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_CONST 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 # include <crt_externs.h>
88
89 # if __LP64__
90 # define MACH_HEADER_TYPE struct mach_header_64
91 # define GETSECTIONDATA_VARIANT getsectdatafromheader_64
92 # define SECTDATA_SIZE_TYPE uint64_t
93 # define MH_EXECUTE_HEADER _NSGetMachExecuteHeader()
94 # else
95 # define MACH_HEADER_TYPE struct mach_header
96 # define GETSECTIONDATA_VARIANT getsectdatafromheader
97 # define SECTDATA_SIZE_TYPE uint32_t
98 # define MH_EXECUTE_HEADER _NSGetMachExecuteHeader()
99 # endif
100 #endif
101
102 #if __LP64__
103 # define LINKER_SET_ENTRY_PACKED
104 # define LINKER_SET_SEGMENT __DATA_CONST
105 # define LINKER_SET_SEGMENT_CSTR "__DATA_CONST"
106 #else
107 # define LINKER_SET_ENTRY_PACKED __attribute__((packed))
108 # define LINKER_SET_SEGMENT __DATA
109 # define LINKER_SET_SEGMENT_CSTR "__DATA"
110 #endif
111
112 /*
113 * Private macros, not to be used outside this header file.
114 *
115 * The objective of this macro stack is to produce the following output,
116 * given SET and SYM as arguments:
117 *
118 * void const * __set_SET_sym_SYM __attribute__((section("__DATA_CONST,SET"))) = & SYM
119 */
120
121 /* Wrap entries in a type that can be blacklisted from KASAN */
122 struct linker_set_entry {
123 void *ptr;
124 } LINKER_SET_ENTRY_PACKED;
125
126 #ifdef __LS_VA_STRINGIFY__
127 # undef __LS_VA_STRINGIFY__
128 #endif
129 #ifdef __LS_VA_STRCONCAT__
130 # undef __LS_VA_STRCONCAT__
131 #endif
132 #define __LS_VA_STRINGIFY(_x ...) #_x
133 #define __LS_VA_STRCONCAT(_x, _y) __LS_VA_STRINGIFY(_x,_y)
134 #define __LINKER_MAKE_SET(_set, _sym) \
135 /*__unused*/ /*static*/ const struct linker_set_entry /*const*/ __set_##_set##_sym_##_sym \
136 __attribute__ ((section(__LS_VA_STRCONCAT(LINKER_SET_SEGMENT,_set)),used)) = { (void *)&_sym }
137 /* the line above is very fragile - if your compiler breaks linker sets,
138 * just play around with "static", "const", "used" etc. :-) */
139
140 /*
141 * Public macros.
142 */
143 #define LINKER_SET_ENTRY(_set, _sym) __LINKER_MAKE_SET(_set, _sym)
144
145 /*
146 * FreeBSD compatibility.
147 */
148 #ifdef __APPLE_API_OBSOLETE
149 # define TEXT_SET(_set, _sym) __LINKER_MAKE_SET(_set, _sym)
150 # define DATA_SET(_set, _sym) __LINKER_MAKE_SET(_set, _sym)
151 # define BSS_SET(_set, _sym) __LINKER_MAKE_SET(_set, _sym)
152 # define ABS_SET(_set, _sym) __LINKER_MAKE_SET(_set, _sym)
153 # define SET_ENTRY(_set, _sym) __LINKER_MAKE_SET(_set, _sym)
154 #endif /* __APPLE_API_OBSOLETE */
155
156 /*
157 * Extended linker set API.
158 *
159 * Since linker sets are per-object-file, and we may have multiple
160 * object files, we need to be able to specify which object's set
161 * to scan.
162 *
163 * The set itself is a contiguous array of pointers to the objects
164 * within the set.
165 */
166
167 /*
168 * Public interface.
169 *
170 * void **LINKER_SET_OBJECT_BEGIN(_object, _set)
171 * Preferred interface to linker_set_object_begin(), takes set name unquoted.
172 * void **LINKER_SET_OBJECT_LIMIT(_object, _set)
173 * Preferred interface to linker_set_object_begin(), takes set name unquoted.
174 * LINKER_SET_OBJECT_FOREACH(_object, (set_member_type **)_pvar, _cast, _set)
175 * Iterates over the members of _set within _object. Since the set contains
176 * pointers to its elements, for a set of elements of type etyp, _pvar must
177 * be (etyp **).
178 * LINKER_SET_FOREACH((set_member_type **)_pvar, _cast, _set)
179 *
180 * Example of _cast: For the _pvar "struct sysctl_oid **oidpp", _cast would be
181 * "struct sysctl_oid **"
182 *
183 */
184
185 #define LINKER_SET_OBJECT_BEGIN(_object, _set) __linker_set_object_begin(_object, _set)
186 #define LINKER_SET_OBJECT_LIMIT(_object, _set) __linker_set_object_limit(_object, _set)
187
188 #define LINKER_SET_OBJECT_FOREACH(_object, _pvar, _cast, _set) \
189 for (_pvar = (_cast) LINKER_SET_OBJECT_BEGIN(_object, _set); \
190 _pvar < (_cast) LINKER_SET_OBJECT_LIMIT(_object, _set); \
191 _pvar++)
192
193 #define LINKER_SET_OBJECT_ITEM(_object, _cast, _set, _i) \
194 (((_cast)(LINKER_SET_OBJECT_BEGIN(_object, _set)))[_i])
195
196 #define LINKER_SET_FOREACH(_pvar, _cast, _set) \
197 LINKER_SET_OBJECT_FOREACH((MACH_HEADER_TYPE *)MH_EXECUTE_HEADER, _pvar, _cast, _set)
198
199 /*
200 * Implementation.
201 *
202 * void **__linker_set_object_begin(_header, _set)
203 * Returns a pointer to the first pointer in the linker set.
204 * void **__linker_set_object_limi(_header, _set)
205 * Returns an upper bound to the linker set (base + size).
206 */
207
208 static __inline intptr_t
__linker_get_slide(struct mach_header * _header)209 __linker_get_slide(struct mach_header *_header)
210 {
211 #ifndef KERNEL
212 /*
213 * Gross.
214 *
215 * We cannot get the image slide directly from the header, so we need to
216 * determine the image's index and ask for the slide of that index.
217 */
218 uint32_t i = 0;
219 for (i = 0; i < _dyld_image_count(); i++) {
220 const struct mach_header *hdr = _dyld_get_image_header(i);
221 if (_header == hdr) {
222 return _dyld_get_image_vmaddr_slide(i);
223 }
224 }
225 return 0;
226 #else
227 (void)_header;
228 return 0;
229 #endif
230 }
231
232 static __inline void **
233 __linker_set_object_begin(MACH_HEADER_TYPE *_header, const char *_set)
234 __attribute__((__const__));
235 static __inline void **
__linker_set_object_begin(MACH_HEADER_TYPE * _header,const char * _set)236 __linker_set_object_begin(MACH_HEADER_TYPE *_header, const char *_set)
237 {
238 char *_set_begin;
239 SECTDATA_SIZE_TYPE _size;
240
241 _set_begin = (char *)GETSECTIONDATA_VARIANT(_header, LINKER_SET_SEGMENT_CSTR, _set, &_size);
242 _set_begin += __linker_get_slide((struct mach_header *)_header);
243 return (void **)(uintptr_t)_set_begin;
244 }
245
246 static __inline void **
247 __linker_set_object_limit(MACH_HEADER_TYPE *_header, const char *_set)
248 __attribute__((__const__));
249 static __inline void **
__linker_set_object_limit(MACH_HEADER_TYPE * _header,const char * _set)250 __linker_set_object_limit(MACH_HEADER_TYPE *_header, const char *_set)
251 {
252 char *_set_begin;
253 SECTDATA_SIZE_TYPE _size;
254
255 _set_begin = (char *)GETSECTIONDATA_VARIANT(_header, LINKER_SET_SEGMENT_CSTR, _set, &_size);
256 _set_begin += __linker_get_slide((struct mach_header *)_header);
257
258 return (void **) ((uintptr_t) _set_begin + _size);
259 }
260
261 #endif /* !KERNEL || __APPLE_API_PRIVATE */
262
263 #endif /* _SYS_LINKER_SET_H_ */
264