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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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