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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
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')
-rw-r--r--elf/dl-close.c2
-rw-r--r--elf/dl-fptr.c4
-rw-r--r--elf/dl-load.c221
-rw-r--r--elf/dl-load.h135
-rw-r--r--elf/dl-map-segments.h153
-rw-r--r--elf/dl-unmap-segments.h35
6 files changed, 350 insertions, 200 deletions
diff --git a/elf/dl-close.c b/elf/dl-close.c
index f36ea0f779..d74d55eb87 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -33,6 +33,8 @@
#include <tls.h>
#include <stap-probe.h>
+#include <dl-unmap-segments.h>
+
/* Type of the constructor functions. */
typedef void (*fini_t) (void);
diff --git a/elf/dl-fptr.c b/elf/dl-fptr.c
index 40cb40a3f1..f1478e26bb 100644
--- a/elf/dl-fptr.c
+++ b/elf/dl-fptr.c
@@ -25,6 +25,7 @@
#include <ldsodefs.h>
#include <elf/dynamic-link.h>
#include <dl-fptr.h>
+#include <dl-unmap-segments.h>
#include <atomic.h>
#ifndef ELF_MACHINE_BOOT_FPTR_TABLE_LEN
@@ -269,8 +270,7 @@ _dl_unmap (struct link_map *map)
struct fdesc *head = NULL, *tail = NULL;
size_t i;
- __munmap ((void *) map->l_map_start,
- map->l_map_end - map->l_map_start);
+ _dl_unmap_segments (map);
if (ftab == NULL)
return;
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 16b101af0c..cfa7f2525f 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -38,39 +38,9 @@
#include <stap-probe.h>
#include <dl-dst.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
+#include <dl-load.h>
+#include <dl-map-segments.h>
+#include <dl-unmap-segments.h>
#include <endian.h>
@@ -85,18 +55,6 @@
#define STRING(x) __STRING (x)
-/* 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
-
int __stack_prot attribute_hidden attribute_relro
#if _STACK_GROWS_DOWN && defined PROT_GROWSDOWN
@@ -1093,12 +1051,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
{
/* Scan the program header table, collecting its load commands. */
- struct loadcmd
- {
- ElfW(Addr) mapstart, mapend, dataend, allocend;
- ElfW(Off) mapoff;
- int prot;
- } loadcmds[l->l_phnum], *c;
+ struct loadcmd loadcmds[l->l_phnum];
size_t nloadcmds = 0;
bool has_holes = false;
@@ -1137,7 +1090,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
goto call_lose;
}
- c = &loadcmds[nloadcmds++];
+ struct loadcmd *c = &loadcmds[nloadcmds++];
c->mapstart = ph->p_vaddr & ~(GLRO(dl_pagesize) - 1);
c->mapend = ((ph->p_vaddr + ph->p_filesz + GLRO(dl_pagesize) - 1)
& ~(GLRO(dl_pagesize) - 1));
@@ -1263,154 +1216,26 @@ cannot allocate TLS data structures for initial thread");
goto call_lose;
}
- /* Now process the load commands and map segments into memory. */
- c = loadcmds;
-
- /* Length of the sections to be loaded. */
- maplength = loadcmds[nloadcmds - 1].allocend - c->mapstart;
-
- if (__glibc_likely (type == ET_DYN))
- {
- /* This is a position-independent shared object. We can let the
- kernel map it anywhere it likes, but we must have space for all
- the segments in their specified positions relative to the first.
- So we map the first segment without MAP_FIXED, but with its
- extent increased to cover all the segments. Then we remove
- access from excess portion, and there is known sufficient space
- there to remap from the later segments.
-
- As a refinement, sometimes we have an address that we would
- prefer to map such objects at; but this is only a preference,
- the OS can do whatever it likes. */
- ElfW(Addr) mappref;
- mappref = (ELF_PREFERRED_ADDRESS (loader, maplength,
- c->mapstart & GLRO(dl_use_load_bias))
- - MAP_BASE_ADDR (l));
-
- /* Remember which part of the address space this object uses. */
- l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
- c->prot,
- MAP_COPY|MAP_FILE,
- fd, c->mapoff);
- if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
- {
- map_error:
- errstring = N_("failed to map segment from shared object");
- goto call_lose_errno;
- }
-
- l->l_map_end = l->l_map_start + maplength;
- l->l_addr = l->l_map_start - c->mapstart;
-
- if (has_holes)
- /* Change protection on the excess portion to disallow all access;
- the portions we do not remap later will be inaccessible as if
- unallocated. Then jump into the normal segment-mapping loop to
- handle the portion of the segment past the end of the file
- mapping. */
- __mprotect ((caddr_t) (l->l_addr + c->mapend),
- loadcmds[nloadcmds - 1].mapstart - c->mapend,
- PROT_NONE);
-
- l->l_contiguous = 1;
-
- goto postmap;
- }
-
- /* This object is loaded at a fixed address. This must never
- happen for objects loaded with dlopen(). */
- if (__glibc_unlikely ((mode & __RTLD_OPENEXEC) == 0))
+ if (__glibc_unlikely (type != ET_DYN)
+ && __glibc_unlikely ((mode & __RTLD_OPENEXEC) == 0))
{
+ /* This object is loaded at a fixed address. This must never
+ happen for objects loaded with dlopen. */
errstring = N_("cannot dynamically load executable");
goto call_lose;
}
- /* Notify ELF_PREFERRED_ADDRESS that we have to load this one
- fixed. */
- ELF_FIXED_ADDRESS (loader, c->mapstart);
-
-
- /* Remember which part of the address space this object uses. */
- l->l_map_start = c->mapstart + l->l_addr;
- l->l_map_end = l->l_map_start + maplength;
- l->l_contiguous = !has_holes;
-
- while (c < &loadcmds[nloadcmds])
- {
- if (c->mapend > c->mapstart
- /* Map the segment contents from the file. */
- && (__mmap ((void *) (l->l_addr + c->mapstart),
- c->mapend - c->mapstart, c->prot,
- MAP_FIXED|MAP_COPY|MAP_FILE,
- fd, c->mapoff)
- == MAP_FAILED))
- goto map_error;
-
- postmap:
- 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);
-
- if (c->allocend > c->dataend)
- {
- /* Extra zero pages should appear at the end of this segment,
- after the data mapped from the file. */
- ElfW(Addr) zero, zeroend, zeropage;
-
- zero = l->l_addr + c->dataend;
- zeroend = l->l_addr + c->allocend;
- zeropage = ((zero + GLRO(dl_pagesize) - 1)
- & ~(GLRO(dl_pagesize) - 1));
-
- if (zeroend < zeropage)
- /* All the extra data is in the last page of the segment.
- We can just zero it. */
- zeropage = zeroend;
-
- if (zeropage > zero)
- {
- /* Zero the final part of the last page of the segment. */
- if (__glibc_unlikely ((c->prot & PROT_WRITE) == 0))
- {
- /* Dag nab it. */
- if (__mprotect ((caddr_t) (zero
- & ~(GLRO(dl_pagesize) - 1)),
- GLRO(dl_pagesize), c->prot|PROT_WRITE) < 0)
- {
- errstring = N_("cannot change memory protections");
- goto call_lose_errno;
- }
- }
- memset ((void *) zero, '\0', zeropage - zero);
- if (__glibc_unlikely ((c->prot & PROT_WRITE) == 0))
- __mprotect ((caddr_t) (zero & ~(GLRO(dl_pagesize) - 1)),
- GLRO(dl_pagesize), c->prot);
- }
-
- if (zeroend > zeropage)
- {
- /* Map the remaining zero pages in from the zero fill FD. */
- caddr_t mapat;
- mapat = __mmap ((caddr_t) zeropage, zeroend - zeropage,
- c->prot, MAP_ANON|MAP_PRIVATE|MAP_FIXED,
- -1, 0);
- if (__glibc_unlikely (mapat == MAP_FAILED))
- {
- errstring = N_("cannot map zero-fill pages");
- goto call_lose_errno;
- }
- }
- }
-
- ++c;
- }
+ /* Length of the sections to be loaded. */
+ maplength = loadcmds[nloadcmds - 1].allocend - loadcmds[0].mapstart;
+
+ /* Now process the load commands and map segments into memory.
+ This is responsible for filling in:
+ l_map_start, l_map_end, l_addr, l_contiguous, l_text_end, l_phdr
+ */
+ errstring = _dl_map_segments (l, fd, header, type, loadcmds, nloadcmds,
+ maplength, has_holes, loader);
+ if (__glibc_unlikely (errstring != NULL))
+ goto call_lose;
}
if (l->l_ld == 0)
@@ -1432,7 +1257,7 @@ cannot allocate TLS data structures for initial thread");
&& (mode & __RTLD_DLOPEN))
{
/* We are not supposed to load this object. Free all resources. */
- __munmap ((void *) l->l_map_start, l->l_map_end - l->l_map_start);
+ _dl_unmap_segments (l);
if (!l->l_libname->dont_free)
free (l->l_libname);
@@ -1738,8 +1563,8 @@ open_verify (const char *name, struct filebuf *fbp, struct link_map *loader,
assert (sizeof (fbp->buf) > sizeof (ElfW(Ehdr)));
/* Read in the header. */
do
- {
- ssize_t retlen = __libc_read (fd, fbp->buf + fbp->len,
+ {
+ ssize_t retlen = __libc_read (fd, fbp->buf + fbp->len,
sizeof (fbp->buf) - fbp->len);
if (retlen <= 0)
break;
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 */
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
new file mode 100644
index 0000000000..71671cd573
--- /dev/null
+++ b/elf/dl-map-segments.h
@@ -0,0 +1,153 @@
+/* Map in a shared object's segments. Generic version.
+ 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/>. */
+
+#include <dl-load.h>
+
+/* This implementation assumes (as does the corresponding implementation
+ of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
+ are always laid out with all segments contiguous (or with gaps
+ between them small enough that it's preferable to reserve all whole
+ pages inside the gaps with PROT_NONE mappings rather than permitting
+ other use of those parts of the address space). */
+
+static __always_inline 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)
+{
+ const struct loadcmd *c = loadcmds;
+
+ if (__glibc_likely (type == ET_DYN))
+ {
+ /* This is a position-independent shared object. We can let the
+ kernel map it anywhere it likes, but we must have space for all
+ the segments in their specified positions relative to the first.
+ So we map the first segment without MAP_FIXED, but with its
+ extent increased to cover all the segments. Then we remove
+ access from excess portion, and there is known sufficient space
+ there to remap from the later segments.
+
+ As a refinement, sometimes we have an address that we would
+ prefer to map such objects at; but this is only a preference,
+ the OS can do whatever it likes. */
+ ElfW(Addr) mappref
+ = (ELF_PREFERRED_ADDRESS (loader, maplength,
+ c->mapstart & GLRO(dl_use_load_bias))
+ - MAP_BASE_ADDR (l));
+
+ /* Remember which part of the address space this object uses. */
+ l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
+ c->prot,
+ MAP_COPY|MAP_FILE,
+ fd, c->mapoff);
+ if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
+ return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
+
+ l->l_map_end = l->l_map_start + maplength;
+ l->l_addr = l->l_map_start - c->mapstart;
+
+ if (has_holes)
+ /* Change protection on the excess portion to disallow all access;
+ the portions we do not remap later will be inaccessible as if
+ unallocated. Then jump into the normal segment-mapping loop to
+ handle the portion of the segment past the end of the file
+ mapping. */
+ __mprotect ((caddr_t) (l->l_addr + c->mapend),
+ loadcmds[nloadcmds - 1].mapstart - c->mapend,
+ PROT_NONE);
+
+ l->l_contiguous = 1;
+
+ goto postmap;
+ }
+
+ /* Remember which part of the address space this object uses. */
+ l->l_map_start = c->mapstart + l->l_addr;
+ l->l_map_end = l->l_map_start + maplength;
+ l->l_contiguous = !has_holes;
+
+ while (c < &loadcmds[nloadcmds])
+ {
+ if (c->mapend > c->mapstart
+ /* Map the segment contents from the file. */
+ && (__mmap ((void *) (l->l_addr + c->mapstart),
+ c->mapend - c->mapstart, c->prot,
+ MAP_FIXED|MAP_COPY|MAP_FILE,
+ fd, c->mapoff)
+ == MAP_FAILED))
+ return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
+
+ postmap:
+ _dl_postprocess_loadcmd (l, header, c);
+
+ if (c->allocend > c->dataend)
+ {
+ /* Extra zero pages should appear at the end of this segment,
+ after the data mapped from the file. */
+ ElfW(Addr) zero, zeroend, zeropage;
+
+ zero = l->l_addr + c->dataend;
+ zeroend = l->l_addr + c->allocend;
+ zeropage = ((zero + GLRO(dl_pagesize) - 1)
+ & ~(GLRO(dl_pagesize) - 1));
+
+ if (zeroend < zeropage)
+ /* All the extra data is in the last page of the segment.
+ We can just zero it. */
+ zeropage = zeroend;
+
+ if (zeropage > zero)
+ {
+ /* Zero the final part of the last page of the segment. */
+ if (__glibc_unlikely ((c->prot & PROT_WRITE) == 0))
+ {
+ /* Dag nab it. */
+ if (__mprotect ((caddr_t) (zero
+ & ~(GLRO(dl_pagesize) - 1)),
+ GLRO(dl_pagesize), c->prot|PROT_WRITE) < 0)
+ return DL_MAP_SEGMENTS_ERROR_MPROTECT;
+ }
+ memset ((void *) zero, '\0', zeropage - zero);
+ if (__glibc_unlikely ((c->prot & PROT_WRITE) == 0))
+ __mprotect ((caddr_t) (zero & ~(GLRO(dl_pagesize) - 1)),
+ GLRO(dl_pagesize), c->prot);
+ }
+
+ if (zeroend > zeropage)
+ {
+ /* Map the remaining zero pages in from the zero fill FD. */
+ caddr_t mapat;
+ mapat = __mmap ((caddr_t) zeropage, zeroend - zeropage,
+ c->prot, MAP_ANON|MAP_PRIVATE|MAP_FIXED,
+ -1, 0);
+ if (__glibc_unlikely (mapat == MAP_FAILED))
+ return DL_MAP_SEGMENTS_ERROR_MAP_ZERO_FILL;
+ }
+ }
+
+ ++c;
+ }
+
+ /* Notify ELF_PREFERRED_ADDRESS that we have to load this one
+ fixed. */
+ ELF_FIXED_ADDRESS (loader, c->mapstart);
+
+ return NULL;
+}
diff --git a/elf/dl-unmap-segments.h b/elf/dl-unmap-segments.h
new file mode 100644
index 0000000000..ce9c3fecfa
--- /dev/null
+++ b/elf/dl-unmap-segments.h
@@ -0,0 +1,35 @@
+/* Unmap a shared object's segments. Generic version.
+ Copyright (C) 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_UNMAP_SEGMENTS_H
+#define _DL_UNMAP_SEGMENTS_H 1
+
+#include <link.h>
+#include <sys/mman.h>
+
+/* _dl_map_segments ensures that any whole pages in gaps between segments
+ are filled in with PROT_NONE mappings. So we can just unmap the whole
+ range in one fell swoop. */
+
+static __always_inline void
+_dl_unmap_segments (struct link_map *l)
+{
+ __munmap ((void *) l->l_map_start, l->l_map_end - l->l_map_start);
+}
+
+#endif /* dl-unmap-segments.h */