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Factor file identity rules out of generic rtld code.

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This commit is contained in:
Roland McGrath 2015-07-14 13:15:26 -07:00
parent 38b759496b
commit c01ae97eb8
6 changed files with 125 additions and 12 deletions
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11
ChangeLog
View File

@ -1,3 +1,14 @@
2015-07-14 Roland McGrath <roland@hack.frob.com>
* sysdeps/generic/dl-fileid.h: New file.
* sysdeps/posix/dl-fileid.h: New file.
* sysdeps/nacl/dl-fileid.h: New file.
* include/link.h: Include <dl-fileid.h>.
(struct link_map): Replace l_dev and l_ino with l_file_id.
* elf/dl-load.c (_dl_map_object_from_fd): Use _dl_get_file_id rather
than __fxstat64. Use _dl_file_id_match_p rather than comparing l_dev
and l_ino directly. Initialize l_file_id rather than l_dev and l_ino.
2015-07-14 Siddhesh Poyarekar <siddhesh@redhat.com>
* stdlib/tst-tls-atexit.c (do_test): Fix typo.

18
elf/dl-load.c
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@ -872,7 +872,6 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
const ElfW(Phdr) *ph;
size_t maplength;
int type;
struct stat64 st;
/* Initialize to keep the compiler happy. */
const char *errstring = NULL;
int errval = 0;
@ -880,7 +879,8 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
bool make_consistent = false;
/* Get file information. */
if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &st) < 0))
struct r_file_id id;
if (__glibc_unlikely (!_dl_get_file_id (fd, &id)))
{
errstring = N_("cannot stat shared object");
call_lose_errno:
@ -891,8 +891,8 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
}
/* Look again to see if the real name matched another already loaded. */
for (l = GL(dl_ns)[nsid]._ns_loaded; l; l = l->l_next)
if (l->l_removed == 0 && l->l_ino == st.st_ino && l->l_dev == st.st_dev)
for (l = GL(dl_ns)[nsid]._ns_loaded; l != NULL; l = l->l_next)
if (!l->l_removed && _dl_file_id_match_p (&l->l_file_id, &id))
{
/* The object is already loaded.
Just bump its reference count and return it. */
@ -910,8 +910,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
/* When loading into a namespace other than the base one we must
avoid loading ld.so since there can only be one copy. Ever. */
if (__glibc_unlikely (nsid != LM_ID_BASE)
&& ((st.st_ino == GL(dl_rtld_map).l_ino
&& st.st_dev == GL(dl_rtld_map).l_dev)
&& (_dl_file_id_match_p (&id, &GL(dl_rtld_map).l_file_id)
|| _dl_name_match_p (name, &GL(dl_rtld_map))))
{
/* This is indeed ld.so. Create a new link_map which refers to
@ -1220,7 +1219,7 @@ cannot allocate TLS data structures for initial thread");
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);
maplength, has_holes, loader);
if (__glibc_unlikely (errstring != NULL))
goto call_lose;
}
@ -1390,8 +1389,7 @@ cannot enable executable stack as shared object requires");
GL(dl_initfirst) = l;
/* Finally the file information. */
l->l_dev = st.st_dev;
l->l_ino = st.st_ino;
l->l_file_id = id;
/* When we profile the SONAME might be needed for something else but
loading. Add it right away. */
@ -1890,7 +1888,7 @@ open_path (const char *name, size_t namelen, int mode,
free (sps->dirs);
/* rtld_search_dirs and env_path_list are attribute_relro, therefore
avoid writing into it. */
avoid writing into it. */
if (sps != &rtld_search_dirs && sps != &env_path_list)
sps->dirs = (void *) -1;
}

4
include/link.h
View File

@ -40,6 +40,7 @@ extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
#include <stdint.h>
#include <stddef.h>
#include <bits/linkmap.h>
#include <dl-fileid.h>
#include <dl-lookupcfg.h>
#include <tls.h>
#include <bits/libc-lock.h>
@ -235,8 +236,7 @@ struct link_map
/* This information is kept to check for sure whether a shared
object is the same as one already loaded. */
dev_t l_dev;
ino64_t l_ino;
struct r_file_id l_file_id;
/* Collected information about own RUNPATH directories. */
struct r_search_path_struct l_runpath_dirs;

46
sysdeps/generic/dl-fileid.h Normal file
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@ -0,0 +1,46 @@
/* File identity for the dynamic linker. Stub version.
Copyright (C) 2015 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 <stdbool.h>
/* This type stores whatever information is fetched by _dl_get_file_id
and compared by _dl_file_id_match_p. */
struct r_file_id
{
/* In the stub version, we don't record anything at all. */
};
/* Sample FD to fill in *ID. Returns true on success.
On error, returns false, with errno set. */
static inline bool
_dl_get_file_id (int fd __attribute__ ((unused)),
struct r_file_id *id __attribute__ ((unused)))
{
return true;
}
/* Compare two results from _dl_get_file_id for equality.
It's crucial that this never return false-positive matches.
It's ideal that it never return false-negative mismatches either,
but lack of matches is survivable. */
static inline bool
_dl_file_id_match_p (const struct r_file_id *a __attribute__ ((unused)),
const struct r_file_id *b __attribute__ ((unused)))
{
return false;
}

8
sysdeps/nacl/dl-fileid.h Normal file
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@ -0,0 +1,8 @@
/* Bypass sysdeps/posix/dl-fileid.h, which relies on st_dev/st_ino being
reliable. Under NaCl, we cannot always expect them to be useful.
Fortunately, in the ways NaCl is used it's far less likely that two
different names for the same file would be used in dlopen or the like,
so failing to notice re-opening the same file is not so likely to be a
problem in practice. */
#include <sysdeps/generic/dl-fileid.h>

50
sysdeps/posix/dl-fileid.h Normal file
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@ -0,0 +1,50 @@
/* File identity for the dynamic linker. Generic POSIX.1 version.
Copyright (C) 2015 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 <stdbool.h>
#include <sys/stat.h>
/* For POSIX.1 systems, the pair of st_dev and st_ino constitute
a unique identifier for a file. */
struct r_file_id
{
dev_t dev;
ino64_t ino;
};
/* Sample FD to fill in *ID. Returns true on success.
On error, returns false, with errno set. */
static inline bool
_dl_get_file_id (int fd, struct r_file_id *id)
{
struct stat64 st;
if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &st) < 0))
return false;
id->dev = st.st_dev;
id->ino = st.st_ino;
return true;
}
/* Compare two results from _dl_get_file_id for equality. */
static inline bool
_dl_file_id_match_p (const struct r_file_id *a, const struct r_file_id *b)
{
return a->dev == b->dev && a->ino == b->ino;
}