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

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Message-ID: <241fa310-b13f-0444-0fa6-ca448a875917@kapsi.fi>
Date:   Thu, 17 Jun 2021 15:03:55 +0300
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Mark Rutland <mark.rutland@....com>,
        Mikko Perttunen <mperttunen@...dia.com>
Cc:     catalin.marinas@....com, will@...nel.org, thierry.reding@...il.com,
        jonathanh@...dia.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 1/2] arm64: traps: Support for registering SError hooks

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@...dia.com>
> 
> 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
>>