os/linker_set.h

   1 /*
   2  * Copyright (c) 2006-2008 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  *
  28  *
  29  * Copyright (c) 1999 John D. Polstra
  30  * All rights reserved.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  */
  54
  55 #ifndef _SYS_LINKER_SET_H_
  56 #define _SYS_LINKER_SET_H_
  57
  58 #include <sys/appleapiopts.h>
  59 #if !defined(KERNEL) || defined(__APPLE_API_PRIVATE)
  60
  61 /*
  62  * The following macros are used to declare global sets of objects, which
  63  * are collected by the linker into a `linker set' as defined below.
  64  * For Mach-O, this is done by constructing a separate segment inside the
  65  * __DATA section for each set.  The contents of this segment are an array
  66  * of pointers to the objects in the set.
  67  *
  68  * Note that due to limitations of the Mach-O format, there cannot
  69  * be more than 255 sections in a segment, so linker set usage should be
  70  * conserved.  Set names may not exceed 16 characters.
  71  */
  72
  73 #ifdef KERNEL
  74 # include <mach-o/loader.h>
  75 # include <libkern/kernel_mach_header.h>
  76
  77 # define MACH_HEADER_TYPE kernel_mach_header_t
  78 # define GETSECTIONDATA_VARIANT getsectdatafromheader
  79 # define SECTDATA_SIZE_TYPE unsigned long
  80 # define MH_EXECUTE_HEADER &_mh_execute_header
  81 # define IMAGE_SLIDE_CORRECT 0
  82 #else
  83 # include <mach-o/ldsyms.h>
  84 # include <mach-o/getsect.h>
  85 # include <mach-o/loader.h>
  86 # include <mach-o/dyld.h>
  87
  88 # if __LP64__
  89 #  define MACH_HEADER_TYPE struct mach_header_64
  90 #  define GETSECTIONDATA_VARIANT getsectdatafromheader_64
  91 #  define SECTDATA_SIZE_TYPE uint64_t
  92 #  define MH_EXECUTE_HEADER _NSGetMachExecuteHeader()
  93 # else
  94 #  define MACH_HEADER_TYPE struct mach_header
  95 #  define GETSECTIONDATA_VARIANT getsectdatafromheader
  96 #  define SECTDATA_SIZE_TYPE uint32_t
  97 #  define MH_EXECUTE_HEADER _NSGetMachExecuteHeader()
  98 # endif
  99 #endif
 100
 101
 102 /*
 103  * Private macros, not to be used outside this header file.
 104  *
 105  * The objective of this macro stack is to produce the following output,
 106  * given SET and SYM as arguments:
 107  *
 108  *  void const * __set_SET_sym_SYM __attribute__((section("__DATA,SET"))) = & SYM
 109  */
 110
 111 /* Wrap entries in a type that can be blacklisted from KASAN */
 112 struct linker_set_entry {
 113         void *ptr;
 114 } __attribute__((packed));
 115
 116 #ifdef __LS_VA_STRINGIFY__
 117 #  undef __LS_VA_STRINGIFY__
 118 #endif
 119 #ifdef __LS_VA_STRCONCAT__
 120 #  undef __LS_VA_STRCONCAT__
 121 #endif
 122 #define __LS_VA_STRINGIFY(_x ...)        #_x
 123 #define __LS_VA_STRCONCAT(_x, _y)        __LS_VA_STRINGIFY(_x,_y)
 124 #define __LINKER_MAKE_SET(_set, _sym)                                   \
 125         /*__unused*/ /*static*/ const struct linker_set_entry /*const*/ __set_##_set##_sym_##_sym               \
 126         __attribute__ ((section(__LS_VA_STRCONCAT(__DATA,_set)),used)) = { (void *)&_sym }
 127 /* the line above is very fragile - if your compiler breaks linker sets,
 128  *  just play around with "static", "const", "used" etc. :-) */
 129
 130 /*
 131  * Public macros.
 132  */
 133 #define LINKER_SET_ENTRY(_set, _sym)    __LINKER_MAKE_SET(_set, _sym)
 134
 135 /*
 136  * FreeBSD compatibility.
 137  */
 138 #ifdef __APPLE_API_OBSOLETE
 139 # define TEXT_SET(_set, _sym)   __LINKER_MAKE_SET(_set, _sym)
 140 # define DATA_SET(_set, _sym)   __LINKER_MAKE_SET(_set, _sym)
 141 # define BSS_SET(_set, _sym)    __LINKER_MAKE_SET(_set, _sym)
 142 # define ABS_SET(_set, _sym)    __LINKER_MAKE_SET(_set, _sym)
 143 # define SET_ENTRY(_set, _sym)  __LINKER_MAKE_SET(_set, _sym)
 144 #endif /* __APPLE_API_OBSOLETE */
 145
 146 /*
 147  * Extended linker set API.
 148  *
 149  * Since linker sets are per-object-file, and we may have multiple
 150  * object files, we need to be able to specify which object's set
 151  * to scan.
 152  *
 153  * The set itself is a contiguous array of pointers to the objects
 154  * within the set.
 155  */
 156
 157 /*
 158  * Public interface.
 159  *
 160  * void **LINKER_SET_OBJECT_BEGIN(_object, _set)
 161  *      Preferred interface to linker_set_object_begin(), takes set name unquoted.
 162  * void **LINKER_SET_OBJECT_LIMIT(_object, _set)
 163  *      Preferred interface to linker_set_object_begin(), takes set name unquoted.
 164  * LINKER_SET_OBJECT_FOREACH(_object, (set_member_type **)_pvar, _cast, _set)
 165  *      Iterates over the members of _set within _object.  Since the set contains
 166  *      pointers to its elements, for a set of elements of type etyp, _pvar must
 167  *      be (etyp **).
 168  * LINKER_SET_FOREACH((set_member_type **)_pvar, _cast, _set)
 169  *
 170  * Example of _cast: For the _pvar "struct sysctl_oid **oidpp", _cast would be
 171  *                   "struct sysctl_oid **"
 172  *
 173  */
 174
 175 #define LINKER_SET_OBJECT_BEGIN(_object, _set)  __linker_set_object_begin(_object, _set)
 176 #define LINKER_SET_OBJECT_LIMIT(_object, _set)  __linker_set_object_limit(_object, _set)
 177
 178 #define LINKER_SET_OBJECT_FOREACH(_object, _pvar, _cast, _set)          \
 179         for (_pvar = (_cast) LINKER_SET_OBJECT_BEGIN(_object, _set);    \
 180              _pvar < (_cast) LINKER_SET_OBJECT_LIMIT(_object, _set);    \
 181              _pvar++)
 182
 183 #define LINKER_SET_OBJECT_ITEM(_object, _cast, _set, _i)                \
 184         (((_cast)(LINKER_SET_OBJECT_BEGIN(_object, _set)))[_i])
 185
 186 #define LINKER_SET_FOREACH(_pvar, _cast, _set)                                  \
 187         LINKER_SET_OBJECT_FOREACH((MACH_HEADER_TYPE *)MH_EXECUTE_HEADER, _pvar, _cast, _set)
 188
 189 /*
 190  * Implementation.
 191  *
 192  * void **__linker_set_object_begin(_header, _set)
 193  *      Returns a pointer to the first pointer in the linker set.
 194  * void **__linker_set_object_limi(_header, _set)
 195  *      Returns an upper bound to the linker set (base + size).
 196  */
 197
 198 static __inline intptr_t
 199 __linker_get_slide(struct mach_header *_header)
 200 {
 201 #ifndef KERNEL
 202         /*
 203          * Gross.
 204          *
 205          * We cannot get the image slide directly from the header, so we need to
 206          * determine the image's index and ask for the slide of that index.
 207          */
 208         uint32_t i = 0;
 209         for (i = 0; i < _dyld_image_count(); i++) {
 210                 const struct mach_header *hdr = _dyld_get_image_header(i);
 211                 if (_header == hdr) {
 212                         return _dyld_get_image_vmaddr_slide(i);
 213                 }
 214         }
 215         return 0;
 216 #else
 217         return 0;
 218 #endif
 219 }
 220
 221 static __inline void **
 222 __linker_set_object_begin(MACH_HEADER_TYPE *_header, const char *_set)
 223 __attribute__((__const__));
 224 static __inline void **
 225 __linker_set_object_begin(MACH_HEADER_TYPE *_header, const char *_set)
 226 {
 227         void *_set_begin;
 228         SECTDATA_SIZE_TYPE _size;
 229
 230         _set_begin = GETSECTIONDATA_VARIANT(_header, "__DATA", _set, &_size);
 231         _set_begin += __linker_get_slide((struct mach_header *)_header);
 232         return (void **) _set_begin;
 233 }
 234
 235 static __inline void **
 236 __linker_set_object_limit(MACH_HEADER_TYPE *_header, const char *_set)
 237 __attribute__((__const__));
 238 static __inline void **
 239 __linker_set_object_limit(MACH_HEADER_TYPE *_header, const char *_set)
 240 {
 241         void *_set_begin;
 242         SECTDATA_SIZE_TYPE _size;
 243
 244         _set_begin = GETSECTIONDATA_VARIANT(_header, "__DATA", _set, &_size);
 245         _set_begin += __linker_get_slide((struct mach_header *)_header);
 246
 247         return (void **) ((uintptr_t) _set_begin + _size);
 248 }
 249
 250 #endif /* !KERNEL || __APPLE_API_PRIVATE */
 251
 252 #endif /* _SYS_LINKER_SET_H_ */