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    SubjectRe: [PATCH v4 2/4] x86: simplify _TIF_SYSCALL_EMU handling
    On Thu, May 23, 2019 at 10:06:16AM +0100, Sudeep Holla wrote:
    > The usage of emulated/_TIF_SYSCALL_EMU flags in syscall_trace_enter
    > seems to be bit overcomplicated than required. Let's simplify it.
    >
    > Cc: Andy Lutomirski <luto@kernel.org>
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: Borislav Petkov <bp@alien8.de>
    > Acked-by: Oleg Nesterov <oleg@redhat.com>
    > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
    > ---
    > arch/x86/entry/common.c | 17 ++++++-----------
    > 1 file changed, 6 insertions(+), 11 deletions(-)
    >
    > diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
    > index a986b3c8294c..0a61705d62ec 100644
    > --- a/arch/x86/entry/common.c
    > +++ b/arch/x86/entry/common.c
    > @@ -72,23 +72,18 @@ static long syscall_trace_enter(struct pt_regs *regs)
    >
    > struct thread_info *ti = current_thread_info();
    > unsigned long ret = 0;
    > - bool emulated = false;
    > u32 work;
    >
    > if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
    > BUG_ON(regs != task_pt_regs(current));
    >
    > - work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
    > + work = READ_ONCE(ti->flags);
    >
    > - if (unlikely(work & _TIF_SYSCALL_EMU))
    > - emulated = true;
    > -
    > - if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
    > - tracehook_report_syscall_entry(regs))
    > - return -1L;
    > -
    > - if (emulated)
    > - return -1L;
    > + if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
    > + ret = tracehook_report_syscall_entry(regs);
    > + if (ret || (work & _TIF_SYSCALL_EMU))
    > + return -1L;
    > + }

    Andy (or the other x86 folk), could I please get an ack on this patch? I
    plan to queue this series through the arm64 tree (though if you want to
    merge it separately, it looks like an independent clean-up with no
    dependencies on the other patches).

    Thanks.

    --
    Catalin

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