New UTCB implementation almost working.

- KIP's pointer to UTCB seems to work with existing l4lib ipc functions.
- Works up to clone()
- In clone we mmap() the same UTCB on each new thread - excessive.
- Generally during page fault handling, cloned threads may fault on the same page
  multiple times even though a single handling would be enough for all of them.
  Need to detect and handle this.

tasks/mm0/include/init.h

@@ -19,6 +19,8 @@
 struct initdata {
 	struct bootdesc *bootdesc;
 	struct page_bitmap page_map;
+	unsigned long pager_utcb_virt;
+	unsigned long pager_utcb_phys;
 	struct list_head boot_file_list;
 };
 

tasks/mm0/include/lib/idpool.h

@@ -5,8 +5,8 @@
 #include <lib/spinlock.h>
 
 struct id_pool {
-	struct spinlock lock;
 	int nwords;
+	int bitlimit;
 	u32 bitmap[];
 };
 

tasks/mm0/include/task.h

@@ -54,21 +54,18 @@ struct task_vma_head {
 	int tcb_refs;
 };
 
-/*
- * TLS and UTCB bookkeeping:
- *
- * This structure is shared among threads whose utcbs are on the same
- * physical page. Threads with utcbs on different physical pages have
- * their own utcb_data structure, even though they are in the same
- * address space, and share their vm_area_list structure.
- */
-struct utcb_data {
-	unsigned long phys;	/* Physical utcb address */
-	unsigned long virt;	/* Virtual utcb address */
-	u32 bit;		/* Bitvector of free utcb slots on page */
-	struct page *p;		/* Physical page */
+struct utcb_desc {
+	struct list_head list;
+	unsigned long utcb_base;
+	struct id_pool *slots;
 };
 
+struct utcb_head {
+	struct list_head list;
+	int tcb_refs;
+};
+
+
 /* Stores all task information that can be kept in userspace. */
 struct tcb {
 	/* Task list */
@@ -119,8 +116,11 @@ struct tcb {
 	/* Default ipc-shared-page information */
 	void *shared_page;
 
-	/* Task's utcb data */
-	struct utcb_data *utcb;
+	/* Chain of utcb descriptors */
+	struct utcb_head *utcb_head;
+
+	/* Unique utcb address of this task */
+	unsigned long utcb_address;
 
 	/* Virtual memory areas */
 	struct task_vma_head *vm_area_head;