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    Subject[PATCH 4.14 051/159] x86/entry/64: Remove all remaining direct thread_struct::sp0 reads
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Andy Lutomirski <luto@kernel.org>

    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@kernel.org>
    Reviewed-by: Borislav Petkov <bp@suse.de>
    Cc: Borislav Petkov <bpetkov@suse.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/2d231687f4ff288c9d9e98d7861b7df374246ac3.1509609304.git.luto@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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(-)

    --- 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)

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