1 /* Unaligned memory access functionality.
2 Copyright (C) 2000-2014 Red Hat, Inc.
3 This file is part of elfutils.
4 Written by Ulrich Drepper <drepper@redhat.com>, 2001.
5
6 This file is free software; you can redistribute it and/or modify
7 it under the terms of either
8
9 * the GNU Lesser General Public License as published by the Free
10 Software Foundation; either version 3 of the License, or (at
11 your option) any later version
12
13 or
14
15 * the GNU General Public License as published by the Free
16 Software Foundation; either version 2 of the License, or (at
17 your option) any later version
18
19 or both in parallel, as here.
20
21 elfutils is distributed in the hope that it will be useful, but
22 WITHOUT ANY WARRANTY; without even the implied warranty of
23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
24 General Public License for more details.
25
26 You should have received copies of the GNU General Public License and
27 the GNU Lesser General Public License along with this program. If
28 not, see <http://www.gnu.org/licenses/>. */
29
30 #ifndef _MEMORY_ACCESS_H
31 #define _MEMORY_ACCESS_H 1
32
33 #include <byteswap.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 /* Note, addr needs to me smaller than end. */
91 #define get_uleb128(var, addr, end) ((var) = __libdw_get_uleb128 (&(addr), end))
92
93 /* The signed case is similar, but we sign-extend the result. */
94
95 #define get_sleb128_step(var, addr, nth) \
96 do { \
97 unsigned char __b = *(addr)++; \
98 if (likely ((__b & 0x80) == 0)) \
99 { \
100 struct { signed int i:7; } __s = { .i = __b }; \
101 (var) |= (typeof (var)) __s.i * ((typeof (var)) 1 << ((nth) * 7)); \
102 return (var); \
103 } \
104 (var) |= (typeof (var)) (__b & 0x7f) << ((nth) * 7); \
105 } while (0)
106
107 static inline int64_t
__libdw_get_sleb128(const unsigned char ** addrp,const unsigned char * end)108 __libdw_get_sleb128 (const unsigned char **addrp, const unsigned char *end)
109 {
110 int64_t acc = 0;
111
112 /* Unroll the first step to help the compiler optimize
113 for the common single-byte case. */
114 get_sleb128_step (acc, *addrp, 0);
115
116 const size_t max = __libdw_max_len_sleb128 (*addrp - 1, end);
117 for (size_t i = 1; i < max; ++i)
118 get_sleb128_step (acc, *addrp, i);
119 /* Other implementations set VALUE to INT_MAX in this
120 case. So we better do this as well. */
121 return INT64_MAX;
122 }
123
124 #define get_sleb128(var, addr, end) ((var) = __libdw_get_sleb128 (&(addr), end))
125
126
127 /* We use simple memory access functions in case the hardware allows it.
128 The caller has to make sure we don't have alias problems. */
129 #if ALLOW_UNALIGNED
130
131 # define read_2ubyte_unaligned(Dbg, Addr) \
132 (unlikely ((Dbg)->other_byte_order) \
133 ? bswap_16 (*((const uint16_t *) (Addr))) \
134 : *((const uint16_t *) (Addr)))
135 # define read_2sbyte_unaligned(Dbg, Addr) \
136 (unlikely ((Dbg)->other_byte_order) \
137 ? (int16_t) bswap_16 (*((const int16_t *) (Addr))) \
138 : *((const int16_t *) (Addr)))
139
140 # define read_4ubyte_unaligned_noncvt(Addr) \
141 *((const uint32_t *) (Addr))
142 # define read_4ubyte_unaligned(Dbg, Addr) \
143 (unlikely ((Dbg)->other_byte_order) \
144 ? bswap_32 (*((const uint32_t *) (Addr))) \
145 : *((const uint32_t *) (Addr)))
146 # define read_4sbyte_unaligned(Dbg, Addr) \
147 (unlikely ((Dbg)->other_byte_order) \
148 ? (int32_t) bswap_32 (*((const int32_t *) (Addr))) \
149 : *((const int32_t *) (Addr)))
150
151 # define read_8ubyte_unaligned_noncvt(Addr) \
152 *((const uint64_t *) (Addr))
153 # define read_8ubyte_unaligned(Dbg, Addr) \
154 (unlikely ((Dbg)->other_byte_order) \
155 ? bswap_64 (*((const uint64_t *) (Addr))) \
156 : *((const uint64_t *) (Addr)))
157 # define read_8sbyte_unaligned(Dbg, Addr) \
158 (unlikely ((Dbg)->other_byte_order) \
159 ? (int64_t) bswap_64 (*((const int64_t *) (Addr))) \
160 : *((const int64_t *) (Addr)))
161
162 #else
163
164 union unaligned
165 {
166 void *p;
167 uint16_t u2;
168 uint32_t u4;
169 uint64_t u8;
170 int16_t s2;
171 int32_t s4;
172 int64_t s8;
173 } __attribute__ ((packed));
174
175 # define read_2ubyte_unaligned(Dbg, Addr) \
176 read_2ubyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
177 # define read_2sbyte_unaligned(Dbg, Addr) \
178 read_2sbyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
179 # define read_4ubyte_unaligned(Dbg, Addr) \
180 read_4ubyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
181 # define read_4sbyte_unaligned(Dbg, Addr) \
182 read_4sbyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
183 # define read_8ubyte_unaligned(Dbg, Addr) \
184 read_8ubyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
185 # define read_8sbyte_unaligned(Dbg, Addr) \
186 read_8sbyte_unaligned_1 ((Dbg)->other_byte_order, (Addr))
187
188 static inline uint16_t
read_2ubyte_unaligned_1(bool other_byte_order,const void * p)189 read_2ubyte_unaligned_1 (bool other_byte_order, const void *p)
190 {
191 const union unaligned *up = p;
192 if (unlikely (other_byte_order))
193 return bswap_16 (up->u2);
194 return up->u2;
195 }
196 static inline int16_t
read_2sbyte_unaligned_1(bool other_byte_order,const void * p)197 read_2sbyte_unaligned_1 (bool other_byte_order, const void *p)
198 {
199 const union unaligned *up = p;
200 if (unlikely (other_byte_order))
201 return (int16_t) bswap_16 (up->u2);
202 return up->s2;
203 }
204
205 static inline uint32_t
read_4ubyte_unaligned_noncvt(const void * p)206 read_4ubyte_unaligned_noncvt (const void *p)
207 {
208 const union unaligned *up = p;
209 return up->u4;
210 }
211 static inline uint32_t
read_4ubyte_unaligned_1(bool other_byte_order,const void * p)212 read_4ubyte_unaligned_1 (bool other_byte_order, const void *p)
213 {
214 const union unaligned *up = p;
215 if (unlikely (other_byte_order))
216 return bswap_32 (up->u4);
217 return up->u4;
218 }
219 static inline int32_t
read_4sbyte_unaligned_1(bool other_byte_order,const void * p)220 read_4sbyte_unaligned_1 (bool other_byte_order, const void *p)
221 {
222 const union unaligned *up = p;
223 if (unlikely (other_byte_order))
224 return (int32_t) bswap_32 (up->u4);
225 return up->s4;
226 }
227
228 static inline uint64_t
read_8ubyte_unaligned_noncvt(const void * p)229 read_8ubyte_unaligned_noncvt (const void *p)
230 {
231 const union unaligned *up = p;
232 return up->u8;
233 }
234 static inline uint64_t
read_8ubyte_unaligned_1(bool other_byte_order,const void * p)235 read_8ubyte_unaligned_1 (bool other_byte_order, const void *p)
236 {
237 const union unaligned *up = p;
238 if (unlikely (other_byte_order))
239 return bswap_64 (up->u8);
240 return up->u8;
241 }
242 static inline int64_t
read_8sbyte_unaligned_1(bool other_byte_order,const void * p)243 read_8sbyte_unaligned_1 (bool other_byte_order, const void *p)
244 {
245 const union unaligned *up = p;
246 if (unlikely (other_byte_order))
247 return (int64_t) bswap_64 (up->u8);
248 return up->s8;
249 }
250
251 #endif /* allow unaligned */
252
253
254 #define read_2ubyte_unaligned_inc(Dbg, Addr) \
255 ({ uint16_t t_ = read_2ubyte_unaligned (Dbg, Addr); \
256 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 2); \
257 t_; })
258 #define read_2sbyte_unaligned_inc(Dbg, Addr) \
259 ({ int16_t t_ = read_2sbyte_unaligned (Dbg, Addr); \
260 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 2); \
261 t_; })
262
263 #define read_4ubyte_unaligned_inc(Dbg, Addr) \
264 ({ uint32_t t_ = read_4ubyte_unaligned (Dbg, Addr); \
265 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 4); \
266 t_; })
267 #define read_4sbyte_unaligned_inc(Dbg, Addr) \
268 ({ int32_t t_ = read_4sbyte_unaligned (Dbg, Addr); \
269 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 4); \
270 t_; })
271
272 #define read_8ubyte_unaligned_inc(Dbg, Addr) \
273 ({ uint64_t t_ = read_8ubyte_unaligned (Dbg, Addr); \
274 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 8); \
275 t_; })
276 #define read_8sbyte_unaligned_inc(Dbg, Addr) \
277 ({ int64_t t_ = read_8sbyte_unaligned (Dbg, Addr); \
278 Addr = (__typeof (Addr)) (((uintptr_t) (Addr)) + 8); \
279 t_; })
280
281
282 #define read_addr_unaligned_inc(Nbytes, Dbg, Addr) \
283 (assert ((Nbytes) == 4 || (Nbytes) == 8), \
284 ((Nbytes) == 4 ? read_4ubyte_unaligned_inc (Dbg, Addr) \
285 : read_8ubyte_unaligned_inc (Dbg, Addr)))
286
287 #endif /* memory-access.h */
288