x86/entry: Merge thunk_64.S and thunk_32.S into thunk.S

The code in thunk_64.S and thunk_32.S are exactly the same except for
the comments. Merge them in to thunk.S.

And since thunk_32.S was originated from thunk_64.S, the new merged
thunk.S is actually renamed from thunk_64.S.
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240407090558.3395-9-jiangshanlai@gmail.com

arch/x86/entry/Makefile

@@ -17,7 +17,7 @@ obj-y				+= common.o
 obj-y				+= vdso/
 obj-y				+= vsyscall/
 
-obj-$(CONFIG_PREEMPTION)	+= thunk_$(BITS).o
+obj-$(CONFIG_PREEMPTION)	+= thunk.o
 CFLAGS_entry_fred.o		+= -fno-stack-protector
 CFLAGS_REMOVE_entry_fred.o	+= -pg $(CC_FLAGS_FTRACE)
 obj-$(CONFIG_X86_FRED)		+= entry_64_fred.o entry_fred.o

arch/x86/entry/thunk_32.S

-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Trampoline to trace irqs off. (otherwise CALLER_ADDR1 might crash)
- * Copyright 2008 by Steven Rostedt, Red Hat, Inc
- *  (inspired by Andi Kleen's thunk_64.S)
- */
-
-#include <linux/export.h>
-#include <linux/linkage.h>
-#include <asm/asm.h>
-
-#include "calling.h"
-
-THUNK preempt_schedule_thunk, preempt_schedule
-THUNK preempt_schedule_notrace_thunk, preempt_schedule_notrace
-EXPORT_SYMBOL(preempt_schedule_thunk)
-EXPORT_SYMBOL(preempt_schedule_notrace_thunk)
-