Add mmap() API

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@916 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 171 insertions, 0 deletions

diff --git a/nuttx/fs/fs_mmap.c b/nuttx/fs/fs_mmap.c
new file mode 100644
index 000000000..57ab57fa1
--- /dev/null
+++ b/nuttx/fs/fs_mmap.c
@@ -0,0 +1,171 @@
+/****************************************************************************
+ * fs/fs_mmap.c
+ *
+ *   Copyright (C) 2008 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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 NuttX 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 OWNER 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <errno.h>
+#include <debug.h>
+
+#include "fs_internal.h"
+
+/****************************************************************************
+ * Global Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: mmap
+ *
+ * Description:
+ *   NuttX operates in a flat open address space.  Therefore, it generally
+ *   does not require mmap() functionality.  There is one one exception:
+ *   mmap is the API that is used to support direct access to random
+ *   access media under the following very restrictive conditions:
+ *
+ *   1. The filesystem supports the FIOC_MMAP ioctl command.  Any file system
+ *      that maps files contiguously on the media should support this ioctl.
+ *      (vs. file system that scatter files over the media in non-contigous
+ *      sectors).  As of this writing, ROMFS is the only file system that
+ *      meets this requirement.
+ *   2. The underly block driver supports the BIOC_XIPBASE ioctl command.
+ *      that maps the underlying media to a randomly accessible address. At
+ *      present, on the RAM/ROM disk driver does this.
+ *
+ * Parameters:
+ *   start   A hint at where to map the memory -- ignored.  The address
+ *           of the underlying media is fixed and cannot be re-mapped with
+ *           MMU support.
+ *   length  The length of the mapping -- ignored.  The entire underlying
+ *           media is always accessible.
+ *   prot    See the PROT_* definitions in sys/mman.h.
+ *           PROT_NONE      - Will cause an error
+ *           PROT_READ      - PROT_WRITE and PROT_EXEC also assumed
+ *           PROT_WRITE     - PROT_READ and PROT_EXEC also assumed
+ *           PROT_EXEC      - PROT_READ and PROT_WRITE also assumed
+ *   flags   See the MAP_* definitions in sys/mman.h.
+ *           MAP_SHARED     - Required
+ *           MAP_PRIVATE    - Will cause an error
+ *           MAP_FIXED      - Will cause an error
+ *           MAP_FILE       - Ignored
+ *           MAP_ANONYMOUS  - Will cause an error
+ *           MAP_ANON       - Will cause an error
+ *           MAP_GROWSDOWN  - Ignored
+ *           MAP_DENYWRITE  - Will cause an error
+ *           MAP_EXECUTABLE - Ignored
+ *           MAP_LOCKED     - Ignored
+ *           MAP_NORESERVE  - Ignored
+ *           MAP_POPULATE   - Ignored
+ *           MAP_NONBLOCK   - Ignored
+ *   fd      file descriptor of backing file -- required.
+ *   offset  The offset into the file to map
+ *
+ * Return:
+ *   On success, mmap() returns a pointer to the mapped area. 
+ *   On error, the value MAP_FAILED is returned, and errno is set appropriately.
+ *
+ *     ENOSYS
+ *       Returned if any of the unsupported mmap() features are attempted
+ *     EBADF
+ *      'fd' is not a valid file descriptor.
+ *     EINVAL
+ *      Length is 0. flags contained neither MAP_PRIVATE or MAP_SHARED, or
+ *      contained both of these values.
+ *     ENODEV
+ *      The underlying filesystem of the specified file does not support
+ *      memory mapping.
+ *
+ ****************************************************************************/
+
+FAR void *mmap(FAR void *start, size_t length, int prot, int flags,
+               int fd, off_t offset)
+{
+  FAR void *addr;
+  int ret;
+
+  /* Since only a tiny subset of mmap() functionality, we have to verify many
+   * things.
+   */
+
+#ifdef CONFIG_DEBUG
+  if (prot == PROT_NONE ||
+      (flags & (MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS|MAP_DENYWRITE)) != 0)
+    {
+      fdbg("Unsupported options, prot=%x flags=%04x\n", prot, flags);
+      ret = ENOSYS;
+      goto errout_with_ret;
+    }
+
+  if (length == 0 ||
+      (flags & MAP_SHARED) == 0)
+    {
+      fdbg("Invalid options, lengt=%d flags=%04x\n", length, flags);
+      ret = EINVAL;
+      goto errout_with_ret;
+    }
+#endif
+
+  /* Okay now we can assume a shared mapping from a file.  This is the
+   * only option supported
+   *
+   * Perform the ioctl to get the base address of the file in 'mapped'
+   * in memory.
+   */
+
+  ret = ioctl(fd, FIOC_MMAP, (unsigned long)&addr);
+  if (ret < 0)
+    {
+      fdbg("ioctl(FIOC_MMAP) failed: %d\n", errno);
+      goto errout;
+    }
+
+  /* Return the offset address */
+
+  return (void*)(((ubyte*)addr) + offset);
+
+#ifdef CONFIG_DEBUG
+errout_with_ret:
+  errno = ret;
+#endif
+
+errout:
+  return MAP_FAILED;
+}
+