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    Subject[RFC PATCH 2/5] x86: check stack overflow in detail
    Date
    Currently, only kernel stack is checked for the overflow, which is
    not suffcient for enterprise systems. To enhance reliability,
    it is required to check the IRQ and exception stacks, as well.

    This patch optionally checks all the stack types and will cause
    messages of stacks in detail when free stack space drops below a
    certain limit except user stack. This is disabled by default in
    Kconfig.

    Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    ---

    arch/x86/Kconfig.debug | 11 +++++++++++
    arch/x86/kernel/irq_64.c | 28 ++++++++++++++++++++++++++++
    2 files changed, 39 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
    index bf56e17..0d98beb 100644
    --- a/arch/x86/Kconfig.debug
    +++ b/arch/x86/Kconfig.debug
    @@ -66,6 +66,17 @@ config DEBUG_STACKOVERFLOW
    This option will cause messages to be printed if free stack space
    drops below a certain limit.

    +config DEBUG_STACKOVERFLOW_DETAIL
    + bool "Check for stack overflows in detail"
    + depends on DEBUG_KERNEL && DEBUG_STACKOVERFLOW
    + depends on X86_64
    + ---help---
    + Say Y here if you want to check the overflows of IRQ and
    + exception stacks in addition to kernel stack. This option will
    + cause messages of the stacks in detail when free stack space
    + drops below a certain limit.
    + If in doubt, say "N".
    +
    config X86_PTDUMP
    bool "Export kernel pagetable layout to userspace via debugfs"
    depends on DEBUG_KERNEL
    diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
    index 69bca46..530cfd0 100644
    --- a/arch/x86/kernel/irq_64.c
    +++ b/arch/x86/kernel/irq_64.c
    @@ -37,10 +37,37 @@ static inline void stack_overflow_check(struct pt_regs *regs)
    {
    #ifdef CONFIG_DEBUG_STACKOVERFLOW
    u64 curbase = (u64)task_stack_page(current);
    +#ifdef CONFIG_DEBUG_STACKOVERFLOW_DETAIL
    + struct orig_ist *oist;
    + u64 irq_stack_top, irq_stack_bottom;
    + u64 estack_top, estack_bottom;
    +#endif

    if (user_mode_vm(regs))
    return;

    +#ifdef CONFIG_DEBUG_STACKOVERFLOW_DETAIL
    + if (regs->sp >= curbase + sizeof(struct thread_info) +
    + sizeof(struct pt_regs) + 128 &&
    + regs->sp <= curbase + THREAD_SIZE)
    + return;
    +
    + irq_stack_top = (u64)__get_cpu_var(irq_stack_union.irq_stack);
    + irq_stack_bottom = (u64)__get_cpu_var(irq_stack_ptr);
    + if (regs->sp >= irq_stack_top && regs->sp <= irq_stack_bottom)
    + return;
    +
    + oist = &__get_cpu_var(orig_ist);
    + estack_top = (u64)oist->ist[0] - EXCEPTION_STKSZ;
    + estack_bottom = (u64)oist->ist[N_EXCEPTION_STACKS - 1];
    + if (regs->sp >= estack_top && regs->sp <= estack_bottom)
    + return;
    +
    + WARN_ONCE(1, "do_IRQ: %s near or already stack stack overflow (cur:%Lx,sp:%lx,irq stk top-bottom:%Lx-%Lx,exception stk top-bottom:%Lx-%Lx)\n",
    + current->comm, curbase, regs->sp,
    + irq_stack_top, irq_stack_bottom,
    + estack_top, estack_bottom);
    +#else
    WARN_ONCE(regs->sp >= curbase &&
    regs->sp <= curbase + THREAD_SIZE &&
    regs->sp < curbase + sizeof(struct thread_info) +
    @@ -48,6 +75,7 @@ static inline void stack_overflow_check(struct pt_regs *regs)

    "do_IRQ: %s near stack overflow (cur:%Lx,sp:%lx)\n",
    current->comm, curbase, regs->sp);
    +#endif /* CONFIG_DEBUG_STACKOVERFLOW_DETAIL */
    #endif
    }



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