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 | |
24 | static inline void |
25 | __attribute ((always_inline)) |
26 | determine_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 | |
123 | int |
124 | internal_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 | } |
146 | libc_hidden_def (_dl_addr) |
147 | |