Filesystem: Reference counting for locations

 o A new data structure rtems_filesystem_global_location_t was
   introduced to be used for
    o the mount point location in the mount table entry,
    o the file system root location in the mount table entry,
    o the root directory location in the user environment, and
    o the current directory location in the user environment.
   During the path evaluation global start locations are obtained to
   ensure that the current file system instance will be not unmounted in
   the meantime.
 o The user environment uses now reference counting and is protected
   from concurrent access.
 o The path evaluation process was completely rewritten and simplified.
   The IMFS, RFS, NFS, and DOSFS use now a generic path evaluation
   method.  Recursive calls in the path evaluation have been replaced
   with iteration to avoid stack overflows.  Only the evaluation of
   symbolic links is recursive.  No dynamic memory allocations and
   intermediate buffers are used in the high level path evaluation.  No
   global locks are held during the file system instance specific path
   evaluation process.
 o Recursive symbolic link evaluation is now limited by
   RTEMS_FILESYSTEM_SYMLOOP_MAX.  Applications can retrieve this value
   via sysconf().
 o The device file system (devFS) uses now no global variables and
   allocation from the workspace.  Node names are allocated from the
   heap.
 o The upper layer lseek() performs now some parameter checks.
 o The upper layer ftruncate() performs now some parameter checks.
 o unmask() is now restricted to the RWX flags and protected from
   concurrent access.
 o The fchmod_h and rmnod_h file system node handlers are now a file
   system operation.
 o The unlink_h operation has been removed.  All nodes are now destroyed
   with the rmnod_h operation.
 o New lock_h, unlock_h, clonenod_h, and are_nodes_equal_h file system
   operations.
 o The path evaluation and file system operations are now protected by
   per file system instance lock and unlock operations.
 o Fix and test file descriptor duplicate in fcntl().
 o New test fstests/fsnofs01.

1 files changed, 333 insertions, 0 deletions

diff --git a/cpukit/libcsupport/src/sup_fs_eval_path.c b/cpukit/libcsupport/src/sup_fs_eval_path.c
new file mode 100644
index 0000000000..1940cce745
--- /dev/null
+++ b/cpukit/libcsupport/src/sup_fs_eval_path.c
@@ -0,0 +1,333 @@
+/*
+ * Copyright (c) 2012 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Obere Lagerstr. 30
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems@embedded-brains.de>
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rtems.com/license/LICENSE.
+ */
+
+#if HAVE_CONFIG_H
+  #include "config.h"
+#endif
+
+#include <rtems/libio_.h>
+
+static size_t get_parentpathlen(const char *path, size_t pathlen)
+{
+  while (pathlen > 0) {
+    size_t i = pathlen - 1;
+
+    if (rtems_filesystem_is_delimiter(path [i])) {
+      return pathlen;
+    }
+
+    pathlen = i;
+  }
+
+  return 0;
+}
+
+static void set_startloc(
+  rtems_filesystem_eval_path_context_t *ctx,
+  rtems_filesystem_global_location_t *const *global_root_ptr,
+  rtems_filesystem_global_location_t *const *global_current_ptr
+)
+{
+  if (ctx->pathlen > 0) {
+    char c = ctx->path [0];
+
+    ctx->rootloc = rtems_filesystem_global_location_obtain(global_root_ptr);
+
+    if (rtems_filesystem_is_delimiter(c)) {
+      ++ctx->path;
+      --ctx->pathlen;
+      ctx->startloc = rtems_filesystem_global_location_obtain(
+        &ctx->rootloc
+      );
+    } else {
+      ctx->startloc = rtems_filesystem_global_location_obtain(
+        global_current_ptr
+      );
+    }
+  } else {
+    ctx->rootloc = rtems_filesystem_global_location_obtain_null();
+    ctx->startloc = rtems_filesystem_global_location_obtain_null();
+    errno = ENOENT;
+  }
+}
+
+static void check_access(
+  rtems_filesystem_eval_path_context_t *ctx,
+  int eval_flags
+)
+{
+  const rtems_filesystem_location_info_t *currentloc = &ctx->currentloc;
+  struct stat st;
+  int rv;
+
+  st.st_mode = 0;
+  st.st_uid = 0;
+  st.st_gid = 0;
+  rv = (*currentloc->handlers->fstat_h)(currentloc, &st);
+  if (rv == 0) {
+    bool access_ok = rtems_filesystem_check_access(
+      eval_flags,
+      st.st_mode,
+      st.st_uid,
+      st.st_gid
+    );
+
+    if (!access_ok) {
+      rtems_filesystem_eval_path_error(ctx, EACCES);
+    }
+  } else {
+    rtems_filesystem_eval_path_error(ctx, 0);
+  }
+}
+
+void rtems_filesystem_eval_path_continue(
+  rtems_filesystem_eval_path_context_t *ctx
+)
+{
+  int eval_flags;
+
+  while (ctx->pathlen > 0) {
+    (*ctx->currentloc.ops->eval_path_h)(ctx);
+  }
+
+  eval_flags = rtems_filesystem_eval_path_get_flags(ctx);
+  if (rtems_filesystem_eval_path_has_token(ctx)) {
+    bool make = (eval_flags & RTEMS_LIBIO_MAKE) != 0;
+
+    if (make) {
+      check_access(ctx, RTEMS_LIBIO_PERMS_WRITE);
+    } else {
+      rtems_filesystem_eval_path_error(ctx, ENOENT);
+    }
+  } else {
+    bool exclusive = (eval_flags & RTEMS_LIBIO_EXCLUSIVE) != 0;
+
+    if (!exclusive) {
+      check_access(ctx, ctx->flags);
+    } else {
+      rtems_filesystem_eval_path_error(ctx, EEXIST);
+    }
+  }
+}
+
+static rtems_filesystem_location_info_t *
+eval_path_start(
+  rtems_filesystem_eval_path_context_t *ctx,
+  const char *path,
+  size_t pathlen,
+  int eval_flags,
+  rtems_filesystem_global_location_t *const *global_root_ptr,
+  rtems_filesystem_global_location_t *const *global_current_ptr
+)
+{
+  memset(ctx, 0, sizeof(*ctx));
+
+  ctx->path = path;
+  ctx->pathlen = pathlen;
+  ctx->flags = eval_flags;
+
+  set_startloc(ctx, global_root_ptr, global_current_ptr);
+
+  rtems_filesystem_instance_lock(&ctx->startloc->location);
+
+  rtems_filesystem_location_clone(
+    &ctx->currentloc,
+    &ctx->startloc->location
+  );
+
+  rtems_filesystem_eval_path_continue(ctx);
+
+  return &ctx->currentloc;
+}
+
+rtems_filesystem_location_info_t *
+rtems_filesystem_eval_path_start_with_root_and_current(
+  rtems_filesystem_eval_path_context_t *ctx,
+  const char *path,
+  int eval_flags,
+  rtems_filesystem_global_location_t *const *global_root_ptr,
+  rtems_filesystem_global_location_t *const *global_current_ptr
+)
+{
+  return eval_path_start(
+    ctx,
+    path,
+    strlen(path),
+    eval_flags,
+    global_root_ptr,
+    global_current_ptr
+  );
+}
+
+rtems_filesystem_location_info_t *
+rtems_filesystem_eval_path_start(
+  rtems_filesystem_eval_path_context_t *ctx,
+  const char *path,
+  int eval_flags
+)
+{
+  return rtems_filesystem_eval_path_start_with_root_and_current(
+    ctx,
+    path,
+    eval_flags,
+    &rtems_filesystem_root,
+    &rtems_filesystem_current
+  );
+}
+
+rtems_filesystem_location_info_t *
+rtems_filesystem_eval_path_start_with_parent(
+  rtems_filesystem_eval_path_context_t *ctx,
+  const char *path,
+  int eval_flags,
+  rtems_filesystem_location_info_t *parentloc,
+  int parent_eval_flags
+)
+{
+  size_t pathlen = strlen(path);
+  const char *parentpath = path;
+  size_t parentpathlen = get_parentpathlen(path, pathlen);
+  const char *name = NULL;
+  size_t namelen = 0;
+  const rtems_filesystem_location_info_t *currentloc = NULL;
+
+  if (pathlen > 0) {
+    if (parentpathlen == 0) {
+      parentpath = ".";
+      parentpathlen = 1;
+      name = path;
+      namelen = pathlen;
+    } else {
+      name = path + parentpathlen;
+      namelen = pathlen - parentpathlen;
+    }
+  }
+
+  currentloc = eval_path_start(
+    ctx,
+    parentpath,
+    parentpathlen,
+    parent_eval_flags,
+    &rtems_filesystem_root,
+    &rtems_filesystem_current
+  );
+
+  rtems_filesystem_location_clone(parentloc, currentloc);
+
+  ctx->path = name;
+  ctx->pathlen = namelen;
+  ctx->flags = eval_flags;
+
+  rtems_filesystem_eval_path_continue(ctx);
+
+  return &ctx->currentloc;
+}
+
+void rtems_filesystem_eval_path_recursive(
+  rtems_filesystem_eval_path_context_t *ctx,
+  const char *path,
+  size_t pathlen
+)
+{
+  if (pathlen > 0) {
+    if (ctx->recursionlevel < RTEMS_FILESYSTEM_SYMLOOP_MAX) {
+      const char *saved_path = ctx->path;
+      size_t saved_pathlen = ctx->pathlen;
+
+      if (rtems_filesystem_is_delimiter(path [0])) {
+        rtems_filesystem_eval_path_restart(ctx, &ctx->rootloc);
+      }
+
+      ctx->path = path;
+      ctx->pathlen = pathlen;
+
+      ++ctx->recursionlevel;
+      while (ctx->pathlen > 0) {
+        (*ctx->currentloc.ops->eval_path_h)(ctx);
+      }
+      --ctx->recursionlevel;
+
+      ctx->path = saved_path;
+      ctx->pathlen = saved_pathlen;
+    } else {
+      rtems_filesystem_eval_path_error(ctx, ELOOP);
+    }
+  } else {
+    rtems_filesystem_eval_path_error(ctx, ENOENT);
+  }
+}
+
+void rtems_filesystem_eval_path_error(
+  rtems_filesystem_eval_path_context_t *ctx,
+  int eno
+)
+{
+  ctx->path = NULL;
+  ctx->pathlen = 0;
+  ctx->token = NULL;
+  ctx->tokenlen = 0;
+
+  if (!rtems_filesystem_location_is_null(&ctx->currentloc)) {
+    if (eno != 0) {
+      errno = eno;
+    }
+
+    rtems_filesystem_location_detach(&ctx->currentloc);
+  }
+}
+
+static void free_location(rtems_filesystem_location_info_t *loc)
+{
+  rtems_filesystem_mt_entry_declare_lock_context(lock_context);
+
+  (*loc->ops->freenod_h)(loc);
+
+  rtems_filesystem_mt_entry_lock(lock_context);
+  rtems_chain_extract_unprotected(&loc->mt_entry_node);
+  rtems_filesystem_mt_entry_unlock(lock_context);
+}
+
+void rtems_filesystem_eval_path_cleanup(
+  rtems_filesystem_eval_path_context_t *ctx
+)
+{
+  free_location(&ctx->currentloc);
+  rtems_filesystem_instance_unlock(&ctx->startloc->location);
+  rtems_filesystem_global_location_release(ctx->startloc);
+  rtems_filesystem_global_location_release(ctx->rootloc);
+}
+
+void rtems_filesystem_eval_path_cleanup_with_parent(
+  rtems_filesystem_eval_path_context_t *ctx,
+  rtems_filesystem_location_info_t *parentloc
+)
+{
+  free_location(parentloc);
+  rtems_filesystem_eval_path_cleanup(ctx);
+}
+
+void rtems_filesystem_eval_path_restart(
+  rtems_filesystem_eval_path_context_t *ctx,
+  rtems_filesystem_global_location_t **newstartloc_ptr
+)
+{
+  free_location(&ctx->currentloc);
+  rtems_filesystem_instance_unlock(&ctx->startloc->location);
+  rtems_filesystem_global_location_assign(
+    &ctx->startloc,
+    rtems_filesystem_global_location_obtain(newstartloc_ptr)
+  );
+  rtems_filesystem_instance_lock(&ctx->startloc->location);
+  rtems_filesystem_location_clone(&ctx->currentloc, &ctx->startloc->location);
+}