freebsd-skq/sys/sys/linker_set.h
peter f10fa038c1 With this commit, I hereby pronounce gensetdefs past its use-by date.
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
2001-06-13 10:58:39 +00:00

141 lines
4.7 KiB
C

/*-
* Copyright (c) 1999 John D. Polstra
* Copyright (c) 1999,2001 Peter Wemm <peter@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _SYS_LINKER_SET_H_
#define _SYS_LINKER_SET_H_
/*
* The following macros are used to declare global sets of objects, which
* are collected by the linker into a `linker_set' as defined below.
* For ELF, this is done by constructing a separate segment for each set.
* For a.out, it is done automatically by the linker.
*/
#if defined(__ELF__)
/*
* Private macros, not to be used outside this header file.
*/
/* this bit of h0h0magic brought to you by cpp */
#define __GLOBL(sym) __GLOBL2(sym)
#define __GLOBL2(sym) __asm(".globl " #sym)
#define __MAKE_SET(set, sym) \
__GLOBL(__CONCAT(__start_set_,set)); \
__GLOBL(__CONCAT(__stop_set_,set)); \
static void const * const __set_##set##_sym_##sym \
__attribute__((__section__("set_" #set),__unused__)) = &sym
/*
* Public macros.
*/
#define TEXT_SET(set, sym) __MAKE_SET(set, sym)
#define DATA_SET(set, sym) __MAKE_SET(set, sym)
#define BSS_SET(set, sym) __MAKE_SET(set, sym)
#define ABS_SET(set, sym) __MAKE_SET(set, sym)
#define SET_ENTRY(set, sym) __MAKE_SET(set, sym)
/*
* Initialize before referring to a give linker set
*/
#define SET_DECLARE(set, ptype) \
extern ptype *__CONCAT(__start_set_,set); \
extern ptype *__CONCAT(__stop_set_,set)
#define SET_BEGIN(set) \
(&__CONCAT(__start_set_,set))
#define SET_LIMIT(set) \
(&__CONCAT(__stop_set_,set))
#else /* __ELF__ */
/*
* The old way. This depends on GNU ld extensions that are not widely
* available outside of the a.out format.
*
* NB: the constants defined below must match those defined in
* ld/ld.h. Since their calculation requires arithmetic, we
* can't name them symbolically (e.g., 23 is N_SETT | N_EXT).
*
* In the __MAKE_SET macro below, the line:
* static void const * const __set_##set##_sym_##sym = &sym;
* is present only to prevent the compiler from producing bogus
* warnings about unused symbols.
*/
/* Private macros */
#ifdef __UNDERSCORES__
#define __MAKE_SET(set, sym, type) \
static void const * const __set_##set##_sym_##sym = &sym; \
__asm(".stabs \"_" #set "\", " #type ", 0, 0, _" #sym)
#else
#define __MAKE_SET(set, sym, type) \
static void const * const __set_##set##_sym_##sym = &sym; \
__asm(".stabs \"" #set "\", " #type ", 0, 0, " #sym)
#endif
/* Public Macros */
#define TEXT_SET(set, sym) __MAKE_SET(set, sym, 23)
#define DATA_SET(set, sym) __MAKE_SET(set, sym, 25)
#define BSS_SET(set, sym) __MAKE_SET(set, sym, 27)
#define ABS_SET(set, sym) __MAKE_SET(set, sym, 21)
#define SET_ENTRY(set, sym) error error must provide text/data type
#define SET_DECLARE(set, ptype) \
extern struct { \
int ls_length; \
ptype *ls_items[1]; \
} set
#define SET_BEGIN(set) \
(&((set).ls_items[0]))
#define SET_LIMIT(set) \
(&((set).ls_items[(set).ls_length]))
#endif /* __ELF__ */
/*
* Iterate over all the elements of a set.
*
* Sets always contain addresses of things, and "pvar" points to words
* containing those addresses. Thus is must be declared as "type **pvar",
* and the address of each set item is obtained inside the loop by "*pvar".
*/
#define SET_FOREACH(pvar, set) \
for (pvar = SET_BEGIN(set); pvar < SET_LIMIT(set); pvar++)
#define SET_ITEM(set, i) \
((SET_BEGIN(set))[i])
/*
* Provide a count of the items in a set.
*/
#define SET_COUNT(set) \
(SET_LIMIT(set) - SET_BEGIN(set))
#endif /* _SYS_LINKER_SET_H_ */