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