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    Subject[tip:perf/kprobes] kprobes, x86: Prohibit probing on debug_stack_*()
    Commit-ID:  0f46efeb44e360b78f54a968b4d92e6877c35891
    Gitweb: http://git.kernel.org/tip/0f46efeb44e360b78f54a968b4d92e6877c35891
    Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    AuthorDate: Thu, 17 Apr 2014 17:17:12 +0900
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Thu, 24 Apr 2014 10:02:57 +0200

    kprobes, x86: Prohibit probing on debug_stack_*()

    Prohibit probing on debug_stack_reset and debug_stack_set_zero.
    Since the both functions are called from TRACE_IRQS_ON/OFF_DEBUG
    macros which run in int3 ist entry, probing it may cause a soft
    lockup.

    This happens when the kernel built with CONFIG_DYNAMIC_FTRACE=y
    and CONFIG_TRACE_IRQFLAGS=y.

    Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Jan Beulich <JBeulich@suse.com>
    Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
    Cc: Seiji Aguchi <seiji.aguchi@hds.com>
    Link: http://lkml.kernel.org/r/20140417081712.26341.32994.stgit@ltc230.yrl.intra.hitachi.co.jp
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/cpu/common.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
    index a135239..5af696d 100644
    --- a/arch/x86/kernel/cpu/common.c
    +++ b/arch/x86/kernel/cpu/common.c
    @@ -8,6 +8,7 @@
    #include <linux/delay.h>
    #include <linux/sched.h>
    #include <linux/init.h>
    +#include <linux/kprobes.h>
    #include <linux/kgdb.h>
    #include <linux/smp.h>
    #include <linux/io.h>
    @@ -1160,6 +1161,7 @@ int is_debug_stack(unsigned long addr)
    (addr <= __get_cpu_var(debug_stack_addr) &&
    addr > (__get_cpu_var(debug_stack_addr) - DEBUG_STKSZ));
    }
    +NOKPROBE_SYMBOL(is_debug_stack);

    DEFINE_PER_CPU(u32, debug_idt_ctr);

    @@ -1168,6 +1170,7 @@ void debug_stack_set_zero(void)
    this_cpu_inc(debug_idt_ctr);
    load_current_idt();
    }
    +NOKPROBE_SYMBOL(debug_stack_set_zero);

    void debug_stack_reset(void)
    {
    @@ -1176,6 +1179,7 @@ void debug_stack_reset(void)
    if (this_cpu_dec_return(debug_idt_ctr) == 0)
    load_current_idt();
    }
    +NOKPROBE_SYMBOL(debug_stack_reset);

    #else /* CONFIG_X86_64 */


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