Messages in this thread | | | Date | Mon, 24 Jul 2017 12:21:40 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86/debug: Handle warnings before the notifier chain |
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On Mon, Jul 24, 2017 at 01:04:28PM +0300, Alexander Shishkin wrote: > Commit > > 9a93848fe787 ("x86/debug: Implement __WARN() using UD0") > > turned warnings into UD0, but the fixup code only runs after the > notify_die() chain. This is a problem, in particular, with kgdb, > which kicks in as if it was a BUG(). > > Fix this by running the fixup code before the notifier chain in > the invalid op handler path.
So arguable it might be nice to have kgdb trap on a WARN, but it treating it as a BUG is obviously undesirable.
Jason, what would you want kgdb to do here?
> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> > Cc: Arjan van de Ven <arjan@linux.intel.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Richard Weinberger <richard.weinberger@gmail.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: linux-kernel@vger.kernel.org > --- > arch/x86/kernel/traps.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index bf54309b85..b2157d4a53 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -221,9 +221,6 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str, > if (fixup_exception(regs, trapnr)) > return 0; > > - if (fixup_bug(regs, trapnr)) > - return 0; > - > tsk->thread.error_code = error_code; > tsk->thread.trap_nr = trapnr; > die(str, regs, error_code); > @@ -304,6 +301,13 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str, > > RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > > + /* > + * WARN*()s end up here; fix them up before we call the > + * notifier chain. > + */ > + if (!user_mode(regs) && fixup_bug(regs, trapnr)) > + return; > + > if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != > NOTIFY_STOP) { > cond_local_irq_enable(regs); > -- > 2.13.2 >
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