1/* Locate the shared object symbol nearest a given address.
2 Copyright (C) 1996-2016 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 && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
92 && (symtab->st_shndx != SHN_UNDEF
93 || symtab->st_value != 0)
94 && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
95 && symtab->st_name < strtabsize)
96 matchsym = (ElfW(Sym) *) symtab;
97 }
98
99 if (mapp)
100 *mapp = match;
101 if (symbolp)
102 *symbolp = matchsym;
103
104 if (matchsym)
105 {
106 /* We found a symbol close by. Fill in its name and exact
107 address. */
108 lookup_t matchl = LOOKUP_VALUE (match);
109
110 info->dli_sname = strtab + matchsym->st_name;
111 info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
112 }
113 else
114 {
115 /* No symbol matches. We return only the containing object. */
116 info->dli_sname = NULL;
117 info->dli_saddr = NULL;
118 }
119}
120
121
122int
123internal_function
124_dl_addr (const void *address, Dl_info *info,
125 struct link_map **mapp, const ElfW(Sym) **symbolp)
126{
127 const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
128 int result = 0;
129
130 /* Protect against concurrent loads and unloads. */
131 __rtld_lock_lock_recursive (GL(dl_load_lock));
132
133 struct link_map *l = _dl_find_dso_for_object (addr);
134
135 if (l)
136 {
137 determine_info (addr, l, info, mapp, symbolp);
138 result = 1;
139 }
140
141 __rtld_lock_unlock_recursive (GL(dl_load_lock));
142
143 return result;
144}
145libc_hidden_def (_dl_addr)
146
147/* Return non-zero if ADDR lies within one of L's segments. */
148int
149internal_function
150_dl_addr_inside_object (struct link_map *l, const ElfW(Addr) addr)
151{
152 int n = l->l_phnum;
153 const ElfW(Addr) reladdr = addr - l->l_addr;
154
155 while (--n >= 0)
156 if (l->l_phdr[n].p_type == PT_LOAD
157 && reladdr - l->l_phdr[n].p_vaddr >= 0
158 && reladdr - l->l_phdr[n].p_vaddr < l->l_phdr[n].p_memsz)
159 return 1;
160 return 0;
161}
162