Messages in this thread | | | Date | Fri, 01 Mar 2013 10:57:50 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 2/5] signal x86: Clear RF EFLAGS bit for signal handler |
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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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