1/* Locate the shared object symbol nearest a given address.
2 Copyright (C) 1996-2023 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 <https://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[ELF_MACHINE_GNU_HASH_ADDRIDX] != NULL)
46 {
47 /* We look at all symbol table entries referenced by the hash
48 table. */
49 for (Elf_Symndx bucket = 0; bucket < match->l_nbuckets; ++bucket)
50 {
51 Elf32_Word symndx = match->l_gnu_buckets[bucket];
52 if (symndx != 0)
53 {
54 const Elf32_Word *hasharr = &match->l_gnu_chain_zero[symndx];
55
56 do
57 {
58 /* The hash table never references local symbols so
59 we can omit that test here. */
60 symndx = ELF_MACHINE_HASH_SYMIDX (match, hasharr);
61 if ((symtab[symndx].st_shndx != SHN_UNDEF
62 || symtab[symndx].st_value != 0)
63 && symtab[symndx].st_shndx != SHN_ABS
64 && ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
65 && DL_ADDR_SYM_MATCH (match, &symtab[symndx],
66 matchsym, addr)
67 && symtab[symndx].st_name < strtabsize)
68 matchsym = (ElfW(Sym) *) &symtab[symndx];
69 }
70 while ((*hasharr++ & 1u) == 0);
71 }
72 }
73 }
74 else if (match->l_info[DT_HASH] != NULL)
75 {
76 const ElfW (Sym) *symtabend
77 = (symtab + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
78
79 for (; (void *) symtab < (void *) symtabend; ++symtab)
80 if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
81 || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
82 && __glibc_likely (!dl_symbol_visibility_binds_local_p (symtab))
83 && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
84 && (symtab->st_shndx != SHN_UNDEF
85 || symtab->st_value != 0)
86 && symtab->st_shndx != SHN_ABS
87 && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
88 && symtab->st_name < strtabsize)
89 matchsym = (ElfW(Sym) *) symtab;
90 }
91 /* In the absence of a hash table, treat the object as if it has no symbol.
92 */
93
94 if (mapp)
95 *mapp = match;
96 if (symbolp)
97 *symbolp = matchsym;
98
99 if (matchsym)
100 {
101 /* We found a symbol close by. Fill in its name and exact
102 address. */
103 lookup_t matchl = LOOKUP_VALUE (match);
104
105 info->dli_sname = strtab + matchsym->st_name;
106 info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
107 }
108 else
109 {
110 /* No symbol matches. We return only the containing object. */
111 info->dli_sname = NULL;
112 info->dli_saddr = NULL;
113 }
114}
115
116
117int
118_dl_addr (const void *address, Dl_info *info,
119 struct link_map **mapp, const ElfW(Sym) **symbolp)
120{
121 const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
122 int result = 0;
123
124 /* Protect against concurrent loads and unloads. */
125 __rtld_lock_lock_recursive (GL(dl_load_lock));
126
127 struct link_map *l = _dl_find_dso_for_object (addr);
128
129 if (l)
130 {
131 determine_info (addr, l, info, mapp, symbolp);
132 result = 1;
133 }
134
135 __rtld_lock_unlock_recursive (GL(dl_load_lock));
136
137 return result;
138}
139