linux-kernel - RE: [PATCH 1/2] x86: initialize stack canary in secondary start

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Date:	Fri, 18 Dec 2009 09:31:19 -0800
From:	"Pan, Jacob jun" <jacob.jun.pan@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] x86: initialize stack canary in secondary start



>-----Original Message-----
>From: Thomas Gleixner [mailto:tglx@...utronix.de]
>Sent: Friday, December 18, 2009 8:03 AM
>To: Pan, Jacob jun
>Cc: H. Peter Anvin; x86@...nel.org; linux-kernel@...r.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@...el.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@...el.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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