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    SubjectRE: [PATCH 1/2] x86: initialize stack canary in secondary start


    >-----Original Message-----
    >From: Thomas Gleixner [mailto:tglx@linutronix.de]
    >Sent: Friday, December 18, 2009 8:03 AM
    >To: Pan, Jacob jun
    >Cc: H. Peter Anvin; x86@kernel.org; linux-kernel@vger.kernel.org
    >Subject: Re: [PATCH 1/2] x86: initialize stack canary in secondary start
    >
    >On Thu, 17 Dec 2009, Pan, Jacob jun wrote:
    >> >From 06503838368350268a46528e134c1dad9f4f8c93 Mon Sep 17 00:00:00 2001
    >> From: Jacob Pan <jacob.jun.pan@intel.com>
    >> Date: Thu, 17 Sep 2009 07:36:43 -0700
    >> Subject: [PATCH 1/2] x86: initialize stack canary in secondary start
    >>
    >> some secondary clockevent setup code needs to call request_irq, which will
    >> cause fake stack check failure in schedule() if voluntary preemption
    >> model is chosen, it is safe to have stack canary initialized here early,
    >> since start_secondary() does not return.
    >
    >Where is it initialized now ? Shouldnt the current init be removed ?
    >
    [[JPAN]] it is currently in cpu_idle(), i don't think it can be removed since
    there are other path calling it. calling boot_init_stack_canary() is redundant
    in some case but harmless.

    >Thanks,
    >
    > tglx
    >
    >> Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
    >> ---
    >> arch/x86/kernel/smpboot.c | 4 ++++
    >> 1 files changed, 4 insertions(+), 0 deletions(-)
    >>
    >> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
    >> index 678d0b8..56ce974 100644
    >> --- a/arch/x86/kernel/smpboot.c
    >> +++ b/arch/x86/kernel/smpboot.c
    >> @@ -48,6 +48,7 @@
    >> #include <linux/err.h>
    >> #include <linux/nmi.h>
    >> #include <linux/tboot.h>
    >> +#include <linux/stackprotector.h>
    >>
    >> #include <asm/acpi.h>
    >> #include <asm/desc.h>
    >> @@ -324,6 +325,9 @@ notrace static void __cpuinit start_secondary(void
    >*unused)
    >> /* enable local interrupts */
    >> local_irq_enable();
    >>
    >> + /* to prevent fake stack check failure in clock setup */
    >> + boot_init_stack_canary();
    >> +
    >> x86_cpuinit.setup_percpu_clockev();
    >>
    >> wmb();
    >> --
    >> 1.6.5.3
    >>
    >>


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