998 lines
25 KiB
Diff
998 lines
25 KiB
Diff
From: Al Viro <viro@zeniv.linux.org.uk>
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Date: Mon, 5 Mar 2018 19:15:50 -0500
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Subject: [PATCH 09/17] split d_path() and friends into a separate file
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.8-rt3.tar.xz
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Upstream commit 7a5cf791a747640adb2a1b5e3838321b26953a23
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Those parts of fs/dcache.c are pretty much self-contained.
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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fs/Makefile | 2
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fs/d_path.c | 470 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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fs/dcache.c | 467 -----------------------------------------------------------
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3 files changed, 472 insertions(+), 467 deletions(-)
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create mode 100644 fs/d_path.c
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--- a/fs/Makefile
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+++ b/fs/Makefile
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@@ -11,7 +11,7 @@ obj-y := open.o read_write.o file_table.
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ioctl.o readdir.o select.o dcache.o inode.o \
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attr.o bad_inode.o file.o filesystems.o namespace.o \
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seq_file.o xattr.o libfs.o fs-writeback.o \
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- pnode.o splice.o sync.o utimes.o \
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+ pnode.o splice.o sync.o utimes.o d_path.o \
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stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
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ifeq ($(CONFIG_BLOCK),y)
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--- /dev/null
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+++ b/fs/d_path.c
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@@ -0,0 +1,470 @@
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+/* SPDX-License-Identifier: GPL-2.0 */
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+#include <linux/syscalls.h>
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+#include <linux/export.h>
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+#include <linux/uaccess.h>
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+#include <linux/fs_struct.h>
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+#include <linux/fs.h>
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+#include <linux/slab.h>
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+#include <linux/prefetch.h>
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+#include "mount.h"
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+
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+static int prepend(char **buffer, int *buflen, const char *str, int namelen)
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+{
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+ *buflen -= namelen;
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+ if (*buflen < 0)
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+ return -ENAMETOOLONG;
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+ *buffer -= namelen;
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+ memcpy(*buffer, str, namelen);
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+ return 0;
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+}
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+
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+/**
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+ * prepend_name - prepend a pathname in front of current buffer pointer
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+ * @buffer: buffer pointer
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+ * @buflen: allocated length of the buffer
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+ * @name: name string and length qstr structure
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+ *
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+ * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to
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+ * make sure that either the old or the new name pointer and length are
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+ * fetched. However, there may be mismatch between length and pointer.
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+ * The length cannot be trusted, we need to copy it byte-by-byte until
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+ * the length is reached or a null byte is found. It also prepends "/" at
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+ * the beginning of the name. The sequence number check at the caller will
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+ * retry it again when a d_move() does happen. So any garbage in the buffer
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+ * due to mismatched pointer and length will be discarded.
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+ *
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+ * Load acquire is needed to make sure that we see that terminating NUL.
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+ */
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+static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
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+{
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+ const char *dname = smp_load_acquire(&name->name); /* ^^^ */
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+ u32 dlen = READ_ONCE(name->len);
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+ char *p;
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+
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+ *buflen -= dlen + 1;
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+ if (*buflen < 0)
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+ return -ENAMETOOLONG;
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+ p = *buffer -= dlen + 1;
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+ *p++ = '/';
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+ while (dlen--) {
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+ char c = *dname++;
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+ if (!c)
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+ break;
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+ *p++ = c;
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+ }
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+ return 0;
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+}
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+
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+/**
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+ * prepend_path - Prepend path string to a buffer
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+ * @path: the dentry/vfsmount to report
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+ * @root: root vfsmnt/dentry
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+ * @buffer: pointer to the end of the buffer
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+ * @buflen: pointer to buffer length
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+ *
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+ * The function will first try to write out the pathname without taking any
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+ * lock other than the RCU read lock to make sure that dentries won't go away.
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+ * It only checks the sequence number of the global rename_lock as any change
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+ * in the dentry's d_seq will be preceded by changes in the rename_lock
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+ * sequence number. If the sequence number had been changed, it will restart
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+ * the whole pathname back-tracing sequence again by taking the rename_lock.
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+ * In this case, there is no need to take the RCU read lock as the recursive
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+ * parent pointer references will keep the dentry chain alive as long as no
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+ * rename operation is performed.
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+ */
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+static int prepend_path(const struct path *path,
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+ const struct path *root,
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+ char **buffer, int *buflen)
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+{
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+ struct dentry *dentry;
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+ struct vfsmount *vfsmnt;
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+ struct mount *mnt;
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+ int error = 0;
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+ unsigned seq, m_seq = 0;
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+ char *bptr;
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+ int blen;
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+
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+ rcu_read_lock();
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+restart_mnt:
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+ read_seqbegin_or_lock(&mount_lock, &m_seq);
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+ seq = 0;
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+ rcu_read_lock();
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+restart:
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+ bptr = *buffer;
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+ blen = *buflen;
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+ error = 0;
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+ dentry = path->dentry;
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+ vfsmnt = path->mnt;
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+ mnt = real_mount(vfsmnt);
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+ read_seqbegin_or_lock(&rename_lock, &seq);
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+ while (dentry != root->dentry || vfsmnt != root->mnt) {
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+ struct dentry * parent;
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+
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+ if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
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+ struct mount *parent = READ_ONCE(mnt->mnt_parent);
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+ /* Escaped? */
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+ if (dentry != vfsmnt->mnt_root) {
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+ bptr = *buffer;
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+ blen = *buflen;
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+ error = 3;
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+ break;
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+ }
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+ /* Global root? */
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+ if (mnt != parent) {
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+ dentry = READ_ONCE(mnt->mnt_mountpoint);
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+ mnt = parent;
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+ vfsmnt = &mnt->mnt;
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+ continue;
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+ }
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+ if (!error)
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+ error = is_mounted(vfsmnt) ? 1 : 2;
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+ break;
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+ }
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+ parent = dentry->d_parent;
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+ prefetch(parent);
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+ error = prepend_name(&bptr, &blen, &dentry->d_name);
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+ if (error)
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+ break;
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+
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+ dentry = parent;
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+ }
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+ if (!(seq & 1))
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+ rcu_read_unlock();
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+ if (need_seqretry(&rename_lock, seq)) {
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+ seq = 1;
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+ goto restart;
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+ }
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+ done_seqretry(&rename_lock, seq);
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+
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+ if (!(m_seq & 1))
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+ rcu_read_unlock();
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+ if (need_seqretry(&mount_lock, m_seq)) {
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+ m_seq = 1;
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+ goto restart_mnt;
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+ }
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+ done_seqretry(&mount_lock, m_seq);
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+
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+ if (error >= 0 && bptr == *buffer) {
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+ if (--blen < 0)
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+ error = -ENAMETOOLONG;
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+ else
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+ *--bptr = '/';
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+ }
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+ *buffer = bptr;
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+ *buflen = blen;
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+ return error;
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+}
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+
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+/**
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+ * __d_path - return the path of a dentry
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+ * @path: the dentry/vfsmount to report
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+ * @root: root vfsmnt/dentry
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+ * @buf: buffer to return value in
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+ * @buflen: buffer length
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+ *
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+ * Convert a dentry into an ASCII path name.
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+ *
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+ * Returns a pointer into the buffer or an error code if the
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+ * path was too long.
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+ *
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+ * "buflen" should be positive.
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+ *
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+ * If the path is not reachable from the supplied root, return %NULL.
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+ */
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+char *__d_path(const struct path *path,
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+ const struct path *root,
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+ char *buf, int buflen)
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+{
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+ char *res = buf + buflen;
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+ int error;
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+
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+ prepend(&res, &buflen, "\0", 1);
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+ error = prepend_path(path, root, &res, &buflen);
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+
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+ if (error < 0)
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+ return ERR_PTR(error);
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+ if (error > 0)
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+ return NULL;
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+ return res;
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+}
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+
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+char *d_absolute_path(const struct path *path,
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+ char *buf, int buflen)
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+{
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+ struct path root = {};
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+ char *res = buf + buflen;
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+ int error;
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+
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+ prepend(&res, &buflen, "\0", 1);
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+ error = prepend_path(path, &root, &res, &buflen);
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+
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+ if (error > 1)
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+ error = -EINVAL;
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+ if (error < 0)
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+ return ERR_PTR(error);
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+ return res;
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+}
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+
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+/*
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+ * same as __d_path but appends "(deleted)" for unlinked files.
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+ */
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+static int path_with_deleted(const struct path *path,
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+ const struct path *root,
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+ char **buf, int *buflen)
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+{
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+ prepend(buf, buflen, "\0", 1);
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+ if (d_unlinked(path->dentry)) {
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+ int error = prepend(buf, buflen, " (deleted)", 10);
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+ if (error)
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+ return error;
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+ }
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+
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+ return prepend_path(path, root, buf, buflen);
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+}
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+
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+static int prepend_unreachable(char **buffer, int *buflen)
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+{
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+ return prepend(buffer, buflen, "(unreachable)", 13);
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+}
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+
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+static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
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+{
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+ unsigned seq;
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+
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+ do {
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+ seq = read_seqcount_begin(&fs->seq);
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+ *root = fs->root;
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+ } while (read_seqcount_retry(&fs->seq, seq));
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+}
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+
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+/**
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+ * d_path - return the path of a dentry
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+ * @path: path to report
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+ * @buf: buffer to return value in
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+ * @buflen: buffer length
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+ *
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+ * Convert a dentry into an ASCII path name. If the entry has been deleted
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+ * the string " (deleted)" is appended. Note that this is ambiguous.
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+ *
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+ * Returns a pointer into the buffer or an error code if the path was
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+ * too long. Note: Callers should use the returned pointer, not the passed
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+ * in buffer, to use the name! The implementation often starts at an offset
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+ * into the buffer, and may leave 0 bytes at the start.
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+ *
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+ * "buflen" should be positive.
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+ */
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+char *d_path(const struct path *path, char *buf, int buflen)
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+{
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+ char *res = buf + buflen;
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+ struct path root;
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+ int error;
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+
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+ /*
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+ * We have various synthetic filesystems that never get mounted. On
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+ * these filesystems dentries are never used for lookup purposes, and
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+ * thus don't need to be hashed. They also don't need a name until a
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+ * user wants to identify the object in /proc/pid/fd/. The little hack
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+ * below allows us to generate a name for these objects on demand:
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+ *
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+ * Some pseudo inodes are mountable. When they are mounted
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+ * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
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+ * and instead have d_path return the mounted path.
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+ */
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+ if (path->dentry->d_op && path->dentry->d_op->d_dname &&
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+ (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
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+ return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
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+
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+ rcu_read_lock();
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+ get_fs_root_rcu(current->fs, &root);
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+ error = path_with_deleted(path, &root, &res, &buflen);
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+ rcu_read_unlock();
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+
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+ if (error < 0)
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+ res = ERR_PTR(error);
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+ return res;
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+}
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+EXPORT_SYMBOL(d_path);
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+
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+/*
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+ * Helper function for dentry_operations.d_dname() members
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+ */
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+char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
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+ const char *fmt, ...)
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+{
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+ va_list args;
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+ char temp[64];
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+ int sz;
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+
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+ va_start(args, fmt);
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+ sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
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+ va_end(args);
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+
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+ if (sz > sizeof(temp) || sz > buflen)
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+ return ERR_PTR(-ENAMETOOLONG);
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+
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+ buffer += buflen - sz;
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+ return memcpy(buffer, temp, sz);
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+}
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+
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+char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
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+{
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+ char *end = buffer + buflen;
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+ /* these dentries are never renamed, so d_lock is not needed */
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+ if (prepend(&end, &buflen, " (deleted)", 11) ||
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+ prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
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+ prepend(&end, &buflen, "/", 1))
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+ end = ERR_PTR(-ENAMETOOLONG);
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+ return end;
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+}
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+EXPORT_SYMBOL(simple_dname);
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+
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+/*
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+ * Write full pathname from the root of the filesystem into the buffer.
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+ */
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+static char *__dentry_path(struct dentry *d, char *buf, int buflen)
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+{
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+ struct dentry *dentry;
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+ char *end, *retval;
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+ int len, seq = 0;
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+ int error = 0;
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+
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+ if (buflen < 2)
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+ goto Elong;
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+
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+ rcu_read_lock();
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+restart:
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+ dentry = d;
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+ end = buf + buflen;
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+ len = buflen;
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+ prepend(&end, &len, "\0", 1);
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+ /* Get '/' right */
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+ retval = end-1;
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+ *retval = '/';
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+ read_seqbegin_or_lock(&rename_lock, &seq);
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+ while (!IS_ROOT(dentry)) {
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+ struct dentry *parent = dentry->d_parent;
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+
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+ prefetch(parent);
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+ error = prepend_name(&end, &len, &dentry->d_name);
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+ if (error)
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+ break;
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+
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+ retval = end;
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+ dentry = parent;
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+ }
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+ if (!(seq & 1))
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+ rcu_read_unlock();
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+ if (need_seqretry(&rename_lock, seq)) {
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+ seq = 1;
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+ goto restart;
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+ }
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+ done_seqretry(&rename_lock, seq);
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+ if (error)
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+ goto Elong;
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+ return retval;
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+Elong:
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+ return ERR_PTR(-ENAMETOOLONG);
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+}
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+
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+char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
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+{
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+ return __dentry_path(dentry, buf, buflen);
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+}
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+EXPORT_SYMBOL(dentry_path_raw);
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+
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+char *dentry_path(struct dentry *dentry, char *buf, int buflen)
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+{
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+ char *p = NULL;
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+ char *retval;
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+
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+ if (d_unlinked(dentry)) {
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+ p = buf + buflen;
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+ if (prepend(&p, &buflen, "//deleted", 10) != 0)
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+ goto Elong;
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+ buflen++;
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+ }
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+ retval = __dentry_path(dentry, buf, buflen);
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+ if (!IS_ERR(retval) && p)
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+ *p = '/'; /* restore '/' overriden with '\0' */
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+ return retval;
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+Elong:
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+ return ERR_PTR(-ENAMETOOLONG);
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+}
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+
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+static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
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+ struct path *pwd)
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+{
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+ unsigned seq;
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+
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+ do {
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+ seq = read_seqcount_begin(&fs->seq);
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+ *root = fs->root;
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+ *pwd = fs->pwd;
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+ } while (read_seqcount_retry(&fs->seq, seq));
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+}
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+
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+/*
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+ * NOTE! The user-level library version returns a
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+ * character pointer. The kernel system call just
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+ * returns the length of the buffer filled (which
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+ * includes the ending '\0' character), or a negative
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+ * error value. So libc would do something like
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+ *
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+ * char *getcwd(char * buf, size_t size)
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+ * {
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+ * int retval;
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+ *
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+ * retval = sys_getcwd(buf, size);
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+ * if (retval >= 0)
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+ * return buf;
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+ * errno = -retval;
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+ * return NULL;
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+ * }
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+ */
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+SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
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+{
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+ int error;
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+ struct path pwd, root;
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+ char *page = __getname();
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+
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+ if (!page)
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+ return -ENOMEM;
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+
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+ rcu_read_lock();
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+ get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
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+
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+ error = -ENOENT;
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+ if (!d_unlinked(pwd.dentry)) {
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+ unsigned long len;
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+ char *cwd = page + PATH_MAX;
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+ int buflen = PATH_MAX;
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+
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+ prepend(&cwd, &buflen, "\0", 1);
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+ error = prepend_path(&pwd, &root, &cwd, &buflen);
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+ rcu_read_unlock();
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+
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+ if (error < 0)
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+ goto out;
|
|
+
|
|
+ /* Unreachable from current root */
|
|
+ if (error > 0) {
|
|
+ error = prepend_unreachable(&cwd, &buflen);
|
|
+ if (error)
|
|
+ goto out;
|
|
+ }
|
|
+
|
|
+ error = -ERANGE;
|
|
+ len = PATH_MAX + page - cwd;
|
|
+ if (len <= size) {
|
|
+ error = len;
|
|
+ if (copy_to_user(buf, cwd, len))
|
|
+ error = -EFAULT;
|
|
+ }
|
|
+ } else {
|
|
+ rcu_read_unlock();
|
|
+ }
|
|
+
|
|
+out:
|
|
+ __putname(page);
|
|
+ return error;
|
|
+}
|
|
--- a/fs/dcache.c
|
|
+++ b/fs/dcache.c
|
|
@@ -14,7 +14,7 @@
|
|
* the dcache entry is deleted or garbage collected.
|
|
*/
|
|
|
|
-#include <linux/syscalls.h>
|
|
+#include <linux/ratelimit.h>
|
|
#include <linux/string.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/fs.h>
|
|
@@ -24,15 +24,11 @@
|
|
#include <linux/hash.h>
|
|
#include <linux/cache.h>
|
|
#include <linux/export.h>
|
|
-#include <linux/mount.h>
|
|
-#include <linux/uaccess.h>
|
|
#include <linux/security.h>
|
|
#include <linux/seqlock.h>
|
|
#include <linux/bootmem.h>
|
|
-#include <linux/fs_struct.h>
|
|
#include <linux/bit_spinlock.h>
|
|
#include <linux/rculist_bl.h>
|
|
-#include <linux/prefetch.h>
|
|
#include <linux/list_lru.h>
|
|
#include "internal.h"
|
|
#include "mount.h"
|
|
@@ -3072,467 +3068,6 @@ struct dentry *d_splice_alias(struct ino
|
|
}
|
|
EXPORT_SYMBOL(d_splice_alias);
|
|
|
|
-static int prepend(char **buffer, int *buflen, const char *str, int namelen)
|
|
-{
|
|
- *buflen -= namelen;
|
|
- if (*buflen < 0)
|
|
- return -ENAMETOOLONG;
|
|
- *buffer -= namelen;
|
|
- memcpy(*buffer, str, namelen);
|
|
- return 0;
|
|
-}
|
|
-
|
|
-/**
|
|
- * prepend_name - prepend a pathname in front of current buffer pointer
|
|
- * @buffer: buffer pointer
|
|
- * @buflen: allocated length of the buffer
|
|
- * @name: name string and length qstr structure
|
|
- *
|
|
- * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to
|
|
- * make sure that either the old or the new name pointer and length are
|
|
- * fetched. However, there may be mismatch between length and pointer.
|
|
- * The length cannot be trusted, we need to copy it byte-by-byte until
|
|
- * the length is reached or a null byte is found. It also prepends "/" at
|
|
- * the beginning of the name. The sequence number check at the caller will
|
|
- * retry it again when a d_move() does happen. So any garbage in the buffer
|
|
- * due to mismatched pointer and length will be discarded.
|
|
- *
|
|
- * Load acquire is needed to make sure that we see that terminating NUL.
|
|
- */
|
|
-static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
|
|
-{
|
|
- const char *dname = smp_load_acquire(&name->name); /* ^^^ */
|
|
- u32 dlen = READ_ONCE(name->len);
|
|
- char *p;
|
|
-
|
|
- *buflen -= dlen + 1;
|
|
- if (*buflen < 0)
|
|
- return -ENAMETOOLONG;
|
|
- p = *buffer -= dlen + 1;
|
|
- *p++ = '/';
|
|
- while (dlen--) {
|
|
- char c = *dname++;
|
|
- if (!c)
|
|
- break;
|
|
- *p++ = c;
|
|
- }
|
|
- return 0;
|
|
-}
|
|
-
|
|
-/**
|
|
- * prepend_path - Prepend path string to a buffer
|
|
- * @path: the dentry/vfsmount to report
|
|
- * @root: root vfsmnt/dentry
|
|
- * @buffer: pointer to the end of the buffer
|
|
- * @buflen: pointer to buffer length
|
|
- *
|
|
- * The function will first try to write out the pathname without taking any
|
|
- * lock other than the RCU read lock to make sure that dentries won't go away.
|
|
- * It only checks the sequence number of the global rename_lock as any change
|
|
- * in the dentry's d_seq will be preceded by changes in the rename_lock
|
|
- * sequence number. If the sequence number had been changed, it will restart
|
|
- * the whole pathname back-tracing sequence again by taking the rename_lock.
|
|
- * In this case, there is no need to take the RCU read lock as the recursive
|
|
- * parent pointer references will keep the dentry chain alive as long as no
|
|
- * rename operation is performed.
|
|
- */
|
|
-static int prepend_path(const struct path *path,
|
|
- const struct path *root,
|
|
- char **buffer, int *buflen)
|
|
-{
|
|
- struct dentry *dentry;
|
|
- struct vfsmount *vfsmnt;
|
|
- struct mount *mnt;
|
|
- int error = 0;
|
|
- unsigned seq, m_seq = 0;
|
|
- char *bptr;
|
|
- int blen;
|
|
-
|
|
- rcu_read_lock();
|
|
-restart_mnt:
|
|
- read_seqbegin_or_lock(&mount_lock, &m_seq);
|
|
- seq = 0;
|
|
- rcu_read_lock();
|
|
-restart:
|
|
- bptr = *buffer;
|
|
- blen = *buflen;
|
|
- error = 0;
|
|
- dentry = path->dentry;
|
|
- vfsmnt = path->mnt;
|
|
- mnt = real_mount(vfsmnt);
|
|
- read_seqbegin_or_lock(&rename_lock, &seq);
|
|
- while (dentry != root->dentry || vfsmnt != root->mnt) {
|
|
- struct dentry * parent;
|
|
-
|
|
- if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
|
|
- struct mount *parent = READ_ONCE(mnt->mnt_parent);
|
|
- /* Escaped? */
|
|
- if (dentry != vfsmnt->mnt_root) {
|
|
- bptr = *buffer;
|
|
- blen = *buflen;
|
|
- error = 3;
|
|
- break;
|
|
- }
|
|
- /* Global root? */
|
|
- if (mnt != parent) {
|
|
- dentry = READ_ONCE(mnt->mnt_mountpoint);
|
|
- mnt = parent;
|
|
- vfsmnt = &mnt->mnt;
|
|
- continue;
|
|
- }
|
|
- if (!error)
|
|
- error = is_mounted(vfsmnt) ? 1 : 2;
|
|
- break;
|
|
- }
|
|
- parent = dentry->d_parent;
|
|
- prefetch(parent);
|
|
- error = prepend_name(&bptr, &blen, &dentry->d_name);
|
|
- if (error)
|
|
- break;
|
|
-
|
|
- dentry = parent;
|
|
- }
|
|
- if (!(seq & 1))
|
|
- rcu_read_unlock();
|
|
- if (need_seqretry(&rename_lock, seq)) {
|
|
- seq = 1;
|
|
- goto restart;
|
|
- }
|
|
- done_seqretry(&rename_lock, seq);
|
|
-
|
|
- if (!(m_seq & 1))
|
|
- rcu_read_unlock();
|
|
- if (need_seqretry(&mount_lock, m_seq)) {
|
|
- m_seq = 1;
|
|
- goto restart_mnt;
|
|
- }
|
|
- done_seqretry(&mount_lock, m_seq);
|
|
-
|
|
- if (error >= 0 && bptr == *buffer) {
|
|
- if (--blen < 0)
|
|
- error = -ENAMETOOLONG;
|
|
- else
|
|
- *--bptr = '/';
|
|
- }
|
|
- *buffer = bptr;
|
|
- *buflen = blen;
|
|
- return error;
|
|
-}
|
|
-
|
|
-/**
|
|
- * __d_path - return the path of a dentry
|
|
- * @path: the dentry/vfsmount to report
|
|
- * @root: root vfsmnt/dentry
|
|
- * @buf: buffer to return value in
|
|
- * @buflen: buffer length
|
|
- *
|
|
- * Convert a dentry into an ASCII path name.
|
|
- *
|
|
- * Returns a pointer into the buffer or an error code if the
|
|
- * path was too long.
|
|
- *
|
|
- * "buflen" should be positive.
|
|
- *
|
|
- * If the path is not reachable from the supplied root, return %NULL.
|
|
- */
|
|
-char *__d_path(const struct path *path,
|
|
- const struct path *root,
|
|
- char *buf, int buflen)
|
|
-{
|
|
- char *res = buf + buflen;
|
|
- int error;
|
|
-
|
|
- prepend(&res, &buflen, "\0", 1);
|
|
- error = prepend_path(path, root, &res, &buflen);
|
|
-
|
|
- if (error < 0)
|
|
- return ERR_PTR(error);
|
|
- if (error > 0)
|
|
- return NULL;
|
|
- return res;
|
|
-}
|
|
-
|
|
-char *d_absolute_path(const struct path *path,
|
|
- char *buf, int buflen)
|
|
-{
|
|
- struct path root = {};
|
|
- char *res = buf + buflen;
|
|
- int error;
|
|
-
|
|
- prepend(&res, &buflen, "\0", 1);
|
|
- error = prepend_path(path, &root, &res, &buflen);
|
|
-
|
|
- if (error > 1)
|
|
- error = -EINVAL;
|
|
- if (error < 0)
|
|
- return ERR_PTR(error);
|
|
- return res;
|
|
-}
|
|
-
|
|
-/*
|
|
- * same as __d_path but appends "(deleted)" for unlinked files.
|
|
- */
|
|
-static int path_with_deleted(const struct path *path,
|
|
- const struct path *root,
|
|
- char **buf, int *buflen)
|
|
-{
|
|
- prepend(buf, buflen, "\0", 1);
|
|
- if (d_unlinked(path->dentry)) {
|
|
- int error = prepend(buf, buflen, " (deleted)", 10);
|
|
- if (error)
|
|
- return error;
|
|
- }
|
|
-
|
|
- return prepend_path(path, root, buf, buflen);
|
|
-}
|
|
-
|
|
-static int prepend_unreachable(char **buffer, int *buflen)
|
|
-{
|
|
- return prepend(buffer, buflen, "(unreachable)", 13);
|
|
-}
|
|
-
|
|
-static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
|
|
-{
|
|
- unsigned seq;
|
|
-
|
|
- do {
|
|
- seq = read_seqcount_begin(&fs->seq);
|
|
- *root = fs->root;
|
|
- } while (read_seqcount_retry(&fs->seq, seq));
|
|
-}
|
|
-
|
|
-/**
|
|
- * d_path - return the path of a dentry
|
|
- * @path: path to report
|
|
- * @buf: buffer to return value in
|
|
- * @buflen: buffer length
|
|
- *
|
|
- * Convert a dentry into an ASCII path name. If the entry has been deleted
|
|
- * the string " (deleted)" is appended. Note that this is ambiguous.
|
|
- *
|
|
- * Returns a pointer into the buffer or an error code if the path was
|
|
- * too long. Note: Callers should use the returned pointer, not the passed
|
|
- * in buffer, to use the name! The implementation often starts at an offset
|
|
- * into the buffer, and may leave 0 bytes at the start.
|
|
- *
|
|
- * "buflen" should be positive.
|
|
- */
|
|
-char *d_path(const struct path *path, char *buf, int buflen)
|
|
-{
|
|
- char *res = buf + buflen;
|
|
- struct path root;
|
|
- int error;
|
|
-
|
|
- /*
|
|
- * We have various synthetic filesystems that never get mounted. On
|
|
- * these filesystems dentries are never used for lookup purposes, and
|
|
- * thus don't need to be hashed. They also don't need a name until a
|
|
- * user wants to identify the object in /proc/pid/fd/. The little hack
|
|
- * below allows us to generate a name for these objects on demand:
|
|
- *
|
|
- * Some pseudo inodes are mountable. When they are mounted
|
|
- * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
|
|
- * and instead have d_path return the mounted path.
|
|
- */
|
|
- if (path->dentry->d_op && path->dentry->d_op->d_dname &&
|
|
- (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
|
|
- return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
|
|
-
|
|
- rcu_read_lock();
|
|
- get_fs_root_rcu(current->fs, &root);
|
|
- error = path_with_deleted(path, &root, &res, &buflen);
|
|
- rcu_read_unlock();
|
|
-
|
|
- if (error < 0)
|
|
- res = ERR_PTR(error);
|
|
- return res;
|
|
-}
|
|
-EXPORT_SYMBOL(d_path);
|
|
-
|
|
-/*
|
|
- * Helper function for dentry_operations.d_dname() members
|
|
- */
|
|
-char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
|
|
- const char *fmt, ...)
|
|
-{
|
|
- va_list args;
|
|
- char temp[64];
|
|
- int sz;
|
|
-
|
|
- va_start(args, fmt);
|
|
- sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
|
|
- va_end(args);
|
|
-
|
|
- if (sz > sizeof(temp) || sz > buflen)
|
|
- return ERR_PTR(-ENAMETOOLONG);
|
|
-
|
|
- buffer += buflen - sz;
|
|
- return memcpy(buffer, temp, sz);
|
|
-}
|
|
-
|
|
-char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
|
|
-{
|
|
- char *end = buffer + buflen;
|
|
- /* these dentries are never renamed, so d_lock is not needed */
|
|
- if (prepend(&end, &buflen, " (deleted)", 11) ||
|
|
- prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
|
|
- prepend(&end, &buflen, "/", 1))
|
|
- end = ERR_PTR(-ENAMETOOLONG);
|
|
- return end;
|
|
-}
|
|
-EXPORT_SYMBOL(simple_dname);
|
|
-
|
|
-/*
|
|
- * Write full pathname from the root of the filesystem into the buffer.
|
|
- */
|
|
-static char *__dentry_path(struct dentry *d, char *buf, int buflen)
|
|
-{
|
|
- struct dentry *dentry;
|
|
- char *end, *retval;
|
|
- int len, seq = 0;
|
|
- int error = 0;
|
|
-
|
|
- if (buflen < 2)
|
|
- goto Elong;
|
|
-
|
|
- rcu_read_lock();
|
|
-restart:
|
|
- dentry = d;
|
|
- end = buf + buflen;
|
|
- len = buflen;
|
|
- prepend(&end, &len, "\0", 1);
|
|
- /* Get '/' right */
|
|
- retval = end-1;
|
|
- *retval = '/';
|
|
- read_seqbegin_or_lock(&rename_lock, &seq);
|
|
- while (!IS_ROOT(dentry)) {
|
|
- struct dentry *parent = dentry->d_parent;
|
|
-
|
|
- prefetch(parent);
|
|
- error = prepend_name(&end, &len, &dentry->d_name);
|
|
- if (error)
|
|
- break;
|
|
-
|
|
- retval = end;
|
|
- dentry = parent;
|
|
- }
|
|
- if (!(seq & 1))
|
|
- rcu_read_unlock();
|
|
- if (need_seqretry(&rename_lock, seq)) {
|
|
- seq = 1;
|
|
- goto restart;
|
|
- }
|
|
- done_seqretry(&rename_lock, seq);
|
|
- if (error)
|
|
- goto Elong;
|
|
- return retval;
|
|
-Elong:
|
|
- return ERR_PTR(-ENAMETOOLONG);
|
|
-}
|
|
-
|
|
-char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
|
|
-{
|
|
- return __dentry_path(dentry, buf, buflen);
|
|
-}
|
|
-EXPORT_SYMBOL(dentry_path_raw);
|
|
-
|
|
-char *dentry_path(struct dentry *dentry, char *buf, int buflen)
|
|
-{
|
|
- char *p = NULL;
|
|
- char *retval;
|
|
-
|
|
- if (d_unlinked(dentry)) {
|
|
- p = buf + buflen;
|
|
- if (prepend(&p, &buflen, "//deleted", 10) != 0)
|
|
- goto Elong;
|
|
- buflen++;
|
|
- }
|
|
- retval = __dentry_path(dentry, buf, buflen);
|
|
- if (!IS_ERR(retval) && p)
|
|
- *p = '/'; /* restore '/' overriden with '\0' */
|
|
- return retval;
|
|
-Elong:
|
|
- return ERR_PTR(-ENAMETOOLONG);
|
|
-}
|
|
-
|
|
-static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
|
|
- struct path *pwd)
|
|
-{
|
|
- unsigned seq;
|
|
-
|
|
- do {
|
|
- seq = read_seqcount_begin(&fs->seq);
|
|
- *root = fs->root;
|
|
- *pwd = fs->pwd;
|
|
- } while (read_seqcount_retry(&fs->seq, seq));
|
|
-}
|
|
-
|
|
-/*
|
|
- * NOTE! The user-level library version returns a
|
|
- * character pointer. The kernel system call just
|
|
- * returns the length of the buffer filled (which
|
|
- * includes the ending '\0' character), or a negative
|
|
- * error value. So libc would do something like
|
|
- *
|
|
- * char *getcwd(char * buf, size_t size)
|
|
- * {
|
|
- * int retval;
|
|
- *
|
|
- * retval = sys_getcwd(buf, size);
|
|
- * if (retval >= 0)
|
|
- * return buf;
|
|
- * errno = -retval;
|
|
- * return NULL;
|
|
- * }
|
|
- */
|
|
-SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
|
|
-{
|
|
- int error;
|
|
- struct path pwd, root;
|
|
- char *page = __getname();
|
|
-
|
|
- if (!page)
|
|
- return -ENOMEM;
|
|
-
|
|
- rcu_read_lock();
|
|
- get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
|
|
-
|
|
- error = -ENOENT;
|
|
- if (!d_unlinked(pwd.dentry)) {
|
|
- unsigned long len;
|
|
- char *cwd = page + PATH_MAX;
|
|
- int buflen = PATH_MAX;
|
|
-
|
|
- prepend(&cwd, &buflen, "\0", 1);
|
|
- error = prepend_path(&pwd, &root, &cwd, &buflen);
|
|
- rcu_read_unlock();
|
|
-
|
|
- if (error < 0)
|
|
- goto out;
|
|
-
|
|
- /* Unreachable from current root */
|
|
- if (error > 0) {
|
|
- error = prepend_unreachable(&cwd, &buflen);
|
|
- if (error)
|
|
- goto out;
|
|
- }
|
|
-
|
|
- error = -ERANGE;
|
|
- len = PATH_MAX + page - cwd;
|
|
- if (len <= size) {
|
|
- error = len;
|
|
- if (copy_to_user(buf, cwd, len))
|
|
- error = -EFAULT;
|
|
- }
|
|
- } else {
|
|
- rcu_read_unlock();
|
|
- }
|
|
-
|
|
-out:
|
|
- __putname(page);
|
|
- return error;
|
|
-}
|
|
-
|
|
/*
|
|
* Test whether new_dentry is a subdirectory of old_dentry.
|
|
*
|