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    SubjectRe: [PATCH v2 4/6] powerpc: use common ptrace_syscall_enter hook to handle _TIF_SYSCALL_EMU
    On Mon, Mar 18, 2019 at 10:49:23AM +0000, Sudeep Holla wrote:
    > Now that we have a new hook ptrace_syscall_enter that can be called from
    > syscall entry code and it handles PTRACE_SYSEMU in generic code, we
    > can do some cleanup using the same in do_syscall_trace_enter.
    >
    > Cc: Oleg Nesterov <oleg@redhat.com>
    > Cc: Paul Mackerras <paulus@samba.org>
    > Cc: Michael Ellerman <mpe@ellerman.id.au>
    > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
    > ---
    > arch/powerpc/kernel/ptrace.c | 48 ++++++++++++++++--------------------
    > 1 file changed, 21 insertions(+), 27 deletions(-)
    >
    > diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
    > index 2e2183b800a8..05579a5dcb12 100644
    > --- a/arch/powerpc/kernel/ptrace.c
    > +++ b/arch/powerpc/kernel/ptrace.c
    > @@ -3278,35 +3278,29 @@ long do_syscall_trace_enter(struct pt_regs *regs)
    >
    > user_exit();
    >
    > - flags = READ_ONCE(current_thread_info()->flags) &
    > - (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE);
    > -
    > - if (flags) {
    > - int rc = tracehook_report_syscall_entry(regs);
    > + if (unlikely(ptrace_syscall_enter(regs))) {
    > + /*
    > + * A nonzero return code from tracehook_report_syscall_entry()
    > + * tells us to prevent the syscall execution, but we are not
    > + * going to execute it anyway.
    > + *
    > + * Returning -1 will skip the syscall execution. We want to
    > + * avoid clobbering any registers, so we don't goto the skip
    > + * label below.
    > + */
    > + return -1;
    > + }

    This comment is out of sync with the changed code.


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