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    Subject[PATCH -v2 2/4] x86: check stack overflow in detail
    Date
    Currently, only kernel stack is checked for the overflow, which is
    not sufficient for systems that need a high reliability. To enhance
    it, it is required to check the IRQ and exception stacks, as well.

    This patch 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.

    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 | 7 +++++--
    arch/x86/kernel/irq_64.c | 29 +++++++++++++++++++++++------
    2 files changed, 28 insertions(+), 8 deletions(-)

    diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
    index bf56e17..4caec12 100644
    --- a/arch/x86/Kconfig.debug
    +++ b/arch/x86/Kconfig.debug
    @@ -63,8 +63,11 @@ config DEBUG_STACKOVERFLOW
    bool "Check for stack overflows"
    depends on DEBUG_KERNEL
    ---help---
    - This option will cause messages to be printed if free stack space
    - drops below a certain limit.
    + Say Y here if you want to check the overflows of kernel, IRQ
    + and exception stacks. 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"
    diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
    index 69bca46..11ae893 100644
    --- a/arch/x86/kernel/irq_64.c
    +++ b/arch/x86/kernel/irq_64.c
    @@ -36,18 +36,35 @@ EXPORT_PER_CPU_SYMBOL(irq_regs);
    static inline void stack_overflow_check(struct pt_regs *regs)
    {
    #ifdef CONFIG_DEBUG_STACKOVERFLOW
    + struct orig_ist *oist;
    + u64 irq_stack_top, irq_stack_bottom;
    + u64 estack_top, estack_bottom;
    u64 curbase = (u64)task_stack_page(current);

    if (user_mode_vm(regs))
    return;

    - 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)
    + 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;

    - "do_IRQ: %s near stack overflow (cur:%Lx,sp:%lx)\n",
    - current->comm, curbase, regs->sp);
    + WARN_ONCE(1, "do_IRQ: %s near or already 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);
    #endif
    }



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