The Tcpdump Group git mirrors - tcpdump/blob - extract.h

   1 /*
   2  * Copyright (c) 1992, 1993, 1994, 1995, 1996
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  */
  21
  22 /*
  23  * For 8-bit values; provided for the sake of completeness.  Byte order
  24  * isn't relevant, and alignment isn't an issue.
  25  */
  26 #define EXTRACT_8BITS(p)        (*(p))
  27 #define EXTRACT_LE_8BITS(p)     (*(p))
  28
  29 /*
  30  * Inline functions or macros to extract possibly-unaligned big-endian
  31  * integral values.
  32  */
  33 #include "funcattrs.h"
  34
  35 /*
  36  * If we have versions of GCC or Clang that support an __attribute__
  37  * to say "if we're building with unsigned behavior sanitization,
  38  * don't complain about undefined behavior in this function", we
  39  * label these functions with that attribute - we *know* it's undefined
  40  * in the C standard, but we *also* know it does what we want with
  41  * the ISA we're targeting and the compiler we're using.
  42  *
  43  * For GCC 4.9.0 and later, we use __attribute__((no_sanitize_undefined));
  44  * pre-5.0 GCC doesn't have __has_attribute, and I'm not sure whether
  45  * GCC or Clang first had __attribute__((no_sanitize(XXX)).
  46  *
  47  * For Clang, we check for __attribute__((no_sanitize(XXX)) with
  48  * __has_attribute, as there are versions of Clang that support
  49  * __attribute__((no_sanitize("undefined")) but don't support
  50  * __attribute__((no_sanitize_undefined)).
  51  *
  52  * We define this here, rather than in funcattrs.h, because we
  53  * only want it used here, we don't want it to be broadly used.
  54  * (Any printer will get this defined, but this should at least
  55  * make it harder for people to find.)
  56  */
  57 #if defined(__GNUC__) && ((__GNUC__ * 100 + __GNUC_MINOR__) >= 409)
  58 #define UNALIGNED_OK    __attribute__((no_sanitize_undefined))
  59 #elif __has_attribute(no_sanitize)
  60 #define UNALIGNED_OK    __attribute__((no_sanitize("undefined")))
  61 #else
  62 #define UNALIGNED_OK
  63 #endif
  64
  65 #ifdef LBL_ALIGN
  66 /*
  67  * The processor doesn't natively handle unaligned loads.
  68  */
  69 #if defined(__GNUC__) && defined(HAVE___ATTRIBUTE__) && \
  70     (defined(__alpha) || defined(__alpha__) || \
  71      defined(__mips) || defined(__mips__))
  72
  73 /*
  74 * This is a GCC-compatible compiler and we have __attribute__, which
  75  * we assume that mean we have __attribute__((packed)), and this is
  76  * MIPS or Alpha, which has instructions that can help when doing
  77  * unaligned loads.
  78  *
  79  * Declare packed structures containing a uint16_t and a uint32_t,
  80  * cast the pointer to point to one of those, and fetch through it;
  81  * the GCC manual doesn't appear to explicitly say that
  82  * __attribute__((packed)) causes the compiler to generate unaligned-safe
  83  * code, but it apppears to do so.
  84  *
  85  * We do this in case the compiler can generate code using those
  86  * instructions to do an unaligned load and pass stuff to "ntohs()" or
  87  * "ntohl()", which might be better than than the code to fetch the
  88  * bytes one at a time and assemble them.  (That might not be the
  89  * case on a little-endian platform, such as DEC's MIPS machines and
  90  * Alpha machines, where "ntohs()" and "ntohl()" might not be done
  91  * inline.)
  92  *
  93  * We do this only for specific architectures because, for example,
  94  * at least some versions of GCC, when compiling for 64-bit SPARC,
  95  * generate code that assumes alignment if we do this.
  96  *
  97  * XXX - add other architectures and compilers as possible and
  98  * appropriate.
  99  *
 100  * HP's C compiler, indicated by __HP_cc being defined, supports
 101  * "#pragma unaligned N" in version A.05.50 and later, where "N"
 102  * specifies a number of bytes at which the typedef on the next
 103  * line is aligned, e.g.
 104  *
 105  *      #pragma unalign 1
 106  *      typedef uint16_t unaligned_uint16_t;
 107  *
 108  * to define unaligned_uint16_t as a 16-bit unaligned data type.
 109  * This could be presumably used, in sufficiently recent versions of
 110  * the compiler, with macros similar to those below.  This would be
 111  * useful only if that compiler could generate better code for PA-RISC
 112  * or Itanium than would be generated by a bunch of shifts-and-ORs.
 113  *
 114  * DEC C, indicated by __DECC being defined, has, at least on Alpha,
 115  * an __unaligned qualifier that can be applied to pointers to get the
 116  * compiler to generate code that does unaligned loads and stores when
 117  * dereferencing the pointer in question.
 118  *
 119  * XXX - what if the native C compiler doesn't support
 120  * __attribute__((packed))?  How can we get it to generate unaligned
 121  * accesses for *specific* items?
 122  */
 123 typedef struct {
 124         uint16_t        val;
 125 } __attribute__((packed)) unaligned_uint16_t;
 126
 127 typedef struct {
 128         uint32_t        val;
 129 } __attribute__((packed)) unaligned_uint32_t;
 130
 131 UNALIGNED_OK static inline uint16_t
 132 EXTRACT_16BITS(const void *p)
 133 {
 134         return ((uint16_t)ntohs(((const unaligned_uint16_t *)(p))->val));
 135 }
 136
 137 UNALIGNED_OK static inline uint32_t
 138 EXTRACT_32BITS(const void *p)
 139 {
 140         return ((uint32_t)ntohl(((const unaligned_uint32_t *)(p))->val));
 141 }
 142
 143 UNALIGNED_OK static inline uint64_t
 144 EXTRACT_64BITS(const void *p)
 145 {
 146         return ((uint64_t)(((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 0)->val)) << 32 |
 147                 ((uint64_t)ntohl(((const unaligned_uint32_t *)(p) + 1)->val)) << 0));
 148 }
 149
 150 #else /* have to do it a byte at a time */
 151 /*
 152  * This isn't a GCC-compatible compiler, we don't have __attribute__,
 153  * or we do but we don't know of any better way with this instruction
 154  * set to do unaligned loads, so do unaligned loads of big-endian
 155  * quantities the hard way - fetch the bytes one at a time and
 156  * assemble them.
 157  */
 158 #define EXTRACT_16BITS(p) \
 159         ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 0)) << 8) | \
 160                     ((uint16_t)(*((const uint8_t *)(p) + 1)) << 0)))
 161 #define EXTRACT_32BITS(p) \
 162         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 24) | \
 163                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 16) | \
 164                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 8) | \
 165                     ((uint32_t)(*((const uint8_t *)(p) + 3)) << 0)))
 166 #define EXTRACT_64BITS(p) \
 167         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 56) | \
 168                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 48) | \
 169                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 40) | \
 170                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 32) | \
 171                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 24) | \
 172                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 16) | \
 173                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 8) | \
 174                     ((uint64_t)(*((const uint8_t *)(p) + 7)) << 0)))
 175 #endif /* must special-case unaligned accesses */
 176 #else /* LBL_ALIGN */
 177 /*
 178  * The processor natively handles unaligned loads, so we can just
 179  * cast the pointer and fetch through it.
 180  */
 181 static inline uint16_t UNALIGNED_OK
 182 EXTRACT_16BITS(const void *p)
 183 {
 184         return ((uint16_t)ntohs(*(const uint16_t *)(p)));
 185 }
 186
 187 static inline uint32_t UNALIGNED_OK
 188 EXTRACT_32BITS(const void *p)
 189 {
 190         return ((uint32_t)ntohl(*(const uint32_t *)(p)));
 191 }
 192
 193 static inline uint64_t UNALIGNED_OK
 194 EXTRACT_64BITS(const void *p)
 195 {
 196         return ((uint64_t)(((uint64_t)ntohl(*((const uint32_t *)(p) + 0))) << 32 |
 197                 ((uint64_t)ntohl(*((const uint32_t *)(p) + 1))) << 0));
 198
 199 }
 200
 201 #endif /* LBL_ALIGN */
 202
 203 #define EXTRACT_24BITS(p) \
 204         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 0)) << 16) | \
 205                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 206                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 0)))
 207
 208 #define EXTRACT_40BITS(p) \
 209         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 32) | \
 210                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 24) | \
 211                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 212                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 8) | \
 213                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 0)))
 214
 215 #define EXTRACT_48BITS(p) \
 216         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 40) | \
 217                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 32) | \
 218                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 24) | \
 219                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 16) | \
 220                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 8) | \
 221                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 0)))
 222
 223 #define EXTRACT_56BITS(p) \
 224         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 0)) << 48) | \
 225                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 40) | \
 226                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 32) | \
 227                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 228                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 16) | \
 229                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 8) | \
 230                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 0)))
 231
 232 /*
 233  * Macros to extract possibly-unaligned little-endian integral values.
 234  * XXX - do loads on little-endian machines that support unaligned loads?
 235  */
 236 #define EXTRACT_LE_16BITS(p) \
 237         ((uint16_t)(((uint16_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 238                     ((uint16_t)(*((const uint8_t *)(p) + 0)) << 0)))
 239 #define EXTRACT_LE_32BITS(p) \
 240         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 241                     ((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 242                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 243                     ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0)))
 244 #define EXTRACT_LE_24BITS(p) \
 245         ((uint32_t)(((uint32_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 246                     ((uint32_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 247                     ((uint32_t)(*((const uint8_t *)(p) + 0)) << 0)))
 248 #define EXTRACT_LE_64BITS(p) \
 249         ((uint64_t)(((uint64_t)(*((const uint8_t *)(p) + 7)) << 56) | \
 250                     ((uint64_t)(*((const uint8_t *)(p) + 6)) << 48) | \
 251                     ((uint64_t)(*((const uint8_t *)(p) + 5)) << 40) | \
 252                     ((uint64_t)(*((const uint8_t *)(p) + 4)) << 32) | \
 253                     ((uint64_t)(*((const uint8_t *)(p) + 3)) << 24) | \
 254                     ((uint64_t)(*((const uint8_t *)(p) + 2)) << 16) | \
 255                     ((uint64_t)(*((const uint8_t *)(p) + 1)) << 8) | \
 256                     ((uint64_t)(*((const uint8_t *)(p) + 0)) << 0)))
 257
 258 /*
 259  * Macros to check the presence of the values in question.
 260  */
 261 #define ND_TTEST_8BITS(p) ND_TTEST2(*(p), 1)
 262 #define ND_TCHECK_8BITS(p) ND_TCHECK2(*(p), 1)
 263
 264 #define ND_TTEST_16BITS(p) ND_TTEST2(*(p), 2)
 265 #define ND_TCHECK_16BITS(p) ND_TCHECK2(*(p), 2)
 266
 267 #define ND_TTEST_24BITS(p) ND_TTEST2(*(p), 3)
 268 #define ND_TCHECK_24BITS(p) ND_TCHECK2(*(p), 3)
 269
 270 #define ND_TTEST_32BITS(p) ND_TTEST2(*(p), 4)
 271 #define ND_TCHECK_32BITS(p) ND_TCHECK2(*(p), 4)
 272
 273 #define ND_TTEST_40BITS(p) ND_TTEST2(*(p), 5)
 274 #define ND_TCHECK_40BITS(p) ND_TCHECK2(*(p), 5)
 275
 276 #define ND_TTEST_48BITS(p) ND_TTEST2(*(p), 6)
 277 #define ND_TCHECK_48BITS(p) ND_TCHECK2(*(p), 6)
 278
 279 #define ND_TTEST_56BITS(p) ND_TTEST2(*(p), 7)
 280 #define ND_TCHECK_56BITS(p) ND_TCHECK2(*(p), 7)
 281
 282 #define ND_TTEST_64BITS(p) ND_TTEST2(*(p), 8)
 283 #define ND_TCHECK_64BITS(p) ND_TCHECK2(*(p), 8)
 284
 285 #define ND_TTEST_128BITS(p) ND_TTEST2(*(p), 16)
 286 #define ND_TCHECK_128BITS(p) ND_TCHECK2(*(p), 16)