[PATCH 4.14 051/159] x86/entry/64: Remove all remaining direct thread_struct::sp0 reads

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@xxxxxxxxxx>

commit 46f5a10a721ce8dce8cc8fe55279b49e1c6b3288 upstream.

The only remaining readers in context switch code or vm86(), and
they all just want to update TSS.sp0 to match the current task.
Replace them all with a new helper update_sp0().

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Cc: Borislav Petkov <bpetkov@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/2d231687f4ff288c9d9e98d7861b7df374246ac3.1509609304.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/include/asm/switch_to.h |    6 ++++++
 arch/x86/kernel/process_32.c     |    2 +-
 arch/x86/kernel/process_64.c     |    2 +-
 arch/x86/kernel/vm86_32.c        |    4 ++--
 4 files changed, 10 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -85,4 +85,10 @@ static inline void refresh_sysenter_cs(s
 }
 #endif
 
+/* This is used when switching tasks or entering/exiting vm86 mode. */
+static inline void update_sp0(struct task_struct *task)
+{
+	load_sp0(task->thread.sp0);
+}
+
 #endif /* _ASM_X86_SWITCH_TO_H */
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -287,7 +287,7 @@ __switch_to(struct task_struct *prev_p,
 	 * current_thread_info().  Refresh the SYSENTER configuration in
 	 * case prev or next is vm86.
 	 */
-	load_sp0(next->sp0);
+	update_sp0(next_p);
 	refresh_sysenter_cs(next);
 	this_cpu_write(cpu_current_top_of_stack,
 		       (unsigned long)task_stack_page(next_p) +
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -465,7 +465,7 @@ __switch_to(struct task_struct *prev_p,
 	this_cpu_write(current_task, next_p);
 
 	/* Reload sp0. */
-	load_sp0(next->sp0);
+	update_sp0(next_p);
 
 	/*
 	 * Now maybe reload the debug registers and handle I/O bitmaps
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -149,7 +149,7 @@ void save_v86_state(struct kernel_vm86_r
 	preempt_disable();
 	tsk->thread.sp0 = vm86->saved_sp0;
 	tsk->thread.sysenter_cs = __KERNEL_CS;
-	load_sp0(tsk->thread.sp0);
+	update_sp0(tsk);
 	refresh_sysenter_cs(&tsk->thread);
 	vm86->saved_sp0 = 0;
 	preempt_enable();
@@ -374,7 +374,7 @@ static long do_sys_vm86(struct vm86plus_
 		refresh_sysenter_cs(&tsk->thread);
 	}
 
-	load_sp0(tsk->thread.sp0);
+	update_sp0(tsk);
 	preempt_enable();
 
 	if (vm86->flags & VM86_SCREEN_BITMAP)