1 /* _dl_map_object -- Map in a shared object's segments from the file.
2 Copyright (C) 1995, 1996 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public License as
7 published by the Free Software Foundation; either version 2 of the
8 License, or (at your option) any later version.
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 Library General Public License for more details.
15 You should have received a copy of the GNU Library General Public
16 License along with the GNU C Library; see the file COPYING.LIB. If
17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
18 Cambridge, MA 02139, USA. */
21 #include <sys/types.h>
28 #include "dynamic-link.h"
31 /* On some systems, no flag bits are given to specify file mapping. */
36 /* The right way to map in the shared library files is MAP_COPY, which
37 makes a virtual copy of the data at the time of the mmap call; this
38 guarantees the mapped pages will be consistent even if the file is
39 overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we
40 get is MAP_PRIVATE, which copies each page when it is modified; this
41 means if the file is overwritten, we may at some point get some pages
42 from the new version after starting with pages from the old version. */
44 #define MAP_COPY MAP_PRIVATE
49 #if BYTE_ORDER == BIG_ENDIAN
50 #define byteorder ELFDATA2MSB
51 #define byteorder_name "big-endian"
52 #elif BYTE_ORDER == LITTLE_ENDIAN
53 #define byteorder ELFDATA2LSB
54 #define byteorder_name "little-endian"
56 #error "Unknown BYTE_ORDER " BYTE_ORDER
57 #define byteorder ELFDATANONE
63 /* The fd is not examined when using MAP_ANON. */
67 #define ANONFD _dl_zerofd
73 /* Local version of `strdup' function. */
75 local_strdup (const char *s
)
77 size_t len
= strlen (s
) + 1;
78 void *new = malloc (len
);
83 return (char *) memcpy (new, s
, len
);
87 /* Map in the shared object NAME, actually located in REALNAME, and already
91 _dl_map_object_from_fd (char *name
, int fd
, char *realname
,
92 struct link_map
*loader
, int l_type
)
94 struct link_map
*l
= NULL
;
95 void *file_mapping
= NULL
;
96 size_t mapping_size
= 0;
98 #define LOSE(s) lose (0, (s))
99 void lose (int code
, const char *msg
)
103 __munmap (file_mapping
, mapping_size
);
106 /* Remove the stillborn object from the list and free it. */
108 l
->l_prev
->l_next
= l
->l_next
;
110 l
->l_next
->l_prev
= l
->l_prev
;
115 _dl_signal_error (code
, name
, msg
);
118 inline caddr_t
map_segment (ElfW(Addr
) mapstart
, size_t len
,
119 int prot
, int fixed
, off_t offset
)
121 caddr_t mapat
= __mmap ((caddr_t
) mapstart
, len
, prot
,
122 fixed
|MAP_COPY
|MAP_FILE
,
124 if (mapat
== (caddr_t
) -1)
125 lose (errno
, "failed to map segment from shared object");
129 /* Make sure LOCATION is mapped in. */
130 void *map (off_t location
, size_t size
)
132 if ((off_t
) mapping_size
<= location
+ (off_t
) size
)
136 __munmap (file_mapping
, mapping_size
);
137 mapping_size
= (location
+ size
+ 1 + _dl_pagesize
- 1);
138 mapping_size
&= ~(_dl_pagesize
- 1);
139 result
= __mmap (file_mapping
, mapping_size
, PROT_READ
,
140 MAP_COPY
|MAP_FILE
, fd
, 0);
141 if (result
== (void *) -1)
142 lose (errno
, "cannot map file data");
143 file_mapping
= result
;
145 return file_mapping
+ location
;
148 const ElfW(Ehdr
) *header
;
149 const ElfW(Phdr
) *phdr
;
150 const ElfW(Phdr
) *ph
;
153 /* Look again to see if the real name matched another already loaded. */
154 for (l
= _dl_loaded
; l
; l
= l
->l_next
)
155 if (! strcmp (realname
, l
->l_name
))
157 /* The object is already loaded.
158 Just bump its reference count and return it. */
166 if (_dl_pagesize
== 0)
167 _dl_pagesize
= __getpagesize ();
169 /* Map in the first page to read the header. */
170 header
= map (0, sizeof *header
);
172 /* Check the header for basic validity. */
173 if (*(Elf32_Word
*) &header
->e_ident
!=
174 #if BYTE_ORDER == LITTLE_ENDIAN
175 ((ELFMAG0
<< (EI_MAG0
* 8)) |
176 (ELFMAG1
<< (EI_MAG1
* 8)) |
177 (ELFMAG2
<< (EI_MAG2
* 8)) |
178 (ELFMAG3
<< (EI_MAG3
* 8)))
180 ((ELFMAG0
<< (EI_MAG3
* 8)) |
181 (ELFMAG1
<< (EI_MAG2
* 8)) |
182 (ELFMAG2
<< (EI_MAG1
* 8)) |
183 (ELFMAG3
<< (EI_MAG0
* 8)))
186 LOSE ("invalid ELF header");
187 #define ELF32_CLASS ELFCLASS32
188 #define ELF64_CLASS ELFCLASS64
189 if (header
->e_ident
[EI_CLASS
] != ELFW(CLASS
))
190 LOSE ("ELF file class not " STRING(__ELF_WORDSIZE
) "-bit");
191 if (header
->e_ident
[EI_DATA
] != byteorder
)
192 LOSE ("ELF file data encoding not " byteorder_name
);
193 if (header
->e_ident
[EI_VERSION
] != EV_CURRENT
)
194 LOSE ("ELF file version ident not " STRING(EV_CURRENT
));
195 if (header
->e_version
!= EV_CURRENT
)
196 LOSE ("ELF file version not " STRING(EV_CURRENT
));
197 if (! elf_machine_matches_host (header
->e_machine
))
198 LOSE ("ELF file machine architecture not " ELF_MACHINE_NAME
);
199 if (header
->e_phentsize
!= sizeof (ElfW(Phdr
)))
200 LOSE ("ELF file's phentsize not the expected size");
204 if (_dl_zerofd
== -1)
206 _dl_zerofd
= _dl_sysdep_open_zero_fill ();
207 if (_dl_zerofd
== -1)
210 _dl_signal_error (errno
, NULL
, "cannot open zero fill device");
215 /* Enter the new object in the list of loaded objects. */
216 l
= _dl_new_object (realname
, name
, l_type
);
218 lose (ENOMEM
, "cannot create shared object descriptor");
220 l
->l_loader
= loader
;
222 /* Extract the remaining details we need from the ELF header
223 and then map in the program header table. */
224 l
->l_entry
= header
->e_entry
;
225 type
= header
->e_type
;
226 l
->l_phnum
= header
->e_phnum
;
227 phdr
= map (header
->e_phoff
, l
->l_phnum
* sizeof (ElfW(Phdr
)));
230 /* Scan the program header table, collecting its load commands. */
233 ElfW(Addr
) mapstart
, mapend
, dataend
, allocend
;
236 } loadcmds
[l
->l_phnum
], *c
;
237 size_t nloadcmds
= 0;
242 for (ph
= phdr
; ph
< &phdr
[l
->l_phnum
]; ++ph
)
245 /* These entries tell us where to find things once the file's
246 segments are mapped in. We record the addresses it says
247 verbatim, and later correct for the run-time load address. */
249 l
->l_ld
= (void *) ph
->p_vaddr
;
252 l
->l_phdr
= (void *) ph
->p_vaddr
;
256 /* A load command tells us to map in part of the file.
257 We record the load commands and process them all later. */
258 if (ph
->p_align
% _dl_pagesize
!= 0)
259 LOSE ("ELF load command alignment not page-aligned");
260 if ((ph
->p_vaddr
- ph
->p_offset
) % ph
->p_align
)
261 LOSE ("ELF load command address/offset not properly aligned");
263 struct loadcmd
*c
= &loadcmds
[nloadcmds
++];
264 c
->mapstart
= ph
->p_vaddr
& ~(ph
->p_align
- 1);
265 c
->mapend
= ((ph
->p_vaddr
+ ph
->p_filesz
+ _dl_pagesize
- 1)
266 & ~(_dl_pagesize
- 1));
267 c
->dataend
= ph
->p_vaddr
+ ph
->p_filesz
;
268 c
->allocend
= ph
->p_vaddr
+ ph
->p_memsz
;
269 c
->mapoff
= ph
->p_offset
& ~(ph
->p_align
- 1);
271 if (ph
->p_flags
& PF_R
)
272 c
->prot
|= PROT_READ
;
273 if (ph
->p_flags
& PF_W
)
274 c
->prot
|= PROT_WRITE
;
275 if (ph
->p_flags
& PF_X
)
276 c
->prot
|= PROT_EXEC
;
281 /* We are done reading the file's headers now. Unmap them. */
282 __munmap (file_mapping
, mapping_size
);
284 /* Now process the load commands and map segments into memory. */
287 if (type
== ET_DYN
|| type
== ET_REL
)
289 /* This is a position-independent shared object. We can let the
290 kernel map it anywhere it likes, but we must have space for all
291 the segments in their specified positions relative to the first.
292 So we map the first segment without MAP_FIXED, but with its
293 extent increased to cover all the segments. Then we remove
294 access from excess portion, and there is known sufficient space
295 there to remap from the later segments. */
297 mapat
= map_segment (c
->mapstart
,
298 loadcmds
[nloadcmds
- 1].allocend
- c
->mapstart
,
299 c
->prot
, 0, c
->mapoff
);
300 l
->l_addr
= (ElfW(Addr
)) mapat
- c
->mapstart
;
302 /* Change protection on the excess portion to disallow all access;
303 the portions we do not remap later will be inaccessible as if
304 unallocated. Then jump into the normal segment-mapping loop to
305 handle the portion of the segment past the end of the file
307 __mprotect ((caddr_t
) (l
->l_addr
+ c
->mapend
),
308 loadcmds
[nloadcmds
- 1].allocend
- c
->mapend
,
313 while (c
< &loadcmds
[nloadcmds
])
315 if (c
->mapend
> c
->mapstart
)
316 /* Map the segment contents from the file. */
317 map_segment (l
->l_addr
+ c
->mapstart
, c
->mapend
- c
->mapstart
,
318 c
->prot
, MAP_FIXED
, c
->mapoff
);
321 if (c
->allocend
> c
->dataend
)
323 /* Extra zero pages should appear at the end of this segment,
324 after the data mapped from the file. */
325 ElfW(Addr
) zero
, zeroend
, zeropage
;
327 zero
= l
->l_addr
+ c
->dataend
;
328 zeroend
= l
->l_addr
+ c
->allocend
;
329 zeropage
= (zero
+ _dl_pagesize
- 1) & ~(_dl_pagesize
- 1);
331 if (zeroend
< zeropage
)
332 /* All the extra data is in the last page of the segment.
333 We can just zero it. */
338 /* Zero the final part of the last page of the segment. */
339 if ((c
->prot
& PROT_WRITE
) == 0)
342 if (__mprotect ((caddr_t
) (zero
& ~(_dl_pagesize
- 1)),
343 _dl_pagesize
, c
->prot
|PROT_WRITE
) < 0)
344 lose (errno
, "cannot change memory protections");
346 memset ((void *) zero
, 0, zeropage
- zero
);
347 if ((c
->prot
& PROT_WRITE
) == 0)
348 __mprotect ((caddr_t
) (zero
& ~(_dl_pagesize
- 1)),
349 _dl_pagesize
, c
->prot
);
352 if (zeroend
> zeropage
)
354 /* Map the remaining zero pages in from the zero fill FD. */
356 mapat
= __mmap ((caddr_t
) zeropage
, zeroend
- zeropage
,
357 c
->prot
, MAP_ANON
|MAP_PRIVATE
|MAP_FIXED
,
359 if (mapat
== (caddr_t
) -1)
360 lose (errno
, "cannot map zero-fill pages");
369 /* There was no PT_PHDR specified. We need to find the phdr in the
370 load image ourselves. We assume it is in fact in the load image
371 somewhere, and that the first load command starts at the
372 beginning of the file and thus contains the ELF file header. */
373 ElfW(Addr
) bof
= l
->l_addr
+ loadcmds
[0].mapstart
;
374 assert (loadcmds
[0].mapoff
== 0);
375 l
->l_phdr
= (void *) (bof
+ ((const ElfW(Ehdr
) *) bof
)->e_phoff
);
378 /* Adjust the PT_PHDR value by the runtime load address. */
379 (ElfW(Addr
)) l
->l_phdr
+= l
->l_addr
;
382 /* We are done mapping in the file. We no longer need the descriptor. */
385 if (l
->l_type
== lt_library
&& type
== ET_EXEC
)
386 l
->l_type
= lt_executable
;
391 LOSE ("object file has no dynamic section");
394 (ElfW(Addr
)) l
->l_ld
+= l
->l_addr
;
396 l
->l_entry
+= l
->l_addr
;
398 elf_get_dynamic_info (l
->l_ld
, l
->l_info
);
399 if (l
->l_info
[DT_HASH
])
405 /* Try to open NAME in one of the directories in DIRPATH.
406 Return the fd, or -1. If successful, fill in *REALNAME
407 with the malloc'd full directory name. */
410 open_path (const char *name
, size_t namelen
,
419 if (p
== NULL
|| *p
== '\0')
425 buf
= __alloca (strlen (dirpath
) + 1 + namelen
);
431 p
= strpbrk (dirpath
, ":;");
433 p
= strchr (dirpath
, '\0');
437 /* Two adjacent colons, or a colon at the beginning or the end of
438 the path means to search the current directory. */
439 (void) memcpy (buf
, name
, namelen
);
444 /* Construct the pathname to try. */
445 (void) memcpy (buf
, dirpath
, p
- dirpath
);
446 buf
[p
- dirpath
] = '/';
447 (void) memcpy (&buf
[(p
- dirpath
) + 1], name
, namelen
);
448 buflen
= p
- dirpath
+ 1 + namelen
;
451 fd
= __open (buf
, O_RDONLY
);
454 *realname
= malloc (buflen
);
457 memcpy (*realname
, buf
, buflen
);
462 /* No memory for the name, we certainly won't be able
463 to load and link it. */
468 if (errno
!= ENOENT
&& errno
!= EACCES
)
469 /* The file exists and is readable, but something went wrong. */
472 while (*p
++ != '\0');
477 /* Map in the shared object file NAME. */
480 _dl_map_object (struct link_map
*loader
, const char *name
, int type
)
487 /* Look for this name among those already loaded. */
488 for (l
= _dl_loaded
; l
; l
= l
->l_next
)
489 if (! strcmp (name
, l
->l_libname
) || /* NAME was requested before. */
490 ! strcmp (name
, l
->l_name
) || /* NAME was found before. */
491 /* If the requested name matches the soname of a loaded object,
493 (l
->l_info
[DT_SONAME
] &&
494 ! strcmp (name
, (const char *) (l
->l_addr
+
495 l
->l_info
[DT_STRTAB
]->d_un
.d_ptr
+
496 l
->l_info
[DT_SONAME
]->d_un
.d_val
))))
498 /* The object is already loaded.
499 Just bump its reference count and return it. */
504 if (strchr (name
, '/') == NULL
)
506 /* Search for NAME in several places. */
508 size_t namelen
= strlen (name
) + 1;
510 inline void trypath (const char *dirpath
)
512 fd
= open_path (name
, namelen
, dirpath
, &realname
);
517 /* First try the DT_RPATH of the dependent object that caused NAME
518 to be loaded. Then that object's dependent, and on up. */
519 for (l
= loader
; fd
== -1 && l
; l
= l
->l_loader
)
520 if (l
&& l
->l_info
[DT_RPATH
])
521 trypath ((const char *) (l
->l_addr
+
522 l
->l_info
[DT_STRTAB
]->d_un
.d_ptr
+
523 l
->l_info
[DT_RPATH
]->d_un
.d_val
));
524 /* If dynamically linked, try the DT_RPATH of the executable itself. */
526 if (fd
== -1 && l
&& l
->l_type
!= lt_loaded
&& l
->l_info
[DT_RPATH
])
527 trypath ((const char *) (l
->l_addr
+
528 l
->l_info
[DT_STRTAB
]->d_un
.d_ptr
+
529 l
->l_info
[DT_RPATH
]->d_un
.d_val
));
530 /* Try an environment variable (unless setuid). */
531 if (fd
== -1 && ! __libc_enable_secure
)
532 trypath (getenv ("LD_LIBRARY_PATH"));
535 /* Check the list of libraries in the file /etc/ld.so.cache,
536 for compatibility with Linux's ldconfig program. */
537 extern const char *_dl_load_cache_lookup (const char *name
);
538 const char *cached
= _dl_load_cache_lookup (name
);
541 fd
= __open (cached
, O_RDONLY
);
544 realname
= local_strdup (cached
);
545 if (realname
== NULL
)
553 /* Finally, try the default path. */
556 extern const char *_dl_rpath
; /* Set in rtld.c. */
562 fd
= __open (name
, O_RDONLY
);
565 realname
= local_strdup (name
);
566 if (realname
== NULL
)
576 name_copy
= local_strdup (name
);
577 if (name_copy
== NULL
)
585 _dl_signal_error (errno
, name
, "cannot open shared object file");
587 return _dl_map_object_from_fd (name_copy
, fd
, realname
, loader
, type
);