308 lines
13 KiB
C
308 lines
13 KiB
C
/* Run-time dynamic linker data structures for loaded ELF shared objects.
|
||
Copyright (C) 1995, 1996 Free Software Foundation, Inc.
|
||
This file is part of the GNU C Library.
|
||
|
||
The GNU C Library is free software; you can redistribute it and/or
|
||
modify it under the terms of the GNU Library General Public License as
|
||
published by the Free Software Foundation; either version 2 of the
|
||
License, or (at your option) any later version.
|
||
|
||
The GNU C Library is distributed in the hope that it will be useful,
|
||
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
Library General Public License for more details.
|
||
|
||
You should have received a copy of the GNU Library General Public
|
||
License along with the GNU C Library; see the file COPYING.LIB. If
|
||
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
|
||
Cambridge, MA 02139, USA. */
|
||
|
||
#ifndef _LINK_H
|
||
#define _LINK_H 1
|
||
|
||
#define __need_size_t
|
||
#include <stddef.h>
|
||
|
||
#include <elf.h>
|
||
|
||
/* We use this macro to refer to ELF types independent of the native wordsize.
|
||
`ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */
|
||
#define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type)
|
||
#define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
|
||
#define _ElfW(e,w,t) _ElfW_1 (e, w, _##t)
|
||
#define _ElfW_1(e,w,t) e##w##t
|
||
#include <elfclass.h> /* Defines __ELF_NATIVE_CLASS. */
|
||
|
||
/* Rendezvous structure used by the run-time dynamic linker to communicate
|
||
details of shared object loading to the debugger. If the executable's
|
||
dynamic section has a DT_DEBUG element, the run-time linker sets that
|
||
element's value to the address where this structure can be found. */
|
||
|
||
struct r_debug
|
||
{
|
||
int r_version; /* Version number for this protocol. */
|
||
|
||
struct link_map *r_map; /* Head of the chain of loaded objects. */
|
||
|
||
/* This is the address of a function internal to the run-time linker,
|
||
that will always be called when the linker begins to map in a
|
||
library or unmap it, and again when the mapping change is complete.
|
||
The debugger can set a breakpoint at this address if it wants to
|
||
notice shared object mapping changes. */
|
||
ElfW(Addr) r_brk;
|
||
enum
|
||
{
|
||
/* This state value describes the mapping change taking place when
|
||
the `r_brk' address is called. */
|
||
RT_CONSISTENT, /* Mapping change is complete. */
|
||
RT_ADD, /* Beginning to add a new object. */
|
||
RT_DELETE, /* Beginning to remove an object mapping. */
|
||
} r_state;
|
||
|
||
ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */
|
||
};
|
||
|
||
/* This is the instance of that structure used by the dynamic linker. */
|
||
extern struct r_debug _r_debug;
|
||
|
||
/* This symbol refers to the "dynamic structure" in the `.dynamic' section
|
||
of whatever module refers to `_DYNAMIC'. So, to find its own
|
||
`struct r_debug', a program could do:
|
||
for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL)
|
||
if (dyn->d_tag == DT_DEBUG) r_debug = (struct r_debug) dyn->d_un.d_ptr;
|
||
*/
|
||
|
||
extern ElfW(Dyn) _DYNAMIC[];
|
||
|
||
|
||
/* Structure describing a loaded shared object. The `l_next' and `l_prev'
|
||
members form a chain of all the shared objects loaded at startup.
|
||
|
||
These data structures exist in space used by the run-time dynamic linker;
|
||
modifying them may have disastrous results. */
|
||
|
||
struct link_map
|
||
{
|
||
/* These first few members are part of the protocol with the debugger.
|
||
This is the same format used in SVR4. */
|
||
|
||
ElfW(Addr) l_addr; /* Base address shared object is loaded at. */
|
||
char *l_name; /* Absolute file name object was found in. */
|
||
ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */
|
||
struct link_map *l_next, *l_prev; /* Chain of loaded objects. */
|
||
|
||
/* All following members are internal to the dynamic linker.
|
||
They may change without notice. */
|
||
|
||
const char *l_libname; /* Name requested (before search). */
|
||
/* Indexed pointers to dynamic section.
|
||
[0,DT_NUM) are indexed by the processor-independent tags.
|
||
[DT_NUM,DT_NUM+DT_PROCNUM] are indexed by the tag minus DT_LOPROC. */
|
||
ElfW(Dyn) *l_info[DT_NUM + DT_PROCNUM];
|
||
const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */
|
||
ElfW(Addr) l_entry; /* Entry point location. */
|
||
ElfW(Half) l_phnum; /* Number of program header entries. */
|
||
|
||
/* Array of DT_NEEDED dependencies and their dependencies, in
|
||
dependency order for symbol lookup. This is null before the
|
||
dependencies have been loaded. */
|
||
struct link_map **l_searchlist;
|
||
unsigned int l_nsearchlist;
|
||
|
||
/* Dependent object that first caused this object to be loaded. */
|
||
struct link_map *l_loader;
|
||
|
||
/* Symbol hash table. */
|
||
ElfW(Symndx) l_nbuckets;
|
||
const ElfW(Symndx) *l_buckets, *l_chain;
|
||
|
||
unsigned int l_opencount; /* Reference count for dlopen/dlclose. */
|
||
enum /* Where this object came from. */
|
||
{
|
||
lt_executable, /* The main executable program. */
|
||
lt_library, /* Library needed by main executable. */
|
||
lt_loaded, /* Extra run-time loaded shared object. */
|
||
} l_type:2;
|
||
unsigned int l_relocated:1; /* Nonzero if object's relocations done. */
|
||
unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */
|
||
unsigned int l_init_running:1; /* Nonzero while DT_INIT function runs. */
|
||
unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */
|
||
unsigned int l_reserved:2; /* Reserved for internal use. */
|
||
};
|
||
|
||
/* Internal functions of the run-time dynamic linker.
|
||
These can be accessed if you link again the dynamic linker
|
||
as a shared library, as in `-lld' or `/lib/ld.so' explicitly;
|
||
but are not normally of interest to user programs.
|
||
|
||
The `-ldl' library functions in <dlfcn.h> provide a simple
|
||
user interface to run-time dynamic linking. */
|
||
|
||
|
||
/* Cached value of `getpagesize ()'. */
|
||
extern size_t _dl_pagesize;
|
||
|
||
/* File descriptor referring to the zero-fill device. */
|
||
extern int _dl_zerofd;
|
||
|
||
/* OS-dependent function to open the zero-fill device. */
|
||
extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
|
||
|
||
/* OS-dependent function to write a message on the standard output.
|
||
All arguments are `const char *'; args until a null pointer
|
||
are concatenated to form the message to print. */
|
||
extern void _dl_sysdep_message (const char *string, ...);
|
||
|
||
/* OS-dependent function to give a fatal error message and exit
|
||
when the dynamic linker fails before the program is fully linked.
|
||
All arguments are `const char *'; args until a null pointer
|
||
are concatenated to form the message to print. */
|
||
extern void _dl_sysdep_fatal (const char *string, ...)
|
||
__attribute__ ((__noreturn__));
|
||
|
||
/* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch).
|
||
This tells the dynamic linker to ignore environment variables. */
|
||
extern int _dl_secure;
|
||
|
||
/* This function is called by all the internal dynamic linker functions
|
||
when they encounter an error. ERRCODE is either an `errno' code or
|
||
zero; OBJECT is the name of the problematical shared object, or null if
|
||
it is a general problem; ERRSTRING is a string describing the specific
|
||
problem. */
|
||
|
||
extern void _dl_signal_error (int errcode,
|
||
const char *object,
|
||
const char *errstring)
|
||
__attribute__ ((__noreturn__));
|
||
|
||
/* Call OPERATE, catching errors from `dl_signal_error'. If there is no
|
||
error, *ERRSTRING is set to null. If there is an error, *ERRSTRING and
|
||
*OBJECT are set to the strings passed to _dl_signal_error, and the error
|
||
code passed is the return value. */
|
||
extern int _dl_catch_error (const char **errstring,
|
||
const char **object,
|
||
void (*operate) (void));
|
||
|
||
|
||
/* Helper function for <dlfcn.h> functions. Runs the OPERATE function via
|
||
_dl_catch_error. Returns zero for success, nonzero for failure; and
|
||
arranges for `dlerror' to return the error details. */
|
||
extern int _dlerror_run (void (*operate) (void));
|
||
|
||
|
||
/* Open the shared object NAME and map in its segments.
|
||
LOADER's DT_RPATH is used in searching for NAME.
|
||
If the object is already opened, returns its existing map. */
|
||
extern struct link_map *_dl_map_object (struct link_map *loader,
|
||
const char *name, int type);
|
||
|
||
/* Call _dl_map_object on the dependencies of MAP, and set up
|
||
MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously
|
||
loaded objects that will be inserted into MAP->l_searchlist after MAP
|
||
but before its dependencies. */
|
||
extern void _dl_map_object_deps (struct link_map *map,
|
||
struct link_map **preloads,
|
||
unsigned int npreloads);
|
||
|
||
/* Cache the locations of MAP's hash table. */
|
||
extern void _dl_setup_hash (struct link_map *map);
|
||
|
||
|
||
/* Open the shared object NAME, relocate it, and run its initializer if it
|
||
hasn't already been run. MODE is as for `dlopen' (see <dlfcn.h>). If
|
||
the object is already opened, returns its existing map. */
|
||
extern struct link_map *_dl_open (const char *name, int mode);
|
||
|
||
/* Close an object previously opened by _dl_open. */
|
||
extern void _dl_close (struct link_map *map);
|
||
|
||
|
||
/* Search loaded objects' symbol tables for a definition of the symbol
|
||
referred to by UNDEF. *SYM is the symbol table entry containing the
|
||
reference; it is replaced with the defining symbol, and the base load
|
||
address of the defining object is returned. SYMBOL_SCOPE is a
|
||
null-terminated list of object scopes to search; each object's
|
||
l_searchlist (i.e. the segment of the dependency tree starting at that
|
||
object) is searched in turn. REFERENCE_NAME should name the object
|
||
containing the reference; it is used in error messages. RELOC_ADDR is
|
||
the address being fixed up and the chosen symbol cannot be one with this
|
||
value. If NOPLT is nonzero, then the reference must not be resolved to
|
||
a PLT entry. */
|
||
extern ElfW(Addr) _dl_lookup_symbol (const char *undef,
|
||
const ElfW(Sym) **sym,
|
||
struct link_map *symbol_scope[],
|
||
const char *reference_name,
|
||
ElfW(Addr) reloc_addr,
|
||
int noplt);
|
||
|
||
/* Look up symbol NAME in MAP's scope and return its run-time address. */
|
||
extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name);
|
||
|
||
|
||
/* Structure describing the dynamic linker itself. */
|
||
extern struct link_map _dl_rtld_map;
|
||
|
||
/* The list of objects currently loaded is the third element of the
|
||
`_dl_default_scope' array, and the fourth element is always null.
|
||
This leaves two slots before it that are used when resolving
|
||
DT_SYMBOLIC objects' references one after it for normal references
|
||
(see below). */
|
||
#define _dl_loaded (_dl_default_scope[2])
|
||
extern struct link_map *_dl_default_scope[5];
|
||
|
||
/* Null-terminated list of objects in the dynamic `global scope'. The
|
||
list starts at [2]; i.e. &_dl_global_scope[2] is the argument
|
||
passed to _dl_lookup_symbol to search the global scope. To search
|
||
a specific object and its dependencies in preference to the global
|
||
scope, fill in the [1] slot and pass its address; for two specific
|
||
object scopes, fill [0] and [1]. The list is double-terminated; to
|
||
search the global scope and then a specific object and its
|
||
dependencies, set *_dl_global_scope_end. This variable initially
|
||
points to _dl_default_scope, and _dl_loaded is always kept in [2]
|
||
of this list. A new list is malloc'd when new objects are loaded
|
||
with RTLD_GLOBAL. */
|
||
extern struct link_map **_dl_global_scope, **_dl_global_scope_end;
|
||
extern size_t _dl_global_scope_alloc; /* Number of slots malloc'd. */
|
||
|
||
/* Hack _dl_global_scope[0] and [1] as necessary, and return a pointer into
|
||
_dl_global_scope that should be passed to _dl_lookup_symbol for symbol
|
||
references made in the object MAP's relocations. */
|
||
extern struct link_map **_dl_object_relocation_scope (struct link_map *map);
|
||
|
||
|
||
/* Allocate a `struct link_map' for a new object being loaded,
|
||
and enter it into the _dl_loaded list. */
|
||
extern struct link_map *_dl_new_object (char *realname, const char *libname,
|
||
int type);
|
||
|
||
/* Relocate the given object (if it hasn't already been).
|
||
SCOPE is passed to _dl_lookup_symbol in symbol lookups.
|
||
If LAZY is nonzero, don't relocate its PLT. */
|
||
extern void _dl_relocate_object (struct link_map *map,
|
||
struct link_map *scope[],
|
||
int lazy);
|
||
|
||
/* Return the address of the next initializer function for MAP or one of
|
||
its dependencies that has not yet been run. When there are no more
|
||
initializers to be run, this returns zero. The functions are returned
|
||
in the order they should be called. */
|
||
extern ElfW(Addr) _dl_init_next (struct link_map *map);
|
||
|
||
/* Call the finalizer functions of all shared objects whose
|
||
initializer functions have completed. */
|
||
extern void _dl_fini (void);
|
||
|
||
/* The dynamic linker calls this function before and having changing
|
||
any shared object mappings. The `r_state' member of `struct r_debug'
|
||
says what change is taking place. This function's address is
|
||
the value of the `r_brk' member. */
|
||
extern void _dl_debug_state (void);
|
||
|
||
/* Initialize `struct r_debug' if it has not already been done. The
|
||
argument is the run-time load address of the dynamic linker, to be put
|
||
in the `r_ldbase' member. Returns the address of the structure. */
|
||
extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase);
|
||
|
||
|
||
#endif /* link.h */
|