[PATCH V6 12/49] x86/entry: Add arch/x86/entry/entry64.c for C entry code

[Lai Jiangshan <jiangshanlai@gmail.com>]

From: Lai Jiangshan <laijs@linux.alibaba.com>

Add a C file "entry64.c" to deposit C entry code for traps and faults
which will be as the same logic as the existing ASM code in entry_64.S.

The file is as low level as entry_64.S and its code can be running in
the environments that the GS base is user controlled value, or the CR3
is PTI user CR3 or both.

All the code in this file should not be instrumentable.  Many instrument
facilities can be disabled by per-function attributes which are included
in __noinstr_section.  But stack-protector can not be disabled function-
granularly by many versions of GCC that can be supported for compiling
the kernel.  So stack-protector is disabled for the whole file in Makefile.

It is prepared for later patches that implement C version of the entry
code in entry64.c.

Suggested-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
 arch/x86/entry/Makefile  |  3 ++-
 arch/x86/entry/entry64.c | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/entry/entry64.c

diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile
index 7fec5dcf6438..792f7009ff32 100644
--- a/arch/x86/entry/Makefile
+++ b/arch/x86/entry/Makefile
@@ -10,13 +10,14 @@ KCOV_INSTRUMENT := n
 CFLAGS_REMOVE_common.o		= $(CC_FLAGS_FTRACE)
 
 CFLAGS_common.o			+= -fno-stack-protector
+CFLAGS_entry64.o		+= -fno-stack-protector
 
 obj-y				:= entry_$(BITS).o thunk_$(BITS).o syscall_$(BITS).o
 obj-y				+= common.o
+obj-$(CONFIG_X86_64)		+= entry64.o
 
 obj-y				+= vdso/
 obj-y				+= vsyscall/
 
 obj-$(CONFIG_IA32_EMULATION)	+= entry_64_compat.o syscall_32.o
 obj-$(CONFIG_X86_X32_ABI)	+= syscall_x32.o
-
diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c
new file mode 100644
index 000000000000..762595603ce7
--- /dev/null
+++ b/arch/x86/entry/entry64.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 2000, 2001, 2002  Andi Kleen SuSE Labs
+ *  Copyright (C) 2000  Pavel Machek <pavel@suse.cz>
+ *  Copyright (C) 2021 Lai Jiangshan, Alibaba
+ *
+ * Handle entries and exits for hardware traps and faults.
+ *
+ * It is as low level as entry_64.S and its code can be running in the
+ * environments that the GS base is user controlled value, or the CR3
+ * is PTI user CR3 or both.
+ */
+#include <asm/traps.h>
-- 
2.19.1.6.gb485710b