Re: [PATCH 1/2] arm64: traps: Support for registering SError hooks

[Mikko Perttunen <cyndis@xxxxxxxx>]

On 6/17/21 2:46 PM, Mark Rutland wrote:
> On Thu, Jun 17, 2021 at 01:40:52PM +0300, Mikko Perttunen wrote:
> > Add the ability for drivers to register SError hooks to be run
> > on a fatal SError interrupt. This allows printing of system-specific
> > error information to aid with debugging.
> >
> > Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
>
> Can't you dump information unconditionally in a panic notifier?
>
> That wouldn't require any new infrastructure.

That does indeed work also, thanks for the tip! Will change to use those.

Thanks,
Mikko

> Thanks,
> Mark.
>
> > ---
> >   arch/arm64/include/asm/traps.h |  6 ++++++
> >   arch/arm64/kernel/traps.c      | 20 ++++++++++++++++++++
> >   2 files changed, 26 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
> > index 54f32a0675df..054fecfa22f0 100644
> > --- a/arch/arm64/include/asm/traps.h
> > +++ b/arch/arm64/include/asm/traps.h
> > @@ -22,8 +22,14 @@ struct undef_hook {
> >   	int (*fn)(struct pt_regs *regs, u32 instr);
> >   };
> >   
> > +struct serror_hook {
> > +	struct list_head node;
> > +	void (*fn)(void);
> > +};
> > +
> >   void register_undef_hook(struct undef_hook *hook);
> >   void unregister_undef_hook(struct undef_hook *hook);
> > +void register_serror_hook(struct serror_hook *hook);
> >   void force_signal_inject(int signal, int code, unsigned long address, unsigned int err);
> >   void arm64_notify_segfault(unsigned long addr);
> >   void arm64_force_sig_fault(int signo, int code, unsigned long far, const char *str);
> > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> > index 273066279bb5..02dbaab71ea3 100644
> > --- a/arch/arm64/kernel/traps.c
> > +++ b/arch/arm64/kernel/traps.c
> > @@ -890,8 +890,23 @@ void panic_bad_stack(struct pt_regs *regs, unsigned int esr, unsigned long far)
> >   }
> >   #endif
> >   
> > +static LIST_HEAD(serror_hook);
> > +static DEFINE_RAW_SPINLOCK(serror_lock);
> > +
> > +void register_serror_hook(struct serror_hook *hook)
> > +{
> > +	unsigned long flags;
> > +
> > +	raw_spin_lock_irqsave(&serror_lock, flags);
> > +	list_add(&hook->node, &serror_hook);
> > +	raw_spin_unlock_irqrestore(&serror_lock, flags);
> > +}
> > +
> >   void __noreturn arm64_serror_panic(struct pt_regs *regs, u32 esr)
> >   {
> > +	struct serror_hook *hook;
> > +	unsigned long flags;
> > +
> >   	console_verbose();
> >   
> >   	pr_crit("SError Interrupt on CPU%d, code 0x%08x -- %s\n",
> > @@ -899,6 +914,11 @@ void __noreturn arm64_serror_panic(struct pt_regs *regs, u32 esr)
> >   	if (regs)
> >   		__show_regs(regs);
> >   
> > +	raw_spin_lock_irqsave(&serror_lock, flags);
> > +	list_for_each_entry(hook, &serror_hook, node)
> > +		hook->fn();
> > +	raw_spin_unlock_irqrestore(&serror_lock, flags);
> > +
> >   	nmi_panic(regs, "Asynchronous SError Interrupt");
> >   
> >   	cpu_park_loop();
> > --
> > 2.30.1