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author | peter <peter@FreeBSD.org> | 2001-06-13 10:58:39 +0000 |
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committer | peter <peter@FreeBSD.org> | 2001-06-13 10:58:39 +0000 |
commit | f10fa038c14063eaf2da32ed734e644e5f569694 (patch) | |
tree | 88aef8097c80f09c2f725d61b6da4d433a595a61 /sys/sys/linker_set.h | |
parent | 2514663dd721b9ac234d35a4dac65dfc457ff6bc (diff) | |
download | FreeBSD-src-f10fa038c14063eaf2da32ed734e644e5f569694.zip FreeBSD-src-f10fa038c14063eaf2da32ed734e644e5f569694.tar.gz |
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
Diffstat (limited to 'sys/sys/linker_set.h')
-rw-r--r-- | sys/sys/linker_set.h | 124 |
1 files changed, 89 insertions, 35 deletions
diff --git a/sys/sys/linker_set.h b/sys/sys/linker_set.h index 2bffa9b..0fa115f 100644 --- a/sys/sys/linker_set.h +++ b/sys/sys/linker_set.h @@ -1,5 +1,6 @@ /*- * 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 @@ -31,56 +32,109 @@ /* * The following macros are used to declare global sets of objects, which - * are collected by the linker into a `struct linker_set' as defined below. + * 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. * - * In the MAKE_SET macros below, the lines: + * 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; - * - * are present only to prevent the compiler from producing bogus + * is present only to prevent the compiler from producing bogus * warnings about unused symbols. */ -#ifdef __ELF__ - -#if defined(__alpha__) || defined(__ia64__) -#define MAKE_SET(set, sym) \ +/* Private macros */ +#ifdef __UNDERSCORES__ +#define __MAKE_SET(set, sym, type) \ static void const * const __set_##set##_sym_##sym = &sym; \ - __asm(".section .set." #set ",\"aw\""); \ - __asm(".p2align 3"); \ - __asm(".quad " #sym); \ - __asm(".previous") + __asm(".stabs \"_" #set "\", " #type ", 0, 0, _" #sym) #else -#define MAKE_SET(set, sym) \ +#define __MAKE_SET(set, sym, type) \ static void const * const __set_##set##_sym_##sym = &sym; \ - __asm(".section .set." #set ",\"aw\""); \ - __asm(".p2align 2"); \ - __asm(".long " #sym); \ - __asm(".previous") + __asm(".stabs \"" #set "\", " #type ", 0, 0, " #sym) #endif -#define TEXT_SET(set, sym) MAKE_SET(set, sym) -#define DATA_SET(set, sym) MAKE_SET(set, sym) -#else +/* 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__ */ /* - * 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). + * 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 MAKE_SET(set, sym, type) \ - static void const * const __set_##set##_sym_##sym = &sym; \ - __asm(".stabs \"" #set "\", " #type ", 0, 0, " #sym) -#define TEXT_SET(set, sym) MAKE_SET(set, sym, 23) -#define DATA_SET(set, sym) MAKE_SET(set, sym, 25) +#define SET_FOREACH(pvar, set) \ + for (pvar = SET_BEGIN(set); pvar < SET_LIMIT(set); pvar++) -#endif +#define SET_ITEM(set, i) \ + ((SET_BEGIN(set))[i]) -struct linker_set { - int ls_length; - void *ls_items[1]; /* really ls_length of them, - * trailing NULL */ -}; +/* + * Provide a count of the items in a set. + */ +#define SET_COUNT(set) \ + (SET_LIMIT(set) - SET_BEGIN(set)) -#endif /* _SYS_LINKER_SET_H_ */ +#endif /* _SYS_LINKER_SET_H_ */ |