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authorRoland McGrath <roland@hack.frob.com>2014-04-03 10:47:14 -0700
committerRoland McGrath <roland@hack.frob.com>2014-04-03 10:47:14 -0700
commitfcccd51286acbf9c19ac57ab7143e257d58323fd (patch)
tree011b737ea7df67117682d2fd4e0a6998c8eca840 /elf/dl-load.h
parentf6488e2b7f13529cde762d02a0352071c078ff9a (diff)
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Factor mmap/munmap of PT_LOAD segments out of _dl_map_object_from_fd et al.
Diffstat (limited to 'elf/dl-load.h')
-rw-r--r--elf/dl-load.h135
1 files changed, 135 insertions, 0 deletions
diff --git a/elf/dl-load.h b/elf/dl-load.h
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+/* 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 */