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    Subject[tip:x86/asm] x86/entry: Use pt_regs_to_thread_info() in syscall entry tracing
    Commit-ID:  dd636071c3d8044c802b7a365e9934724a929530
    Gitweb: http://git.kernel.org/tip/dd636071c3d8044c802b7a365e9934724a929530
    Author: Andy Lutomirski <luto@kernel.org>
    AuthorDate: Mon, 5 Oct 2015 17:48:22 -0700
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Fri, 9 Oct 2015 09:41:12 +0200

    x86/entry: Use pt_regs_to_thread_info() in syscall entry tracing

    It generates simpler and faster code than current_thread_info().

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-kernel@vger.kernel.org
    Link: http://lkml.kernel.org/r/a3b6633e7dcb9f673c1b619afae602d29d27d2cf.1444091585.git.luto@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/entry/common.c | 22 +++++++++++-----------
    1 file changed, 11 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
    index 778ca70..d087421 100644
    --- a/arch/x86/entry/common.c
    +++ b/arch/x86/entry/common.c
    @@ -30,6 +30,13 @@
    #define CREATE_TRACE_POINTS
    #include <trace/events/syscalls.h>

    +static struct thread_info *pt_regs_to_thread_info(struct pt_regs *regs)
    +{
    + unsigned long top_of_stack =
    + (unsigned long)(regs + 1) + TOP_OF_KERNEL_STACK_PADDING;
    + return (struct thread_info *)(top_of_stack - THREAD_SIZE);
    +}
    +
    #ifdef CONFIG_CONTEXT_TRACKING
    /* Called on entry from user mode with IRQs off. */
    __visible void enter_from_user_mode(void)
    @@ -68,14 +75,14 @@ static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
    */
    unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
    {
    + struct thread_info *ti = pt_regs_to_thread_info(regs);
    unsigned long ret = 0;
    u32 work;

    if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
    BUG_ON(regs != task_pt_regs(current));

    - work = ACCESS_ONCE(current_thread_info()->flags) &
    - _TIF_WORK_SYSCALL_ENTRY;
    + work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;

    #ifdef CONFIG_CONTEXT_TRACKING
    /*
    @@ -157,9 +164,9 @@ unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
    long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
    unsigned long phase1_result)
    {
    + struct thread_info *ti = pt_regs_to_thread_info(regs);
    long ret = 0;
    - u32 work = ACCESS_ONCE(current_thread_info()->flags) &
    - _TIF_WORK_SYSCALL_ENTRY;
    + u32 work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;

    if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
    BUG_ON(regs != task_pt_regs(current));
    @@ -211,13 +218,6 @@ long syscall_trace_enter(struct pt_regs *regs)
    return syscall_trace_enter_phase2(regs, arch, phase1_result);
    }

    -static struct thread_info *pt_regs_to_thread_info(struct pt_regs *regs)
    -{
    - unsigned long top_of_stack =
    - (unsigned long)(regs + 1) + TOP_OF_KERNEL_STACK_PADDING;
    - return (struct thread_info *)(top_of_stack - THREAD_SIZE);
    -}
    -
    /* Called with IRQs disabled. */
    __visible void prepare_exit_to_usermode(struct pt_regs *regs)
    {

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