Factor file identity rules out of generic rtld code.

3 files changed, 104 insertions, 0 deletions

diff --git a/sysdeps/generic/dl-fileid.h b/sysdeps/generic/dl-fileid.h
new file mode 100644
index 0000000000..2cbd21dcbe
--- /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 0000000000..4c34581701
--- /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 0000000000..d0d5436641
--- /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;
+}