On 03/01/2013 10:11 AM, Jiri Olsa wrote:
> Clearing RF EFLAGS bit for signal handler. The reason is,
> that this flag is set by debug exception code to prevent
> the recursive exception entry.
>
> Leaving it set for signal handler might prevent debug
> exception of the signal handler itself.
>
> diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
> index b6fe116..e273571 100644
> --- a/arch/x86/kernel/signal.c
> +++ b/arch/x86/kernel/signal.c
> @@ -726,6 +726,13 @@ handle_signal(unsigned long sig, siginfo_t *info, struct
> k_sigaction *ka,
> regs->flags &= ~X86_EFLAGS_DF;
>
> /*
> + * Clear RF when entering the signal handler, because
> + * it might disable possible debug exception from the
> + * signal handler.
> + */
> + regs->flags &= ~X86_EFLAGS_RF;
> +
> + /*
> * Clear TF when entering the signal handler, but
> * notify any tracer that was single-stepping it.
> * The tracer may want to single-step inside the
>
Makes sense. However, can you combine all the flags-clearing into one
statement while you are at it?
-hpa
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