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

[Pan, Jacob jun]

From 06503838368350268a46528e134c1dad9f4f8c93 Mon Sep 17 00:00:00 2001
From: Jacob Pan <jacob....@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.

Signed-off-by: Jacob Pan <jacob....@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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[Thomas Gleixner]

On Thu, 17 Dec 2009, Pan, Jacob jun wrote:
> >From 06503838368350268a46528e134c1dad9f4f8c93 Mon Sep 17 00:00:00 2001
> From: Jacob Pan <jacob....@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 ?

Thanks,

tglx

[Pan, Jacob jun]

>-----Original Message-----
>From: Thomas Gleixner [mailto:tg...@linutronix.de]
>Sent: Friday, December 18, 2009 8:03 AM
>To: Pan, Jacob jun
>Cc: H. Peter Anvin; x...@kernel.org; linux-...@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....@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.