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