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>

6 files changed, 6 insertions, 49 deletions

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 49583c5a5d44..315c51f58811 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -43,7 +43,7 @@ config IA64
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_IOMAP
 	select GENERIC_SMP_IDLE_THREAD
-	select ARCH_INIT_TASK
+	select ARCH_TASK_STRUCT_ON_STACK
 	select ARCH_TASK_STRUCT_ALLOCATOR
 	select ARCH_THREAD_STACK_ALLOCATOR
 	select ARCH_CLOCKSOURCE_DATA
diff --git a/arch/ia64/Makefile b/arch/ia64/Makefile
index c100d780f1eb..2dd7f519ad0b 100644
--- a/arch/ia64/Makefile
+++ b/arch/ia64/Makefile
@@ -42,7 +42,7 @@ $(error Sorry, you need a newer version of the assember, one that is built from
 endif
 
 KBUILD_CFLAGS += $(cflags-y)
-head-y := arch/ia64/kernel/head.o arch/ia64/kernel/init_task.o
+head-y := arch/ia64/kernel/head.o
 
 libs-y				+= arch/ia64/lib/
 core-y				+= arch/ia64/kernel/ arch/ia64/mm/
diff --git a/arch/ia64/include/asm/thread_info.h b/arch/ia64/include/asm/thread_info.h
index 1d172a4119a7..64a1011f6812 100644
--- a/arch/ia64/include/asm/thread_info.h
+++ b/arch/ia64/include/asm/thread_info.h
@@ -12,6 +12,8 @@
 #include <asm/processor.h>
 #include <asm/ptrace.h>
 
+#define THREAD_SIZE			KERNEL_STACK_SIZE
+
 #ifndef __ASSEMBLY__
 
 /*
@@ -41,8 +43,6 @@ struct thread_info {
 #endif
 };
 
-#define THREAD_SIZE			KERNEL_STACK_SIZE
-
 #define INIT_THREAD_INFO(tsk)			\
 {						\
 	.task		= &tsk,			\
diff --git a/arch/ia64/kernel/Makefile b/arch/ia64/kernel/Makefile
index 14ad79f394e5..0b4c65a1af25 100644
--- a/arch/ia64/kernel/Makefile
+++ b/arch/ia64/kernel/Makefile
@@ -7,7 +7,7 @@ ifdef CONFIG_DYNAMIC_FTRACE
 CFLAGS_REMOVE_ftrace.o = -pg
 endif
 
-extra-y	:= head.o init_task.o vmlinux.lds
+extra-y	:= head.o vmlinux.lds
 
 obj-y := entry.o efi.o efi_stub.o gate-data.o fsys.o ia64_ksyms.o irq.o irq_ia64.o	\
 	 irq_lsapic.o ivt.o machvec.o pal.o patch.o process.o perfmon.o ptrace.o sal.o		\
diff --git a/arch/ia64/kernel/init_task.c b/arch/ia64/kernel/init_task.c
deleted file mode 100644
index 8df9245e29d9..000000000000
--- a/arch/ia64/kernel/init_task.c
+++ /dev/null
@@ -1,44 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * This is where we statically allocate and initialize the initial
- * task.
- *
- * Copyright (C) 1999, 2002-2003 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-
-#include <linux/init.h>
-#include <linux/mm.h>
-#include <linux/fs.h>
-#include <linux/module.h>
-#include <linux/sched.h>
-#include <linux/init_task.h>
-#include <linux/mqueue.h>
-
-#include <linux/uaccess.h>
-#include <asm/pgtable.h>
-
-static struct signal_struct init_signals = INIT_SIGNALS(init_signals);
-static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);
-/*
- * Initial task structure.
- *
- * We need to make sure that this is properly aligned due to the way process stacks are
- * handled. This is done by having a special ".data..init_task" section...
- */
-#define init_thread_info	init_task_mem.s.thread_info
-#define init_stack		init_task_mem.stack
-
-union {
-	struct {
-		struct task_struct task;
-		struct thread_info thread_info;
-	} s;
-	unsigned long stack[KERNEL_STACK_SIZE/sizeof (unsigned long)];
-} init_task_mem asm ("init_task") __init_task_data =
-	{{
-	.task =		INIT_TASK(init_task_mem.s.task),
-	.thread_info =	INIT_THREAD_INFO(init_task_mem.s.task)
-}};
-
-EXPORT_SYMBOL(init_task);
diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
index 58db59da0bd8..b0b2070e0591 100644
--- a/arch/ia64/kernel/vmlinux.lds.S
+++ b/arch/ia64/kernel/vmlinux.lds.S
@@ -3,6 +3,7 @@
 #include <asm/cache.h>
 #include <asm/ptrace.h>
 #include <asm/pgtable.h>
+#include <asm/thread_info.h>
 
 #include <asm-generic/vmlinux.lds.h>