x86: Increase exception stack sizes

Message ID YUIO9Ye98S5Eb68w@hirez.programming.kicks-ass.net
State New
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Series
  • x86: Increase exception stack sizes
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Commit Message

Peter Zijlstra Sept. 15, 2021, 3:19 p.m.
On Wed, Sep 15, 2021 at 03:34:20PM +0800, 王贇 wrote:
> Hi, Dave, Peter
> 
> What if we just increase the stack size when ftrace enabled?

I think we can do an unconditional increase. But please first test that
guard page patch :-)

---
Subject: x86: Increase exception stack sizes
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed Sep 15 16:19:46 CEST 2021

It turns out that a single page of stack is trivial to overflow with
all the tracing gunk enabled. Raise the exception stacks to 2 pages,
which is still half the interrupt stacks, which are at 4 pages.

Reported-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/include/asm/page_64_types.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

王贇 Sept. 16, 2021, 3:42 a.m. | #1
On 2021/9/15 下午11:19, Peter Zijlstra wrote:
> On Wed, Sep 15, 2021 at 03:34:20PM +0800, 王贇 wrote:

>> Hi, Dave, Peter

>>

>> What if we just increase the stack size when ftrace enabled?

> 

> I think we can do an unconditional increase. But please first test that

> guard page patch :-)


Nice~ let's focus on the guard one firstly.

Regards,
Michael Wang

> 

> ---

> Subject: x86: Increase exception stack sizes

> From: Peter Zijlstra <peterz@infradead.org>

> Date: Wed Sep 15 16:19:46 CEST 2021

> 

> It turns out that a single page of stack is trivial to overflow with

> all the tracing gunk enabled. Raise the exception stacks to 2 pages,

> which is still half the interrupt stacks, which are at 4 pages.

> 

> Reported-by: Michael Wang <yun.wang@linux.alibaba.com>

> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---

>  arch/x86/include/asm/page_64_types.h |    2 +-

>  1 file changed, 1 insertion(+), 1 deletion(-)

> 

> --- a/arch/x86/include/asm/page_64_types.h

> +++ b/arch/x86/include/asm/page_64_types.h

> @@ -15,7 +15,7 @@

>  #define THREAD_SIZE_ORDER	(2 + KASAN_STACK_ORDER)

>  #define THREAD_SIZE  (PAGE_SIZE << THREAD_SIZE_ORDER)

>  

> -#define EXCEPTION_STACK_ORDER (0 + KASAN_STACK_ORDER)

> +#define EXCEPTION_STACK_ORDER (1 + KASAN_STACK_ORDER)

>  #define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)

>  

>  #define IRQ_STACK_ORDER (2 + KASAN_STACK_ORDER)

>

Patch

--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -15,7 +15,7 @@ 
 #define THREAD_SIZE_ORDER	(2 + KASAN_STACK_ORDER)
 #define THREAD_SIZE  (PAGE_SIZE << THREAD_SIZE_ORDER)
 
-#define EXCEPTION_STACK_ORDER (0 + KASAN_STACK_ORDER)
+#define EXCEPTION_STACK_ORDER (1 + KASAN_STACK_ORDER)
 #define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
 
 #define IRQ_STACK_ORDER (2 + KASAN_STACK_ORDER)