1/* Locate the shared object symbol nearest a given address.
2 Copyright (C) 1996-2017 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <dlfcn.h>
20#include <stddef.h>
21#include <ldsodefs.h>
22
23
24static inline void
25__attribute ((always_inline))
26determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
27 struct link_map **mapp, const ElfW(Sym) **symbolp)
28{
29 /* Now we know what object the address lies in. */
30 info->dli_fname = match->l_name;
31 info->dli_fbase = (void *) match->l_map_start;
32
33 /* If this is the main program the information is incomplete. */
34 if (__builtin_expect (match->l_name[0], 'a') == '\0'
35 && match->l_type == lt_executable)
36 info->dli_fname = _dl_argv[0];
37
38 const ElfW(Sym) *symtab
39 = (const ElfW(Sym) *) D_PTR (match, l_info[DT_SYMTAB]);
40 const char *strtab = (const char *) D_PTR (match, l_info[DT_STRTAB]);
41
42 ElfW(Word) strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
43
44 const ElfW(Sym) *matchsym = NULL;
45 if (match->l_info[DT_ADDRTAGIDX (DT_GNU_HASH) + DT_NUM + DT_THISPROCNUM
46 + DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM] != NULL)
47 {
48 /* We look at all symbol table entries referenced by the hash
49 table. */
50 for (Elf_Symndx bucket = 0; bucket < match->l_nbuckets; ++bucket)
51 {
52 Elf32_Word symndx = match->l_gnu_buckets[bucket];
53 if (symndx != 0)
54 {
55 const Elf32_Word *hasharr = &match->l_gnu_chain_zero[symndx];
56
57 do
58 {
59 /* The hash table never references local symbols so
60 we can omit that test here. */
61 if ((symtab[symndx].st_shndx != SHN_UNDEF
62 || symtab[symndx].st_value != 0)
63 && ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
64 && DL_ADDR_SYM_MATCH (match, &symtab[symndx],
65 matchsym, addr)
66 && symtab[symndx].st_name < strtabsize)
67 matchsym = (ElfW(Sym) *) &symtab[symndx];
68
69 ++symndx;
70 }
71 while ((*hasharr++ & 1u) == 0);
72 }
73 }
74 }
75 else
76 {
77 const ElfW(Sym) *symtabend;
78 if (match->l_info[DT_HASH] != NULL)
79 symtabend = (symtab
80 + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
81 else
82 /* There is no direct way to determine the number of symbols in the
83 dynamic symbol table and no hash table is present. The ELF
84 binary is ill-formed but what shall we do? Use the beginning of
85 the string table which generally follows the symbol table. */
86 symtabend = (const ElfW(Sym) *) strtab;
87
88 for (; (void *) symtab < (void *) symtabend; ++symtab)
89 if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
90 || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
91 && __glibc_likely (!dl_symbol_visibility_binds_local_p (symtab))
92 && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
93 && (symtab->st_shndx != SHN_UNDEF
94 || symtab->st_value != 0)
95 && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
96 && symtab->st_name < strtabsize)
97 matchsym = (ElfW(Sym) *) symtab;
98 }
99
100 if (mapp)
101 *mapp = match;
102 if (symbolp)
103 *symbolp = matchsym;
104
105 if (matchsym)
106 {
107 /* We found a symbol close by. Fill in its name and exact
108 address. */
109 lookup_t matchl = LOOKUP_VALUE (match);
110
111 info->dli_sname = strtab + matchsym->st_name;
112 info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
113 }
114 else
115 {
116 /* No symbol matches. We return only the containing object. */
117 info->dli_sname = NULL;
118 info->dli_saddr = NULL;
119 }
120}
121
122
123int
124internal_function
125_dl_addr (const void *address, Dl_info *info,
126 struct link_map **mapp, const ElfW(Sym) **symbolp)
127{
128 const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
129 int result = 0;
130
131 /* Protect against concurrent loads and unloads. */
132 __rtld_lock_lock_recursive (GL(dl_load_lock));
133
134 struct link_map *l = _dl_find_dso_for_object (addr);
135
136 if (l)
137 {
138 determine_info (addr, l, info, mapp, symbolp);
139 result = 1;
140 }
141
142 __rtld_lock_unlock_recursive (GL(dl_load_lock));
143
144 return result;
145}
146libc_hidden_def (_dl_addr)
147