[PATCH 15/18] x86/asm/64: Remove all remaining direct thread_struct::sp0 reads

Andy Lutomirski
2017-10-26T08:29:03Z

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@kernel.org>
---
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(-)

diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index f3fa19925ae1..d9bb491ba45c 100644
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -83,4 +83,10 @@ static inline void refresh_sysenter_cs(struct thread_struct *thread)
}
#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 */
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 8bdf9aaa92a0..070bdaaa7c86 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -286,7 +286,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* Reload esp0 and cpu_current_top_of_stack. This changes
* current_thread_info().
*/
- load_sp0(next->sp0);
+ update_sp0(next_p);
refresh_sysenter_cs(next); /* in case prev or next is vm86 */
this_cpu_write(cpu_current_top_of_stack,
(unsigned long)task_stack_page(next_p) +
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 2124304fb77a..45e380958392 100644
--- 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, struct task_struct *next_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
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 0f1d92cd20ad..a7b44c75c642 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -148,7 +148,7 @@ void save_v86_state(struct kernel_vm86_regs *regs, int retval)
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();
@@ -373,7 +373,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
refresh_sysenter_cs(&tsk->thread);
}

- load_sp0(tsk->thread.sp0);
+ update_sp0(tsk);
preempt_enable();

if (vm86->flags & VM86_SCREEN_BITMAP)
--
2.13.6