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

[Mark Rutland]

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.

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
>