Soft links: Eliminate in-stack allocation of path working buffer needed for traversal fo paths with soft links.

Documentation/NuttxUserGuide.html

@@ -8584,6 +8584,8 @@ int        telldir(FAR DIR *dirp);
 <ul><pre>
 #include &lt;unistd.h&gt;
 
+/* Task Control Interfaces */
+
 pid_t   vfork(void);
 pid_t   getpid(void);
 void    _exit(int status) noreturn_function;
@@ -8591,6 +8593,8 @@ unsigned int sleep(unsigned int seconds);
 void    usleep(unsigned long usec);
 int     pause(void);
 
+/* File descriptor operations */
+
 int     close(int fd);
 int     dup(int fd);
 int     dup2(int fd1, int fd2);
@@ -8598,21 +8602,58 @@ int     fsync(int fd);
 off_t   lseek(int fd, off_t offset, int whence);
 ssize_t read(int fd, FAR void *buf, size_t nbytes);
 ssize_t write(int fd, FAR const void *buf, size_t nbytes);
+ssize_t pread(int fd, FAR void *buf, size_t nbytes, off_t offset);
+ssize_t pwrite(int fd, FAR const void *buf, size_t nbytes, off_t offset);
+
+/* Check if a file descriptor corresponds to a terminal I/O file */
+
+int     isatty(int fd);
+
+/* Memory management */
+
+#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_MM_PGALLOC) && \
+    defined(CONFIG_ARCH_USE_MMU)
+FAR void *sbrk(intptr_t incr);
+#endif
+
+/* Special devices */
 
 int     pipe(int fd[2]);
 
+/* Working directory operations */
+
 int     chdir(FAR const char *path);
 FAR char *getcwd(FAR char *buf, size_t size);
 
-int     unlink(FAR const char *pathname);
+/* File path operations */
+
+int     access(FAR const char *path, int amode);
 int     rmdir(FAR const char *pathname);
+int     unlink(FAR const char *pathname);
+
+#ifdef CONFIG_PSEUDOFS_SOFTLINKS
+int     link(FAR const char *path1, FAR const char *path2);
+ssize_t readlink(FAR const char *path, FAR char *buf, size_t bufsize);
+#endif
+
+/* Execution of programs from files */
 
 #ifdef CONFIG_LIBC_EXECFUNCS
 int     execl(FAR const char *path, ...);
 int     execv(FAR const char *path, FAR char *const argv[]);
 #endif
 
+/* Networking */
+
+#ifdef CONFIG_NET
+int     gethostname(FAR char *name, size_t size);
+int     sethostname(FAR const char *name, size_t size);
+#endif
+
+/* Other */
+
 int     getopt(int argc, FAR char *const argv[], FAR const char *optstring);
+
 </pre></ul>
 </a>
 

fs/Kconfig

@@ -43,7 +43,7 @@ config DISABLE_PSEUDOFS_OPERATIONS
 config PSEUDOFS_SOFTLINKS
 	bool "Pseudo-filesystem soft links"
 	default n
-	depends on !DISABLE_PSEUDOFS_OPERATIONSi && EXPERIMENTAL
+	depends on !DISABLE_PSEUDOFS_OPERATIONS
 	---help---
 		Enable support for soft links in the pseudeo file system.  Soft
 		links are not supported within mounted volumes by any NuttX file

fs/inode/fs_inodesearch.c

@@ -515,6 +515,8 @@ int inode_search(FAR struct inode_search_s *desc)
 
       if (desc->linktgt != NULL && INODE_IS_MOUNTPT(node))
         {
+          FAR char *buffer;
+
           /* There would be no problem in this case if the link was to
            * either to the root directory of the MOUNTPOINT or to a
            * regular file within the the mounted volume.  However,
@@ -530,21 +532,30 @@ int inode_search(FAR struct inode_search_s *desc)
 
           if (desc->relpath != NULL && *desc->relpath != '\0')
             {
-              snprintf(desc->fullpath, PATH_MAX, "%s/%s",
+              (void)asprintf(&buffer, "%s/%s",
                              desc->linktgt, desc->relpath);
             }
           else
             {
-              strncpy(desc->fullpath, desc->linktgt, PATH_MAX);
+              buffer = strdup(desc->linktgt);
             }
 
+          if (buffer == NULL)
+            {
+              ret = -ENOMEM;
+            }
+          else
+            {
               /* Reset the search description and perform the search again. */
 
               RELEASE_SEARCH(desc);
-          SETUP_SEARCH(desc, desc->fullpath, false);
+              SETUP_SEARCH(desc, buffer, false);
+              desc->buffer = buffer;
+
               ret = _inode_search(desc);
             }
         }
+    }
 #endif
 
   return ret;

fs/inode/inode.h

@@ -48,6 +48,7 @@
 #include <stdbool.h>
 #include <dirent.h>
 
+#include <nuttx/kmalloc.h>
 #include <nuttx/fs/fs.h>
 
 /****************************************************************************
@@ -55,6 +56,7 @@
  ****************************************************************************/
 
 #ifdef CONFIG_PSEUDOFS_SOFTLINKS
+
 #  define SETUP_SEARCH(d,p,n) \
     do \
       { \
@@ -64,10 +66,20 @@
         (d)->parent   = NULL; \
         (d)->relpath  = NULL; \
         (d)->linktgt  = NULL; \
+        (d)->buffer   = NULL; \
         (d)->nofollow = (n); \
       } \
     while (0)
+
+#  define RELEASE_SEARCH(d) \
+     if ((d)->buffer != NULL) \
+       { \
+         kmm_free((d)->buffer); \
+         (d)->buffer  = NULL; \
+       }
+
 #else
+
 #  define SETUP_SEARCH(d,p,n) \
     do \
       { \
@@ -78,9 +90,10 @@
         (d)->relpath  = NULL; \
       } \
     while (0)
-#endif
 
-#define RELEASE_SEARCH(d)
+#  define RELEASE_SEARCH(d)
+
+#endif
 
 /****************************************************************************
  * Public Types
@@ -109,9 +122,10 @@
  *                     terminal is a soft link, then return the inode of
  *                     the link target.
  *           - OUTPUT: (not used)
- *  fullpath - INPUT:  Not used
- *           - OUTPUT: May hold an intermediate path which is probably of
- *                     no interest to the caller.
+ *  buffer   - INPUT:  Not used
+ *           - OUTPUT: May hold an allocated intermediate path which is
+ *                     probably of no interest to the caller unless it holds
+ *                     the relpath.
  */
 
 struct inode_search_s
@@ -123,8 +137,8 @@ struct inode_search_s
   FAR const char *relpath;   /* Relative path into the mountpoint */
 #ifdef CONFIG_PSEUDOFS_SOFTLINKS
   FAR const char *linktgt;   /* Target of symbolic link if linked to a directory */
+  FAR char *buffer;          /* Path expansion buffer */
   bool nofollow;             /* true: Don't follow terminal soft link */
-  char fullpath[PATH_MAX];         /* Path expansion buffer */
 #endif
 };