1/* Data structure for communication from the run-time dynamic linker for
2   loaded ELF shared objects.
3   Copyright (C) 1995-2001, 2004, 2005, 2006 Free Software Foundation, Inc.
4   This file is part of the GNU C Library.
5
6   The GNU C Library is free software; you can redistribute it and/or
7   modify it under the terms of the GNU Lesser General Public
8   License as published by the Free Software Foundation; either
9   version 2.1 of the License, or (at your option) any later version.
10
11   The GNU C Library is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   Lesser General Public License for more details.
15
16   You should have received a copy of the GNU Lesser General Public
17   License along with the GNU C Library; if not, write to the Free
18   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19   02111-1307 USA.  */
20
21#ifndef	_LINK_H
22#define	_LINK_H	1
23
24#include <features.h>
25#include <elf.h>
26#include <dlfcn.h>
27#include <sys/types.h>
28
29/* We use this macro to refer to ELF types independent of the native wordsize.
30   `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
31#define ElfW(type)	_ElfW (Elf, __ELF_NATIVE_CLASS, type)
32#define _ElfW(e,w,t)	_ElfW_1 (e, w, _##t)
33#define _ElfW_1(e,w,t)	e##w##t
34
35#include <bits/elfclass.h>		/* Defines __ELF_NATIVE_CLASS.  */
36#include <bits/link.h>
37
38/* Rendezvous structure used by the run-time dynamic linker to communicate
39   details of shared object loading to the debugger.  If the executable's
40   dynamic section has a DT_DEBUG element, the run-time linker sets that
41   element's value to the address where this structure can be found.  */
42
43struct r_debug
44  {
45    int r_version;		/* Version number for this protocol.  */
46
47    struct link_map *r_map;	/* Head of the chain of loaded objects.  */
48
49    /* This is the address of a function internal to the run-time linker,
50       that will always be called when the linker begins to map in a
51       library or unmap it, and again when the mapping change is complete.
52       The debugger can set a breakpoint at this address if it wants to
53       notice shared object mapping changes.  */
54    ElfW(Addr) r_brk;
55    enum
56      {
57	/* This state value describes the mapping change taking place when
58	   the `r_brk' address is called.  */
59	RT_CONSISTENT,		/* Mapping change is complete.  */
60	RT_ADD,			/* Beginning to add a new object.  */
61	RT_DELETE		/* Beginning to remove an object mapping.  */
62      } r_state;
63
64    ElfW(Addr) r_ldbase;	/* Base address the linker is loaded at.  */
65  };
66
67/* This is the instance of that structure used by the dynamic linker.  */
68extern struct r_debug _r_debug;
69
70/* This symbol refers to the "dynamic structure" in the `.dynamic' section
71   of whatever module refers to `_DYNAMIC'.  So, to find its own
72   `struct r_debug', a program could do:
73     for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn)
74       if (dyn->d_tag == DT_DEBUG)
75	 r_debug = (struct r_debug *) dyn->d_un.d_ptr;
76   */
77extern ElfW(Dyn) _DYNAMIC[];
78
79/* Structure describing a loaded shared object.  The `l_next' and `l_prev'
80   members form a chain of all the shared objects loaded at startup.
81
82   These data structures exist in space used by the run-time dynamic linker;
83   modifying them may have disastrous results.  */
84
85struct link_map
86  {
87    /* These first few members are part of the protocol with the debugger.
88       This is the same format used in SVR4.  */
89
90    ElfW(Addr) l_addr;		/* Base address shared object is loaded at.  */
91    char *l_name;		/* Absolute file name object was found in.  */
92    ElfW(Dyn) *l_ld;		/* Dynamic section of the shared object.  */
93    struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
94  };
95
96#ifdef __USE_GNU
97
98/* Version numbers for la_version handshake interface.  */
99#define LAV_CURRENT	1
100
101/* Activity types signaled through la_activity.  */
102enum
103  {
104    LA_ACT_CONSISTENT,		/* Link map consistent again.  */
105    LA_ACT_ADD,			/* New object will be added.  */
106    LA_ACT_DELETE		/* Objects will be removed.  */
107  };
108
109/* Values representing origin of name for dynamic loading.  */
110enum
111  {
112    LA_SER_ORIG = 0x01,		/* Original name.  */
113    LA_SER_LIBPATH = 0x02,	/* Directory from LD_LIBRARY_PATH.  */
114    LA_SER_RUNPATH = 0x04,	/* Directory from RPATH/RUNPATH.  */
115    LA_SER_CONFIG = 0x08,	/* Found through ldconfig.  */
116    LA_SER_DEFAULT = 0x40,	/* Default directory.  */
117    LA_SER_SECURE = 0x80	/* Unused.  */
118  };
119
120/* Values for la_objopen return value.  */
121enum
122  {
123    LA_FLG_BINDTO = 0x01,	/* Audit symbols bound to this object.  */
124    LA_FLG_BINDFROM = 0x02	/* Audit symbols bound from this object.  */
125  };
126
127/* Values for la_symbind flags parameter.  */
128enum
129  {
130    LA_SYMB_NOPLTENTER = 0x01,	/* la_pltenter will not be called.  */
131    LA_SYMB_NOPLTEXIT = 0x02,	/* la_pltexit will not be called.  */
132    LA_SYMB_STRUCTCALL = 0x04,	/* Return value is a structure.  */
133    LA_SYMB_DLSYM = 0x08,	/* Binding due to dlsym call.  */
134    LA_SYMB_ALTVALUE = 0x10	/* Value has been changed by a previous
135				   la_symbind call.  */
136  };
137
138struct dl_phdr_info
139  {
140    ElfW(Addr) dlpi_addr;
141    const char *dlpi_name;
142    const ElfW(Phdr) *dlpi_phdr;
143    ElfW(Half) dlpi_phnum;
144
145    /* Note: Following members were introduced after the first
146       version of this structure was available.  Check the SIZE
147       argument passed to the dl_iterate_phdr callback to determine
148       whether or not each later member is available.  */
149
150    /* Incremented when a new object may have been added.  */
151    unsigned long long int dlpi_adds;
152    /* Incremented when an object may have been removed.  */
153    unsigned long long int dlpi_subs;
154
155    /* If there is a PT_TLS segment, its module ID as used in
156       TLS relocations, else zero.  */
157    size_t dlpi_tls_modid;
158
159    /* The address of the calling thread's instance of this module's
160       PT_TLS segment, if it has one and it has been allocated
161       in the calling thread, otherwise a null pointer.  */
162    void *dlpi_tls_data;
163  };
164
165__BEGIN_DECLS
166
167extern int dl_iterate_phdr (int (*__callback) (struct dl_phdr_info *,
168					       size_t, void *),
169			    void *__data);
170
171
172/* Prototypes for the ld.so auditing interfaces.  These are not
173   defined anywhere in ld.so but instead have to be provided by the
174   auditing DSO.  */
175extern unsigned int la_version (unsigned int __version);
176extern void la_activity (uintptr_t *__cookie, unsigned int __flag);
177extern char *la_objsearch (const char *__name, uintptr_t *__cookie,
178			   unsigned int __flag);
179extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
180				uintptr_t *__cookie);
181extern void la_preinit (uintptr_t *__cookie);
182extern uintptr_t la_symbind32 (Elf32_Sym *__sym, unsigned int __ndx,
183			       uintptr_t *__refcook, uintptr_t *__defcook,
184			       unsigned int *__flags, const char *__symname);
185extern uintptr_t la_symbind64 (Elf64_Sym *__sym, unsigned int __ndx,
186			       uintptr_t *__refcook, uintptr_t *__defcook,
187			       unsigned int *__flags, const char *__symname);
188extern unsigned int la_objclose (uintptr_t *__cookie);
189
190__END_DECLS
191
192#endif
193
194#endif /* link.h */
195