linux-kernel - Re: [RFC PATCH 4/5] x86: panic on detection of stack overflow

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Date:	Thu, 10 Nov 2011 14:59:10 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Randy Dunlap <rdunlap@...otime.net>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [RFC PATCH 4/5] x86: panic on detection of stack overflow

On Mon, Nov 07, 2011 at 02:53:08PM +0900, Mitsuo Hayasaka wrote:
> Currently, messages are just output on the detection of stack overflow,
> which is not sufficient for enterprise systems since it may corrupt data.
> To enhance reliability, it is required to stop the systems.

Why not just make the stack_overflow_check() return a value that it should
not handle the IRQ and perhaps silence (disable_chip) the IRQ line?

That will still let the system run, albeit .. without certain parts
not working right.. So perhaps re-enable the chip later on?

Or is there really no way to recover from this?
> 
> This patch causes a panic according to a sysctl parameter
> panic_on_stackoverflow when detecting it. It is disabled by default.
> 
> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> ---
> 
>  arch/x86/kernel/irq_32.c |    2 ++
>  arch/x86/kernel/irq_64.c |   16 +++++++++++-----
>  2 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
> index 7209070..e16e99eb 100644
> --- a/arch/x86/kernel/irq_32.c
> +++ b/arch/x86/kernel/irq_32.c
> @@ -43,6 +43,8 @@ static void print_stack_overflow(void)
>  {
>  	printk(KERN_WARNING "low stack detected by irq handler\n");
>  	dump_stack();
> +	if (sysctl_panic_on_stackoverflow)
> +		panic("low stack detected by irq handler - check messages\n");
>  }
>  
>  #else
> diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
> index d720813..f7baedd 100644
> --- a/arch/x86/kernel/irq_64.c
> +++ b/arch/x86/kernel/irq_64.c
> @@ -69,14 +69,20 @@ static inline void stack_overflow_check(struct pt_regs *regs)
>  		current->comm, curbase, regs->sp,
>  		irq_stack_top, irq_stack_bottom,
>  		estack_top, estack_bottom);
> +	if (sysctl_panic_on_stackoverflow)
> +		panic("low stack detected by irq handler - check messages\n");
>  #else
> -	WARN_ONCE(regs->sp >= curbase &&
> -		  regs->sp <= curbase + THREAD_SIZE &&
> -		  regs->sp <  curbase + sizeof(struct thread_info) +
> -					sizeof(struct pt_regs) + 128,
> -
> +	if (regs->sp >= curbase &&
> +		regs->sp <= curbase + THREAD_SIZE &&
> +		regs->sp <  curbase + sizeof(struct thread_info) +
> +					sizeof(struct pt_regs) + 128) {
> +		WARN_ONCE(1,
>  		  "do_IRQ: %s near stack overflow (cur:%Lx,sp:%lx)\n",
>  			current->comm, curbase, regs->sp);
> +		if (sysctl_panic_on_stackoverflow)
> +			panic("low stack detected by irq handler - check messages\n");
> +	}
> +
>  #endif /* CONFIG_DEBUG_STACKOVERFLOW_DETAIL */
>  #endif
>  }
> 
> --
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