vm: implement private and shared address space mappings

whether a mapping is private or shared determines how the mapping is handled
when a task is duplicated.

kernel/bsp.c

@@ -120,6 +120,7 @@ static kern_status_t map_executable_exec(
 		bsp->bsp_vmo,
 		text_foffset,
 		bsp->bsp_trailer.bsp_text_size,
+		VM_SHARED,
 		VM_PROT_READ | VM_PROT_EXEC | VM_PROT_USER,
 		&text_base);
 	if (status != KERN_OK) {
@@ -132,6 +133,7 @@ static kern_status_t map_executable_exec(
 		data,
 		data_foffset,
 		bsp->bsp_trailer.bsp_data_size,
+		VM_PRIVATE,
 		VM_PROT_READ | VM_PROT_WRITE | VM_PROT_USER,
 		&data_base);
 	if (status != KERN_OK) {
@@ -165,6 +167,7 @@ kern_status_t bsp_launch_async(struct bsp *bsp, struct task *task)
 		user_stack,
 		0,
 		BOOTSTRAP_STACK_SIZE,
+		VM_PRIVATE,
 		VM_PROT_READ | VM_PROT_WRITE | VM_PROT_USER,
 		&stack_buffer);
 
@@ -178,6 +181,7 @@ kern_status_t bsp_launch_async(struct bsp *bsp, struct task *task)
 		bsp->bsp_vmo,
 		0,
 		bsp->bsp_trailer.bsp_exec_offset,
+		VM_PRIVATE,
 		VM_PROT_READ | VM_PROT_USER,
 		&bsp_data_base);