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    Subject[PATCH 3/6] signal x86: Merge EFLAGS bit clearing into single statement
    Date
    Merging EFLAGS bit clearing into a single statement, to
    ensure EFLAGS bits being cleared in single instruction.

    Signed-off-by: Jiri Olsa <jolsa@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Cc: Stephane Eranian <eranian@google.com>
    ---
    arch/x86/kernel/signal.c | 10 +++-------
    1 file changed, 3 insertions(+), 7 deletions(-)

    diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
    index cb12fc9..cf91358 100644
    --- a/arch/x86/kernel/signal.c
    +++ b/arch/x86/kernel/signal.c
    @@ -662,21 +662,17 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
    if (!failed) {
    /*
    * Clear the direction flag as per the ABI for function entry.
    - */
    - regs->flags &= ~X86_EFLAGS_DF;
    - /*
    + *
    * Clear RF when entering the signal handler, because
    * it might disable possible debug exception from the
    * signal handler.
    - */
    - regs->flags &= ~X86_EFLAGS_RF;
    - /*
    + *
    * Clear TF when entering the signal handler, but
    * notify any tracer that was single-stepping it.
    * The tracer may want to single-step inside the
    * handler too.
    */
    - regs->flags &= ~X86_EFLAGS_TF;
    + regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
    }
    signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));
    }
    --
    1.7.11.7


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