Added ipc to notify vfs about a forked child.

TODO: Need to ensure child shmat()s its own utcb
after a fork (possibly in libposix/fork.c)

src/api/thread.c

@@ -128,10 +128,6 @@ int thread_create(struct task_ids *ids, unsigned int flags)
 		/* Allocate new pgd and copy all kernel areas */
 		new->pgd = alloc_pgd();
 		copy_pgd_kern_all(new->pgd);
-
-		/* New space id, or requested id if available */
-		if ((ids->spid = id_get(space_id_pool, ids->spid)) < 0)
-			ids->spid = id_new(space_id_pool);
 	} else {
 		/* Existing space will be used, find it from all tasks */
 		list_for_each_entry(task, &global_task_list, task_list) {
@@ -149,10 +145,22 @@ int thread_create(struct task_ids *ids, unsigned int flags)
 		BUG();
 	}
 out:
-	/* New thread id, or requested id if available */
+	/* Allocate requested id if it's available, else a new one */
 	if ((ids->tid = id_get(thread_id_pool, ids->tid)) < 0)
 		ids->tid = id_new(thread_id_pool);
 
+	/* If thread space is new or copied, it gets a new space id */
+	if (flags == THREAD_CREATE_NEWSPC ||
+	    flags == THREAD_CREATE_COPYSPC) {
+		/*
+		 * Allocate requested id if
+		 * it's available, else a new one
+		 */
+		if ((ids->spid = id_get(space_id_pool,
+					ids->spid)) < 0)
+			ids->spid = id_new(space_id_pool);
+	}
+
 	/* Set all ids */
 	set_task_ids(new, ids);
 

tasks/fs0/include/lib/idpool.h

@@ -8,6 +8,14 @@ struct id_pool {
 	u32 bitmap[];
 };
 
+/* Copy one id pool to another by calculating its size */
+static inline void id_pool_copy(struct idpool *to, struct idpool *from, int totalbits)
+{
+	int nwords = BITWISE_GETWORD(totalbits);
+
+	memcpy(to, from, nwords * SZ_WORD + sizeof(struct id_pool));
+}
+
 struct id_pool *id_pool_new_init(int mapsize);
 int id_new(struct id_pool *pool);
 int id_del(struct id_pool *pool, int id);

tasks/fs0/include/task.h

@@ -24,6 +24,17 @@ struct tcb {
 	struct vnode *rootdir;
 };
 
+/* Structures used when receiving new task info from pager */
+struct task_data {
+	unsigned long tid;
+	unsigned long utcb_address;
+};
+
+struct task_data_head {
+	unsigned long total;
+	struct task_data tdata[];
+};
+
 static inline int task_is_utcb_mapped(struct tcb *t)
 {
 	return t->utcb_mapped;

tasks/fs0/main.c

@@ -99,6 +99,10 @@ void handle_fs_requests(void)
 		pager_update_stats(sender, (unsigned long)mr[0],
 				   (unsigned long)mr[1]);
 		break;
+	case L4_IPC_TAG_NOTIFY_FORK:
+		pager_notify_fork(sender, (l4id_t)mr[0], (l4id_t)mr[1],
+				  (unsigned long)mr[2]);
+		break;
 
 	default:
 		printf("%s: Unrecognised ipc tag (%d) "

tasks/fs0/src/lib/idpool.c

@@ -10,6 +10,12 @@
 #include INC_GLUE(memory.h)
 #include <stdio.h>
 
+static inline void id_pool_copy(struct idpool *to, struct idpool *from, int totalbits)
+{
+	int nwords = BITWISE_GETWORD(totalbits);
+
+	memcpy(to, from, nwords * SZ_WORD + sizeof(struct id_pool));
+}
 struct id_pool *id_pool_new_init(int totalbits)
 {
 	int nwords = BITWISE_GETWORD(totalbits);

tasks/fs0/src/task.c

@@ -72,15 +72,44 @@ int receive_pager_taskdata_orig(l4id_t *tdata)
 	return 0;
 }
 
-struct task_data {
-	unsigned long tid;
-	unsigned long utcb_address;
-};
+/*
+ * Receives ipc from pager about a new fork event and
+ * the information on the resulting child task.
+ */
+int pager_notify_fork(l4id_t sender, l4id_t parid,
+		      l4id_t chid, unsigned long utcb_address)
+{
+	struct tcb *child, *parent;
+	int err;
+
+	// printf("%s/%s\n", __TASKNAME__, __FUNCTION__);
+	BUG_ON(!(parent = find_task(parid)));
+
+	if (IS_ERR(child = create_tcb())) {
+		l4_ipc_return((int)child);
+		return 0;
+	}
+
+	/* Initialise fields sent by pager */
+	child->tid = chid;
+	child->utcb_address = utcb_address;
+
+	/*
+	 * Initialise vfs specific fields.
+	 * FIXME: Or copy from parent???
+	 */
+	child->rootdir = vfs_root.pivot;
+	child->curdir = vfs_root.pivot;
+
+	/* Copy file descriptors from parent */
+	id_pool_copy(child->fdpool, parent->fdpool, TASK_FILES_MAX);
+	memcpy(child->fd, parent->fd, TASK_FILES_MAX * sizeof(int));
+
+	l4_ipc_return(0);
+
+	return 0;
+}
 
-struct task_data_head {
-	unsigned long total;
-	struct task_data tdata[];
-};
 
 /* Read task information into the utcb page, since it won't fit into mrs. */
 struct task_data_head *receive_pager_taskdata(void)

tasks/libl4/include/l4lib/ipcdefs.h

@@ -55,5 +55,6 @@
 #define L4_IPC_TAG_PAGER_WRITE		43	/* Pager writes file contents to vfs */
 #define L4_IPC_TAG_PAGER_CLOSE		44	/* Pager notifies vfs of file close */
 #define L4_IPC_TAG_PAGER_UPDATE_STATS	45	/* Pager updates file stats in vfs */
+#define L4_IPC_TAG_NOTIFY_FORK		46	/* Pager notifies vfs of process fork */
 
 #endif /* __IPCDEFS_H__ */

tasks/mm0/include/task.h

@@ -82,6 +82,17 @@ struct tcb {
 	struct file_descriptor fd[TASK_FILES_MAX];
 };
 
+/* Structures to use when sending new task information to vfs */
+struct task_data {
+	unsigned long tid;
+	unsigned long utcb_address;
+};
+
+struct task_data_head {
+	unsigned long total;
+	struct task_data tdata[];
+};
+
 struct tcb *find_task(int tid);
 
 struct initdata;

tasks/mm0/src/clone.c

@@ -72,7 +72,6 @@ int copy_tcb(struct tcb *to, struct tcb *from)
 	to->map_start = from->map_start;
 	to->map_end = from->map_end;
 
-
 	/* Copy all vm areas */
 	copy_vmas(to, from);
 
@@ -81,24 +80,48 @@ int copy_tcb(struct tcb *to, struct tcb *from)
 	       TASK_FILES_MAX * sizeof(struct file_descriptor));
 }
 
+/*
+ * Sends vfs task information about forked child, and its utcb
+ */
+void vfs_notify_fork(struct tcb *child, struct tcb *parent)
+{
+	int err;
+	struct task_data_head *tdata_head;
+	struct tcb *vfs;
+
+	printf("%s/%s\n", __TASKNAME__, __FUNCTION__);
+
+	l4_save_ipcregs();
+
+	/* Write parent and child information */
+	write_mr(L4SYS_ARG0, parent->tid);
+	write_mr(L4SYS_ARG1, child->tid);
+	write_mr(L4SYS_ARG2, child->utcb);
+
+	if ((err = l4_sendrecv(VFS_TID, VFS_TID,
+			       L4_IPC_TAG_NOTIFY_FORK)) < 0) {
+		printf("%s: L4 IPC Error: %d.\n", __FUNCTION__, err);
+		return err;
+	}
+
+	/* Check if syscall was successful */
+	if ((err = l4_get_retval()) < 0) {
+		printf("%s: Pager from VFS read error: %d.\n",
+		       __FUNCTION__, err);
+		return err;
+	}
+	l4_restore_ipcregs();
+
+	return err;
+}
+
 int do_fork(struct tcb *parent)
 {
-	struct task_ids ids = { .tid = TASK_ID_INVALID, .spid = parent->spid };
 	struct tcb *child;
-
-	/*
-	 * Allocate and copy parent pgd + all pmds to child.
-	 *
-	 * When a write fault occurs on any of the frozen shadows,
-	 * fault handler creates a new shadow on top, if it hasn't,
-	 * and then starts adding writeable pages to the new shadow.
-	 * Every forked task will fault on every page of the frozen shadow,
-	 * until all pages have been made copy-on-write'ed, in which case
-	 * the underlying frozen shadow is collapsed.
-	 *
-	 * Every forked task must have its own copy of pgd + pmds because
-	 * every one of them will have to fault on frozen shadows individually.
-	 */
+	struct task_ids ids = {
+		.tid = TASK_ID_INVALID,
+		.spid = parent->spid,
+	};
 
 	/* Make all shadows in this task read-only */
 	vm_freeze_shadows(parent);
@@ -115,18 +138,22 @@ int do_fork(struct tcb *parent)
 	/* Create new utcb for child since it can't use its parent's */
 	child->utcb = utcb_vaddr_new();
 
-	/* Create the utcb shared memory segment available for child to shmat() */
-	if (IS_ERR(shm = shm_new((key_t)child->utcb, __pfn(DEFAULT_UTCB_SIZE)))) {
+	/*
+	 * Create the utcb shared memory segment
+	 * available for child to shmat()
+	 */
+	if (IS_ERR(shm = shm_new((key_t)child->utcb,
+				 __pfn(DEFAULT_UTCB_SIZE)))) {
 		l4_ipc_return((int)shm);
 		return 0;
 	}
 	/* FIXME: We should munmap() parent's utcb page from child */
 
 	/* Notify fs0 about forked process */
-	vfs_send_fork(parent, child);
+	vfs_notify_fork(child, parent);
 
-	/* Start forked child. FIXME: Return ipc to child as well ??? */
-	l4_thread_control(THREAD_START, child);
+	/* Start forked child. */
+	l4_thread_control(THREAD_RUN, ids);
 
 	/* Return back to parent */
 	l4_ipc_return(0);

tasks/mm0/src/task.c

@@ -481,16 +481,6 @@ void init_pm(struct initdata *initdata)
 	start_boot_tasks(initdata);
 }
 
-struct task_data {
-	unsigned long tid;
-	unsigned long utcb_address;
-};
-
-struct task_data_head {
-	unsigned long total;
-	struct task_data tdata[];
-};
-
 /*
  * During its initialisation FS0 wants to learn how many boot tasks
  * are running, and their tids, which includes itself. This function