include/sys/cdefs_elf.h

   1 /*      $NetBSD: cdefs_elf.h,v 1.34 2010/12/08 01:18:55 joerg Exp $     */
   2
   3 /*
   4  * Copyright (c) 1995, 1996 Carnegie-Mellon University.
   5  * All rights reserved.
   6  *
   7  * Author: Chris G. Demetriou
   8  *
   9  * Permission to use, copy, modify and distribute this software and
  10  * its documentation is hereby granted, provided that both the copyright
  11  * notice and this permission notice appear in all copies of the
  12  * software, derivative works or modified versions, and any portions
  13  * thereof, and that both notices appear in supporting documentation.
  14  *
  15  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  16  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  17  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  18  *
  19  * Carnegie Mellon requests users of this software to return to
  20  *
  21  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  22  *  School of Computer Science
  23  *  Carnegie Mellon University
  24  *  Pittsburgh PA 15213-3890
  25  *
  26  * any improvements or extensions that they make and grant Carnegie the
  27  * rights to redistribute these changes.
  28  */
  29
  30 #ifndef _SYS_CDEFS_ELF_H_
  31 #define _SYS_CDEFS_ELF_H_
  32
  33 #ifdef __LEADING_UNDERSCORE
  34 #define _C_LABEL(x)     __CONCAT(_,x)
  35 #define _C_LABEL_STRING(x)      "_"x
  36 #else
  37 #define _C_LABEL(x)     x
  38 #define _C_LABEL_STRING(x)      x
  39 #endif
  40
  41 #if __STDC__
  42 #define ___RENAME(x)    __asm(___STRING(_C_LABEL(x)))
  43 #else
  44 #ifdef __LEADING_UNDERSCORE
  45 #define ___RENAME(x)    ____RENAME(_/**/x)
  46 #define ____RENAME(x)   __asm(___STRING(x))
  47 #else
  48 #define ___RENAME(x)    __asm(___STRING(x))
  49 #endif
  50 #endif
  51
  52 #define __indr_reference(sym,alias)     /* nada, since we do weak refs */
  53
  54 #if __STDC__
  55 #define __strong_alias(alias,sym)                                       \
  56     __asm(".global " _C_LABEL_STRING(#alias) "\n"                       \
  57             _C_LABEL_STRING(#alias) " = " _C_LABEL_STRING(#sym));
  58
  59 #define __weak_alias(alias,sym)                                         \
  60     __asm(".weak " _C_LABEL_STRING(#alias) "\n"                 \
  61             _C_LABEL_STRING(#alias) " = " _C_LABEL_STRING(#sym));
  62
  63 /* Do not use __weak_extern, use __weak_reference instead */
  64 #define __weak_extern(sym)                                              \
  65     __asm(".weak " _C_LABEL_STRING(#sym));
  66
  67 #if __GNUC_PREREQ__(4, 0)
  68 #define __weak_reference(sym)   __attribute__((__weakref__))
  69 #else
  70 #define __weak_reference(sym)   ; __asm(".weak " _C_LABEL_STRING(#sym))
  71 #endif
  72
  73 #if defined(__clang__)
  74 #define __warn_references(sym,msg)                                      \
  75     static __attribute__((__used__, __section__(".gnu.warning." #sym))) \
  76     const char ___CONCAT(__warn_reference_##sym,__COUNTER__)[] = msg;
  77 #else
  78 #define __warn_references(sym,msg)                                      \
  79     __asm(".pushsection .gnu.warning." #sym "\n"                        \
  80           ".ascii \"" msg "\"\n"                                        \
  81           ".popsection");
  82 #endif
  83
  84 #else /* !__STDC__ */
  85
  86 #ifdef __LEADING_UNDERSCORE
  87 #define __weak_alias(alias,sym) ___weak_alias(_/**/alias,_/**/sym)
  88 #define ___weak_alias(alias,sym)                                        \
  89     __asm(".weak alias\nalias = sym");
  90 #else
  91 #define __weak_alias(alias,sym)                                         \
  92     __asm(".weak alias\nalias = sym");
  93 #endif
  94 #ifdef __LEADING_UNDERSCORE
  95 #define __weak_extern(sym) ___weak_extern(_/**/sym)
  96 #define ___weak_extern(sym)                                             \
  97     __asm(".weak sym");
  98 #else
  99 #define __weak_extern(sym)                                              \
 100     __asm(".weak sym");
 101 #endif
 102 #define __warn_references(sym,msg)                                      \
 103     __asm(".pushsection .gnu.warning.sym\n"                             \
 104           ".ascii \"" msg "\"\n"                                        \
 105           ".popsection");
 106
 107 #endif /* !__STDC__ */
 108
 109 #if defined(__clang__)
 110 #define __SECTIONSTRING(_sec, _str)                                     \
 111         static __attribute__((__used__, __section__(#_sec))) const char \
 112         ___CONCAT(__sectstr,__COUNTER__)[] = _str
 113 #elif __STDC__
 114 #define __SECTIONSTRING(_sec, _str)                                     \
 115         __asm(".pushsection " #_sec "\n"                                \
 116               ".asciz \"" _str "\"\n"                                   \
 117               ".popsection")
 118 #else
 119 #define __SECTIONSTRING(_sec, _str)                                     \
 120         __asm(".pushsection _sec\n"                                     \
 121               ".asciz \"" _str "\"\n"                                   \
 122               ".popsection")
 123 #endif
 124
 125 #define __IDSTRING(_n,_s)               __SECTIONSTRING(.ident,_s)
 126
 127 #define __RCSID(_s)                     __IDSTRING(rcsid,_s)
 128 #define __SCCSID(_s)
 129 #define __SCCSID2(_s)
 130 #define __COPYRIGHT(_s)                 __SECTIONSTRING(.copyright,_s)
 131
 132 #define __KERNEL_RCSID(_n, _s)          __RCSID(_s)
 133 #define __KERNEL_SCCSID(_n, _s)
 134 #define __KERNEL_COPYRIGHT(_n, _s)      __COPYRIGHT(_s)
 135
 136 #ifndef __lint__
 137 #define __link_set_make_entry(set, sym)                                 \
 138         static void const * const __link_set_##set##_sym_##sym          \
 139             __section("link_set_" #set) __used = &sym
 140 #define __link_set_make_entry2(set, sym, n)                             \
 141         static void const * const __link_set_##set##_sym_##sym##_##n    \
 142             __section("link_set_" #set) __used = &sym[n]
 143 #else
 144 #define __link_set_make_entry(set, sym)                                 \
 145         extern void const * const __link_set_##set##_sym_##sym
 146 #define __link_set_make_entry2(set, sym, n)                             \
 147         extern void const * const __link_set_##set##_sym_##sym##_##n
 148 #endif /* __lint__ */
 149
 150 #define __link_set_add_text(set, sym)   __link_set_make_entry(set, sym)
 151 #define __link_set_add_rodata(set, sym) __link_set_make_entry(set, sym)
 152 #define __link_set_add_data(set, sym)   __link_set_make_entry(set, sym)
 153 #define __link_set_add_bss(set, sym)    __link_set_make_entry(set, sym)
 154 #define __link_set_add_text2(set, sym, n)   __link_set_make_entry2(set, sym, n)
 155 #define __link_set_add_rodata2(set, sym, n) __link_set_make_entry2(set, sym, n)
 156 #define __link_set_add_data2(set, sym, n)   __link_set_make_entry2(set, sym, n)
 157 #define __link_set_add_bss2(set, sym, n)    __link_set_make_entry2(set, sym, n)
 158
 159 #define __link_set_decl(set, ptype)                                     \
 160         extern ptype * const __start_link_set_##set[];                  \
 161         extern ptype * const __stop_link_set_##set[]                    \
 162
 163 #define __link_set_start(set)   (__start_link_set_##set)
 164 #define __link_set_end(set)     (__stop_link_set_##set)
 165
 166 #define __link_set_count(set)                                           \
 167         (__link_set_end(set) - __link_set_start(set))
 168
 169
 170 #ifdef _KERNEL
 171
 172 /*
 173  * On multiprocessor systems we can gain an improvement in performance
 174  * by being mindful of which cachelines data is placed in.
 175  *
 176  * __read_mostly:
 177  *
 178  *      It makes sense to ensure that rarely modified data is not
 179  *      placed in the same cacheline as frequently modified data.
 180  *      To mitigate the phenomenon known as "false-sharing" we
 181  *      can annotate rarely modified variables with __read_mostly.
 182  *      All such variables are placed into the .data.read_mostly
 183  *      section in the kernel ELF.
 184  *
 185  *      Prime candidates for __read_mostly annotation are variables
 186  *      which are hardly ever modified and which are used in code
 187  *      hot-paths, e.g. pmap_initialized.
 188  *
 189  * __cacheline_aligned:
 190  *
 191  *      Some data structures (mainly locks) benefit from being aligned
 192  *      on a cacheline boundary, and having a cacheline to themselves.
 193  *      This way, the modification of other data items cannot adversely
 194  *      affect the lock and vice versa.
 195  *
 196  *      Any variables annotated with __cacheline_aligned will be
 197  *      placed into the .data.cacheline_aligned ELF section.
 198  */
 199 #define __read_mostly                                           \
 200     __attribute__((__section__(".data.read_mostly")))
 201
 202 #define __cacheline_aligned                                     \
 203     __attribute__((__aligned__(COHERENCY_UNIT)                  \
 204                  __section__(".data.cacheline_aligned")))
 205
 206 #endif /* _KERNEL */
 207
 208 #endif /* !_SYS_CDEFS_ELF_H_ */