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    Subject[RFC PATCH 3/5] x86: add a sysctl parameter to panic on stack overflow
    Date
    This patch adds kernel.panic_on_stackoverflow sysctl parameter,
    which can cause a panic when detecting the stack overflow.

    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;
    +
    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" },
    {}
    };



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