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Diffstat (limited to 'elf/dl-load.h')
| -rw-r--r-- | elf/dl-load.h | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/elf/dl-load.h b/elf/dl-load.h new file mode 100644 index 0000000000..602840e5f8 --- /dev/null +++ b/elf/dl-load.h @@ -0,0 +1,135 @@ +/* Map in a shared object's segments from the file. + Copyright (C) 1995-2014 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#ifndef _DL_LOAD_H +#define _DL_LOAD_H 1 + +#include <link.h> +#include <sys/mman.h> + + +/* On some systems, no flag bits are given to specify file mapping. */ +#ifndef MAP_FILE +# define MAP_FILE 0 +#endif + +/* The right way to map in the shared library files is MAP_COPY, which + makes a virtual copy of the data at the time of the mmap call; this + guarantees the mapped pages will be consistent even if the file is + overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we + get is MAP_PRIVATE, which copies each page when it is modified; this + means if the file is overwritten, we may at some point get some pages + from the new version after starting with pages from the old version. + + To make up for the lack and avoid the overwriting problem, + what Linux does have is MAP_DENYWRITE. This prevents anyone + from modifying the file while we have it mapped. */ +#ifndef MAP_COPY +# ifdef MAP_DENYWRITE +# define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE) +# else +# define MAP_COPY MAP_PRIVATE +# endif +#endif + +/* Some systems link their relocatable objects for another base address + than 0. We want to know the base address for these such that we can + subtract this address from the segment addresses during mapping. + This results in a more efficient address space usage. Defaults to + zero for almost all systems. */ +#ifndef MAP_BASE_ADDR +# define MAP_BASE_ADDR(l) 0 +#endif + + +/* Handle situations where we have a preferred location in memory for + the shared objects. */ +#ifdef ELF_PREFERRED_ADDRESS_DATA +ELF_PREFERRED_ADDRESS_DATA; +#endif +#ifndef ELF_PREFERRED_ADDRESS +# define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) (mapstartpref) +#endif +#ifndef ELF_FIXED_ADDRESS +# define ELF_FIXED_ADDRESS(loader, mapstart) ((void) 0) +#endif + + +/* This structure describes one PT_LOAD command. + Its details have been expanded out and converted. */ +struct loadcmd +{ + ElfW(Addr) mapstart, mapend, dataend, allocend; + ElfW(Off) mapoff; + int prot; /* PROT_* bits. */ +}; + + +/* This is a subroutine of _dl_map_segments. It should be called for each + load command, some time after L->l_addr has been set correctly. It is + responsible for setting up the l_text_end and l_phdr fields. */ +static void __always_inline +_dl_postprocess_loadcmd (struct link_map *l, const ElfW(Ehdr) *header, + const struct loadcmd *c) +{ + if (c->prot & PROT_EXEC) + l->l_text_end = l->l_addr + c->mapend; + + if (l->l_phdr == 0 + && c->mapoff <= header->e_phoff + && ((size_t) (c->mapend - c->mapstart + c->mapoff) + >= header->e_phoff + header->e_phnum * sizeof (ElfW(Phdr)))) + /* Found the program header in this segment. */ + l->l_phdr = (void *) (uintptr_t) (c->mapstart + header->e_phoff + - c->mapoff); +} + + +/* This is a subroutine of _dl_map_object_from_fd. It is responsible + for filling in several fields in *L: l_map_start, l_map_end, l_addr, + l_contiguous, l_text_end, l_phdr. On successful return, all the + segments are mapped (or copied, or whatever) from the file into their + final places in the address space, with the correct page permissions, + and any bss-like regions already zeroed. It returns a null pointer + on success, or an error message string (to be translated) on error + (having also set errno). + + The file <dl-map-segments.h> defines this function. The canonical + implementation in elf/dl-map-segments.h might be replaced by a sysdeps + version. */ +static const char *_dl_map_segments (struct link_map *l, int fd, + const ElfW(Ehdr) *header, int type, + const struct loadcmd loadcmds[], + size_t nloadcmds, + const size_t maplength, + bool has_holes, + struct link_map *loader); + +/* All the error message strings _dl_map_segments might return are + listed here so that different implementations in different sysdeps + dl-map-segments.h files all use consistent strings that are + guaranteed to have translations. */ +#define DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT \ + N_("failed to map segment from shared object") +#define DL_MAP_SEGMENTS_ERROR_MPROTECT \ + N_("cannot change memory protections") +#define DL_MAP_SEGMENTS_ERROR_MAP_ZERO_FILL \ + N_("cannot map zero-fill pages") + + +#endif /* dl-load.h */ |