On Thu, Aug 20, 2020 at 6:53 AM Peter Zijlstra <pet...@infradead.org> wrote:
>
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> ---
> arch/x86/kernel/traps.c | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -820,18 +820,6 @@ static void handle_debug(struct pt_regs
> goto out;
> }
>
> - if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
> - /*
> - * Historical junk that used to handle SYSENTER
> single-stepping.
> - * This should be unreachable now. If we survive for a while
> - * without anyone hitting this warning, we'll turn this into
> - * an oops.
> - */
> - tsk->thread.debugreg6 &= ~DR_STEP;
> - set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
> - regs->flags &= ~X86_EFLAGS_TF;
> - }
> -
> si_code = get_si_code(tsk->thread.debugreg6);
> if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp)
> send_sigtrap(regs, 0, si_code);
> @@ -874,6 +862,18 @@ static __always_inline void exc_debug_ke
> if (kprobe_debug_handler(regs))
> goto out;
>
> + if (WARN_ON_ONCE(dr6 & DR_STEP)) {
> + /*
> + * Historical junk that used to handle SYSENTER
> single-stepping.
> + * This should be unreachable now. If we survive for a while
> + * without anyone hitting this warning, we'll turn this into
> + * an oops.
> + */
> + dr6 &= ~DR_STEP;
> + set_thread_flag(TIF_SINGLESTEP);
> + regs->flags &= ~X86_EFLAGS_TF;
> + }
> +
> handle_debug(regs, dr6, false);
>
> out:
Can this be removed or changed to a BUG()? The warning has been there
since 2016 and nobody has apparently complained about it.
--
Brian Gerst
