!45 新增link/symlink/readlink接口的系统调用及内核实现

Merge pull request !45 from JING/link

fs/vfs/fs_link.c

+/*
+ * Copyright (c) 2021-2021 Huawei Device Co., Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *    of conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "unistd.h"
+#include "errno.h"
+#include "fs/vnode.h"
+
+int do_link(int oldfd, const char *oldpath, int newfd, const char *newpath, int flag)
+{
+  struct Vnode *new_parent_vnode = NULL;
+  struct Vnode *new_vnode = NULL;
+  struct Vnode *old_vnode = NULL;
+  char *fulloldpath = NULL;
+  char *fullnewpath = NULL;
+  char *newname = NULL;
+  int ret;
+
+  if (!oldpath || !newpath)
+    {
+      ret = -EFAULT;
+      goto errout;
+    }
+
+  if (*oldpath == '\0' || *newpath == '\0' || flag & ~AT_SYMLINK_FOLLOW)
+    {
+      ret = -EINVAL;
+      goto errout;
+    }
+
+  ret = vfs_normalize_pathat(newfd, newpath, &fullnewpath);
+  if (ret < 0)
+    {
+      goto errout;
+    }
+
+  if (!(flag & AT_SYMLINK_FOLLOW))
+    {
+      ret = vfs_normalize_pathat(oldfd, oldpath, &fulloldpath);
+      if (ret < 0)
+        {
+          goto errout_with_newpath;
+        }
+    }
+
+  newname = strrchr(fullnewpath, '/') + 1;
+
+  VnodeHold();
+
+  if (flag & AT_SYMLINK_FOLLOW)
+    {
+      ret = follow_symlink(oldfd, oldpath, &old_vnode, &fulloldpath);
+      if (ret < 0)
+        {
+          goto errout_with_vnode;
+        }
+    }
+  else
+    {
+      ret = VnodeLookup(fulloldpath, &old_vnode, 0);
+      if (ret < 0)
+        {
+          goto errout_with_vnode;
+        }
+    }
+
+  if (old_vnode->type != VNODE_TYPE_REG && old_vnode->type != VNODE_TYPE_LNK)
+    {
+      ret = -EPERM;
+      goto errout_with_vnode;
+    }
+
+  ret = VnodeLookup(fullnewpath, &new_parent_vnode, 0);
+  if (ret == OK)
+    {
+      ret = -EEXIST;
+      goto errout_with_vnode;
+    }
+
+  if (old_vnode->originMount != new_parent_vnode->originMount)
+    {
+      ret = -EXDEV;
+      goto errout_with_vnode;
+    }
+
+  if (!old_vnode->vop || !old_vnode->vop->Link)
+    {
+      ret = -ENOSYS;
+      goto errout_with_vnode;
+    }
+  new_parent_vnode->useCount++;
+  ret = old_vnode->vop->Link(old_vnode, new_parent_vnode, &new_vnode, newname);
+  new_parent_vnode->useCount--;
+  if (ret < 0)
+    {
+      goto errout_with_vnode;
+    }
+  PathCacheAlloc(new_parent_vnode, new_vnode, newname, strlen(newname));
+  VnodeDrop();
+
+  free(fulloldpath);
+  free(fullnewpath);
+
+  return OK;
+
+errout_with_vnode:
+  VnodeDrop();
+  free(fulloldpath);
+errout_with_newpath:
+  free(fullnewpath);
+errout:
+  set_errno(-ret);
+  return VFS_ERROR;
+}
+
+int link(const char *oldpath, const char *newpath)
+{
+  return do_link(AT_FDCWD, oldpath, AT_FDCWD, newpath, 0);
+}
+
+int linkat(int olddirfd, const char *oldpath, int newdirfd, const char *newpath, int flags)
+{
+  return do_link(olddirfd, oldpath, newdirfd, newpath, flags);
+}
\ No newline at end of file

fs/vfs/fs_open.c

@@ -158,7 +158,7 @@ static int do_creat(struct Vnode *parentNode, char *fullpath, mode_t mode, struc
   return OK;
 }
 
-int fp_open(char *fullpath, int oflags, mode_t mode)
+int fp_open(int dirfd, const char *path, int oflags, mode_t mode)
 {
   int ret;
   int fd;
@@ -166,9 +166,10 @@ int fp_open(char *fullpath, int oflags, mode_t mode)
   struct file *filep = NULL;
   struct Vnode *vnode = NULL;
   struct Vnode *parentVnode = NULL;
+  char *fullpath = NULL;
 
   VnodeHold();
-  ret = VnodeLookup(fullpath, &vnode, 0);
+  ret = follow_symlink(dirfd, path, &vnode, &fullpath);
   if (ret == OK)
     {
       /* if file exist */
@@ -305,6 +306,10 @@ errout_with_count:
   vnode->useCount--;
   VnodeDrop();
 errout:
+  if (fullpath)
+    {
+      free(fullpath);
+    }
   set_errno(-ret);
   return VFS_ERROR;
 }
@@ -313,25 +318,6 @@ int do_open(int dirfd, const char *path, int oflags, mode_t mode)
 {
   int ret;
   int fd;
-  char *fullpath          = NULL;
-  char *relativepath     = NULL;
-
-  /* Get relative path by dirfd*/
-  ret = get_path_from_fd(dirfd, &relativepath);
-  if (ret < 0)
-    {
-      goto errout;
-    }
-
-  ret = vfs_normalize_path((const char *)relativepath, path, &fullpath);
-  if (relativepath)
-    {
-      free(relativepath);
-    }
-  if (ret < 0)
-    {
-      goto errout;
-    }
 
   if ((oflags & (O_WRONLY | O_CREAT)) != 0)
     {
@@ -339,7 +325,7 @@ int do_open(int dirfd, const char *path, int oflags, mode_t mode)
       mode &= (S_IRWXU | S_IRWXG | S_IRWXO);
     }
 
-  fd = fp_open(fullpath, oflags, mode);
+  fd = fp_open(dirfd, path, oflags, mode);
   if (fd < 0)
     {
       ret = -get_errno();
@@ -349,10 +335,6 @@ int do_open(int dirfd, const char *path, int oflags, mode_t mode)
   return fd;
 
 errout:
-  if (fullpath)
-    {
-      free(fullpath);
-    }
   set_errno(-ret);
   return VFS_ERROR;
 }

fs/vfs/fs_readlink.c

+/*
+ * Copyright (c) 2021-2021 Huawei Device Co., Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *    of conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "unistd.h"
+#include "errno.h"
+#include "fs/vnode.h"
+
+ssize_t do_readlink(int dirfd, const char *path, char *buf, size_t bufsize)
+{
+  struct Vnode *vnode = NULL;
+  char *fullpath = NULL;
+  ssize_t ret;
+
+  if (!path)
+    {
+      ret = -EFAULT;
+      goto errout;
+    }
+
+  if (*path == '\0')
+    {
+      ret = -EINVAL;
+      goto errout;
+    }
+
+  ret = vfs_normalize_pathat(dirfd, path, &fullpath);
+  if (ret < 0)
+    {
+      goto errout;
+    }
+
+  VnodeHold();
+  ret = VnodeLookup(fullpath, &vnode, 0);
+  if (ret < 0)
+    {
+      goto errout_with_vnode;
+    }
+
+  if (vnode->type != VNODE_TYPE_LNK)
+    {
+      ret = -EINVAL;
+      goto errout_with_vnode;
+    }
+
+  if (!vnode->vop || !vnode->vop->Readlink)
+    {
+      ret = -ENOSYS;
+      goto errout_with_vnode;
+    }
+
+  ret = vnode->vop->Readlink(vnode, buf, bufsize);
+  if (ret < 0)
+    {
+      goto errout_with_vnode;
+    }
+
+  VnodeDrop();
+
+  free(fullpath);
+
+  return ret;
+
+errout_with_vnode:
+  VnodeDrop();
+  free(fullpath);
+errout:
+  set_errno(-ret);
+  return VFS_ERROR;
+}
+
+ssize_t readlink(const char *pathname, char *buf, size_t bufsize)
+{
+  return do_readlink(AT_FDCWD, pathname, buf, bufsize);
+}
+
+ssize_t readlinkat(int dirfd, const char *pathname, char *buf, size_t bufsize)
+{
+  return do_readlink(dirfd, pathname, buf, bufsize);
+}

fs/vfs/fs_symlink.c

+/*
+ * Copyright (c) 2021-2021 Huawei Device Co., Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *    of conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "unistd.h"
+#include "errno.h"
+#include "fs/vnode.h"
+
+int follow_symlink(int dirfd, const char *path, struct Vnode **vnode, char **fullpath)
+{
+  int ret;
+  struct Vnode *newvnode = NULL;
+  char pathname[PATH_MAX] = {0};
+
+  (void)strcpy_s(pathname, PATH_MAX, path);
+
+  for (int i = 0; i < CONFIG_FS_MAX_LNK_CNT; i++)
+    {
+      if (*fullpath)
+        {
+          free(*fullpath);
+          *fullpath = NULL;
+        }
+
+      ret = vfs_normalize_pathat(dirfd, pathname, fullpath);
+      if (ret < 0)
+        {
+          return ret;
+        }
+
+      ret = VnodeLookup(*fullpath, &newvnode, 0);
+      if (ret != OK)
+        {
+          /* The object of fullpath is not exist. Return its parent's vnode. */
+          *vnode = newvnode;
+          return ret;
+        }
+      if (newvnode->type != VNODE_TYPE_LNK)
+        {
+          /* The object of fullpath is exist, and is not a symbol link. Return its vnode. */
+          *vnode = newvnode;
+          return ret;
+        }
+      if (newvnode->vop->Readlink == NULL)
+        {
+          ret = -ENOSYS;
+          return ret;
+        }
+
+      /* The object of fullpath is a symbol link. Read its target and find the source file successively. */
+      (void)memset_s(pathname, PATH_MAX, 0, PATH_MAX);
+      ret = newvnode->vop->Readlink(newvnode, pathname, PATH_MAX);
+      if (ret < 0)
+        {
+          return ret;
+        }
+    }
+
+  /* Failed to find the source file in CONFIG_FS_MAX_LNK_CNT times. */
+  return -ELOOP;
+}
+
+int do_symlink(const char *target, int newfd, const char *path)
+{
+  struct Vnode *parent_vnode = NULL;
+  struct Vnode *new_vnode = NULL;
+  char *fullpath = NULL;
+  char *newname = NULL;
+  int ret;
+
+  if (!path)
+    {
+      ret = -EFAULT;
+      goto errout;
+    }
+
+  if (*path == '\0')
+    {
+      ret = -EINVAL;
+      goto errout;
+    }
+
+  if (strlen(target) >= PATH_MAX)
+    {
+      ret = -ENAMETOOLONG;
+      goto errout;
+    }
+
+  ret = vfs_normalize_pathat(newfd, path, &fullpath);
+  if (ret < 0)
+    {
+      goto errout;
+    }
+
+  newname = strrchr(fullpath, '/') + 1;
+
+  VnodeHold();
+  ret = VnodeLookup(fullpath, &parent_vnode, 0);
+  if (ret == 0)
+    {
+      ret = -EEXIST;
+      goto errout_with_vnode;
+    }
+
+  if (!parent_vnode->vop || !parent_vnode->vop->Symlink)
+    {
+      ret = -ENOSYS;
+      goto errout_with_vnode;
+    }
+
+  parent_vnode->useCount++;
+  ret = parent_vnode->vop->Symlink(parent_vnode, &new_vnode, (const char *)newname, (const char *)target);
+  parent_vnode->useCount--;
+  if (ret < 0)
+    {
+      goto errout_with_vnode;
+    }
+
+  PathCacheAlloc(parent_vnode, new_vnode, newname, strlen(newname));
+  VnodeDrop();
+
+  free(fullpath);
+
+  return OK;
+
+errout_with_vnode:
+  VnodeDrop();
+  free(fullpath);
+errout:
+  set_errno(-ret);
+  return VFS_ERROR;
+}
+
+int symlink(const char *target, const char *path)
+{
+  return do_symlink(target, AT_FDCWD, path);
+}
+
+int symlinkat(const char *target, int newdirfd, const char *path)
+{
+  return do_symlink(target, newdirfd, path);
+}

include/nuttx/fs/fs.h

@@ -1110,6 +1110,7 @@ void weak_function files_initialize(void);
 
 int vfs_normalize_path(const char *directory, const char *filename, char **pathname);
 int vfs_normalize_pathat(int fd, const char *filename, char **pathname);
+int follow_symlink(int dirfd, const char *path, struct Vnode **vnode, char **fullpath);
 
 #ifdef __cplusplus
 #if __cplusplus