Full utcb copying partially works now.

include/l4/generic/tcb.h

@@ -145,6 +145,7 @@ void tcb_delete(struct ktcb *tcb);
 
 void init_ktcb_list(void);
 void task_update_utcb(struct ktcb *cur, struct ktcb *next);
+int tcb_check_and_lazy_map_utcb(struct ktcb *task);
 
 #endif /* __TCB_H__ */
 

include/l4/glue/arm/memory.h

@@ -130,6 +130,7 @@ int check_mapping(unsigned long vaddr, unsigned long size,
 void copy_pgd_kern_all(pgd_table_t *);
 pte_t virt_to_pte(unsigned long virtual);
 pte_t virt_to_pte_from_pgd(unsigned long virtual, pgd_table_t *pgd);
+unsigned long virt_to_phys_by_pgd(unsigned long vaddr, pgd_table_t *pgd);
 
 #endif /* __GLUE_ARM_MEMORY_H__ */
 

src/api/ipc.c

@@ -40,11 +40,9 @@ int ipc_full_copy(struct ktcb *to, struct ktcb *from)
 	int ret;
 
 	/* Check that utcb memory accesses won't fault us */
-	if ((ret = check_access(to->utcb_address, UTCB_SIZE,
-				MAP_SVC_RW_FLAGS, 0)) < 0)
+	if ((ret = tcb_check_and_lazy_map_utcb(to)) < 0)
 		return ret;
-	if ((ret = check_access(to->utcb_address, UTCB_SIZE,
-				MAP_SVC_RW_FLAGS, 0)) < 0)
+	if ((ret = tcb_check_and_lazy_map_utcb(from)) < 0)
 		return ret;
 
 	/* Directly copy from one utcb to another */

src/arch/arm/v5/mm.c

@@ -256,7 +256,7 @@ int check_mapping_pgd(unsigned long vaddr, unsigned long size,
 	BUG_ON(!(flags = space_flags_to_ptflags(flags)));
 
 	for (int i = 0; i < npages; i++) {
-		pte = virt_to_pte(vaddr + i * PAGE_SIZE);
+		pte = virt_to_pte_from_pgd(vaddr + i * PAGE_SIZE, pgd);
 
 		/* Check if pte perms are equal or gt given flags */
 		if ((pte & PTE_PROT_MASK) >= (flags & PTE_PROT_MASK))
@@ -268,6 +268,11 @@ int check_mapping_pgd(unsigned long vaddr, unsigned long size,
 	return 1;
 }
 
+unsigned long virt_to_phys_by_pgd(unsigned long vaddr, pgd_table_t *pgd)
+{
+	pte_t pte = virt_to_pte_from_pgd(vaddr, pgd);
+	return pte & ~PAGE_MASK;
+}
 
 int check_mapping(unsigned long vaddr, unsigned long size,
 		  unsigned int flags)

src/generic/tcb.c

@@ -10,6 +10,7 @@
 #include <l4/generic/space.h>
 #include <l4/lib/idpool.h>
 #include <l4/api/kip.h>
+#include <l4/api/errno.h>
 #include INC_ARCH(exception.h)
 #include INC_SUBARCH(mm.h)
 #include INC_GLUE(memory.h)
@@ -164,3 +165,41 @@ void task_update_utcb(struct ktcb *cur, struct ktcb *next)
 	kip.utcb = next->utcb_address;
 }
 
+/*
+ * Checks whether a task's utcb is currently accessible by the kernel
+ * It returns an error if its not paged in yet, and also maps a non-current
+ * task's utcb to current task with kernel-access privileges.
+ */
+int tcb_check_and_lazy_map_utcb(struct ktcb *task)
+{
+	unsigned int phys;
+	int ret;
+
+	BUG_ON(!task->utcb_address);
+
+	if ((ret = check_access(task->utcb_address, UTCB_SIZE,
+				MAP_SVC_RW_FLAGS, 0)) < 0) {
+		/* Current task simply hasn't mapped its utcb */
+		if (task == current) {
+			return -EFAULT;
+		} else {
+			if (!(phys = virt_to_phys_by_pgd(task->utcb_address,
+							 TASK_PGD(task)))) {
+				/* Task hasn't mapped its utcb */
+				return -EFAULT;
+			} else {
+				/*
+				 * Task has utcb but it hasn't yet been mapped
+				 * to current task with kernel access. Do it.
+				 */
+				add_mapping_pgd(phys, task->utcb_address,
+						page_align_up(UTCB_SIZE),
+						MAP_SVC_RW_FLAGS,
+						TASK_PGD(current));
+			}
+		}
+	}
+	return 0;
+}
+
+