[glibc/azanella/bz23960-dirent] linux: Set internal DIR filepos as off64_t [BZ #23960, BZ #24050]

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=460ee0ef99c058186c789df5efd918e80b4ddfb0

commit 460ee0ef99c058186c789df5efd918e80b4ddfb0
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Mon Apr 13 18:09:20 2020 -0300

    linux: Set internal DIR filepos as off64_t [BZ #23960, BZ #24050]
    
    It allows to obtain the expected entry offset on telldir and set
    it correctly on seekdir on platforms where long int is smaller
    than off64_t.
    
    On such cases telldir will mantain an internal list that maps the
    DIR object off64_t offsets to the returned long int (the function
    return value).  The seekdir will then set the correct offset from
    the internal list using the telldir as the list key.
    
    It also removes the overflow check on readdir and the returned value
    will be truncated by the non-LFS off_t size.  As Joseph has noted
    in BZ #23960 comment #22, d_off is an opaque value and since
    telldir/seekdir works regardless of the returned dirent d_off value.
    
    Finally it removed the requirement to check for overflow values on
    telldir (BZ #24050).
    
    Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
    and arm-linux-gnueabihf.

Diff:
---
 dirent/Makefile                     |   2 +-
 dirent/tst-seekdir2.c               | 158 ++++++++++++++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/closedir.c  |   4 +
 sysdeps/unix/sysv/linux/dirstream.h |   6 +-
 sysdeps/unix/sysv/linux/opendir.c   |   3 +
 sysdeps/unix/sysv/linux/readdir.c   |   1 +
 sysdeps/unix/sysv/linux/rewinddir.c |   5 ++
 sysdeps/unix/sysv/linux/seekdir.c   |  36 ++++++--
 sysdeps/unix/sysv/linux/telldir.c   |  47 ++++++++++-
 sysdeps/unix/sysv/linux/telldir.h   |  64 +++++++++++++++
 10 files changed, 317 insertions(+), 9 deletions(-)

diff --git a/dirent/Makefile b/dirent/Makefile
index cfa61826ed..9a9d91b8a5 100644
--- a/dirent/Makefile
+++ b/dirent/Makefile
@@ -31,7 +31,7 @@ routines	:= opendir closedir readdir readdir_r rewinddir \
 		   scandir-cancel scandir-tail scandir64-tail
 
 tests	   := list tst-seekdir opendir-tst1 bug-readdir1 tst-fdopendir \
-	      tst-fdopendir2 tst-scandir tst-scandir64
+	      tst-fdopendir2 tst-scandir tst-scandir64 tst-seekdir2
 
 CFLAGS-scandir.c += $(uses-callbacks)
 CFLAGS-scandir64.c += $(uses-callbacks)
diff --git a/dirent/tst-seekdir2.c b/dirent/tst-seekdir2.c
new file mode 100644
index 0000000000..3e01b361e5
--- /dev/null
+++ b/dirent/tst-seekdir2.c
@@ -0,0 +1,158 @@
+/* Check multiple telldir and seekdir.
+   Copyright (C) 2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dirent.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <support/temp_file.h>
+#include <support/support.h>
+#include <support/check.h>
+
+/* Some filesystems returns a arbitrary value for d_off direnty entry (ext4
+   for instance, where the value is an internal hash key).  The idea of
+   create a large number of file is to try trigger a overflow d_off value
+   in a entry to check if telldir/seekdir does work corretly in such
+   case.  */
+static const char *dirname;
+static const size_t nfiles = 10240;
+
+static void
+do_prepare (int argc, char *argv[])
+{
+  dirname = support_create_temp_directory ("tst-seekdir2-");
+
+  for (size_t i = 0; i < nfiles; i++)
+    {
+      int fd = create_temp_file_in_dir ("tempfile.", dirname, NULL);
+      TEST_VERIFY_EXIT (fd > 0);
+      close (fd);
+    }
+}
+#define PREPARE do_prepare
+
+/* Check for old non Large File Support (LFS).  */
+static int
+do_test_not_lfs (void)
+{
+  DIR *dirp = opendir (dirname);
+  TEST_VERIFY_EXIT (dirp != NULL);
+
+  size_t dirp_count = 0;
+  for (struct dirent *dp = readdir (dirp);
+       dp != NULL;
+       dp = readdir (dirp))
+    dirp_count++;
+
+  /* The 2 extra files are '.' and '..'.  */
+  TEST_COMPARE (dirp_count, nfiles + 2);
+
+  rewinddir (dirp);
+
+  long *tdirp = xmalloc (dirp_count * sizeof (long));
+  struct dirent **ddirp = xmalloc (dirp_count * sizeof (struct dirent *));
+
+  size_t i = 0;
+  do
+    {
+      tdirp[i] = telldir (dirp);
+      struct dirent *dp = readdir (dirp);
+      TEST_VERIFY_EXIT (dp != NULL);
+      ddirp[i] = xmalloc (dp->d_reclen);
+      memcpy (ddirp[i], dp, dp->d_reclen);
+    } while (++i < dirp_count);
+
+  for (i = 0; i < dirp_count - 1; i++)
+    {
+      seekdir (dirp, tdirp[i]);
+      struct dirent *dp = readdir (dirp);
+      TEST_COMPARE (strcmp (dp->d_name, ddirp[i]->d_name), 0);
+      TEST_COMPARE (dp->d_ino, ddirp[i]->d_ino);
+      TEST_COMPARE (dp->d_off, ddirp[i]->d_off);
+    }
+
+  closedir (dirp);
+  free (tdirp);
+  for (i = 0; i < dirp_count; i++)
+    free (ddirp[i]);
+  free (ddirp);
+
+  return 0;
+}
+
+/* Same as before but with LFS support.  */
+static int
+do_test_lfs (void)
+{
+  DIR *dirp = opendir (dirname);
+  TEST_VERIFY_EXIT (dirp != NULL);
+
+  size_t dirp_count = 0;
+  for (struct dirent64 * dp = readdir64 (dirp);
+       dp != NULL;
+       dp = readdir64 (dirp))
+    dirp_count++;
+
+  /* The 2 extra files are '.' and '..'.  */
+  TEST_COMPARE (dirp_count, nfiles + 2);
+
+  rewinddir (dirp);
+
+  long *tdirp = xmalloc (dirp_count * sizeof (long));
+  struct dirent64 **ddirp = xmalloc (dirp_count * sizeof (struct dirent64 *));
+
+  size_t i = 0;
+  do
+    {
+      tdirp[i] = telldir (dirp);
+      struct dirent64 *dp = readdir64 (dirp);
+      TEST_VERIFY_EXIT (dp != NULL);
+      ddirp[i] = xmalloc (dp->d_reclen);
+      memcpy (ddirp[i], dp, dp->d_reclen);
+    } while (++i < dirp_count);
+
+  for (i = 0; i < dirp_count - 1; i++)
+    {
+      seekdir (dirp, tdirp[i]);
+      struct dirent64 *dp = readdir64 (dirp);
+      TEST_COMPARE (strcmp (dp->d_name, ddirp[i]->d_name), 0);
+      TEST_COMPARE (dp->d_ino, ddirp[i]->d_ino);
+      TEST_COMPARE (dp->d_off, ddirp[i]->d_off);
+    }
+
+  closedir (dirp);
+  free (tdirp);
+  for (i = 0; i < dirp_count; i++)
+    free (ddirp[i]);
+  free (ddirp);
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  do_test_not_lfs ();
+  do_test_lfs ();
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/closedir.c b/sysdeps/unix/sysv/linux/closedir.c
index d876d49d78..8e5669963c 100644
--- a/sysdeps/unix/sysv/linux/closedir.c
+++ b/sysdeps/unix/sysv/linux/closedir.c
@@ -43,6 +43,10 @@ __closedir (DIR *dirp)
 
   fd = dirp->fd;
 
+#ifndef __LP64__
+  dirstream_loc_clear (&dirp->locs);
+#endif
+
 #if IS_IN (libc)
   __libc_lock_fini (dirp->lock);
 #endif
diff --git a/sysdeps/unix/sysv/linux/dirstream.h b/sysdeps/unix/sysv/linux/dirstream.h
index 064273cc31..a284292cb2 100644
--- a/sysdeps/unix/sysv/linux/dirstream.h
+++ b/sysdeps/unix/sysv/linux/dirstream.h
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 
 #include <libc-lock.h>
+#include <telldir.h>
 
 /* Directory stream type.
 
@@ -37,7 +38,7 @@ struct __dirstream
     size_t size;		/* Total valid data in the block.  */
     size_t offset;		/* Current offset into the block.  */
 
-    off_t filepos;		/* Position of next entry to read.  */
+    off64_t filepos;		/* Position of next entry to read.  */
 
     int errcode;		/* Delayed error code.  */
 
@@ -45,6 +46,9 @@ struct __dirstream
     char *tbuffer;		/* Translation buffer for non-LFS calls.  */
     size_t tbuffer_size;	/* Size of translation buffer.  */
 #endif
+#ifndef __LP64__
+    struct dirstream_loc_t locs; /* off64_t to long int map for telldir.  */
+#endif
 
     /* Directory block.  We must make sure that this block starts
        at an address that is aligned adequately enough to store
diff --git a/sysdeps/unix/sysv/linux/opendir.c b/sysdeps/unix/sysv/linux/opendir.c
index bfd2f382a6..9a0b7ab4c4 100644
--- a/sysdeps/unix/sysv/linux/opendir.c
+++ b/sysdeps/unix/sysv/linux/opendir.c
@@ -150,6 +150,9 @@ __alloc_dir (int fd, bool close_fd, int flags,
   dirp->offset = 0;
   dirp->filepos = 0;
   dirp->errcode = 0;
+#ifndef __LP64__
+  dirstream_loc_init (&dirp->locs);
+#endif
 
   return dirp;
 }
diff --git a/sysdeps/unix/sysv/linux/readdir.c b/sysdeps/unix/sysv/linux/readdir.c
index c078146d7d..f377e5f268 100644
--- a/sysdeps/unix/sysv/linux/readdir.c
+++ b/sysdeps/unix/sysv/linux/readdir.c
@@ -17,6 +17,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <dirent.h>
+#include <unistd.h>
 
 #if !_DIRENT_MATCHES_DIRENT64
 #include <dirstream.h>
diff --git a/sysdeps/unix/sysv/linux/rewinddir.c b/sysdeps/unix/sysv/linux/rewinddir.c
index b1e8259703..0194d29e38 100644
--- a/sysdeps/unix/sysv/linux/rewinddir.c
+++ b/sysdeps/unix/sysv/linux/rewinddir.c
@@ -33,6 +33,11 @@ __rewinddir (DIR *dirp)
   dirp->offset = 0;
   dirp->size = 0;
   dirp->errcode = 0;
+
+#ifndef __LP64__
+  dirstream_loc_clear (&dirp->locs);
+#endif
+
 #if IS_IN (libc)
   __libc_lock_unlock (dirp->lock);
 #endif
diff --git a/sysdeps/unix/sysv/linux/seekdir.c b/sysdeps/unix/sysv/linux/seekdir.c
index f4e1a9f8e0..0c3e58a2ed 100644
--- a/sysdeps/unix/sysv/linux/seekdir.c
+++ b/sysdeps/unix/sysv/linux/seekdir.c
@@ -22,14 +22,40 @@
 #include <dirstream.h>
 
 /* Seek to position POS in DIRP.  */
-/* XXX should be __seekdir ? */
 void
 seekdir (DIR *dirp, long int pos)
 {
+  off64_t filepos;
+
   __libc_lock_lock (dirp->lock);
-  (void) __lseek (dirp->fd, pos, SEEK_SET);
-  dirp->size = 0;
-  dirp->offset = 0;
-  dirp->filepos = pos;
+
+#ifndef __LP64__
+  union dirstream_packed dsp;
+
+  dsp.l = pos;
+
+  if (dsp.p.is_packed == 1)
+    filepos = dsp.p.info;
+  else
+    {
+      size_t index = dsp.p.info;
+
+      if (index >= dirstream_loc_size (&dirp->locs))
+	return;
+      struct dirstream_loc *loc = dirstream_loc_at (&dirp->locs, index);
+      filepos = loc->filepos;
+    }
+#else
+  filepos = pos;
+#endif
+
+  if (dirp->filepos != filepos)
+    {
+      __lseek64 (dirp->fd, filepos, SEEK_SET);
+      dirp->filepos = filepos;
+      dirp->offset = 0;
+      dirp->size = 0;
+    }
+
   __libc_lock_unlock (dirp->lock);
 }
diff --git a/sysdeps/unix/sysv/linux/telldir.c b/sysdeps/unix/sysv/linux/telldir.c
index b60b231e48..874905489f 100644
--- a/sysdeps/unix/sysv/linux/telldir.c
+++ b/sysdeps/unix/sysv/linux/telldir.c
@@ -18,16 +18,59 @@
 #include <dirent.h>
 
 #include <dirstream.h>
+#include <telldir.h>
 
 /* Return the current position of DIRP.  */
 long int
 telldir (DIR *dirp)
 {
-  long int ret;
+#ifndef __LP64__
+  /* If the directory position fits in the packet structure returns it.
+     Otherwise, check if the position is already been recorded in the
+     dynamic array.  If not, add the new record.  */
+
+  union dirstream_packed dsp;
+  size_t i;
 
   __libc_lock_lock (dirp->lock);
-  ret = dirp->filepos;
+
+  if (dirp->filepos < (1U << 31))
+    {
+      dsp.p.is_packed = 1;
+      dsp.p.info = dirp->filepos;
+      goto out;
+    }
+
+  dsp.l = -1;
+
+  for (i = 0; i < dirstream_loc_size (&dirp->locs); i++)
+    {
+      struct dirstream_loc *loc = dirstream_loc_at (&dirp->locs, i);
+      if (loc->filepos == dirp->filepos)
+	break;
+    }
+  if (i == dirstream_loc_size (&dirp->locs))
+    {
+      dirstream_loc_add (&dirp->locs,
+	(struct dirstream_loc) { dirp->filepos });
+      if (dirstream_loc_has_failed (&dirp->locs))
+	goto out;
+    }
+
+  dsp.p.is_packed = 0;
+  /* This assignment might overflow, however most likely ENOMEM would happen
+     long before.  */
+  dsp.p.info = i;
+
+out:
   __libc_lock_unlock (dirp->lock);
 
+  return dsp.l;
+#else
+  long int ret;
+  __libc_lock_lock (dirp->lock);
+  ret = dirp->filepos;
+  __libc_lock_unlock (dirp->lock);
   return ret;
+#endif
 }
diff --git a/sysdeps/unix/sysv/linux/telldir.h b/sysdeps/unix/sysv/linux/telldir.h
new file mode 100644
index 0000000000..7c45886341
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/telldir.h
@@ -0,0 +1,64 @@
+/* Linux internal telldir definitions.
+   Copyright (C) 2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _TELLDIR_H
+#define _TELLDIR_H 1
+
+#ifndef __LP64__
+
+/* On platforms where long int is smaller than off64_t this is how the
+   returned value is encoded and returned by 'telldir'.  If the directory
+   offset can be enconded in 31 bits it is returned in the 'info' member
+   with 'is_packed' set to 1.
+
+   Otherwise, the 'info' member describes an index in a dynamic array at
+   'DIR' structure.  */
+
+union dirstream_packed
+{
+  long int l;
+  struct
+  {
+    unsigned long is_packed:1;
+    unsigned long info:31;
+  } p;
+};
+
+_Static_assert (sizeof (long int) == sizeof (union dirstream_packed),
+		"sizeof (long int) != sizeof (union dirstream_packed)");
+
+/* telldir will mantain a list of offsets that describe the obtained diretory
+   position if it can fit this information in the returned 'dirstream_packed'
+   struct.  */
+
+struct dirstream_loc
+{
+  off64_t filepos;
+};
+
+# define DYNARRAY_STRUCT  dirstream_loc_t
+# define DYNARRAY_ELEMENT struct dirstream_loc
+# define DYNARRAY_PREFIX  dirstream_loc_
+# include <malloc/dynarray-skeleton.c>
+#else
+
+_Static_assert (sizeof (long int) == sizeof (off64_t),
+		"sizeof (long int) != sizeof (off64_t)");
+#endif /* __LP64__  */
+
+#endif /* _TELLDIR_H  */