136 lines
5.2 KiB
C
136 lines
5.2 KiB
C
/* Map in a shared object's segments from the file.
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Copyright (C) 1995-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _DL_LOAD_H
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#define _DL_LOAD_H 1
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#include <link.h>
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#include <sys/mman.h>
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/* On some systems, no flag bits are given to specify file mapping. */
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#ifndef MAP_FILE
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# define MAP_FILE 0
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#endif
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/* The right way to map in the shared library files is MAP_COPY, which
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makes a virtual copy of the data at the time of the mmap call; this
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guarantees the mapped pages will be consistent even if the file is
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overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we
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get is MAP_PRIVATE, which copies each page when it is modified; this
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means if the file is overwritten, we may at some point get some pages
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from the new version after starting with pages from the old version.
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To make up for the lack and avoid the overwriting problem,
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what Linux does have is MAP_DENYWRITE. This prevents anyone
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from modifying the file while we have it mapped. */
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#ifndef MAP_COPY
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# ifdef MAP_DENYWRITE
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# define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE)
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# else
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# define MAP_COPY MAP_PRIVATE
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# endif
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#endif
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/* Some systems link their relocatable objects for another base address
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than 0. We want to know the base address for these such that we can
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subtract this address from the segment addresses during mapping.
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This results in a more efficient address space usage. Defaults to
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zero for almost all systems. */
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#ifndef MAP_BASE_ADDR
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# define MAP_BASE_ADDR(l) 0
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#endif
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/* Handle situations where we have a preferred location in memory for
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the shared objects. */
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#ifdef ELF_PREFERRED_ADDRESS_DATA
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ELF_PREFERRED_ADDRESS_DATA;
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#endif
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#ifndef ELF_PREFERRED_ADDRESS
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# define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) (mapstartpref)
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#endif
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#ifndef ELF_FIXED_ADDRESS
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# define ELF_FIXED_ADDRESS(loader, mapstart) ((void) 0)
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#endif
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/* This structure describes one PT_LOAD command.
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Its details have been expanded out and converted. */
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struct loadcmd
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{
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ElfW(Addr) mapstart, mapend, dataend, allocend;
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ElfW(Off) mapoff;
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int prot; /* PROT_* bits. */
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};
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/* This is a subroutine of _dl_map_segments. It should be called for each
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load command, some time after L->l_addr has been set correctly. It is
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responsible for setting up the l_text_end and l_phdr fields. */
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static void __always_inline
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_dl_postprocess_loadcmd (struct link_map *l, const ElfW(Ehdr) *header,
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const struct loadcmd *c)
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{
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if (c->prot & PROT_EXEC)
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l->l_text_end = l->l_addr + c->mapend;
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if (l->l_phdr == 0
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&& c->mapoff <= header->e_phoff
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&& ((size_t) (c->mapend - c->mapstart + c->mapoff)
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>= header->e_phoff + header->e_phnum * sizeof (ElfW(Phdr))))
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/* Found the program header in this segment. */
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l->l_phdr = (void *) (uintptr_t) (c->mapstart + header->e_phoff
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- c->mapoff);
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}
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/* This is a subroutine of _dl_map_object_from_fd. It is responsible
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for filling in several fields in *L: l_map_start, l_map_end, l_addr,
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l_contiguous, l_text_end, l_phdr. On successful return, all the
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segments are mapped (or copied, or whatever) from the file into their
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final places in the address space, with the correct page permissions,
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and any bss-like regions already zeroed. It returns a null pointer
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on success, or an error message string (to be translated) on error
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(having also set errno).
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The file <dl-map-segments.h> defines this function. The canonical
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implementation in elf/dl-map-segments.h might be replaced by a sysdeps
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version. */
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static const char *_dl_map_segments (struct link_map *l, int fd,
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const ElfW(Ehdr) *header, int type,
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const struct loadcmd loadcmds[],
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size_t nloadcmds,
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const size_t maplength,
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bool has_holes,
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struct link_map *loader);
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/* All the error message strings _dl_map_segments might return are
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listed here so that different implementations in different sysdeps
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dl-map-segments.h files all use consistent strings that are
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guaranteed to have translations. */
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#define DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT \
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N_("failed to map segment from shared object")
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#define DL_MAP_SEGMENTS_ERROR_MPROTECT \
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N_("cannot change memory protections")
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#define DL_MAP_SEGMENTS_ERROR_MAP_ZERO_FILL \
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N_("cannot map zero-fill pages")
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#endif /* dl-load.h */
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