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312 lines
13 KiB
C
312 lines
13 KiB
C
/* Run-time dynamic linker data structures for loaded ELF shared objects.
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Copyright (C) 1995, 1996 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef _LINK_H
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#define _LINK_H 1
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#define __need_size_t
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#include <stddef.h>
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#include <elf.h>
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/* We use this macro to refer to ELF types independent of the native wordsize.
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`ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
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#define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type)
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#define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
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#define _ElfW(e,w,t) _ElfW_1 (e, w, _##t)
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#define _ElfW_1(e,w,t) e##w##t
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#include <elfclass.h> /* Defines __ELF_NATIVE_CLASS. */
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/* Rendezvous structure used by the run-time dynamic linker to communicate
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details of shared object loading to the debugger. If the executable's
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dynamic section has a DT_DEBUG element, the run-time linker sets that
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element's value to the address where this structure can be found. */
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struct r_debug
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{
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int r_version; /* Version number for this protocol. */
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struct link_map *r_map; /* Head of the chain of loaded objects. */
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/* This is the address of a function internal to the run-time linker,
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that will always be called when the linker begins to map in a
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library or unmap it, and again when the mapping change is complete.
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The debugger can set a breakpoint at this address if it wants to
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notice shared object mapping changes. */
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ElfW(Addr) r_brk;
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enum
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{
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/* This state value describes the mapping change taking place when
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the `r_brk' address is called. */
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RT_CONSISTENT, /* Mapping change is complete. */
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RT_ADD, /* Beginning to add a new object. */
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RT_DELETE, /* Beginning to remove an object mapping. */
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} r_state;
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ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */
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};
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/* This is the instance of that structure used by the dynamic linker. */
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extern struct r_debug _r_debug;
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/* This symbol refers to the "dynamic structure" in the `.dynamic' section
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of whatever module refers to `_DYNAMIC'. So, to find its own
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`struct r_debug', a program could do:
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for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL)
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if (dyn->d_tag == DT_DEBUG) r_debug = (struct r_debug) dyn->d_un.d_ptr;
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*/
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extern ElfW(Dyn) _DYNAMIC[];
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/* Structure describing a loaded shared object. The `l_next' and `l_prev'
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members form a chain of all the shared objects loaded at startup.
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These data structures exist in space used by the run-time dynamic linker;
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modifying them may have disastrous results. */
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struct link_map
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{
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/* These first few members are part of the protocol with the debugger.
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This is the same format used in SVR4. */
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ElfW(Addr) l_addr; /* Base address shared object is loaded at. */
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char *l_name; /* Absolute file name object was found in. */
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ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */
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struct link_map *l_next, *l_prev; /* Chain of loaded objects. */
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/* All following members are internal to the dynamic linker.
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They may change without notice. */
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const char *l_libname; /* Name requested (before search). */
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/* Indexed pointers to dynamic section.
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[0,DT_NUM) are indexed by the processor-independent tags.
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[DT_NUM,DT_NUM+DT_PROCNUM] are indexed by the tag minus DT_LOPROC. */
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ElfW(Dyn) *l_info[DT_NUM + DT_PROCNUM];
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const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */
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ElfW(Addr) l_entry; /* Entry point location. */
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ElfW(Half) l_phnum; /* Number of program header entries. */
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/* Array of DT_NEEDED dependencies and their dependencies, in
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dependency order for symbol lookup. This is null before the
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dependencies have been loaded. */
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struct link_map **l_searchlist;
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unsigned int l_nsearchlist;
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/* Dependent object that first caused this object to be loaded. */
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struct link_map *l_loader;
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/* Symbol hash table. */
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ElfW(Symndx) l_nbuckets;
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const ElfW(Symndx) *l_buckets, *l_chain;
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unsigned int l_opencount; /* Reference count for dlopen/dlclose. */
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enum /* Where this object came from. */
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{
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lt_executable, /* The main executable program. */
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lt_library, /* Library needed by main executable. */
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lt_loaded, /* Extra run-time loaded shared object. */
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} l_type:2;
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unsigned int l_relocated:1; /* Nonzero if object's relocations done. */
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unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */
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unsigned int l_init_running:1; /* Nonzero while DT_INIT function runs. */
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unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */
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unsigned int l_reserved:2; /* Reserved for internal use. */
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};
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/* Internal functions of the run-time dynamic linker.
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These can be accessed if you link again the dynamic linker
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as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
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but are not normally of interest to user programs.
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The `-ldl' library functions in <dlfcn.h> provide a simple
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user interface to run-time dynamic linking. */
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/* Cached value of `getpagesize ()'. */
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extern size_t _dl_pagesize;
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/* File descriptor referring to the zero-fill device. */
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extern int _dl_zerofd;
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/* OS-dependent function to open the zero-fill device. */
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extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
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/* OS-dependent function to write a message on the standard output.
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All arguments are `const char *'; args until a null pointer
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are concatenated to form the message to print. */
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extern void _dl_sysdep_message (const char *string, ...);
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/* OS-dependent function to give a fatal error message and exit
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when the dynamic linker fails before the program is fully linked.
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All arguments are `const char *'; args until a null pointer
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are concatenated to form the message to print. */
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extern void _dl_sysdep_fatal (const char *string, ...)
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__attribute__ ((__noreturn__));
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/* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch).
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This tells the dynamic linker to ignore environment variables. */
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extern int _dl_secure;
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/* This function is called by all the internal dynamic linker functions
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when they encounter an error. ERRCODE is either an `errno' code or
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zero; OBJECT is the name of the problematical shared object, or null if
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it is a general problem; ERRSTRING is a string describing the specific
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problem. */
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extern void _dl_signal_error (int errcode,
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const char *object,
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const char *errstring)
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__attribute__ ((__noreturn__));
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/* Call OPERATE, catching errors from `dl_signal_error'. If there is no
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error, *ERRSTRING is set to null. If there is an error, *ERRSTRING and
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*OBJECT are set to the strings passed to _dl_signal_error, and the error
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code passed is the return value. ERRSTRING if nonzero points to a
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malloc'ed string which the caller has to free after use. */
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extern int _dl_catch_error (char **errstring,
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const char **object,
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void (*operate) (void));
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/* Helper function for <dlfcn.h> functions. Runs the OPERATE function via
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_dl_catch_error. Returns zero for success, nonzero for failure; and
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arranges for `dlerror' to return the error details. */
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extern int _dlerror_run (void (*operate) (void));
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/* Open the shared object NAME and map in its segments.
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LOADER's DT_RPATH is used in searching for NAME.
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If the object is already opened, returns its existing map. */
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extern struct link_map *_dl_map_object (struct link_map *loader,
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const char *name, int type,
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int trace_mode);
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/* Call _dl_map_object on the dependencies of MAP, and set up
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MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
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loaded objects that will be inserted into MAP->l_searchlist after MAP
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but before its dependencies. */
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extern void _dl_map_object_deps (struct link_map *map,
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struct link_map **preloads,
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unsigned int npreloads, int trace_mode);
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/* Cache the locations of MAP's hash table. */
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extern void _dl_setup_hash (struct link_map *map);
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/* Open the shared object NAME, relocate it, and run its initializer if it
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hasn't already been run. MODE is as for `dlopen' (see <dlfcn.h>). If
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the object is already opened, returns its existing map. */
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extern struct link_map *_dl_open (const char *name, int mode);
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/* Close an object previously opened by _dl_open. */
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extern void _dl_close (struct link_map *map);
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/* Search loaded objects' symbol tables for a definition of the symbol
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referred to by UNDEF. *SYM is the symbol table entry containing the
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reference; it is replaced with the defining symbol, and the base load
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address of the defining object is returned. SYMBOL_SCOPE is a
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null-terminated list of object scopes to search; each object's
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l_searchlist (i.e. the segment of the dependency tree starting at that
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object) is searched in turn. REFERENCE_NAME should name the object
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containing the reference; it is used in error messages. FLAGS is a
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set of flags: */
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#define DL_LOOKUP_NOEXEC 1 /* Don't search the executable for a
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definition; this is used for copy
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relocs. */
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#define DL_LOOKUP_NOPLT 2 /* The reference must not be resolved
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to a PLT entry. */
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extern ElfW(Addr) _dl_lookup_symbol (const char *undef,
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const ElfW(Sym) **sym,
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struct link_map *symbol_scope[],
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const char *reference_name,
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int flags);
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/* Look up symbol NAME in MAP's scope and return its run-time address. */
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extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name);
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/* Structure describing the dynamic linker itself. */
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extern struct link_map _dl_rtld_map;
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/* The list of objects currently loaded is the third element of the
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`_dl_default_scope' array, and the fourth element is always null.
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This leaves two slots before it that are used when resolving
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DT_SYMBOLIC objects' references one after it for normal references
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(see below). */
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#define _dl_loaded (_dl_default_scope[2])
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extern struct link_map *_dl_default_scope[5];
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/* Null-terminated list of objects in the dynamic `global scope'. The
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list starts at [2]; i.e. &_dl_global_scope[2] is the argument
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passed to _dl_lookup_symbol to search the global scope. To search
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a specific object and its dependencies in preference to the global
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scope, fill in the [1] slot and pass its address; for two specific
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object scopes, fill [0] and [1]. The list is double-terminated; to
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search the global scope and then a specific object and its
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dependencies, set *_dl_global_scope_end. This variable initially
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points to _dl_default_scope, and _dl_loaded is always kept in [2]
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of this list. A new list is malloc'd when new objects are loaded
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with RTLD_GLOBAL. */
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extern struct link_map **_dl_global_scope, **_dl_global_scope_end;
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extern size_t _dl_global_scope_alloc; /* Number of slots malloc'd. */
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/* Hack _dl_global_scope[0] and [1] as necessary, and return a pointer into
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_dl_global_scope that should be passed to _dl_lookup_symbol for symbol
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references made in the object MAP's relocations. */
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extern struct link_map **_dl_object_relocation_scope (struct link_map *map);
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/* Allocate a `struct link_map' for a new object being loaded,
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and enter it into the _dl_loaded list. */
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extern struct link_map *_dl_new_object (char *realname, const char *libname,
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int type);
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/* Relocate the given object (if it hasn't already been).
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SCOPE is passed to _dl_lookup_symbol in symbol lookups.
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If LAZY is nonzero, don't relocate its PLT. */
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extern void _dl_relocate_object (struct link_map *map,
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struct link_map *scope[],
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int lazy);
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/* Return the address of the next initializer function for MAP or one of
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its dependencies that has not yet been run. When there are no more
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initializers to be run, this returns zero. The functions are returned
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in the order they should be called. */
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extern ElfW(Addr) _dl_init_next (struct link_map *map);
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/* Call the finalizer functions of all shared objects whose
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initializer functions have completed. */
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extern void _dl_fini (void);
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/* The dynamic linker calls this function before and having changing
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any shared object mappings. The `r_state' member of `struct r_debug'
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says what change is taking place. This function's address is
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the value of the `r_brk' member. */
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extern void _dl_debug_state (void);
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/* Initialize `struct r_debug' if it has not already been done. The
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argument is the run-time load address of the dynamic linker, to be put
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in the `r_ldbase' member. Returns the address of the structure. */
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extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase);
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#endif /* link.h */
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