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authorRoland McGrath <roland@hack.frob.com>2015-07-14 13:15:26 -0700
committerRoland McGrath <roland@hack.frob.com>2015-07-14 13:15:26 -0700
commitc01ae97eb8986600488332f4db98f4b6d6ebedbc (patch)
treead6174a92b8436b96b3ac1819c2b81fa898cc9c2
parent38b759496b0483491e54f3946ae8f0e55d8c079f (diff)
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Factor file identity rules out of generic rtld code.
-rw-r--r--ChangeLog11
-rw-r--r--elf/dl-load.c18
-rw-r--r--include/link.h4
-rw-r--r--sysdeps/generic/dl-fileid.h46
-rw-r--r--sysdeps/nacl/dl-fileid.h8
-rw-r--r--sysdeps/posix/dl-fileid.h50
6 files changed, 125 insertions, 12 deletions
diff --git a/ChangeLog b/ChangeLog
index 120588a..3bc1ba9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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.
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 41b91fc..0c052e4 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -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;
}
diff --git a/include/link.h b/include/link.h
index 7ccd9c3..423a695 100644
--- a/include/link.h
+++ b/include/link.h
@@ -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;
diff --git a/sysdeps/generic/dl-fileid.h b/sysdeps/generic/dl-fileid.h
new file mode 100644
index 0000000..2cbd21d
--- /dev/null
+++ b/sysdeps/generic/dl-fileid.h
@@ -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;
+}
diff --git a/sysdeps/nacl/dl-fileid.h b/sysdeps/nacl/dl-fileid.h
new file mode 100644
index 0000000..4c34581
--- /dev/null
+++ b/sysdeps/nacl/dl-fileid.h
@@ -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>
diff --git a/sysdeps/posix/dl-fileid.h b/sysdeps/posix/dl-fileid.h
new file mode 100644
index 0000000..d0d5436
--- /dev/null
+++ b/sysdeps/posix/dl-fileid.h
@@ -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;
+}