On 03/18, Sudeep Holla wrote:
>
> --- 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;
> + }
>
> - if (unlikely(flags & _TIF_SYSCALL_EMU)) {
> - /*
> - * 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;
> - }
> + flags = READ_ONCE(current_thread_info()->flags) & _TIF_SYSCALL_TRACE;
Why do we need READ_ONCE() with this change?
And now that we change a single bit "flags" doesn't look like a good name.
Again, to me this patch just makes the code look worse. Honestly, I don't
think that the new (badly named) ptrace_syscall_enter() hook makes any sense.
Oleg.
