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From 057920ea715c979638045d2966d6a7c616f3cbc2 Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Tue, 20 Oct 2020 13:37:15 -0300
Subject: [PATCH 08/14] linux: Use getdents64 on non-LFS readdir
The opendir allocates a translation buffer to be used to return the
non-LFS readdir entry. The obtained dirent64 struct is translated
to the temporary buffer on each readdir call.
Entries that overflow d_off/d_ino and the buffer reallocation failure
(in case of large d_name) are ignored.
Checked on x86_64-linux-gnu and i686-linux-gnu.
---
sysdeps/unix/sysv/linux/closedir.c | 4 ++
sysdeps/unix/sysv/linux/dirstream.h | 5 ++
sysdeps/unix/sysv/linux/opendir.c | 21 +++++++
sysdeps/unix/sysv/linux/readdir.c | 97 +++++++++++++++++++++--------
4 files changed, 101 insertions(+), 26 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/closedir.c b/sysdeps/unix/sysv/linux/closedir.c
index eee0193fc4..d876d49d78 100644
--- a/sysdeps/unix/sysv/linux/closedir.c
+++ b/sysdeps/unix/sysv/linux/closedir.c
@@ -47,6 +47,10 @@ __closedir (DIR *dirp)
__libc_lock_fini (dirp->lock);
#endif
+#if !_DIRENT_MATCHES_DIRENT64
+ free (dirp->tbuffer);
+#endif
+
free ((void *) dirp);
return __close_nocancel (fd);
diff --git a/sysdeps/unix/sysv/linux/dirstream.h b/sysdeps/unix/sysv/linux/dirstream.h
index a0d8acf08d..064273cc31 100644
--- a/sysdeps/unix/sysv/linux/dirstream.h
+++ b/sysdeps/unix/sysv/linux/dirstream.h
@@ -41,6 +41,11 @@ struct __dirstream
int errcode; /* Delayed error code. */
+#if !defined __OFF_T_MATCHES_OFF64_T || !defined __INO_T_MATCHES_INO64_T
+ char *tbuffer; /* Translation buffer for non-LFS calls. */
+ size_t tbuffer_size; /* Size of translation buffer. */
+#endif
+
/* Directory block. We must make sure that this block starts
at an address that is aligned adequately enough to store
dirent entries. Using the alignment of "void *" is not
diff --git a/sysdeps/unix/sysv/linux/opendir.c b/sysdeps/unix/sysv/linux/opendir.c
index 9e81d00630..bfd2f382a6 100644
--- a/sysdeps/unix/sysv/linux/opendir.c
+++ b/sysdeps/unix/sysv/linux/opendir.c
@@ -120,6 +120,27 @@ __alloc_dir (int fd, bool close_fd, int flags,
return NULL;
}
+#if !_DIRENT_MATCHES_DIRENT64
+ /* Allocates a translation buffer to use as the returned 'struct direct'
+ for non-LFS 'readdir' calls.
+
+ The initial NAME_MAX size should handle most cases, while readdir might
+ expand the buffer if required. */
+ enum
+ {
+ tbuffer_size = sizeof (struct dirent) + NAME_MAX + 1
+ };
+ dirp->tbuffer = malloc (tbuffer_size);
+ if (dirp->tbuffer == NULL)
+ {
+ free (dirp);
+ if (close_fd)
+ __close_nocancel_nostatus (fd);
+ return NULL;
+ }
+ dirp->tbuffer_size = tbuffer_size;
+#endif
+
dirp->fd = fd;
#if IS_IN (libc)
__libc_lock_init (dirp->lock);
diff --git a/sysdeps/unix/sysv/linux/readdir.c b/sysdeps/unix/sysv/linux/readdir.c
index 7743f50071..7b4571839e 100644
--- a/sysdeps/unix/sysv/linux/readdir.c
+++ b/sysdeps/unix/sysv/linux/readdir.c
@@ -21,42 +21,87 @@
#if !_DIRENT_MATCHES_DIRENT64
#include <dirstream.h>
+/* Translate the DP64 entry to the non-LFS one in the translation buffer
+ at dirstream DS. Return true is the translation was possible or
+ false if either an internal fields can be represented in the non-LFS
+ entry or if the translation can not be resized. */
+static bool
+dirstream_entry (struct __dirstream *ds, const struct dirent64 *dp64)
+{
+ off_t d_off = dp64->d_off;
+ if (d_off != dp64->d_off)
+ return false;
+ ino_t d_ino = dp64->d_ino;
+ if (d_ino != dp64->d_ino)
+ return false;
+
+ /* Expand the translation buffer to hold the new name size. */
+ size_t new_reclen = sizeof (struct dirent)
+ + dp64->d_reclen - offsetof (struct dirent64, d_name);
+ if (new_reclen > ds->tbuffer_size)
+ {
+ char *newbuffer = realloc (ds->tbuffer, new_reclen);
+ if (newbuffer == NULL)
+ return false;
+ ds->tbuffer = newbuffer;
+ ds->tbuffer_size = new_reclen;
+ }
+
+ struct dirent *dp = (struct dirent *) ds->tbuffer;
+
+ dp->d_off = d_off;
+ dp->d_ino = d_ino;
+ dp->d_reclen = new_reclen;
+ dp->d_type = dp64->d_type;
+ memcpy (dp->d_name, dp64->d_name,
+ dp64->d_reclen - offsetof (struct dirent64, d_name));
+
+ return true;
+}
+
/* Read a directory entry from DIRP. */
struct dirent *
__readdir_unlocked (DIR *dirp)
{
const int saved_errno = errno;
- if (dirp->offset >= dirp->size)
+ while (1)
{
- /* We've emptied out our buffer. Refill it. */
- ssize_t bytes = __getdents (dirp->fd, dirp->data, dirp->allocation);
- if (bytes <= 0)
+ if (dirp->offset >= dirp->size)
{
- /* On some systems getdents fails with ENOENT when the
- open directory has been rmdir'd already. POSIX.1
- requires that we treat this condition like normal EOF. */
- if (bytes < 0 && errno == ENOENT)
- bytes = 0;
-
- /* Don't modifiy errno when reaching EOF. */
- if (bytes == 0)
- __set_errno (saved_errno);
- return NULL;
+ /* We've emptied out our buffer. Refill it. */
+ ssize_t bytes = __getdents64 (dirp->fd, dirp->data,
+ dirp->allocation);
+ if (bytes <= 0)
+ {
+ /* On some systems getdents fails with ENOENT when the
+ open directory has been rmdir'd already. POSIX.1
+ requires that we treat this condition like normal EOF. */
+ if (bytes < 0 && errno == ENOENT)
+ bytes = 0;
+
+ /* Don't modifiy errno when reaching EOF. */
+ if (bytes == 0)
+ __set_errno (saved_errno);
+ return NULL;
+ }
+ dirp->size = bytes;
+
+ /* Reset the offset into the buffer. */
+ dirp->offset = 0;
+ }
+
+ struct dirent64 *dp64 = (struct dirent64 *) &dirp->data[dirp->offset];
+ dirp->offset += dp64->d_reclen;
+
+ /* Skip entries which might overflow d_off/d_ino or if the translation
+ buffer can't be resized. */
+ if (dirstream_entry (dirp, dp64))
+ {
+ dirp->filepos = dp64->d_off;
+ return (struct dirent *) dirp->tbuffer;
}
- dirp->size = bytes;
-
- /* Reset the offset into the buffer. */
- dirp->offset = 0;
}
-
- struct dirent *dp = (struct dirent *) &dirp->data[dirp->offset];
-
- dirp->offset += dp->d_reclen;
-
- dirp->filepos = dp->d_off;
-
- return dp;
}
struct dirent *
--
2.34.1
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