 int16_t s2;
240 int32_t s4;
241 int64_t s8;
242 } attribute_packed;
243
244 # define read_2ubyte_unaligned(Dbg, Addr) \
245 read_2ubyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
246 # define read_2sbyte_unaligned(Dbg, Addr) \
247 read_2sbyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
248 # define read_4ubyte_unaligned(Dbg, Addr) \
249 read_4ubyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
250 # define read_4sbyte_unaligned(Dbg, Addr) \
251 read_4sbyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
252 # define read_8ubyte_unaligned(Dbg, Addr) \
253 read_8ubyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
254 # define read_8sbyte_unaligned(Dbg, Addr) \
255 read_8sbyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
256
257 static inline uint16_t
read_2ubyte_unaligned_1(bool other_byte_order,const void * p)258 read_2ubyte_unaligned_1 (bool other_byte_order, const void *p)
259 {
260 const union unaligned *up = p;
261 if (unlikely (other_byte_order))
262 return bswap_16 (up->u2);
263 return up->u2;
264 }
265 static inline int16_t
read_2sbyte_unaligned_1(bool other_byte_order,const void * p)266 read_2sbyte_unaligned_1 (bool other_byte_order, const void *p)
267 {
268 const union unaligned *up = p;
269 if (unlikely (other_byte_order))
270 return (int16_t) bswap_16 (up->u2);
271 return up->s2;
272 }
273
274 static inline uint32_t
read_4ubyte_unaligned_noncvt(const void * p)275 read_4ubyte_unaligned_noncvt (const void *p)
276 {
277 const union unaligned *up = p;
278 return up->u4;
279 }
280 static inline uint32_t
read_4ubyte_unaligned_1(bool other_byte_order,const void * p)281 read_4ubyte_unaligned_1 (bool other_byte_order, const void *p)
282 {
283 const union unaligned *up = p;
284 if (unlikely (other_byte_order))
285 return bswap_32 (up->u4);
286 return up->u4;
287 }
288 static inline int32_t
read_4sbyte_unaligned_1(bool other_byte_order,const void * p)289 read_4sbyte_unaligned_1 (bool other_byte_order, const void *p)
290 {
291 const union unaligned *up = p;
292 if (unlikely (other_byte_order))
293 return (int32_t) bswap_32 (up->u4);
294 return up->s4;
295 }
296
297 static inline uint64_t
read_8ubyte_unaligned_noncvt(const void * p)298 read_8ubyte_unaligned_noncvt (const void *p)
299 {
300 const union unaligned *up = p;
301 return up->u8;
302 }
303 static inline uint64_t
read_8ubyte_unaligned_1(bool other_byte_order,const void * p)304 read_8ubyte_unaligned_1 (bool other_byte_order, const void *p)
305 {
306 const union unaligned *up = p;
307 if (unlikely (other_byte_order))
308 return bswap_64 (up->u8);
309 return up->u8;
310 }
311 static inline int64_t
read_8sbyte_unaligned_1(bool other_byte_order,const void * p)312 read_8sbyte_unaligned_1 (bool other_byte_order, const void *p)
313 {
314 const union unaligned *up = p;
315 if (unlikely (other_byte_order))
316 return (int64_t) bswap_64 (up->u8);
317 return up->s8;
318 }
319
320 #endif /* allow unaligned */
321
322
323 #define read_2ubyte_unaligned_inc(Dbg, Addr) \
324 ({ uint16_t t_ = read_2ubyte_unaligned (Dbg, Addr); \
325 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 2); \
326 t_; })
327 #define read_2sbyte_unaligned_inc(Dbg, Addr) \
328 ({ int16_t t_ = read_2sbyte_unaligned (Dbg, Addr); \
329 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 2); \
330 t_; })
331
332 #define read_4ubyte_unaligned_inc(Dbg, Addr) \
333 ({ uint32_t t_ = read_4ubyte_unaligned (Dbg, Addr); \
334 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 4); \
335 t_; })
336 #define read_4sbyte_unaligned_inc(Dbg, Addr) \
337 ({ int32_t t_ = read_4sbyte_unaligned (Dbg, Addr); \
338 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 4); \
339 t_; })
340
341 #define read_8ubyte_unaligned_inc(Dbg, Addr) \
342 ({ uint64_t t_ = read_8ubyte_unaligned (Dbg, Addr); \
343 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 8); \
344 t_; })
345 #define read_8sbyte_unaligned_inc(Dbg, Addr) \
346 ({ int64_t t_ = read_8sbyte_unaligned (Dbg, Addr); \
347 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 8); \
348 t_; })
349
350 /* 3ubyte reads are only used for DW_FORM_addrx3 and DW_FORM_strx3.
351 And are probably very rare. They are not optimized. They are
352 handled as if reading a 4byte value with the first (for big endian)
353 or last (for little endian) byte zero. */
354
355 static inline int
file_byte_order(bool other_byte_order)356 file_byte_order (bool other_byte_order)
357 {
358 #if __BYTE_ORDER == __LITTLE_ENDIAN
359 return other_byte_order ? __BIG_ENDIAN : __LITTLE_ENDIAN;
360 #else
361 return other_byte_order ? __LITTLE_ENDIAN : __BIG_ENDIAN;
362 #endif
363 }
364
365 static inline uint32_t
read_3ubyte_unaligned(Dwarf * dbg,const unsigned char * p)366 read_3ubyte_unaligned (Dwarf *dbg, const unsigned char *p)
367 {
368 union
369 {
370 uint32_t u4;
371 unsigned char c[4];
372 } d;
373 bool other_byte_order = dbg->other_byte_order;
374
375 if (file_byte_order (other_byte_order) == __BIG_ENDIAN)
376 {
377 d.c[0] = 0x00;
378 d.c[1] = p[0];
379 d.c[2] = p[1];
380 d.c[3] = p[2];
381 }
382 else
383 {
384 d.c[0] = p[0];
385 d.c[1] = p[1];
386 d.c[2] = p[2];
387 d.c[3] = 0x00;
388 }
389
390 if (other_byte_order)
391 return bswap_32 (d.u4);
392 else
393 return d.u4;
394 }
395
396
397 #define read_3ubyte_unaligned_inc(Dbg, Addr) \
398 ({ uint32_t t_ = read_3ubyte_unaligned (Dbg, Addr); \
399 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 3); \
400 t_; })
401
402 #define read_addr_unaligned_inc(Nbytes, Dbg, Addr) \
403 (assert ((Nbytes) == 4 || (Nbytes) == 8), \
404 ((Nbytes) == 4 ? read_4ubyte_unaligned_inc (Dbg, Addr) \
405 : read_8ubyte_unaligned_inc (Dbg, Addr)))
406
407 #endif /* memory-access.h */
408