bsd/sys/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 #else
  77 # include <mach-o/ldsyms.h>
  78 # include <mach-o/getsect.h>
  79 # include <mach-o/loader.h>
  80 #endif
  81
  82
  83 /*
  84  * Private macros, not to be used outside this header file.
  85  *
  86  * The objective of this macro stack is to produce the following output,
  87  * given SET and SYM as arguments:
  88  *
  89  *  void const * __set_SET_sym_SYM __attribute__((section("__DATA,SET"))) = & SYM
  90  */
  91
  92 /* Wrap entries in a type that can be blacklisted from KASAN */
  93 struct linker_set_entry {
  94         void *ptr;
  95 } __attribute__((packed));
  96
  97 #ifdef __LS_VA_STRINGIFY__
  98 #  undef __LS_VA_STRINGIFY__
  99 #endif
 100 #ifdef __LS_VA_STRCONCAT__
 101 #  undef __LS_VA_STRCONCAT__
 102 #endif
 103 #define __LS_VA_STRINGIFY(_x ...)        #_x
 104 #define __LS_VA_STRCONCAT(_x, _y)        __LS_VA_STRINGIFY(_x,_y)
 105 #define __LINKER_MAKE_SET(_set, _sym)                                   \
 106         /*__unused*/ /*static*/ const struct linker_set_entry /*const*/ __set_##_set##_sym_##_sym               \
 107         __attribute__ ((section(__LS_VA_STRCONCAT(__DATA,_set)),used)) = { (void *)&_sym }
 108 /* the line above is very fragile - if your compiler breaks linker sets,
 109  *  just play around with "static", "const", "used" etc. :-) */
 110
 111 /*
 112  * Public macros.
 113  */
 114 #define LINKER_SET_ENTRY(_set, _sym)    __LINKER_MAKE_SET(_set, _sym)
 115
 116 /*
 117  * FreeBSD compatibility.
 118  */
 119 #ifdef __APPLE_API_OBSOLETE
 120 # define TEXT_SET(_set, _sym)   __LINKER_MAKE_SET(_set, _sym)
 121 # define DATA_SET(_set, _sym)   __LINKER_MAKE_SET(_set, _sym)
 122 # define BSS_SET(_set, _sym)    __LINKER_MAKE_SET(_set, _sym)
 123 # define ABS_SET(_set, _sym)    __LINKER_MAKE_SET(_set, _sym)
 124 # define SET_ENTRY(_set, _sym)  __LINKER_MAKE_SET(_set, _sym)
 125 #endif /* __APPLE_API_OBSOLETE */
 126
 127 /*
 128  * Extended linker set API.
 129  *
 130  * Since linker sets are per-object-file, and we may have multiple
 131  * object files, we need to be able to specify which object's set
 132  * to scan.
 133  *
 134  * The set itself is a contiguous array of pointers to the objects
 135  * within the set.
 136  */
 137
 138 /*
 139  * Public interface.
 140  *
 141  * void **LINKER_SET_OBJECT_BEGIN(_object, _set)
 142  *      Preferred interface to linker_set_object_begin(), takes set name unquoted.
 143  * void **LINKER_SET_OBJECT_LIMIT(_object, _set)
 144  *      Preferred interface to linker_set_object_begin(), takes set name unquoted.
 145  * LINKER_SET_OBJECT_FOREACH(_object, (set_member_type **)_pvar, _cast, _set)
 146  *      Iterates over the members of _set within _object.  Since the set contains
 147  *      pointers to its elements, for a set of elements of type etyp, _pvar must
 148  *      be (etyp **).
 149  * LINKER_SET_FOREACH((set_member_type **)_pvar, _cast, _set)
 150  *
 151  * Example of _cast: For the _pvar "struct sysctl_oid **oidpp", _cast would be
 152  *                   "struct sysctl_oid **"
 153  *
 154  */
 155
 156 #define LINKER_SET_OBJECT_BEGIN(_object, _set)  __linker_set_object_begin(_object, _set)
 157 #define LINKER_SET_OBJECT_LIMIT(_object, _set)  __linker_set_object_limit(_object, _set)
 158
 159 #define LINKER_SET_OBJECT_FOREACH(_object, _pvar, _cast, _set)          \
 160         for (_pvar = (_cast) LINKER_SET_OBJECT_BEGIN(_object, _set);    \
 161              _pvar < (_cast) LINKER_SET_OBJECT_LIMIT(_object, _set);    \
 162              _pvar++)
 163
 164 #define LINKER_SET_OBJECT_ITEM(_object, _cast, _set, _i)                \
 165         (((_cast)(LINKER_SET_OBJECT_BEGIN(_object, _set)))[_i])
 166
 167 #define LINKER_SET_FOREACH(_pvar, _cast, _set)                                  \
 168         LINKER_SET_OBJECT_FOREACH((kernel_mach_header_t *)&_mh_execute_header, _pvar, _cast, _set)
 169
 170 /*
 171  * Implementation.
 172  *
 173  * void **__linker_set_object_begin(_header, _set)
 174  *      Returns a pointer to the first pointer in the linker set.
 175  * void **__linker_set_object_limi(_header, _set)
 176  *      Returns an upper bound to the linker set (base + size).
 177  */
 178
 179 static __inline void **
 180 __linker_set_object_begin(kernel_mach_header_t *_header, const char *_set)
 181 __attribute__((__const__));
 182 static __inline void **
 183 __linker_set_object_begin(kernel_mach_header_t *_header, const char *_set)
 184 {
 185         void *_set_begin;
 186         unsigned long _size;
 187
 188         _set_begin = getsectdatafromheader(_header, "__DATA", _set, &_size);
 189         return (void **) _set_begin;
 190 }
 191
 192 static __inline void **
 193 __linker_set_object_limit(kernel_mach_header_t *_header, const char *_set)
 194 __attribute__((__const__));
 195 static __inline void **
 196 __linker_set_object_limit(kernel_mach_header_t *_header, const char *_set)
 197 {
 198         void *_set_begin;
 199         unsigned long _size;
 200
 201         _set_begin = getsectdatafromheader(_header, "__DATA", _set, &_size);
 202
 203         return (void **) ((uintptr_t) _set_begin + _size);
 204 }
 205
 206 #endif /* !KERNEL || __APPLE_API_PRIVATE */
 207
 208 #endif /* _SYS_LINKER_SET_H_ */