1 | /* Set up the data structures for the system-supplied DSO. |
2 | Copyright (C) 2012-2024 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 | static inline void __attribute__ ((always_inline)) |
20 | setup_vdso (struct link_map *main_map __attribute__ ((unused)), |
21 | struct link_map ***first_preload __attribute__ ((unused))) |
22 | { |
23 | #ifdef NEED_DL_SYSINFO_DSO |
24 | if (GLRO(dl_sysinfo_dso) == NULL) |
25 | return; |
26 | |
27 | /* Do an abridged version of the work _dl_map_object_from_fd would do |
28 | to map in the object. It's already mapped and prelinked (and |
29 | better be, since it's read-only and so we couldn't relocate it). |
30 | We just want our data structures to describe it as if we had just |
31 | mapped and relocated it normally. */ |
32 | struct link_map *l = _dl_new_object (realname: (char *) "" , libname: "" , type: lt_library, NULL, |
33 | __RTLD_VDSO, LM_ID_BASE); |
34 | if (__glibc_likely (l != NULL)) |
35 | { |
36 | l->l_phdr = ((const void *) GLRO(dl_sysinfo_dso) |
37 | + GLRO(dl_sysinfo_dso)->e_phoff); |
38 | l->l_phnum = GLRO(dl_sysinfo_dso)->e_phnum; |
39 | for (unsigned int i = 0; i < l->l_phnum; ++i) |
40 | { |
41 | const ElfW(Phdr) *const ph = &l->l_phdr[i]; |
42 | if (ph->p_type == PT_DYNAMIC) |
43 | { |
44 | l->l_ld = (void *) ph->p_vaddr; |
45 | l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn)); |
46 | l->l_ld_readonly = (ph->p_flags & PF_W) == 0; |
47 | } |
48 | else if (ph->p_type == PT_LOAD) |
49 | { |
50 | if (! l->l_addr) |
51 | l->l_addr = ph->p_vaddr; |
52 | if (ph->p_vaddr + ph->p_memsz >= l->l_map_end) |
53 | l->l_map_end = ph->p_vaddr + ph->p_memsz; |
54 | } |
55 | else |
56 | /* There must be no TLS segment. */ |
57 | assert (ph->p_type != PT_TLS); |
58 | } |
59 | l->l_map_start = (ElfW(Addr)) GLRO(dl_sysinfo_dso); |
60 | l->l_addr = l->l_map_start - l->l_addr; |
61 | l->l_map_end += l->l_addr; |
62 | l->l_ld = (void *) ((ElfW(Addr)) l->l_ld + l->l_addr); |
63 | elf_get_dynamic_info (l, false, false); |
64 | _dl_setup_hash (map: l); |
65 | l->l_relocated = 1; |
66 | |
67 | /* The vDSO is always used. */ |
68 | l->l_used = 1; |
69 | |
70 | /* Initialize l_local_scope to contain just this map. This allows |
71 | the use of dl_lookup_symbol_x to resolve symbols within the vdso. |
72 | So we create a single entry list pointing to l_real as its only |
73 | element */ |
74 | l->l_local_scope[0]->r_nlist = 1; |
75 | l->l_local_scope[0]->r_list = &l->l_real; |
76 | |
77 | /* Now that we have the info handy, use the DSO image's soname |
78 | so this object can be looked up by name. */ |
79 | if (l->l_info[DT_SONAME] != NULL) |
80 | { |
81 | char *dsoname = ((char *) D_PTR (l, l_info[DT_STRTAB]) |
82 | + l->l_info[DT_SONAME]->d_un.d_val); |
83 | l->l_libname->name = dsoname; |
84 | l->l_name = dsoname; |
85 | } |
86 | |
87 | /* Add the vDSO to the object list. */ |
88 | _dl_add_to_namespace_list (new: l, LM_ID_BASE); |
89 | |
90 | # if IS_IN (rtld) |
91 | /* Rearrange the list so this DSO appears after rtld_map. */ |
92 | assert (l->l_next == NULL); |
93 | assert (l->l_prev == main_map); |
94 | GL(dl_rtld_map).l_next = l; |
95 | l->l_prev = &GL(dl_rtld_map); |
96 | *first_preload = &l->l_next; |
97 | # else |
98 | GL(dl_nns) = 1; |
99 | # endif |
100 | |
101 | /* We have a prelinked DSO preloaded by the system. */ |
102 | GLRO(dl_sysinfo_map) = l; |
103 | # ifdef NEED_DL_SYSINFO |
104 | if (GLRO(dl_sysinfo) == DL_SYSINFO_DEFAULT) |
105 | GLRO(dl_sysinfo) = GLRO(dl_sysinfo_dso)->e_entry + l->l_addr; |
106 | # endif |
107 | } |
108 | #endif |
109 | } |
110 | |