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fcccd512 | 1 | /* Map in a shared object's segments from the file. |
04277e02 | 2 | Copyright (C) 1995-2019 Free Software Foundation, Inc. |
fcccd512 RM |
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 | #ifndef _DL_LOAD_H | |
20 | #define _DL_LOAD_H 1 | |
21 | ||
22 | #include <link.h> | |
23 | #include <sys/mman.h> | |
24 | ||
25 | ||
26 | /* On some systems, no flag bits are given to specify file mapping. */ | |
27 | #ifndef MAP_FILE | |
28 | # define MAP_FILE 0 | |
29 | #endif | |
30 | ||
31 | /* The right way to map in the shared library files is MAP_COPY, which | |
32 | makes a virtual copy of the data at the time of the mmap call; this | |
33 | guarantees the mapped pages will be consistent even if the file is | |
34 | overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we | |
35 | get is MAP_PRIVATE, which copies each page when it is modified; this | |
36 | means if the file is overwritten, we may at some point get some pages | |
37 | from the new version after starting with pages from the old version. | |
38 | ||
39 | To make up for the lack and avoid the overwriting problem, | |
40 | what Linux does have is MAP_DENYWRITE. This prevents anyone | |
41 | from modifying the file while we have it mapped. */ | |
42 | #ifndef MAP_COPY | |
43 | # ifdef MAP_DENYWRITE | |
44 | # define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE) | |
45 | # else | |
46 | # define MAP_COPY MAP_PRIVATE | |
47 | # endif | |
48 | #endif | |
49 | ||
50 | /* Some systems link their relocatable objects for another base address | |
51 | than 0. We want to know the base address for these such that we can | |
52 | subtract this address from the segment addresses during mapping. | |
53 | This results in a more efficient address space usage. Defaults to | |
54 | zero for almost all systems. */ | |
55 | #ifndef MAP_BASE_ADDR | |
56 | # define MAP_BASE_ADDR(l) 0 | |
57 | #endif | |
58 | ||
59 | ||
60 | /* Handle situations where we have a preferred location in memory for | |
61 | the shared objects. */ | |
62 | #ifdef ELF_PREFERRED_ADDRESS_DATA | |
63 | ELF_PREFERRED_ADDRESS_DATA; | |
64 | #endif | |
65 | #ifndef ELF_PREFERRED_ADDRESS | |
66 | # define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) (mapstartpref) | |
67 | #endif | |
68 | #ifndef ELF_FIXED_ADDRESS | |
69 | # define ELF_FIXED_ADDRESS(loader, mapstart) ((void) 0) | |
70 | #endif | |
71 | ||
72 | ||
73 | /* This structure describes one PT_LOAD command. | |
74 | Its details have been expanded out and converted. */ | |
75 | struct loadcmd | |
76 | { | |
77 | ElfW(Addr) mapstart, mapend, dataend, allocend; | |
78 | ElfW(Off) mapoff; | |
79 | int prot; /* PROT_* bits. */ | |
80 | }; | |
81 | ||
82 | ||
83 | /* This is a subroutine of _dl_map_segments. It should be called for each | |
84 | load command, some time after L->l_addr has been set correctly. It is | |
85 | responsible for setting up the l_text_end and l_phdr fields. */ | |
c2d8f0b7 | 86 | static __always_inline void |
fcccd512 RM |
87 | _dl_postprocess_loadcmd (struct link_map *l, const ElfW(Ehdr) *header, |
88 | const struct loadcmd *c) | |
89 | { | |
90 | if (c->prot & PROT_EXEC) | |
91 | l->l_text_end = l->l_addr + c->mapend; | |
92 | ||
93 | if (l->l_phdr == 0 | |
94 | && c->mapoff <= header->e_phoff | |
95 | && ((size_t) (c->mapend - c->mapstart + c->mapoff) | |
96 | >= header->e_phoff + header->e_phnum * sizeof (ElfW(Phdr)))) | |
97 | /* Found the program header in this segment. */ | |
98 | l->l_phdr = (void *) (uintptr_t) (c->mapstart + header->e_phoff | |
99 | - c->mapoff); | |
100 | } | |
101 | ||
102 | ||
103 | /* This is a subroutine of _dl_map_object_from_fd. It is responsible | |
104 | for filling in several fields in *L: l_map_start, l_map_end, l_addr, | |
105 | l_contiguous, l_text_end, l_phdr. On successful return, all the | |
106 | segments are mapped (or copied, or whatever) from the file into their | |
107 | final places in the address space, with the correct page permissions, | |
108 | and any bss-like regions already zeroed. It returns a null pointer | |
109 | on success, or an error message string (to be translated) on error | |
110 | (having also set errno). | |
111 | ||
112 | The file <dl-map-segments.h> defines this function. The canonical | |
113 | implementation in elf/dl-map-segments.h might be replaced by a sysdeps | |
114 | version. */ | |
115 | static const char *_dl_map_segments (struct link_map *l, int fd, | |
116 | const ElfW(Ehdr) *header, int type, | |
117 | const struct loadcmd loadcmds[], | |
118 | size_t nloadcmds, | |
119 | const size_t maplength, | |
120 | bool has_holes, | |
121 | struct link_map *loader); | |
122 | ||
123 | /* All the error message strings _dl_map_segments might return are | |
124 | listed here so that different implementations in different sysdeps | |
125 | dl-map-segments.h files all use consistent strings that are | |
126 | guaranteed to have translations. */ | |
127 | #define DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT \ | |
128 | N_("failed to map segment from shared object") | |
129 | #define DL_MAP_SEGMENTS_ERROR_MPROTECT \ | |
130 | N_("cannot change memory protections") | |
131 | #define DL_MAP_SEGMENTS_ERROR_MAP_ZERO_FILL \ | |
132 | N_("cannot map zero-fill pages") | |
133 | ||
134 | ||
135 | #endif /* dl-load.h */ |