Construct init thread stack in the linker script rather than by union

Construct the init thread stack in the linker script rather than doing it
by means of a union so that ia64's init_task.c can be got rid of.

The following symbols are then made available from INIT_TASK_DATA() linker
script macro:

	init_thread_union
	init_stack

INIT_TASK_DATA() also expands the region to THREAD_SIZE to accommodate the
size of the init stack.  init_thread_union is given its own section so that
it can be placed into the stack space in the right order.  I'm assuming
that the ia64 ordering is correct and that the task_struct is first and the
thread_info second.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Tested-by: Will Deacon <will.deacon@arm.com> (arm64)
Tested-by: Palmer Dabbelt <palmer@sifive.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 6 insertions, 4 deletions

diff --git a/init/init_task.c b/init/init_task.c
index 9325fee7dc82..2285aa42cbe1 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -17,15 +17,17 @@ static struct signal_struct init_signals = INIT_SIGNALS(init_signals);
 static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);
 
 /* Initial task structure */
-struct task_struct init_task = INIT_TASK(init_task);
+struct task_struct init_task
+#ifdef CONFIG_ARCH_TASK_STRUCT_ON_STACK
+	__init_task_data
+#endif
+	= INIT_TASK(init_task);
 EXPORT_SYMBOL(init_task);
 
 /*
  * Initial thread structure. Alignment of this is handled by a special
  * linker map entry.
  */
-union thread_union init_thread_union __init_task_data = {
 #ifndef CONFIG_THREAD_INFO_IN_TASK
-	INIT_THREAD_INFO(init_task)
+struct thread_info init_thread_info __init_thread_info = INIT_THREAD_INFO(init_task);
 #endif
-};