f41325db5f
Replace the a.out emulation of 'struct linker_set' with something a little more flexible. <sys/linker_set.h> now provides macros for accessing elements and completely hides the implementation. The linker_set.h macros have been on the back burner in various forms since 1998 and has ideas and code from Mike Smith (SET_FOREACH()), John Polstra (ELF clue) and myself (cleaned up API and the conversion of the rest of the kernel to use it). The macros declare a strongly typed set. They return elements with the type that you declare the set with, rather than a generic void *. For ELF, we use the magic ld symbols (__start_<setname> and __stop_<setname>). Thanks to Richard Henderson <rth@redhat.com> for the trick about how to force ld to provide them for kld's. For a.out, we use the old linker_set struct. NOTE: the item lists are no longer null terminated. This is why the code impact is high in certain areas. The runtime linker has a new method to find the linker set boundaries depending on which backend format is in use. linker sets are still module/kld unfriendly and should never be used for anything that may be modular one day. Reviewed by: eivind
141 lines
4.7 KiB
C
141 lines
4.7 KiB
C
/*-
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* Copyright (c) 1999 John D. Polstra
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* Copyright (c) 1999,2001 Peter Wemm <peter@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _SYS_LINKER_SET_H_
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#define _SYS_LINKER_SET_H_
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/*
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* The following macros are used to declare global sets of objects, which
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* are collected by the linker into a `linker_set' as defined below.
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* For ELF, this is done by constructing a separate segment for each set.
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* For a.out, it is done automatically by the linker.
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*/
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#if defined(__ELF__)
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/*
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* Private macros, not to be used outside this header file.
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*/
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/* this bit of h0h0magic brought to you by cpp */
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#define __GLOBL(sym) __GLOBL2(sym)
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#define __GLOBL2(sym) __asm(".globl " #sym)
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#define __MAKE_SET(set, sym) \
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__GLOBL(__CONCAT(__start_set_,set)); \
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__GLOBL(__CONCAT(__stop_set_,set)); \
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static void const * const __set_##set##_sym_##sym \
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__attribute__((__section__("set_" #set),__unused__)) = &sym
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/*
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* Public macros.
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*/
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#define TEXT_SET(set, sym) __MAKE_SET(set, sym)
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#define DATA_SET(set, sym) __MAKE_SET(set, sym)
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#define BSS_SET(set, sym) __MAKE_SET(set, sym)
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#define ABS_SET(set, sym) __MAKE_SET(set, sym)
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#define SET_ENTRY(set, sym) __MAKE_SET(set, sym)
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/*
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* Initialize before referring to a give linker set
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*/
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#define SET_DECLARE(set, ptype) \
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extern ptype *__CONCAT(__start_set_,set); \
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extern ptype *__CONCAT(__stop_set_,set)
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#define SET_BEGIN(set) \
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(&__CONCAT(__start_set_,set))
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#define SET_LIMIT(set) \
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(&__CONCAT(__stop_set_,set))
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#else /* __ELF__ */
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/*
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* The old way. This depends on GNU ld extensions that are not widely
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* available outside of the a.out format.
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*
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* NB: the constants defined below must match those defined in
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* ld/ld.h. Since their calculation requires arithmetic, we
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* can't name them symbolically (e.g., 23 is N_SETT | N_EXT).
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*
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* In the __MAKE_SET macro below, the line:
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* static void const * const __set_##set##_sym_##sym = &sym;
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* is present only to prevent the compiler from producing bogus
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* warnings about unused symbols.
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*/
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/* Private macros */
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#ifdef __UNDERSCORES__
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#define __MAKE_SET(set, sym, type) \
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static void const * const __set_##set##_sym_##sym = &sym; \
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__asm(".stabs \"_" #set "\", " #type ", 0, 0, _" #sym)
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#else
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#define __MAKE_SET(set, sym, type) \
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static void const * const __set_##set##_sym_##sym = &sym; \
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__asm(".stabs \"" #set "\", " #type ", 0, 0, " #sym)
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#endif
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/* Public Macros */
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#define TEXT_SET(set, sym) __MAKE_SET(set, sym, 23)
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#define DATA_SET(set, sym) __MAKE_SET(set, sym, 25)
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#define BSS_SET(set, sym) __MAKE_SET(set, sym, 27)
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#define ABS_SET(set, sym) __MAKE_SET(set, sym, 21)
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#define SET_ENTRY(set, sym) error error must provide text/data type
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#define SET_DECLARE(set, ptype) \
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extern struct { \
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int ls_length; \
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ptype *ls_items[1]; \
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} set
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#define SET_BEGIN(set) \
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(&((set).ls_items[0]))
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#define SET_LIMIT(set) \
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(&((set).ls_items[(set).ls_length]))
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#endif /* __ELF__ */
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/*
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* Iterate over all the elements of a set.
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*
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* Sets always contain addresses of things, and "pvar" points to words
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* containing those addresses. Thus is must be declared as "type **pvar",
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* and the address of each set item is obtained inside the loop by "*pvar".
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*/
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#define SET_FOREACH(pvar, set) \
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for (pvar = SET_BEGIN(set); pvar < SET_LIMIT(set); pvar++)
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#define SET_ITEM(set, i) \
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((SET_BEGIN(set))[i])
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/*
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* Provide a count of the items in a set.
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*/
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#define SET_COUNT(set) \
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(SET_LIMIT(set) - SET_BEGIN(set))
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#endif /* _SYS_LINKER_SET_H_ */
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