fs: Add the relative path support

all functions which accept the path argument should support the relative path:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

fs/dirent/fs_opendir.c

@@ -231,14 +231,6 @@ FAR DIR *opendir(FAR const char *path)
       goto errout;
     }
 
-  /* We don't know what to do with relative paths */
-
-  if (*path != '/')
-    {
-      ret = ENOTDIR;
-      goto errout_with_semaphore;
-    }
-
   /* Find the node matching the path. */
 
   ret = inode_search(&desc);

fs/inode/fs_inoderemove.c

@@ -74,9 +74,9 @@ FAR struct inode *inode_unlink(FAR const char *path)
   FAR struct inode *node = NULL;
   int ret;
 
-  /* Verify parameters.  Ignore null paths and relative paths */
+  /* Verify parameters.  Ignore null paths */
 
-  if (path == NULL || path[0] != '/')
+  if (path == NULL)
     {
       return NULL;
     }

fs/inode/fs_inodereserve.c

@@ -182,9 +182,7 @@ int inode_reserve(FAR const char *path, FAR struct inode **inode)
   DEBUGASSERT(path != NULL && inode != NULL);
   *inode = NULL;
 
-  /* Handle paths that are interpreted as the root directory */
+  if (path[0] == '\0')
-
-  if (path[0] == '\0' || path[0] != '/')
     {
       return -EINVAL;
     }

fs/inode/fs_inodesearch.c

@@ -42,6 +42,7 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <stdlib.h>
 #include <limits.h>
 #include <assert.h>
 #include <errno.h>
@@ -60,6 +61,7 @@ static int _inode_linktarget(FAR struct inode *node,
                              FAR struct inode_search_s *desc);
 #endif
 static int _inode_search(FAR struct inode_search_s *desc);
+static FAR const char *_inode_getcwd(void);
 
 /****************************************************************************
  * Public Data
@@ -405,8 +407,7 @@ static int _inode_search(FAR struct inode_search_s *desc)
         }
     }
 
-  /* The node may or may not be null as per one of the following four cases
+  /* The node may or may not be null as per one of the following four cases:
-   * cases:
    *
    * With node = NULL
    *
@@ -430,6 +431,29 @@ static int _inode_search(FAR struct inode_search_s *desc)
   return ret;
 }
 
+/****************************************************************************
+ * Name: _inode_getcwd
+ *
+ * Description:
+ *   Return the current working directory
+ *
+ ****************************************************************************/
+
+static FAR const char *_inode_getcwd(void)
+{
+  FAR const char *pwd = "";
+
+#ifndef CONFIG_DISABLE_ENVIRON
+  pwd = getenv("PWD");
+  if (pwd == NULL)
+    {
+      pwd = CONFIG_LIB_HOMEDIR;
+    }
+#endif
+
+  return pwd;
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -467,7 +491,20 @@ int inode_search(FAR struct inode_search_s *desc)
    * node if node is a symbolic link.
    */
 
-  DEBUGASSERT(desc != NULL);
+  DEBUGASSERT(desc != NULL && desc->path != NULL);
+
+  /* Convert the relative path to the absolute path */
+
+  if (*desc->path != '/')
+    {
+      asprintf(&desc->buffer, "%s/%s", _inode_getcwd(), desc->path);
+      if (desc->buffer == NULL)
+        {
+          return -ENOMEM;
+        }
+
+      desc->path = desc->buffer;
+    }
 
   ret = _inode_search(desc);
 

fs/inode/inode.h

@@ -40,8 +40,6 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#ifdef CONFIG_PSEUDOFS_SOFTLINKS
-
 #define SETUP_SEARCH(d,p,n) \
   do \
     { \
@@ -56,29 +54,16 @@
   while (0)
 
 #define RELEASE_SEARCH(d) \
+  do \
+    { \
       if ((d)->buffer != NULL) \
         { \
           kmm_free((d)->buffer); \
           (d)->buffer  = NULL; \
-       }
+        } \
-
-#else
-
-#  define SETUP_SEARCH(d,p,n) \
-    do \
-      { \
-        (d)->path     = (p); \
-        (d)->node     = NULL; \
-        (d)->peer     = NULL; \
-        (d)->parent   = NULL; \
-        (d)->relpath  = NULL; \
     } \
   while (0)
 
-#  define RELEASE_SEARCH(d)
-
-#endif
-
 /****************************************************************************
  * Public Types
  ****************************************************************************/
@@ -119,10 +104,8 @@ struct inode_search_s
   FAR struct inode *peer;    /* Node to the "left" for the found inode */
   FAR struct inode *parent;  /* Node "above" the found inode */
   FAR const char *relpath;   /* Relative path into the mountpoint */
-#ifdef CONFIG_PSEUDOFS_SOFTLINKS
   FAR char *buffer;          /* Path expansion buffer */
   bool nofollow;             /* true: Don't follow terminal soft link */
-#endif
 };
 
 /* Callback used by foreach_inode to traverse all inodes in the pseudo-

fs/mount/fs_automount.c

@@ -114,9 +114,9 @@ static int automount_findinode(FAR const char *path)
   struct inode_search_s desc;
   int ret;
 
-  /* Make sure that we were given an absolute path */
+  /* Make sure that we were given a path */
 
-  DEBUGASSERT(path != NULL && path[0] == '/');
+  DEBUGASSERT(path != NULL);
 
   /* Get exclusive access to the in-memory inode tree. */
 

fs/vfs/fs_rename.c

@@ -457,8 +457,8 @@ int rename(FAR const char *oldpath, FAR const char *newpath)
    * name and cannot be moved
    */
 
-  if (!oldpath || *oldpath == '\0' || oldpath[0] != '/' ||
+  if (!oldpath || *oldpath == '\0' ||
-      !newpath || *newpath == '\0' || newpath[0] != '/')
+      !newpath || *newpath == '\0')
     {
       ret = -EINVAL;
       goto errout;

fs/vfs/fs_symlink.c

@@ -79,11 +79,7 @@ int symlink(FAR const char *path1, FAR const char *path2)
   int errcode;
   int ret;
 
-  /* Both paths must be absolute.  We need only check path1 here. path2 will
+  if (path1 == NULL)
-   * be checked by inode find.
-   */
-
-  if (path1 == NULL || *path1 != '/')
     {
       errcode = EINVAL;
       goto errout;