Re: [RFC PATCH 3/5] x86: add a sysctl parameter to panic on stack overflow

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Nov 07, 2011 at 02:53:01PM +0900, Mitsuo Hayasaka wrote:
> This patch adds kernel.panic_on_stackoverflow sysctl parameter,
> which can cause a panic when detecting the stack overflow.

Why would we want to panic?
> 
> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
> Cc: Randy Dunlap <rdunlap@xenotime.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
> 
>  Documentation/sysctl/kernel.txt |   13 +++++++++++++
>  arch/x86/kernel/irq_64.c        |    2 ++
>  include/linux/kernel.h          |    1 +
>  include/linux/sysctl.h          |    1 +
>  kernel/sysctl.c                 |    9 +++++++++
>  kernel/sysctl_binary.c          |    1 +
>  6 files changed, 27 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index 704e474..eb8d263 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -48,6 +48,7 @@ show up in /proc/sys/kernel:
>  - panic
>  - panic_on_oops
>  - panic_on_unrecovered_nmi
> +- panic_on_stackoverflow
>  - pid_max
>  - powersave-nap               [ PPC only ]
>  - printk
> @@ -385,6 +386,18 @@ Controls the kernel's behaviour when an oops or BUG is encountered.
>  
>  ==============================================================
>  
> +panic_on_stackoverflow:
> +
> +Controls the kernel's behaviour when detecting stack overflow.
> +This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled.
> +
> +0: try to continue operation.
> +
> +1: panic immediately.
> +
> +==============================================================
> +
> +
>  pid_max:
>  
>  PID allocation wrap value.  When the kernel's next PID value
> diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
> index 530cfd0..d720813 100644
> --- a/arch/x86/kernel/irq_64.c
> +++ b/arch/x86/kernel/irq_64.c
> @@ -20,6 +20,8 @@
>  #include <asm/idle.h>
>  #include <asm/apic.h>
>  
> +int sysctl_panic_on_stackoverflow;

__read_mostly

> +
>  DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
>  EXPORT_PER_CPU_SYMBOL(irq_stat);
>  
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 8eefcf7..19b3595 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -339,6 +339,7 @@ extern int panic_timeout;
>  extern int panic_on_oops;
>  extern int panic_on_unrecovered_nmi;
>  extern int panic_on_io_nmi;
> +extern int sysctl_panic_on_stackoverflow;
>  extern const char *print_tainted(void);
>  extern void add_taint(unsigned flag);
>  extern int test_taint(unsigned flag);
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index 9a1ec10..4b9dc3d 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -153,6 +153,7 @@ enum
>  	KERN_MAX_LOCK_DEPTH=74, /* int: rtmutex's maximum lock depth */
>  	KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */
>  	KERN_PANIC_ON_NMI=76, /* int: whether we will panic on an unrecovered */
> +	KERN_PANIC_ON_STACKOVERFLOW = 77, /* int: panic on stack overflow */
>  };
>  
>  
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 11d65b5..08a18f9 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -792,6 +792,15 @@ static struct ctl_table kern_table[] = {
>  		.mode		= 0644,
>  		.proc_handler	= proc_dointvec,
>  	},
> +#if defined(CONFIG_DEBUG_STACKOVERFLOW)
> +	{
> +		.procname	= "panic_on_stackoverflow",
> +		.data		= &sysctl_panic_on_stackoverflow,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_dointvec,
> +	},
> +#endif
>  	{
>  		.procname	= "bootloader_type",
>  		.data		= &bootloader_type,
> diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
> index 6318b51..24fc654 100644
> --- a/kernel/sysctl_binary.c
> +++ b/kernel/sysctl_binary.c
> @@ -137,6 +137,7 @@ static const struct bin_table bin_kern_table[] = {
>  	{ CTL_INT,	KERN_COMPAT_LOG,		"compat-log" },
>  	{ CTL_INT,	KERN_MAX_LOCK_DEPTH,		"max_lock_depth" },
>  	{ CTL_INT,	KERN_PANIC_ON_NMI,		"panic_on_unrecovered_nmi" },
> +	{ CTL_INT,	KERN_PANIC_ON_STACKOVERFLOW,	"panic_on_stackoverflow" },

This shouldn't be wrapped in the #ifdef?

>  	{}
>  };
>  
> 
> --
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