Added copy-on-write shared memory but untested yet.

For anonymous shm, mmap now adds a shm_file and devzero behind it
as two vm_objects. Faults are handled by copy_on_write(). Just as
shadows copy r/w pages from original files, it should copy r/w
pages from devzero into the shm_file in front.

shmat/shmget uses mmap to set-up their areas.

Untested yet so bugs expected.

	modified:   tasks/libl4/src/init.c
	modified:   tasks/mm0/include/shm.h
	modified:   tasks/mm0/include/vm_area.h
	modified:   tasks/mm0/src/fault.c
	modified:   tasks/mm0/src/mmap.c
	modified:   tasks/mm0/src/shm.c

tasks/mm0/include/shm.h

@@ -1,11 +1,23 @@
+/*
+ * Copyright (C) 2008 Bahadir Balban
+ */
 #ifndef __SHM_H__
 #define __SHM_H__
 
-#include <l4/api/space.h>
 #include <l4/lib/list.h>
+#include <l4/api/space.h>
 #include <l4/macros.h>
 #include <l4lib/types.h>
 
+struct shm_descriptor {
+	int key;
+	l4id_t shmid;
+	void *shm_addr;
+	unsigned long npages;
+	struct vm_file *devzero;
+};
+
+#if 0
 struct shm_descriptor {
 	int key;			/* IPC key supplied by user task */
 	l4id_t shmid;			/* SHM area id, allocated by mm0 */
@@ -16,12 +28,13 @@ struct shm_descriptor {
 	unsigned int flags;
 	int refcnt;
 };
+#endif
 
 #define SHM_AREA_MAX			64	/* Up to 64 shm areas */
 
 /* Up to 10 pages per area, and at least 1 byte (implies 1 page) */
 #define SHM_SHMMIN			1
-#define SHM_SHMMAX			(PAGE_SIZE * 10)
+#define SHM_SHMMAX			10
 
 /* Initialises shared memory bookkeeping structures */
 void shm_init();

tasks/mm0/include/vm_area.h

@@ -42,6 +42,7 @@ enum VM_FILE_TYPE {
 	VM_FILE_DEVZERO = 1,
 	VM_FILE_REGULAR,
 	VM_FILE_BOOTFILE,
+	VM_FILE_SHM,
 };
 
 /* Defines the type of object. A file? Just a standalone object? */