fedora core 6 1.2949 + vserver 2.2.0

[linux-2.6.git] / Documentation / nommu-mmap.txt

diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt
index b88ebe4..7714f57 100644 (file)
--- a/Documentation/nommu-mmap.txt
+++ b/Documentation/nommu-mmap.txt
@@ -116,6 +116,9 @@ FURTHER NOTES ON NO-MMU MMAP
  (*) A list of all the mappings on the system is visible through /proc/maps in
      no-MMU mode.
 
  (*) A list of all the mappings on the system is visible through /proc/maps in
      no-MMU mode.
 

+ (*) A list of all the mappings in use by a process is visible through
+     /proc/<pid>/maps in no-MMU mode.
+

  (*) Supplying MAP_FIXED or a requesting a particular mapping address will
      result in an error.
 
  (*) Supplying MAP_FIXED or a requesting a particular mapping address will
      result in an error.
 


@@ -125,6 +128,49 @@ FURTHER NOTES ON NO-MMU MMAP
      error will result if they don't. This is most likely to be encountered
      with character device files, pipes, fifos and sockets.
 
      error will result if they don't. This is most likely to be encountered
      with character device files, pipes, fifos and sockets.
 

+
+==========================
+INTERPROCESS SHARED MEMORY
+==========================
+
+Both SYSV IPC SHM shared memory and POSIX shared memory is supported in NOMMU
+mode.  The former through the usual mechanism, the latter through files created
+on ramfs or tmpfs mounts.
+
+
+=======
+FUTEXES
+=======
+
+Futexes are supported in NOMMU mode if the arch supports them.  An error will
+be given if an address passed to the futex system call lies outside the
+mappings made by a process or if the mapping in which the address lies does not
+support futexes (such as an I/O chardev mapping).
+
+
+=============
+NO-MMU MREMAP
+=============
+
+The mremap() function is partially supported.  It may change the size of a
+mapping, and may move it[*] if MREMAP_MAYMOVE is specified and if the new size
+of the mapping exceeds the size of the slab object currently occupied by the
+memory to which the mapping refers, or if a smaller slab object could be used.
+
+MREMAP_FIXED is not supported, though it is ignored if there's no change of
+address and the object does not need to be moved.
+
+Shared mappings may not be moved.  Shareable mappings may not be moved either,
+even if they are not currently shared.
+
+The mremap() function must be given an exact match for base address and size of
+a previously mapped object.  It may not be used to create holes in existing
+mappings, move parts of existing mappings or resize parts of mappings.  It must
+act on a complete mapping.
+
+[*] Not currently supported.
+
+

 ============================================
 PROVIDING SHAREABLE CHARACTER DEVICE SUPPORT
 ============================================
 ============================================
 PROVIDING SHAREABLE CHARACTER DEVICE SUPPORT
 ============================================