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    Subject[tip:x86/debug] x86: Check stack overflow in detail
    Commit-ID:  37fe6a42b3433b79a159ceb06a94cd1ef00e279d
    Gitweb: http://git.kernel.org/tip/37fe6a42b3433b79a159ceb06a94cd1ef00e279d
    Author: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
    AuthorDate: Tue, 29 Nov 2011 15:08:29 +0900
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Mon, 5 Dec 2011 11:37:45 +0100

    x86: Check stack overflow in detail

    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: yrl.pp-manager.tt@hitachi.com
    Cc: Randy Dunlap <rdunlap@xenotime.net>
    Link: http://lkml.kernel.org/r/20111129060829.11076.51733.stgit@ltc219.sdl.hitachi.co.jp
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    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..928a7e9 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 has overflown the kernel stack (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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