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Message-ID: <4EC4B38B.2010301@hitachi.com>
Date: Thu, 17 Nov 2011 16:11:07 +0900
From: HAYASAKA Mitsuo <mitsuo.hayasaka.hu@...achi.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.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 3/5] x86: add a sysctl parameter to panic on stack
overflow
Hi Konrad,
>> 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
I don't mind if I add __read_mostly here, but I think it's not
necessary because this variable is seldom read as well.
>> 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?
>
It seems that we do not need to add this entry to bin_kern_table[]
according to the following information and patch series:
[Removing binary sysctl]
http://lwn.net/Articles/361453/
[Removal of binary sysctl support]
http://lwn.net/Articles/361001/
So, I'm going to remove this changes for sysctl.h and sysctl_binary.c.
Thanks
(2011/11/11 4:55), Konrad Rzeszutek Wilk wrote:
> 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@...achi.com>
>> Cc: Randy Dunlap <rdunlap@...otime.net>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: "H. Peter Anvin" <hpa@...or.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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