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>

50 files changed, 42 insertions, 155 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 400b9e1..a26d6f8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -234,8 +234,8 @@ config ARCH_HAS_FORTIFY_SOURCE
 config ARCH_HAS_SET_MEMORY
 	bool
 
-# Select if arch init_task initializer is different to init/init_task.c
-config ARCH_INIT_TASK
+# Select if arch init_task must go in the __init_task_data section
+config ARCH_TASK_STRUCT_ON_STACK
        bool
 
 # Select if arch has its private alloc_task_struct() function
diff --git a/arch/alpha/include/asm/thread_info.h b/arch/alpha/include/asm/thread_info.h
index 8c20c5e..807d7b9 100644
--- a/arch/alpha/include/asm/thread_info.h
+++ b/arch/alpha/include/asm/thread_info.h
@@ -39,9 +39,6 @@ struct thread_info {
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* How to get the thread information struct from C.  */
 register struct thread_info *__current_thread_info __asm__("$8");
 #define current_thread_info()  __current_thread_info
diff --git a/arch/arc/include/asm/thread_info.h b/arch/arc/include/asm/thread_info.h
index 2d79e52..c85947b 100644
--- a/arch/arc/include/asm/thread_info.h
+++ b/arch/arc/include/asm/thread_info.h
@@ -62,9 +62,6 @@ struct thread_info {
 	.addr_limit = KERNEL_DS,		\
 }
 
-#define init_thread_info    (init_thread_union.thread_info)
-#define init_stack          (init_thread_union.stack)
-
 static inline __attribute_const__ struct thread_info *current_thread_info(void)
 {
 	register unsigned long sp asm("sp");
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 776757d..e71cc35 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -75,9 +75,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,					\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /*
  * how to get the current stack pointer in C
  */
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index eb43128..740aa03c 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -51,8 +51,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,					\
 }
 
-#define init_stack		(init_thread_union.stack)
-
 #define thread_saved_pc(tsk)	\
 	((unsigned long)(tsk->thread.cpu_context.pc))
 #define thread_saved_sp(tsk)	\
diff --git a/arch/blackfin/include/asm/thread_info.h b/arch/blackfin/include/asm/thread_info.h
index 2966b93..a5aeab4 100644
--- a/arch/blackfin/include/asm/thread_info.h
+++ b/arch/blackfin/include/asm/thread_info.h
@@ -56,8 +56,6 @@ struct thread_info {
 	.cpu		= 0,			\
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 }
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
 
 /* Given a task stack pointer, you can find its corresponding
  * thread_info structure just by masking it to the THREAD_SIZE
diff --git a/arch/c6x/include/asm/thread_info.h b/arch/c6x/include/asm/thread_info.h
index acc70c1..59a5697 100644
--- a/arch/c6x/include/asm/thread_info.h
+++ b/arch/c6x/include/asm/thread_info.h
@@ -60,9 +60,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* get the thread information struct of current task */
 static inline __attribute__((const))
 struct thread_info *current_thread_info(void)
diff --git a/arch/cris/include/asm/processor.h b/arch/cris/include/asm/processor.h
index b509077..ee4d8b0 100644
--- a/arch/cris/include/asm/processor.h
+++ b/arch/cris/include/asm/processor.h
@@ -52,8 +52,6 @@ static inline void release_thread(struct task_struct *dead_task)
         /* Nothing needs to be done.  */
 }
 
-#define init_stack      (init_thread_union.stack)
-
 #define cpu_relax()     barrier()
 
 void default_idle(void);
diff --git a/arch/cris/include/asm/thread_info.h b/arch/cris/include/asm/thread_info.h
index 108f770..996fef3 100644
--- a/arch/cris/include/asm/thread_info.h
+++ b/arch/cris/include/asm/thread_info.h
@@ -63,8 +63,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,			\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-
 #endif /* !__ASSEMBLY__ */
 
 /*
diff --git a/arch/frv/include/asm/thread_info.h b/arch/frv/include/asm/thread_info.h
index ccba3b6..0f95084 100644
--- a/arch/frv/include/asm/thread_info.h
+++ b/arch/frv/include/asm/thread_info.h
@@ -64,9 +64,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 register struct thread_info *__current_thread_info asm("gr15");
 
diff --git a/arch/h8300/include/asm/thread_info.h b/arch/h8300/include/asm/thread_info.h
index 072b92c..0cdaa30 100644
--- a/arch/h8300/include/asm/thread_info.h
+++ b/arch/h8300/include/asm/thread_info.h
@@ -46,9 +46,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
diff --git a/arch/hexagon/include/asm/thread_info.h b/arch/hexagon/include/asm/thread_info.h
index b80fe1d..f41f9c6 100644
--- a/arch/hexagon/include/asm/thread_info.h
+++ b/arch/hexagon/include/asm/thread_info.h
@@ -84,9 +84,6 @@ struct thread_info {
 	.regs = NULL,			\
 }
 
-#define init_thread_info        (init_thread_union.thread_info)
-#define init_stack              (init_thread_union.stack)
-
 /* Tacky preprocessor trickery */
 #define	qqstr(s) qstr(s)
 #define qstr(s) #s
diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 49583c5..315c51f 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 c100d78..2dd7f51 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 1d172a4..64a1011 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 14ad79f..0b4c65a 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 8df9245..0000000
--- 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 58db59d..b0b2070 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>
 
diff --git a/arch/m32r/include/asm/thread_info.h b/arch/m32r/include/asm/thread_info.h
index b3a215b..ba00f10 100644
--- a/arch/m32r/include/asm/thread_info.h
+++ b/arch/m32r/include/asm/thread_info.h
@@ -56,9 +56,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
diff --git a/arch/m68k/include/asm/thread_info.h b/arch/m68k/include/asm/thread_info.h
index 9280355..015f1ca 100644
--- a/arch/m68k/include/asm/thread_info.h
+++ b/arch/m68k/include/asm/thread_info.h
@@ -41,8 +41,6 @@ struct thread_info {
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 }
 
-#define init_stack		(init_thread_union.stack)
-
 #ifndef __ASSEMBLY__
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
@@ -58,8 +56,6 @@ static inline struct thread_info *current_thread_info(void)
 }
 #endif
 
-#define init_thread_info	(init_thread_union.thread_info)
-
 /* entry.S relies on these definitions!
  * bits 0-7 are tested at every exception exit
  * bits 8-15 are also tested at syscall exit
diff --git a/arch/metag/include/asm/thread_info.h b/arch/metag/include/asm/thread_info.h
index 554f73a..a1a9c7f 100644
--- a/arch/metag/include/asm/thread_info.h
+++ b/arch/metag/include/asm/thread_info.h
@@ -74,9 +74,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the current stack pointer from C */
 register unsigned long current_stack_pointer asm("A0StP") __used;
 
diff --git a/arch/microblaze/include/asm/thread_info.h b/arch/microblaze/include/asm/thread_info.h
index e7e8954..9afe4b5 100644
--- a/arch/microblaze/include/asm/thread_info.h
+++ b/arch/microblaze/include/asm/thread_info.h
@@ -86,9 +86,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index 5e8927f..4993db4 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -49,9 +49,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* How to get the thread information struct from C.  */
 register struct thread_info *__current_thread_info __asm__("$28");
 
diff --git a/arch/mn10300/include/asm/thread_info.h b/arch/mn10300/include/asm/thread_info.h
index f5f90bb..1748a7b 100644
--- a/arch/mn10300/include/asm/thread_info.h
+++ b/arch/mn10300/include/asm/thread_info.h
@@ -79,8 +79,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
 #define init_uregs							\
 	((struct pt_regs *)						\
 	 ((unsigned long) init_stack + THREAD_SIZE - sizeof(struct pt_regs)))
diff --git a/arch/nios2/include/asm/thread_info.h b/arch/nios2/include/asm/thread_info.h
index d69c338..7349a4f 100644
--- a/arch/nios2/include/asm/thread_info.h
+++ b/arch/nios2/include/asm/thread_info.h
@@ -63,9 +63,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
diff --git a/arch/openrisc/include/asm/processor.h b/arch/openrisc/include/asm/processor.h
index 396d8f3..af31a9f 100644
--- a/arch/openrisc/include/asm/processor.h
+++ b/arch/openrisc/include/asm/processor.h
@@ -84,8 +84,6 @@ void start_thread(struct pt_regs *regs, unsigned long nip, unsigned long sp);
 void release_thread(struct task_struct *);
 unsigned long get_wchan(struct task_struct *p);
 
-#define init_stack      (init_thread_union.stack)
-
 #define cpu_relax()     barrier()
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/openrisc/include/asm/thread_info.h b/arch/openrisc/include/asm/thread_info.h
index c229aa6..5c15dfa 100644
--- a/arch/openrisc/include/asm/thread_info.h
+++ b/arch/openrisc/include/asm/thread_info.h
@@ -79,8 +79,6 @@ struct thread_info {
 	.ksp            = 0,                            \
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-
 /* how to get the thread information struct from C */
 register struct thread_info *current_thread_info_reg asm("r10");
 #define current_thread_info()   (current_thread_info_reg)
diff --git a/arch/parisc/include/asm/thread_info.h b/arch/parisc/include/asm/thread_info.h
index 598c8d6..28575754 100644
--- a/arch/parisc/include/asm/thread_info.h
+++ b/arch/parisc/include/asm/thread_info.h
@@ -25,9 +25,6 @@ struct thread_info {
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 }
 
-#define init_thread_info        (init_thread_union.thread_info)
-#define init_stack              (init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 #define current_thread_info()	((struct thread_info *)mfctl(30))
 
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index a264c3a..4a12c00 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -58,9 +58,6 @@ struct thread_info {
 	.flags =	0,			\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 #define THREAD_SIZE_ORDER	(THREAD_SHIFT - PAGE_SHIFT)
 
 /* how to get the thread information struct from C */
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 22c3536..f8fa1cd 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -64,8 +64,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_stack		(init_thread_union.stack)
-
 #endif /* !__ASSEMBLY__ */
 
 /*
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index 0880a37..25d6ec3 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -42,8 +42,6 @@ struct thread_info {
 	.flags		= 0,			\
 }
 
-#define init_stack		(init_thread_union.stack)
-
 void arch_release_task_struct(struct task_struct *tsk);
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 
diff --git a/arch/score/include/asm/thread_info.h b/arch/score/include/asm/thread_info.h
index ad51b56..bc4c7c9 100644
--- a/arch/score/include/asm/thread_info.h
+++ b/arch/score/include/asm/thread_info.h
@@ -58,9 +58,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* How to get the thread information struct from C. */
 register struct thread_info *__current_thread_info __asm__("r28");
 #define current_thread_info()	__current_thread_info
diff --git a/arch/sh/include/asm/thread_info.h b/arch/sh/include/asm/thread_info.h
index becb798..cf5c792 100644
--- a/arch/sh/include/asm/thread_info.h
+++ b/arch/sh/include/asm/thread_info.h
@@ -63,9 +63,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the current stack pointer from C */
 register unsigned long current_stack_pointer asm("r15") __used;
 
diff --git a/arch/sparc/include/asm/thread_info_32.h b/arch/sparc/include/asm/thread_info_32.h
index febaaeb..548b366 100644
--- a/arch/sparc/include/asm/thread_info_32.h
+++ b/arch/sparc/include/asm/thread_info_32.h
@@ -63,9 +63,6 @@ struct thread_info {
 	.preempt_count	=	INIT_PREEMPT_COUNT,	\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 register struct thread_info *current_thread_info_reg asm("g6");
 #define current_thread_info()   (current_thread_info_reg)
diff --git a/arch/sparc/include/asm/thread_info_64.h b/arch/sparc/include/asm/thread_info_64.h
index caf9153..f7e7b0b 100644
--- a/arch/sparc/include/asm/thread_info_64.h
+++ b/arch/sparc/include/asm/thread_info_64.h
@@ -120,9 +120,6 @@ struct thread_info {
 	.preempt_count	=	INIT_PREEMPT_COUNT,	\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 register struct thread_info *current_thread_info_reg asm("g6");
 #define current_thread_info()	(current_thread_info_reg)
diff --git a/arch/tile/include/asm/thread_info.h b/arch/tile/include/asm/thread_info.h
index b7659b8..2adcacd 100644
--- a/arch/tile/include/asm/thread_info.h
+++ b/arch/tile/include/asm/thread_info.h
@@ -59,9 +59,6 @@ struct thread_info {
 	.align_ctl	= 0,			\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 #endif /* !__ASSEMBLY__ */
 
 #if PAGE_SIZE < 8192
diff --git a/arch/um/include/asm/processor-generic.h b/arch/um/include/asm/processor-generic.h
index 86942a4..b58b746 100644
--- a/arch/um/include/asm/processor-generic.h
+++ b/arch/um/include/asm/processor-generic.h
@@ -58,7 +58,10 @@ static inline void release_thread(struct task_struct *task)
 {
 }
 
-#define init_stack	(init_thread_union.stack)
+static inline void mm_copy_segments(struct mm_struct *from_mm,
+				    struct mm_struct *new_mm)
+{
+}
 
 /*
  * User space process size: 3GB (default).
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index 9300f76..4eecd96 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -6,6 +6,9 @@
 #ifndef __UM_THREAD_INFO_H
 #define __UM_THREAD_INFO_H
 
+#define THREAD_SIZE_ORDER CONFIG_KERNEL_STACK_ORDER
+#define THREAD_SIZE ((1 << CONFIG_KERNEL_STACK_ORDER) * PAGE_SIZE)
+
 #ifndef __ASSEMBLY__
 
 #include <asm/types.h>
@@ -37,10 +40,6 @@ struct thread_info {
 	.real_thread = NULL,			\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
-#define THREAD_SIZE ((1 << CONFIG_KERNEL_STACK_ORDER) * PAGE_SIZE)
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
@@ -53,8 +52,6 @@ static inline struct thread_info *current_thread_info(void)
 	return ti;
 }
 
-#define THREAD_SIZE_ORDER CONFIG_KERNEL_STACK_ORDER
-
 #endif
 
 #define TIF_SYSCALL_TRACE	0	/* syscall trace active */
diff --git a/arch/um/include/asm/vmlinux.lds.h b/arch/um/include/asm/vmlinux.lds.h
new file mode 100644
index 0000000..149494a
--- /dev/null
+++ b/arch/um/include/asm/vmlinux.lds.h
@@ -0,0 +1,2 @@
+#include <asm/thread_info.h>
+#include <asm-generic/vmlinux.lds.h>
diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
index d417e38..5568cf8 100644
--- a/arch/um/kernel/dyn.lds.S
+++ b/arch/um/kernel/dyn.lds.S
@@ -1,5 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#include <asm-generic/vmlinux.lds.h>
+#include <asm/vmlinux.lds.h>
 #include <asm/page.h>
 
 OUTPUT_FORMAT(ELF_FORMAT)
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index f433690..a818cce 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -54,7 +54,7 @@ struct cpuinfo_um boot_cpu_data = {
 
 union thread_union cpu0_irqstack
 	__attribute__((__section__(".data..init_irqstack"))) =
-		{ INIT_THREAD_INFO(init_task) };
+		{ .thread_info = INIT_THREAD_INFO(init_task) };
 
 /* Changed in setup_arch, which is called in early boot */
 static char host_info[(__NEW_UTS_LEN + 1) * 5];
diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
index 3d6ed6b..36b07ec 100644
--- a/arch/um/kernel/uml.lds.S
+++ b/arch/um/kernel/uml.lds.S
@@ -1,5 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#include <asm-generic/vmlinux.lds.h>
+#include <asm/vmlinux.lds.h>
 #include <asm/page.h>
 
 OUTPUT_FORMAT(ELF_FORMAT)
diff --git a/arch/unicore32/include/asm/thread_info.h b/arch/unicore32/include/asm/thread_info.h
index e79ad6d..5fb728f 100644
--- a/arch/unicore32/include/asm/thread_info.h
+++ b/arch/unicore32/include/asm/thread_info.h
@@ -87,9 +87,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,					\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /*
  * how to get the thread information struct from C
  */
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 0022333..d25a638 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -62,8 +62,6 @@ struct thread_info {
 	.flags		= 0,			\
 }
 
-#define init_stack		(init_thread_union.stack)
-
 #else /* !__ASSEMBLY__ */
 
 #include <asm/asm-offsets.h>
diff --git a/arch/xtensa/include/asm/thread_info.h b/arch/xtensa/include/asm/thread_info.h
index 7be2400..2ccd375 100644
--- a/arch/xtensa/include/asm/thread_info.h
+++ b/arch/xtensa/include/asm/thread_info.h
@@ -77,9 +77,6 @@ struct thread_info {
 	.addr_limit	= KERNEL_DS,		\
 }
 
-#define init_thread_info	(init_thread_union.thread_info)
-#define init_stack		(init_thread_union.stack)
-
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index ee8b707..a564b83 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -268,7 +268,11 @@
 #define INIT_TASK_DATA(align)						\
 	. = ALIGN(align);						\
 	VMLINUX_SYMBOL(__start_init_task) = .;				\
+	VMLINUX_SYMBOL(init_thread_union) = .;				\
+	VMLINUX_SYMBOL(init_stack) = .;					\
 	*(.data..init_task)						\
+	*(.data..init_thread_info)					\
+	. = VMLINUX_SYMBOL(__start_init_task) + THREAD_SIZE;		\
 	VMLINUX_SYMBOL(__end_init_task) = .;
 
 /*
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 6a53262..30a89b9 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -304,5 +304,8 @@ extern struct cred init_cred;
 /* Attach to the init_task data structure for proper alignment */
 #define __init_task_data __attribute__((__section__(".data..init_task")))
 
+/* Attach to the thread_info data structure for proper alignment */
+#define __init_thread_info __attribute__((__section__(".data..init_thread_info")))
+
 
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d258826..68a504f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1446,12 +1446,21 @@ extern void ia64_set_curr_task(int cpu, struct task_struct *p);
 void yield(void);
 
 union thread_union {
+#ifndef CONFIG_ARCH_TASK_STRUCT_ON_STACK
+	struct task_struct task;
+#endif
 #ifndef CONFIG_THREAD_INFO_IN_TASK
 	struct thread_info thread_info;
 #endif
 	unsigned long stack[THREAD_SIZE/sizeof(long)];
 };
 
+#ifndef CONFIG_THREAD_INFO_IN_TASK
+extern struct thread_info init_thread_info;
+#endif
+
+extern unsigned long init_stack[THREAD_SIZE / sizeof(unsigned long)];
+
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 static inline struct thread_info *task_thread_info(struct task_struct *task)
 {
diff --git a/init/Makefile b/init/Makefile
index 1dbb237..a3e5ce2 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -13,9 +13,7 @@ obj-$(CONFIG_BLK_DEV_INITRD)   += initramfs.o
 endif
 obj-$(CONFIG_GENERIC_CALIBRATE_DELAY) += calibrate.o
 
-ifneq ($(CONFIG_ARCH_INIT_TASK),y)
 obj-y                          += init_task.o
-endif
 
 mounts-y			:= do_mounts.o
 mounts-$(CONFIG_BLK_DEV_RAM)	+= do_mounts_rd.o
diff --git a/init/init_task.c b/init/init_task.c
index 9325fee..2285aa4 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
-};